The AsyncZipkinSpanHandler calls 'check' once on startup to let someone
know an error that may affect tracing up front. Before, this didn't
include the endpoint so it is less obvious what could be the problem.
Ex people goof the URL (don't add /api/v2/spans or it is added twice)
I noticed we deleted many things without deprecation in 3.x and figured
deprecation was the right way. However, this doesn't work for auto-config
properties. This replaces deprecation with a TODO note to hide all the
types so that 4.x won't require guessing if someone externally is using
them directly or not.
`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
Types like Properties and AutoConfiguration and internal utilities are
routinely marked public when they needn't be. This causes toil as we
have to preserve signatures even if they were made public by accident.
This deprecates the mass of types marked public to give some hope of
less undifferentiated toil in the future. Ideally, future change will
consider greatly if a type should be public or not as doing so haunts
maintainers.
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
without this change we're reusing the same broker for application logic and sending spans to zipkin
with this change we're adding a property to allow providing a different set of addresses for brokers to send spans to Zipkin
fixes gh-1210
