Thanks to the SpanInjector and SpanExtractor you can customize the way spans
+are created and propagated.
There are currently two built-in ways to pass tracing information between processes:
- via Spring Integration
- via HTTP
Span ids are extracted from Zipkin-compatible (B3) headers (either Message
+or HTTP headers), to start or join an existing trace. Trace information is
+injected into any outbound requests so the next hop can extract them.
The key change in comparison to the previous versions of Sleuth is that Sleuth is implementing
+the Open Tracing’s TextMap notion. In Sleuth it’s called SpanTextMap. Basically the idea
+is that any means of communication (e.g. message, http request, etc.) can be abstracted via
+a SpanTextMap. This abstraction defines how one can insert data into the carrier and
+how to retrieve it from there. Thanks to this if you want to instrument a new HTTP library
+that uses a FooRequest as a mean of sending HTTP requests then you have to create an
+implementation of a SpanTextMap that delegates calls to FooRequest in terms of retrieval
+and insertion of HTTP headers.
For Spring Integration there are 2 interfaces responsible for creation of a Span from a Message.
+These are:
MessagingSpanTextMapExtractorMessagingSpanTextMapInjector
You can override them by providing your own implementation.
For HTTP there are 2 interfaces responsible for creation of a Span from a Message.
+These are:
HttpSpanExtractorHttpSpanInjector
You can override them by providing your own implementation.
Let’s assume that instead of the standard Zipkin compatible tracing HTTP header names
+you have
- for trace id -
correlationId - for span id -
mySpanId
This is a an example of a SpanExtractor
static class CustomHttpSpanExtractor implements HttpSpanExtractor {
+
+ @Override public Span joinTrace(SpanTextMap carrier) {
+ Map<String, String> map = TextMapUtil.asMap(carrier);
+ long traceId = Span.hexToId(map.get("correlationid"));
+ long spanId = Span.hexToId(map.get("myspanid"));
+
+ Span.SpanBuilder builder = Span.builder().traceId(traceId).spanId(spanId);
+
+ return builder.build();
+ }
+}
+
+static class CustomHttpSpanInjector implements HttpSpanInjector {
+
+ @Override
+ public void inject(Span span, SpanTextMap carrier) {
+ carrier.put("correlationId", span.traceIdString());
+ carrier.put("mySpanId", Span.idToHex(span.getSpanId()));
+ }
+}And you could register it like this:
@Bean
+HttpSpanInjector customHttpSpanInjector() {
+ return new CustomHttpSpanInjector();
+}
+
+@Bean
+HttpSpanExtractor customHttpSpanExtractor() {
+ return new CustomHttpSpanExtractor();
+}Spring Cloud Sleuth does not add trace/span related headers to the Http Response for security reasons. If you need the headers then a custom SpanInjector
+that injects the headers into the Http Response and a Servlet filter which makes use of this can be added the following way:
static class CustomHttpServletResponseSpanInjector extends ZipkinHttpSpanInjector {
+
+ @Override
+ public void inject(Span span, SpanTextMap carrier) {
+ super.inject(span, carrier);
+ carrier.put(Span.TRACE_ID_NAME, span.traceIdString());
+ carrier.put(Span.SPAN_ID_NAME, Span.idToHex(span.getSpanId()));
+ }
+}
+
+static class HttpResponseInjectingTraceFilter extends GenericFilterBean {
+
+ private final Tracer tracer;
+ private final HttpSpanInjector spanInjector;
+
+ public HttpResponseInjectingTraceFilter(Tracer tracer, HttpSpanInjector spanInjector) {
+ this.tracer = tracer;
+ this.spanInjector = spanInjector;
+ }
+
+ @Override
+ public void doFilter(ServletRequest request, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
+ HttpServletResponse response = (HttpServletResponse) servletResponse;
+ Span currentSpan = this.tracer.getCurrentSpan();
+ this.spanInjector.inject(currentSpan, new HttpServletResponseTextMap(response));
+ filterChain.doFilter(request, response);
+ }
+
+ class HttpServletResponseTextMap implements SpanTextMap {
+
+ private final HttpServletResponse delegate;
+
+ HttpServletResponseTextMap(HttpServletResponse delegate) {
+ this.delegate = delegate;
+ }
+
+ @Override
+ public Iterator<Map.Entry<String, String>> iterator() {
+ Map<String, String> map = new HashMap<>();
+ for (String header : this.delegate.getHeaderNames()) {
+ map.put(header, this.delegate.getHeader(header));
+ }
+ return map.entrySet().iterator();
+ }
+
+ @Override
+ public void put(String key, String value) {
+ this.delegate.addHeader(key, value);
+ }
+ }
+}And you could register them like this:
@Bean HttpSpanInjector customHttpServletResponseSpanInjector() {
+ return new CustomHttpServletResponseSpanInjector();
+}
+
+@Bean
+HttpResponseInjectingTraceFilter responseInjectingTraceFilter(Tracer tracer) {
+ return new HttpResponseInjectingTraceFilter(tracer, customHttpServletResponseSpanInjector());
+}You can also modify the behaviour of the TraceFilter - the component that is responsible
+for processing the input HTTP request and adding tags basing on the HTTP response. You can customize
+the tags, or modify the response headers by registering your own instance of the TraceFilter bean.
In the following example we will register the TraceFilter bean and we will add the
+ZIPKIN-TRACE-ID response header containing the current Span’s trace id. Also we will
+add to the Span a tag with key custom and a value tag.
@Bean
+TraceFilter myTraceFilter(BeanFactory beanFactory, final Tracer tracer) {
+ return new TraceFilter(beanFactory) {
+ @Override protected void addResponseTags(HttpServletResponse response,
+ Throwable e) {
+
+ super.addResponseTags(response, e);
+
+ response.addHeader("ZIPKIN-TRACE-ID",
+ Span.idToHex(tracer.getCurrentSpan().getTraceId()));
+
+ tracer.addTag("custom", "tag");
+ }
+ };
+}9.5 Custom SA tag in Zipkin
Sometimes you want to create a manual Span that will wrap a call to an external service which is not instrumented.
+What you can do is to create a span with the peer.service tag that will contain a value of the service that you want to call.
+Below you can see an example of a call to Redis that is wrapped in such a span.
org.springframework.cloud.sleuth.Span newSpan = tracer.createSpan("redis");
+try {
+ newSpan.tag("redis.op", "get");
+ newSpan.tag("lc", "redis");
+ newSpan.logEvent(org.springframework.cloud.sleuth.Span.CLIENT_SEND);
+
+
+} finally {
+ newSpan.tag("peer.service", "redisService");
+ newSpan.tag("peer.ipv4", "1.2.3.4");
+ newSpan.tag("peer.port", "1234");
+ newSpan.logEvent(org.springframework.cloud.sleuth.Span.CLIENT_RECV);
+ tracer.close(newSpan);
+}![[Important]](images/important.png) | Important |
|---|
Remember not to add both peer.service tag and the SA tag! You have to add only peer.service. |
By default Sleuth assumes that when you send a span to Zipkin, you want the span’s service name
+ to be equal to spring.application.name value. That’s not always the case though. There
+ are situations in which you want to explicitly provide a different service name for all spans coming
+ from your application. To achieve that it’s enough to just pass the following property
+ to your application to override that value (example for foo service name):
spring.zipkin.service.name: foo
9.7 Customization of reported spans
Before reporting spans to e.g. Zipkin you can be interested in modifying that span in some way.
+ You can achieve that by using the SpanAdjuster interface.
Example of usage:
In Sleuth we’re generating spans with a fixed name. Some users want to modify the name depending on values
+of tags. Implementation of the SpanAdjuster interface can be used to alter that name. Example:
@Bean
+SpanAdjuster customSpanAdjuster() {
+ return span -> span.toBuilder().name(scrub(span.getName())).build();
+}This will lead in changing the name of the reported span just before it gets sent to Zipkin.
| Important |
|---|
Your SpanReporter should inject the SpanAdjuster and
+ allow span manipulation before the actual reporting is done. |
In order to define the host that is corresponding to a particular span we need to resolve the host name
+and port. The default approach is to take it from server properties. If those for some reason are not set
+then we’re trying to retrieve the host name from the network interfaces.
If you have the discovery client enabled and prefer to retrieve the host address from the registered
+instance in a service registry then you have to set the property (it’s applicable for both HTTP and
+Stream based span reporting).
spring.zipkin.locator.discovery.enabled: true
Spring Cloud Sleuth instruments all your Spring application
+automatically, so you shouldn’t have to do anything to activate
+it. The instrumentation is added using a variety of technologies
+according to the stack that is available, e.g. for a servlet web
+application we use a Filter, and for Spring Integration we use
+ChannelInterceptors.
You can customize the keys used in span tags. To limit the volume of
+span data, by default an HTTP request will be tagged only with a
+handful of metadata like the status code, host and URL. You can add
+request headers by configuring spring.sleuth.keys.http.headers (a
+list of header names).
![[Note]](images/note.png) | Note |
|---|
Remember that tags are only collected and exported if there is a
+Sampler that allows it (by default there is not, so there is no
+danger of accidentally collecting too much data without configuring
+something). |
| Note |
|---|
Currently the instrumentation in Spring Cloud Sleuth is eager - it means that
+we’re actively trying to pass the tracing context between threads. Also timing events
+are captured even when sleuth isn’t exporting data to a tracing system.
+This approach may change in the future towards being lazy on this matter. |
13.1 Runnable and Callable
If you’re wrapping your logic in Runnable or Callable it’s enough to wrap those classes in their Sleuth representative.
Example for Runnable:
Runnable runnable = new Runnable() {
+ @Override
+ public void run() {
+
+ }
+
+ @Override
+ public String toString() {
+ return "spanNameFromToStringMethod";
+ }
+};
+
+Runnable traceRunnable = new TraceRunnable(tracer, spanNamer, runnable, "calculateTax");
+
+
+Runnable traceRunnableFromTracer = tracer.wrap(runnable);Example for Callable:
Callable<String> callable = new Callable<String>() {
+ @Override
+ public String call() throws Exception {
+ return someLogic();
+ }
+
+ @Override
+ public String toString() {
+ return "spanNameFromToStringMethod";
+ }
+};
+
+Callable<String> traceCallable = new TraceCallable<>(tracer, spanNamer, callable, "calculateTax");
+
+
+Callable<String> traceCallableFromTracer = tracer.wrap(callable);That way you will ensure that a new Span is created and closed for each execution.
13.2.1 Custom Concurrency Strategy
We’re registering a custom HystrixConcurrencyStrategy
+that wraps all Callable instances into their Sleuth representative -
+the TraceCallable. The strategy either starts or continues a span depending on the fact whether tracing was already going
+on before the Hystrix command was called. To disable the custom Hystrix Concurrency Strategy set the spring.sleuth.hystrix.strategy.enabled to false.
13.2.2 Manual Command setting
Assuming that you have the following HystrixCommand:
HystrixCommand<String> hystrixCommand = new HystrixCommand<String>(setter) {
+ @Override
+ protected String run() throws Exception {
+ return someLogic();
+ }
+};In order to pass the tracing information you have to wrap the same logic in the Sleuth version of the HystrixCommand which is the
+TraceCommand:
TraceCommand<String> traceCommand = new TraceCommand<String>(tracer, traceKeys, setter) {
+ @Override
+ public String doRun() throws Exception {
+ return someLogic();
+ }
+};We’re registering a custom RxJavaSchedulersHook
+that wraps all Action0 instances into their Sleuth representative -
+the TraceAction. The hook either starts or continues a span depending on the fact whether tracing was already going
+on before the Action was scheduled. To disable the custom RxJavaSchedulersHook set the spring.sleuth.rxjava.schedulers.hook.enabled to false.
You can define a list of regular expressions for thread names, for which you don’t want a Span to be created. Just provide a comma separated list
+of regular expressions in the spring.sleuth.rxjava.schedulers.ignoredthreads property.
Features from this section can be disabled by providing the spring.sleuth.web.enabled property with value equal to false.
Via the TraceFilter all sampled incoming requests result in creation of a Span. That Span’s name is http: + the path to which
+ the request was sent. E.g. if the request was sent to /foo/bar then the name will be http:/foo/bar. You can configure which URIs you would
+ like to skip via the spring.sleuth.web.skipPattern property. If you have ManagementServerProperties on classpath then
+ its value of contextPath gets appended to the provided skip pattern.
13.4.2 HandlerInterceptor
Since we want the span names to be precise we’re using a TraceHandlerInterceptor that either wraps an
+ existing HandlerInterceptor or is added directly to the list of existing HandlerInterceptors. The
+ TraceHandlerInterceptor adds a special request attribute to the given HttpServletRequest. If the
+ the TraceFilter doesn’t see this attribute set it will create a "fallback" span which is an additional
+ span created on the server side so that the trace is presented properly in the UI. Seeing that most likely
+ signifies that there is a missing instrumentation. In that case please file an issue in Spring Cloud Sleuth.
13.4.3 Async Servlet support
If your controller returns a Callable or a WebAsyncTask Spring Cloud Sleuth will continue the existing span instead of creating a new one.
13.5 HTTP client integration
13.5.1 Synchronous Rest Template
We’re injecting a RestTemplate interceptor that ensures that all the tracing information is passed to the requests. Each time a
+call is made a new Span is created. It gets closed upon receiving the response. In order to block the synchronous RestTemplate features
+just set spring.sleuth.web.client.enabled to false.
| Important |
|---|
You have to register RestTemplate as a bean so that the interceptors will get injected.
+If you create a RestTemplate instance with a new keyword then the instrumentation WILL NOT work. |
13.5.2 Asynchronous Rest Template
| Important |
|---|
A traced version of an AsyncRestTemplate bean is registered for you out of the box. If you
+have your own bean you have to wrap it in a TraceAsyncRestTemplate representation. The best solution
+is to only customize the ClientHttpRequestFactory and / or AsyncClientHttpRequestFactory.
+If you have your own AsyncRestTemplate and you don’t wrap it your calls WILL NOT GET TRACED. |
Custom instrumentation is set to create and close Spans upon sending and receiving requests. You can customize the ClientHttpRequestFactory
+and the AsyncClientHttpRequestFactory by registering your beans. Remember to use tracing compatible implementations (e.g. don’t forget to
+wrap ThreadPoolTaskScheduler in a TraceAsyncListenableTaskExecutor). Example of custom request factories:
@EnableAutoConfiguration
+@Configuration
+public static class TestConfiguration {
+
+ @Bean
+ ClientHttpRequestFactory mySyncClientFactory() {
+ return new MySyncClientHttpRequestFactory();
+ }
+
+ @Bean
+ AsyncClientHttpRequestFactory myAsyncClientFactory() {
+ return new MyAsyncClientHttpRequestFactory();
+ }
+}To block the AsyncRestTemplate features set spring.sleuth.web.async.client.enabled to false.
+To disable creation of the default TraceAsyncClientHttpRequestFactoryWrapper set spring.sleuth.web.async.client.factory.enabled
+to false. If you don’t want to create AsyncRestClient at all set spring.sleuth.web.async.client.template.enabled to false.
Multiple Asynchronous Rest Templates
Sometimes you need to use multiple implementations of Asynchronous Rest Template. In the following snippet you
+can see an example of how to set up such a custom AsyncRestTemplate.
@Configuration
+@EnableAutoConfiguration
+static class Config {
+ @Autowired Tracer tracer;
+ @Autowired HttpTraceKeysInjector httpTraceKeysInjector;
+ @Autowired HttpSpanInjector spanInjector;
+
+ @Bean(name = "customAsyncRestTemplate")
+ public AsyncRestTemplate traceAsyncRestTemplate(@Qualifier("customHttpRequestFactoryWrapper")
+ TraceAsyncClientHttpRequestFactoryWrapper wrapper, ErrorParser errorParser) {
+ return new TraceAsyncRestTemplate(wrapper, this.tracer, errorParser);
+ }
+
+ @Bean(name = "customHttpRequestFactoryWrapper")
+ public TraceAsyncClientHttpRequestFactoryWrapper traceAsyncClientHttpRequestFactory() {
+ return new TraceAsyncClientHttpRequestFactoryWrapper(this.tracer,
+ this.spanInjector,
+ asyncClientFactory(),
+ clientHttpRequestFactory(),
+ this.httpTraceKeysInjector);
+ }
+
+ private ClientHttpRequestFactory clientHttpRequestFactory() {
+ ClientHttpRequestFactory clientHttpRequestFactory = new CustomClientHttpRequestFactory();
+
+ return clientHttpRequestFactory;
+ }
+
+ private AsyncClientHttpRequestFactory asyncClientFactory() {
+ AsyncClientHttpRequestFactory factory = new CustomAsyncClientHttpRequestFactory();
+
+ return factory;
+ }
+}If you’re using the Traverson library
+it’s enough for you to inject a RestTemplate as a bean into your Traverson object. Since RestTemplate
+is already intercepted, you will get full support of tracing in your client. Below you can find a pseudo code
+of how to do that:
@Autowired RestTemplate restTemplate;
+
+Traverson traverson = new Traverson(URI.create("http://some/address"),
+ MediaType.APPLICATION_JSON, MediaType.APPLICATION_JSON_UTF8).setRestOperations(restTemplate);
+By default Spring Cloud Sleuth provides integration with feign via the TraceFeignClientAutoConfiguration. You can disable it entirely
+by setting spring.sleuth.feign.enabled to false. If you do so then no Feign related instrumentation will take place.
Part of Feign instrumentation is done via a FeignBeanPostProcessor. You can disable it by providing the spring.sleuth.feign.processor.enabled equal to false.
+If you set it like this then Spring Cloud Sleuth will not instrument any of your custom Feign components. All the default instrumentation
+however will be still there.
13.7 Asynchronous communication
13.7.1 @Async annotated methods
In Spring Cloud Sleuth we’re instrumenting async related components so that the tracing information is passed between threads.
+You can disable this behaviour by setting the value of spring.sleuth.async.enabled to false.
If you annotate your method with @Async then we’ll automatically create a new Span with the following characteristics:
- if the method is annotated with
@SpanName then the value of the annotation will be the Span’s name - if the method is not annotated with
@SpanName the Span name will be the annotated method name - the Span will be tagged with that method’s class name and the method name too
13.7.2 @Scheduled annotated methods
In Spring Cloud Sleuth we’re instrumenting scheduled method execution so that the tracing information is passed between threads. You can disable this behaviour
+by setting the value of spring.sleuth.scheduled.enabled to false.
If you annotate your method with @Scheduled then we’ll automatically create a new Span with the following characteristics:
- the Span name will be the annotated method name
- the Span will be tagged with that method’s class name and the method name too
If you want to skip Span creation for some @Scheduled annotated classes you can set the
+spring.sleuth.scheduled.skipPattern with a regular expression that will match the fully qualified name of the
+@Scheduled annotated class.
![[Tip]](images/tip.png) | Tip |
|---|
If you are using spring-cloud-sleuth-stream and spring-cloud-netflix-hystrix-stream together, Span will be created for each Hystrix metrics and sent to Zipkin. This may be annoying. You can prevent this by setting spring.sleuth.scheduled.skipPattern=org.springframework.cloud.netflix.hystrix.stream.HystrixStreamTask |
13.7.3 Executor, ExecutorService and ScheduledExecutorService
We’re providing LazyTraceExecutor, TraceableExecutorService and TraceableScheduledExecutorService. Those implementations
+are creating Spans each time a new task is submitted, invoked or scheduled.
Here you can see an example of how to pass tracing information with TraceableExecutorService when working with CompletableFuture:
CompletableFuture<Long> completableFuture = CompletableFuture.supplyAsync(() -> {
+
+ return 1_000_000L;
+}, new TraceableExecutorService(executorService,
+
+ tracer, traceKeys, spanNamer, "calculateTax"));Customization of Executors
Sometimes you need to set up a custom instance of the AsyncExecutor. In the following snippet you
+can see an example of how to set up such a custom Executor.
@Configuration
+@EnableAutoConfiguration
+@EnableAsync
+static class CustomExecutorConfig extends AsyncConfigurerSupport {
+
+ @Autowired BeanFactory beanFactory;
+
+ @Override public Executor getAsyncExecutor() {
+ ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
+
+ executor.setCorePoolSize(7);
+ executor.setMaxPoolSize(42);
+ executor.setQueueCapacity(11);
+ executor.setThreadNamePrefix("MyExecutor-");
+
+ executor.initialize();
+ return new LazyTraceExecutor(this.beanFactory, executor);
+ }
+}Spring Cloud Sleuth integrates with Spring Integration. It creates spans for publish and
+subscribe events. To disable Spring Integration instrumentation, set spring.sleuth.integration.enabled to false.
You can provide the spring.sleuth.integration.patterns pattern to explicitly
+provide the names of channels that you want to include for tracing. By default all channels
+are included.
| Important |
|---|
When using the Executor to build a Spring Integration IntegrationFlow remember to use the untraced version of the Executor.
+Decorating Spring Integration Executor Channel with TraceableExecutorService will cause the spans to be improperly closed. |
We’re registering Zuul filters to propagate the tracing information (the request header is enriched with tracing data).
+To disable Zuul support set the spring.sleuth.zuul.enabled property to false.
Spring Cloud Sleuth implements a distributed tracing solution for Spring Cloud.
Spring Cloud Sleuth borrows Dapper’s terminology.
Span: The basic unit of work. For example, sending an RPC is a new span, as is sending a response to an
+RPC. Span’s are identified by a unique 64-bit ID for the span and another 64-bit ID for the trace the span
+is a part of. Spans also have other data, such as descriptions, timestamped events, key-value
+annotations (tags), the ID of the span that caused them, and process ID’s (normally IP address).
Spans are started and stopped, and they keep track of their timing information. Once you create a
+span, you must stop it at some point in the future.
| Tip |
|---|
The initial span that starts a trace is called a root span. The value of span id
+of that span is equal to trace id. |
Trace: A set of spans forming a tree-like structure. For example, if you are running a distributed
+big-data store, a trace might be formed by a put request.
Annotation: is used to record existence of an event in time. Some of the core annotations used to define
+the start and stop of a request are:
- cs - Client Sent - The client has made a request. This annotation depicts the start of the span.
- sr - Server Received - The server side got the request and will start processing it.
+If one subtracts the cs timestamp from this timestamp one will receive the network latency.
- ss - Server Sent - Annotated upon completion of request processing (when the response
+got sent back to the client). If one subtracts the sr timestamp from this timestamp one
+will receive the time needed by the server side to process the request.
- cr - Client Received - Signifies the end of the span. The client has successfully received the
+response from the server side. If one subtracts the cs timestamp from this timestamp one
+will receive the whole time needed by the client to receive the response from the server.
Visualization of what Span and Trace will look in a system together with the Zipkin annotations:
Each color of a note signifies a span (7 spans - from A to G). If you have such information in the note:
Trace Id = X
+Span Id = D
+Client Sent
That means that the current span has Trace-Id set to X, Span-Id set to D. It also has emitted
+ Client Sent event.
This is how the visualization of the parent / child relationship of spans would look like:
In the following sections the example from the image above will be taken into consideration.
1.2.1 Distributed tracing with Zipkin
Altogether there are 7 spans . If you go to traces in Zipkin you will see this number in the second trace:
However if you pick a particular trace then you will see 4 spans:
| Note |
|---|
When picking a particular trace you will see merged spans. That means that if there were 2 spans sent to
+Zipkin with Server Received and Server Sent / Client Received and Client Sent
+annotations then they will presented as a single span. |
Why is there a difference between the 7 and 4 spans in this case?
- 2 spans come from
http:/start span. It has the Server Received (SR) and Server Sent (SS) annotations. - 2 spans come from the RPC call from
service1 to service2 to the http:/foo endpoint. It has the Client Sent (CS)
+and Client Received (CR) annotations on service1 side. It also has Server Received (SR) and Server Sent (SS) annotations
+on the service2 side. Physically there are 2 spans but they form 1 logical span related to an RPC call. - 2 spans come from the RPC call from
service2 to service3 to the http:/bar endpoint. It has the Client Sent (CS)
+and Client Received (CR) annotations on service2 side. It also has Server Received (SR) and Server Sent (SS) annotations
+on the service3 side. Physically there are 2 spans but they form 1 logical span related to an RPC call. - 2 spans come from the RPC call from
service2 to service4 to the http:/baz endpoint. It has the Client Sent (CS)
+and Client Received (CR) annotations on service2 side. It also has Server Received (SR) and Server Sent (SS) annotations
+on the service4 side. Physically there are 2 spans but they form 1 logical span related to an RPC call.
So if we count the physical spans we have 1 from http:/start, 2 from service1 calling service2, 2 form service2
+calling service3 and 2 from service2 calling service4. Altogether 7 spans.
Logically we see the information of Total Spans: 4 because we have 1 span related to the incoming request
+to service1 and 3 spans related to RPC calls.
Zipkin allows you to visualize errors in your trace. When an exception was thrown and wasn’t caught then we’re
+setting proper tags on the span which Zipkin can properly colorize. You could see in the list of traces one
+ trace that was in red color. That’s because there was an exception thrown.
If you click that trace then you’ll see a similar picture
Then if you click on one of the spans you’ll see the following
As you can see you can easily see the reason for an error and the whole stacktrace related to it.
The dependency graph in Zipkin would look like this:
When grepping the logs of those four applications by trace id equal to e.g. 2485ec27856c56f4 one would get the following:
service1.log:2016-02-26 11:15:47.561 INFO [service1,2485ec27856c56f4,2485ec27856c56f4,true] 68058 --- [nio-8081-exec-1] i.s.c.sleuth.docs.service1.Application : Hello from service1. Calling service2
+service2.log:2016-02-26 11:15:47.710 INFO [service2,2485ec27856c56f4,9aa10ee6fbde75fa,true] 68059 --- [nio-8082-exec-1] i.s.c.sleuth.docs.service2.Application : Hello from service2. Calling service3 and then service4
+service3.log:2016-02-26 11:15:47.895 INFO [service3,2485ec27856c56f4,1210be13194bfe5,true] 68060 --- [nio-8083-exec-1] i.s.c.sleuth.docs.service3.Application : Hello from service3
+service2.log:2016-02-26 11:15:47.924 INFO [service2,2485ec27856c56f4,9aa10ee6fbde75fa,true] 68059 --- [nio-8082-exec-1] i.s.c.sleuth.docs.service2.Application : Got response from service3 [Hello from service3]
+service4.log:2016-02-26 11:15:48.134 INFO [service4,2485ec27856c56f4,1b1845262ffba49d,true] 68061 --- [nio-8084-exec-1] i.s.c.sleuth.docs.service4.Application : Hello from service4
+service2.log:2016-02-26 11:15:48.156 INFO [service2,2485ec27856c56f4,9aa10ee6fbde75fa,true] 68059 --- [nio-8082-exec-1] i.s.c.sleuth.docs.service2.Application : Got response from service4 [Hello from service4]
+service1.log:2016-02-26 11:15:48.182 INFO [service1,2485ec27856c56f4,2485ec27856c56f4,true] 68058 --- [nio-8081-exec-1] i.s.c.sleuth.docs.service1.Application : Got response from service2 [Hello from service2, response from service3 [Hello from service3] and from service4 [Hello from service4]]
If you’re using a log aggregating tool like Kibana,
+Splunk etc. you can order the events that took place. An example of
+Kibana would look like this:
If you want to use Logstash here is the Grok pattern for Logstash:
filter {
+ # pattern matching logback pattern
+ grok {
+ match => { "message" => "%{TIMESTAMP_ISO8601:timestamp}\s+%{LOGLEVEL:severity}\s+\[%{DATA:service},%{DATA:trace},%{DATA:span},%{DATA:exportable}\]\s+%{DATA:pid}\s+---\s+\[%{DATA:thread}\]\s+%{DATA:class}\s+:\s+%{GREEDYDATA:rest}" }
+ }
+} | Note |
|---|
If you want to use Grok together with the logs from Cloud Foundry you have to use this pattern: |
filter {
+ # pattern matching logback pattern
+ grok {
+ match => { "message" => "(?m)OUT\s+%{TIMESTAMP_ISO8601:timestamp}\s+%{LOGLEVEL:severity}\s+\[%{DATA:service},%{DATA:trace},%{DATA:span},%{DATA:exportable}\]\s+%{DATA:pid}\s+---\s+\[%{DATA:thread}\]\s+%{DATA:class}\s+:\s+%{GREEDYDATA:rest}" }
+ }
+}JSON Logback with Logstash
Often you do not want to store your logs in a text file but in a JSON file that Logstash can immediately pick. To do that you have to do the following (for readability
+we’re passing the dependencies in the groupId:artifactId:version notation.
Dependencies setup
- Ensure that Logback is on the classpath (
ch.qos.logback:logback-core) - Add Logstash Logback encode - example for version
4.6 : net.logstash.logback:logstash-logback-encoder:4.6
Logback setup
Below you can find an example of a Logback configuration (file named logback-spring.xml) that:
- logs information from the application in a JSON format to a
build/${spring.application.name}.json file - has commented out two additional appenders - console and standard log file
- has the same logging pattern as the one presented in the previous section
<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+ <include resource="org/springframework/boot/logging/logback/defaults.xml"/>
+
+ <springProperty scope="context" name="springAppName" source="spring.application.name"/>
+
+ <property name="LOG_FILE" value="${BUILD_FOLDER:-build}/${springAppName}"/>
+
+
+ <property name="CONSOLE_LOG_PATTERN"
+ value="%clr(%d{yyyy-MM-dd HH:mm:ss.SSS}){faint} %clr(${LOG_LEVEL_PATTERN:-%5p}) %clr(${PID:- }){magenta} %clr(---){faint} %clr([%15.15t]){faint} %clr(%-40.40logger{39}){cyan} %clr(:){faint} %m%n${LOG_EXCEPTION_CONVERSION_WORD:-%wEx}"/>
+
+
+ <appender name="console" class="ch.qos.logback.core.ConsoleAppender">
+ <filter class="ch.qos.logback.classic.filter.ThresholdFilter">
+
+ <level>DEBUG</level>
+ </filter>
+ <encoder>
+ <pattern>${CONSOLE_LOG_PATTERN}</pattern>
+ <charset>utf8</charset>
+ </encoder>
+ </appender>
+
+
+ <appender name="flatfile" class="ch.qos.logback.core.rolling.RollingFileAppender">
+ <file>${LOG_FILE}</file>
+ <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
+ <fileNamePattern>${LOG_FILE}.%d{yyyy-MM-dd}.gz</fileNamePattern>
+ <maxHistory>7</maxHistory>
+ </rollingPolicy>
+ <encoder>
+ <pattern>${CONSOLE_LOG_PATTERN}</pattern>
+ <charset>utf8</charset>
+ </encoder>
+ </appender>
+
+
+ <appender name="logstash" class="ch.qos.logback.core.rolling.RollingFileAppender">
+ <file>${LOG_FILE}.json</file>
+ <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
+ <fileNamePattern>${LOG_FILE}.json.%d{yyyy-MM-dd}.gz</fileNamePattern>
+ <maxHistory>7</maxHistory>
+ </rollingPolicy>
+ <encoder class="net.logstash.logback.encoder.LoggingEventCompositeJsonEncoder">
+ <providers>
+ <timestamp>
+ <timeZone>UTC</timeZone>
+ </timestamp>
+ <pattern>
+ <pattern>
+ {
+ "severity": "%level",
+ "service": "${springAppName:-}",
+ "trace": "%X{X-B3-TraceId:-}",
+ "span": "%X{X-B3-SpanId:-}",
+ "parent": "%X{X-B3-ParentSpanId:-}",
+ "exportable": "%X{X-Span-Export:-}",
+ "pid": "${PID:-}",
+ "thread": "%thread",
+ "class": "%logger{40}",
+ "rest": "%message"
+ }
+ </pattern>
+ </pattern>
+ </providers>
+ </encoder>
+ </appender>
+
+ <root level="INFO">
+ <appender-ref ref="console"/>
+
+
+
+ </root>
+</configuration> | Note |
|---|
If you’re using a custom logback-spring.xml then you have to pass the spring.application.name in
+bootstrap instead of application property file. Otherwise your custom logback file won’t read the property properly. |
1.2.5 Propagating Span Context
The span context is the state that must get propagated to any child Spans across process boundaries.
+Part of the Span Context is the Baggage. The trace and span IDs are a required part of the span context.
+Baggage is an optional part.
Baggage is a set of key:value pairs stored in the span context. Baggage travels together with the trace
+and is attached to every span. Spring Cloud Sleuth will understand that a header is baggage related if the HTTP
+ header is prefixed with baggage- and for messaging it starts with baggage_.
| Important |
|---|
There’s currently no limitation of the count or size of baggage items. However, keep in mind that
+too many can decrease system throughput or increase RPC latency. In extreme cases, it could crash the app due
+to exceeding transport-level message or header capacity. |
Example of setting baggage on a span:
Span initialSpan = this.tracer.createSpan("span");
+initialSpan.setBaggageItem("foo", "bar");
+initialSpan.setBaggageItem("UPPER_CASE", "someValue");Baggage travels with the trace (i.e. every child span contains the baggage of its parent). Zipkin has no knowledge of
+baggage and will not even receive that information.
Tags are attached to a specific span - they are presented for that particular span only. However you
+can search by tag to find the trace, where there exists a span having the searched tag value.
If you want to be able to lookup a span based on baggage, you should add corresponding entry as a tag in the root span.
@Autowired Tracer tracer;
+
+Span span = tracer.getCurrentSpan();
+String baggageKey = "key";
+String baggageValue = "foo";
+span.setBaggageItem(baggageKey, baggageValue);
+tracer.addTag(baggageKey, baggageValue);
1.3 Adding to the project
1.3.1 Only Sleuth (log correlation)
If you want to profit only from Spring Cloud Sleuth without the Zipkin integration just add
+the spring-cloud-starter-sleuth module to your project.
Maven.
+
<dependencyManagement> 
+ <dependencies>
+ <dependency>
+ <groupId>org.springframework.cloud</groupId>
+ <artifactId>spring-cloud-dependencies</artifactId>
+ <version>${release.train.version}</version>
+ <type>pom</type>
+ <scope>import</scope>
+ </dependency>
+ </dependencies>
+ </dependencyManagement>
+
+ <dependency> 
+ <groupId>org.springframework.cloud</groupId>
+ <artifactId>spring-cloud-starter-sleuth</artifactId>
+ </dependency>
+
| In order not to pick versions by yourself it’s much better if you add the dependency management via
+the Spring BOM |
| Add the dependency to spring-cloud-starter-sleuth |
Gradle.
+
dependencyManagement {
+ imports {
+ mavenBom "org.springframework.cloud:spring-cloud-dependencies:${releaseTrainVersion}"
+ }
+}
+
+dependencies {
+ compile "org.springframework.cloud:spring-cloud-starter-sleuth"
+}
+
| In order not to pick versions by yourself it’s much better if you add the dependency management via
+the Spring BOM |
| Add the dependency to spring-cloud-starter-sleuth |
1.3.2 Sleuth with Zipkin via HTTP
If you want both Sleuth and Zipkin just add the spring-cloud-starter-zipkin dependency.
Maven.
+
<dependencyManagement>
+ <dependencies>
+ <dependency>
+ <groupId>org.springframework.cloud</groupId>
+ <artifactId>spring-cloud-dependencies</artifactId>
+ <version>${release.train.version}</version>
+ <type>pom</type>
+ <scope>import</scope>
+ </dependency>
+ </dependencies>
+ </dependencyManagement>
+
+ <dependency>
+ <groupId>org.springframework.cloud</groupId>
+ <artifactId>spring-cloud-starter-zipkin</artifactId>
+ </dependency>
+
| In order not to pick versions by yourself it’s much better if you add the dependency management via
+the Spring BOM |
| Add the dependency to spring-cloud-starter-zipkin |
Gradle.
+
dependencyManagement {
+ imports {
+ mavenBom "org.springframework.cloud:spring-cloud-dependencies:${releaseTrainVersion}"
+ }
+}
+
+dependencies {
+ compile "org.springframework.cloud:spring-cloud-starter-zipkin"
+}
+
| In order not to pick versions by yourself it’s much better if you add the dependency management via
+the Spring BOM |
| Add the dependency to spring-cloud-starter-zipkin |
1.3.3 Sleuth with Zipkin via Spring Cloud Stream
If you want both Sleuth and Zipkin just add the spring-cloud-sleuth-stream dependency.
Maven.
+
<dependencyManagement>
+ <dependencies>
+ <dependency>
+ <groupId>org.springframework.cloud</groupId>
+ <artifactId>spring-cloud-dependencies</artifactId>
+ <version>${release.train.version}</version>
+ <type>pom</type>
+ <scope>import</scope>
+ </dependency>
+ </dependencies>
+ </dependencyManagement>
+
+ <dependency>
+ <groupId>org.springframework.cloud</groupId>
+ <artifactId>spring-cloud-sleuth-stream</artifactId>
+ </dependency>
+ <dependency> 
+ <groupId>org.springframework.cloud</groupId>
+ <artifactId>spring-cloud-starter-sleuth</artifactId>
+ </dependency>
+
+ <dependency> 
+ <groupId>org.springframework.cloud</groupId>
+ <artifactId>spring-cloud-stream-binder-rabbit</artifactId>
+ </dependency>
+
| In order not to pick versions by yourself it’s much better if you add the dependency management via
+the Spring BOM |
| Add the dependency to spring-cloud-sleuth-stream |
| Add the dependency to spring-cloud-starter-sleuth - that way all dependant dependencies will be downloaded |
| Add a binder (e.g. Rabbit binder) to tell Spring Cloud Stream what it should bind to |
Gradle.
+
dependencyManagement {
+ imports {
+ mavenBom "org.springframework.cloud:spring-cloud-dependencies:${releaseTrainVersion}"
+ }
+}
+
+dependencies {
+ compile "org.springframework.cloud:spring-cloud-sleuth-stream"
+ compile "org.springframework.cloud:spring-cloud-starter-sleuth"
+
+ compile "org.springframework.cloud:spring-cloud-stream-binder-rabbit"
+}
+
| In order not to pick versions by yourself it’s much better if you add the dependency management via
+the Spring BOM |
| Add the dependency to spring-cloud-sleuth-stream |
| Add the dependency to spring-cloud-starter-sleuth - that way all dependant dependencies will be downloaded |
| Add a binder (e.g. Rabbit binder) to tell Spring Cloud Stream what it should bind to |
1.3.4 Spring Cloud Sleuth Stream Zipkin Collector
If you want to start a Spring Cloud Sleuth Stream Zipkin collector just add the spring-cloud-sleuth-zipkin-stream
+dependency
Maven.
+
<dependencyManagement>
+ <dependencies>
+ <dependency>
+ <groupId>org.springframework.cloud</groupId>
+ <artifactId>spring-cloud-dependencies</artifactId>
+ <version>${release.train.version}</version>
+ <type>pom</type>
+ <scope>import</scope>
+ </dependency>
+ </dependencies>
+ </dependencyManagement>
+
+ <dependency>
+ <groupId>org.springframework.cloud</groupId>
+ <artifactId>spring-cloud-sleuth-zipkin-stream</artifactId>
+ </dependency>
+ <dependency>
+ <groupId>org.springframework.cloud</groupId>
+ <artifactId>spring-cloud-starter-sleuth</artifactId>
+ </dependency>
+
+ <dependency>
+ <groupId>org.springframework.cloud</groupId>
+ <artifactId>spring-cloud-stream-binder-rabbit</artifactId>
+ </dependency>
+
| In order not to pick versions by yourself it’s much better if you add the dependency management via
+the Spring BOM |
| Add the dependency to spring-cloud-sleuth-zipkin-stream |
| Add the dependency to spring-cloud-starter-sleuth - that way all dependant dependencies will be downloaded |
| Add a binder (e.g. Rabbit binder) to tell Spring Cloud Stream what it should bind to |
Gradle.
+
dependencyManagement {
+ imports {
+ mavenBom "org.springframework.cloud:spring-cloud-dependencies:${releaseTrainVersion}"
+ }
+}
+
+dependencies {
+ compile "org.springframework.cloud:spring-cloud-sleuth-zipkin-stream"
+ compile "org.springframework.cloud:spring-cloud-starter-sleuth"
+
+ compile "org.springframework.cloud:spring-cloud-stream-binder-rabbit"
+}
+
| In order not to pick versions by yourself it’s much better if you add the dependency management via
+the Spring BOM |
| Add the dependency to spring-cloud-sleuth-zipkin-stream |
| Add the dependency to spring-cloud-starter-sleuth - that way all dependant dependencies will be downloaded |
| Add a binder (e.g. Rabbit binder) to tell Spring Cloud Stream what it should bind to |
and then just annotate your main class with @EnableZipkinStreamServer annotation:
package example;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.cloud.sleuth.zipkin.stream.EnableZipkinStreamServer;
+
+@SpringBootApplication
+@EnableZipkinStreamServer
+public class ZipkinStreamServerApplication {
+
+ public static void main(String[] args) throws Exception {
+ SpringApplication.run(ZipkinStreamServerApplication.class, args);
+ }
+
+}8. Managing spans with annotations
The main arguments for this features are
api-agnostic means to collaborate with a span
- use of annotations allows users to add to a span with no library dependency on a span api.
+This allows Sleuth to change its core api less impact to user code.
reduced surface area for basic span operations.
- without this feature one has to use the span api, which has lifecycle commands that
+could be used incorrectly. By only exposing scope, tag and log functionality, users can
+collaborate without accidentally breaking span lifecycle.
collaboration with runtime generated code
- with libraries such as Spring Data / Feign the implementations of interfaces are generated
+at runtime thus span wrapping of objects was tedious. Now you can provide annotations
+ over interfaces and arguments of those interfaces
If you really don’t want to take care of creating local spans manually you can profit from the
+@NewSpan annotation. Also we give you the @SpanTag annotation to add tags in an automated
+fashion.
Let’s look at some examples of usage.
@NewSpan
+void testMethod();
Annotating the method without any parameter will lead to a creation of a new span whose name
+will be equal to annotated method name.
@NewSpan("customNameOnTestMethod4")
+void testMethod4();If you provide the value in the annotation (either directly or via the name parameter) then
+the created span will have the name as the provided value.
+@NewSpan(name = "customNameOnTestMethod5")
+void testMethod5(@SpanTag("testTag") String param);
+
+
+this.testBean.testMethod5("test");You can combine both the name and a tag. Let’s focus on the latter. In this case whatever the value of
+the annotated method’s parameter runtime value will be - that will be the value of the tag. In our sample
+the tag key will be testTag and the tag value will be test.
@NewSpan(name = "customNameOnTestMethod3")
+@Override
+public void testMethod3() {
+}You can place the @NewSpan annotation on both the class and an interface. If you override the
+interface’s method and provide a different value of the @NewSpan annotation then the most
+concrete one wins (in this case customNameOnTestMethod3 will be set).
If you want to just add tags and annotations to an existing span it’s enough
+to use the @ContinueSpan annotation as presented below. Note that in contrast
+with the @NewSpan annotation you can also add logs via the log parameter:
+@ContinueSpan(log = "testMethod11")
+void testMethod11(@SpanTag("testTag11") String param);
+
+
+this.testBean.testMethod11("test");That way the span will get continued and:
- logs with name
testMethod11.before and testMethod11.after will be created - if an exception will be thrown a log
testMethod11.afterFailure will also be created - tag with key
testTag11 and value test will be created
8.4 More advanced tag setting
There are 3 different ways to add tags to a span. All of them are controlled by the SpanTag annotation.
+Precedence is:
- try with the bean of
TagValueResolver type and provided name - if one hasn’t provided the bean name, try to evaluate an expression. We’re searching for a
TagValueExpressionResolver bean.
+The default implementation uses SPEL expression resolution. - if one hasn’t provided any expression to evaluate just return a
toString() value of the parameter
The value of the tag for following method will be computed by an implementation of TagValueResolver interface.
+Its class name has to be passed as the value of the resolver attribute.
Having such an annotated method:
@NewSpan
+public void getAnnotationForTagValueResolver(@SpanTag(key = "test", resolver = TagValueResolver.class) String test) {
+}and such a TagValueResolver bean implementation
@Bean(name = "myCustomTagValueResolver")
+public TagValueResolver tagValueResolver() {
+ return parameter -> "Value from myCustomTagValueResolver";
+}Will lead to setting of a tag value equal to Value from myCustomTagValueResolver.
8.4.2 Resolving expressions for value
Having such an annotated method:
@NewSpan
+public void getAnnotationForTagValueExpression(@SpanTag(key = "test", expression = "length() + ' characters'") String test) {
+}and no custom implementation of a TagValueExpressionResolver will lead to evaluation of the SPEL expression and a tag with value 4 characters will be set on the span.
+If you want to use some other expression resolution mechanism you can create your own implementation
+of the bean.
8.4.3 Using toString method
Having such an annotated method:
@NewSpan
+public void getAnnotationForArgumentToString(@SpanTag("test") Long param) {
+}if executed with a value of 15 will lead to setting of a tag with a String value of "15".
Picking a span name is not a trivial task. Span name should depict an operation name. The name should
+be low cardinality (e.g. not include identifiers).
Since there is a lot of instrumentation going on some of the span names will be
+artificial like:
controller-method-name when received by a Controller with a method name conrollerMethodNameasync for asynchronous operations done via wrapped Callable and Runnable.@Scheduled annotated methods will return the simple name of the class.
Fortunately, for the asynchronous processing you can provide explicit naming.
You can name the span explicitly via the @SpanName annotation.
@SpanName("calculateTax")
+class TaxCountingRunnable implements Runnable {
+
+ @Override public void run() {
+
+ }
+}In this case, when processed in the following manner:
Runnable runnable = new TraceRunnable(tracer, spanNamer, new TaxCountingRunnable());
+Future<?> future = executorService.submit(runnable);
+
+future.get();
The span will be named calculateTax.
It’s pretty rare to create separate classes for Runnable or Callable. Typically one creates an anonymous
+instance of those classes. You can’t annotate such classes thus to override that, if there is no @SpanName annotation present,
+we’re checking if the class has a custom implementation of the toString() method.
So executing such code:
Runnable runnable = new TraceRunnable(tracer, spanNamer, new Runnable() {
+ @Override public void run() {
+
+ }
+
+ @Override public String toString() {
+ return "calculateTax";
+ }
+});
+Future<?> future = executorService.submit(runnable);
+
+future.get();will lead in creating a span named calculateTax.
In distributed tracing the data volumes can be very high so sampling
+can be important (you usually don’t need to export all spans to get a
+good picture of what is happening). Spring Cloud Sleuth has a
+Sampler strategy that you can implement to take control of the
+sampling algorithm. Samplers do not stop span (correlation) ids from
+being generated, but they do prevent the tags and events being
+attached and exported. By default you get a strategy that continues to
+trace if a span is already active, but new ones are always marked as
+non-exportable. If all your apps run with this sampler you will see
+traces in logs, but not in any remote store. For testing the default
+is often enough, and it probably is all you need if you are only using
+the logs (e.g. with an ELK aggregator). If you are exporting span data
+to Zipkin or Spring Cloud Stream, there is also an AlwaysSampler
+that exports everything and a PercentageBasedSampler that samples a
+fixed fraction of spans.
| Note |
|---|
the PercentageBasedSampler is the default if you are using
+spring-cloud-sleuth-zipkin or spring-cloud-sleuth-stream. You can
+configure the exports using spring.sleuth.sampler.percentage. The passed
+value needs to be a double from 0.0 to 1.0 so it’s not a percentage.
+For backwards compatibility reasons we’re not changing the property name. |
A sampler can be installed just by creating a bean definition, e.g:
@Bean
+public Sampler defaultSampler() {
+ return new AlwaysSampler();
+} | Tip |
|---|
You can set the HTTP header X-B3-Flags to 1 or when doing messaging you can
+set spanFlags header to 1. Then the current span will be forced to be exportable
+regardless of the sampling decision. |
10. Sending spans to Zipkin
By default if you add spring-cloud-starter-zipkin as a dependency to your project,
+when the span is closed, it will be sent to Zipkin over HTTP. The communication
+is asynchronous. You can configure the URL by setting the spring.zipkin.baseUrl
+property as follows:
spring.zipkin.baseUrl: http://192.168.99.100:9411/
If you want to find Zipkin via service discovery it’s enough to pass the
+Zipkin’s service id inside the URL (example for zipkinserver service id)
spring.zipkin.baseUrl: http://zipkinserver/
11. Span Data as Messages
You can accumulate and send span data over
+Spring Cloud Stream by
+including the spring-cloud-sleuth-stream jar as a dependency, and
+adding a Channel Binder implementation
+(e.g. spring-cloud-starter-stream-rabbit for RabbitMQ or
+spring-cloud-starter-stream-kafka for Kafka). This will
+automatically turn your app into a producer of messages with payload
+type Spans.
There is a special convenience annotation for setting up a message consumer
+for the Span data and pushing it into a Zipkin SpanStore. This application
@SpringBootApplication
+@EnableZipkinStreamServer
+public class Consumer {
+ public static void main(String[] args) {
+ SpringApplication.run(Consumer.class, args);
+ }
+}will listen for the Span data on whatever transport you provide via a
+Spring Cloud Stream Binder (e.g. include
+spring-cloud-starter-stream-rabbit for RabbitMQ, and similar
+starters exist for Redis and Kafka). If you add the following UI dependency
<groupId>io.zipkin.java</groupId>
+<artifactId>zipkin-autoconfigure-ui</artifactId>
Then you’ll have your app a
+Zipkin server, which hosts
+the UI and api on port 9411.
The default SpanStore is in-memory (good for demos and getting
+started quickly). For a more robust solution you can add MySQL and
+spring-boot-starter-jdbc to your classpath and enable the JDBC
+SpanStore via configuration, e.g.:
spring:
+ rabbitmq:
+ host: ${RABBIT_HOST:localhost}
+ datasource:
+ schema: classpath:/mysql.sql
+ url: jdbc:mysql://${MYSQL_HOST:localhost}/test
+ username: root
+ password: root
+
+ initialize: true
+ continueOnError: true
+ sleuth:
+ enabled: false
+zipkin:
+ storage:
+ type: mysql | Note |
|---|
The @EnableZipkinStreamServer is also annotated with
+@EnableZipkinServer so the process will also expose the standard
+Zipkin server endpoints for collecting spans over HTTP, and for
+querying in the Zipkin Web UI. |
A custom consumer can also easily be implemented using
+spring-cloud-sleuth-stream and binding to the SleuthSink. Example:
@EnableBinding(SleuthSink.class)
+@SpringBootApplication(exclude = SleuthStreamAutoConfiguration.class)
+@MessageEndpoint
+public class Consumer {
+
+ @ServiceActivator(inputChannel = SleuthSink.INPUT)
+ public void sink(Spans input) throws Exception {
+
+ }
+} | Note |
|---|
the sample consumer application above explicitly excludes
+SleuthStreamAutoConfiguration so it doesn’t send messages to itself,
+but this is optional (you might actually want to trace requests into
+the consumer app). |
In order to customize the polling mechanism you can create a bean of PollerMetadata type
+with name equal to StreamSpanReporter.POLLER. Here you can find an example of such a configuration.
@Configuration
+public static class CustomPollerConfiguration {
+
+ @Bean(name = StreamSpanReporter.POLLER)
+ PollerMetadata customPoller() {
+ PollerMetadata poller = new PollerMetadata();
+ poller.setMaxMessagesPerPoll(500);
+ poller.setTrigger(new PeriodicTrigger(5000L));
+ return poller;
+ }
+}You can do the following operations on the Span by means of org.springframework.cloud.sleuth.Tracer interface:
- start - when you start a span its name is assigned and start timestamp is recorded.
- close - the span gets finished (the end time of the span is recorded) and if
+the span is exportable then it will be eligible for collection to Zipkin.
+The span is also removed from the current thread.
- continue - a new instance of span will be created whereas it will be a copy of the
+one that it continues.
- detach - the span doesn’t get stopped or closed. It only gets removed from the current thread.
- create with explicit parent - you can create a new span and set an explicit parent to it
| Tip |
|---|
Spring creates the instance of Tracer for you. In order to use it all you need is to just autowire it. |
6.1 Creating and closing spans
You can manually create spans by using the Tracer interface.
+
+Span newSpan = this.tracer.createSpan("calculateTax");
+try {
+
+
+ this.tracer.addTag("taxValue", taxValue);
+
+
+ newSpan.logEvent("taxCalculated");
+} finally {
+
+
+ this.tracer.close(newSpan);
+}In this example we could see how to create a new instance of span. Assuming that there already
+was a span present in this thread then it would become the parent of that span.
| Important |
|---|
Always clean after you create a span! Don’t forget to close a span if you want to send it to Zipkin. |
| Important |
|---|
If your span contains a name greater than 50 chars, then that name will
+be truncated to 50 chars. Your names have to be explicit and concrete. Big names lead to
+latency issues and sometimes even thrown exceptions. |
Sometimes you don’t want to create a new span but you want to continue one. Example of such a
+situation might be (of course it all depends on the use-case):
- AOP - If there was already a span created before an aspect was reached then you might not want to create a new span.
- Hystrix - executing a Hystrix command is most likely a logical part of the current processing. It’s in fact
+only a technical implementation detail that you wouldn’t necessarily want to reflect in tracing as a separate being.
The continued instance of span is equal to the one that it continues:
Span continuedSpan = this.tracer.continueSpan(spanToContinue);
+assertThat(continuedSpan).isEqualTo(spanToContinue);
To continue a span you can use the Tracer interface.
+
+Span continuedSpan = this.tracer.continueSpan(initialSpan);
+try {
+
+
+ this.tracer.addTag("taxValue", taxValue);
+
+
+ continuedSpan.logEvent("taxCalculated");
+} finally {
+
+
+ this.tracer.detach(continuedSpan);
+} | Important |
|---|
Always clean after you create a span! Don’t forget to detach a span if some work was done started in one
+ thread (e.g. thread X) and it’s waiting for other threads (e.g. Y, Z) to finish.
+ Then the spans in the threads Y, Z should be detached at the end of their work. When the results are collected
+ the span in thread X should be closed. |
6.3 Creating spans with an explicit parent
There is a possibility that you want to start a new span and provide an explicit parent of that span.
+Let’s assume that the parent of a span is in one thread and you want to start a new span in another thread. The
+startSpan method of the Tracer interface is the method you are looking for.
+
+
+Span newSpan = this.tracer.createSpan("calculateCommission", initialSpan);
+try {
+
+
+ this.tracer.addTag("commissionValue", commissionValue);
+
+
+ newSpan.logEvent("commissionCalculated");
+} finally {
+
+
+
+ this.tracer.close(newSpan);
+} | Important |
|---|
After having created such a span remember to close it. Otherwise you will see a lot of warnings in your logs
+ related to the fact that you have a span present in the current thread other than the one you’re trying to close.
+ What’s worse your spans won’t get closed properly thus will not get collected to Zipkin. |
