`SpanHandler` is the base type for the now deprecated `FinishedSpanHandler`.
Notable, it can not just handle things at the end of a recording, but also the
beginning.
For example, this permits set-once baggage without the HTTP abstraction:
```java
static final BaggageField EPOCH_SECONDS = BaggageField.create("epoch_seconds");
static final class RootOnlyBaggage extends SpanHandler {
@Override
public boolean begin(TraceContext context, MutableSpan span, @Nullable TraceContext parent) {
if (EPOCH_SECONDS.getValue(context) == null) { // only set at the first span
long epochSeconds = System.currentTimeMillis() / 1000;
EPOCH_SECONDS.updateValue(context, String.valueOf(epochSeconds));
}
return true;
}
@Override public boolean end(TraceContext context, MutableSpan span, Cause cause) {
Tags.BAGGAGE_FIELD.tag(EPOCH_SECONDS, context, span);
return true;
}
}
```
As the parent is available, it can also facilitate advanced tasks like counting
children, or summarizing entire local roots.
See https://github.com/openzipkin/brave/tree/master/brave/src/test/java/brave/features/handler
and https://github.com/openzipkin/brave/blob/master/brave/src/main/java/brave/handler/SpanHandler.java for more
Before, spring-cloud-sleuth-zipkin had to import `SamplerAutoConfiguration`
directly to unwind a sampler ordering problem caused by `TraceAutoConfiguration`
defining the default `Sampler` bean.
This fixes that by moving the default `Sampler` to where it belongs
(`SamplerAutoConfiguration`) and having `TraceAutoConfiguration` import
the sampling configuration directly as opposed to relying on auto-configuration
ordering. Finally it removes the mistake of setting `SamplerAutoConfiguration`
as auto-configuration in the first place.
The name `SamplerAutoConfiguration` was left alone because changing it would
interfere with 3rd party code that formerly imported it to correct this issue
in their non-zipkin setups.
Fixes#1618
uses terrible hacks to verify if the Spring Context is in creation or has already been created. If it has been created then we'll continue as usual. If not then we will NOT wrap any callables and runnables.
fixes#1128
default sender is Kafka when it is detected on the classpath, with this change it will be Web. You have to set `spring.zipkin.kafka.enabled` to `true` to use Kafka
fixes gh-985
There was some doubt on gitter about sleuth generating spans with floating-point
rendered timestamps. While this shouldn't break people we certainly shouldn't
create json like this.
This was presumed to be caused by sleuth's rest template sender by @mojsha who
was trying Jaeger. Jaeger's parser doesn't give any errors with a 400.
```json
[
{
"traceId": "a65dac9d8bbb57f8",
"parentId": "a65dac9d8bbb57f8",
"id": "f223bb97e1eba9b2",
"kind": "SERVER",
"name": "https:\/hello3",
"timestamp": 1.521027116604e+15,
"duration": 1525,
"localEndpoint": {
"serviceName": "${spring.application.name}",
"ipv4": "10.128.6.98",
"port": 8443
},
```
I added a test to make sure it is not the case.
