SpanReporter for Java

SpanReporter forward to backend Tracer and reports trace into Reporter.

public interface Reporter {
    void start(long timestampMicroseconds, SpanR span);
    void finish(long timestampMicroseconds, SpanR span);
    void log(long timestampMicroseconds, SpanR span, Map<String, ?> event);
}

Use Case

• As zero server tracer.
  • To use OpenTracing API, before selection and deployment of your Server Tracer.
  • To log with spanId, context, without using MDC.
• To add log support to some server tracer that doesn't support .log(...)
• To report some metrics (eg. histogram of span)

Slf4jReporter

• Message is reported as structured message (json)
• Message at start and at finish is logged with level TRACE

19:48:36.828 [main] TRACE tracer - {"ts":1490982516828,"elapsed":0,"spanId":"d4f6df3d-8dc0-4287-b1a0-1b2bc52978c6","action":"start","operation":"span-0","tags":{"description":"top level initial span in the original process"},"baggage":{},"references":{}}
19:48:36.828 [main] TRACE tracer - {"ts":1490982516828,"elapsed":0,"spanId":"da7d843a-4564-4480-a6cb-19550c24a344","action":"start","operation":"span-1","tags":{"description":"the first inner span in the original process"},"baggage":{},"references":{"child_of":"d4f6df3d-8dc0-4287-b1a0-1b2bc52978c6"}}
19:48:36.828 [main] TRACE tracer - {"ts":1490982516828,"elapsed":0,"spanId":"c4bf987f-2d0c-49f1-87bd-a23930570b96","action":"start","operation":"span-2","tags":{"description":"the second inner span in the original process"},"baggage":{},"references":{"child_of":"da7d843a-4564-4480-a6cb-19550c24a344"}}
19:48:36.841 [main] TRACE tracer - {"ts":1490982516841,"elapsed":13,"spanId":"c4bf987f-2d0c-49f1-87bd-a23930570b96","action":"finish","operation":"span-2","tags":{"description":"the second inner span in the original process"},"baggage":{},"references":{"child_of":"da7d843a-4564-4480-a6cb-19550c24a344"}}
19:48:36.841 [main] TRACE tracer - {"ts":1490982516841,"elapsed":13,"spanId":"da7d843a-4564-4480-a6cb-19550c24a344","action":"finish","operation":"span-1","tags":{"description":"the first inner span in the original process"},"baggage":{},"references":{"child_of":"d4f6df3d-8dc0-4287-b1a0-1b2bc52978c6"}}
19:48:36.841 [main] TRACE tracer - {"ts":1490982516841,"elapsed":13,"spanId":"d4f6df3d-8dc0-4287-b1a0-1b2bc52978c6","action":"finish","operation":"span-0","tags":{"description":"top level initial span in the original process","http.url":"/orders"},"baggage":{},"references":{}}

• Message for Span.log report with level INFO by default, the level could be set explicitly by setting the key "loglevel"

span.log("blablabala");
span.log(MapMaker.fields(LogLevel.FIELD_NAME, LogLevel.DEBUG, "k0", "v0", "k1", 42));
span.log(MapMaker.fields(LogLevel.FIELD_NAME, LogLevel.WARN, "k0", "v0", "ex", new Exception("boom !")));

22:16:23.911 [main] INFO  tracer - {"ts":1490991383911,"elapsed":1,"spanId":"dbebbda2-501e-4461-b9c6-32020df8008f","action":"log","operation":"span-2","tags":{"description":"the second inner span in the original process"},"fields":{"event":"blablabala"}}
22:16:23.911 [main] DEBUG tracer - {"ts":1490991383911,"elapsed":1,"spanId":"dbebbda2-501e-4461-b9c6-32020df8008f","action":"log","operation":"span-2","tags":{"description":"the second inner span in the original process"},"fields":{"k0":"v0","k1":42.0}}
22:16:23.911 [main] WARN  tracer - {"ts":1490991383911,"elapsed":1,"spanId":"dbebbda2-501e-4461-b9c6-32020df8008f","action":"log","operation":"span-2","tags":{"description":"the second inner span in the original process"},"fields":{"ex":"java.lang.Exception: boom !\n\tat examples.Sample01.run0(Sample01.java:92)\n\tat examples.Sample01.main(Sample01.java:45)\n","k0":"v0"}}

Usage

Application intialization

• Add dependency (format depends of your build tool)

"io.opentracing.contrib" % "java-span-reporter" % "${span-reporter.version}"

• Instantiate the TracerR (For using DI, you can take inspiration from Guice samples ):

tracer = ... // if not backend tracer use NoopTracerFactory.create()
tracer = new TracerR(tracer, new Slf4jReporter(LoggerFactory.getLogger("tracer")));

• Setup your logger (example below use logback, but any slf4j compatible logger should work)
  • add dependencies

  "ch.qos.logback" % "logback-classic" % "1.1.3"
  
  • configure le logger (simplest)

  <logger name="tracer" level="TRACE"/>

Custom Reporter(s)

Developer can provide its own Reporter:

• to report log in an other log system
• to report log in an other format
• to report metrics about span/operation (histogram, nb calls, duration, ...)

To report to several Reporters at once, you can use the CompositeReporter:

Tracer tracer = ...
tracer = new TracerR(tracer, new CompositeReporter(
    new Slf4jReporter(LoggerFactory.getLogger("tracer")),
    new DropwizardMetricsReporter(...)
));

Build

• build localy

  ./gradlew assemble
  
• publish to local maven repository

  ./gradlew publishToMavenLocal
  
• release

  git tag -a "${version}" -m "release"
  git push --tags