Include grpc plugin in agent jar

[felixbarny]

What does this PR do?

Currently, we don't ship the gRPC plugin, this PR fixes that.

Checklist

• My code follows the style guidelines of this project
• I have rebased my changes on top of the latest master branch

• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

• I have updated CHANGELOG.asciidoc
• I have updated supported-technologies.asciidoc
• Added an API method or config option? Document in which version this will be introduced
• Added an instrumentation plugin? How did you make sure that old, non-supported versions are not instrumented by accident?

Author's Checklist

Related issues

Use cases

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[ghost]

💚 Build Succeeded

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Build stats

• Build Cause: [Pull request Include grpc plugin in agent jar #1162 updated]

• Start Time: 2020-04-28T13:56:33.332+0000

• Duration: 36 min 50 sec (2150334)

• Commit: c6b46cd

Test stats 🧪

Test	Results
Failed	0
Passed	1232
Skipped	12
Total	1244

[felixbarny]

There are more issues with the plugin

Failed to start agent
java.lang.reflect.InvocationTargetException
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at co.elastic.apm.agent.bci.AgentMain.init(AgentMain.java:99)
	at co.elastic.apm.agent.bci.AgentMain.agentmain(AgentMain.java:65)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at sun.instrument.InstrumentationImpl.loadClassAndStartAgent(InstrumentationImpl.java:386)
	at sun.instrument.InstrumentationImpl.loadClassAndCallAgentmain(InstrumentationImpl.java:411)
Caused by: java.lang.NoClassDefFoundError: io/grpc/MethodDescriptor
	at co.elastic.apm.agent.grpc.ClientCallImplInstrumentation$Constructor.getMethodMatcher(ClientCallImplInstrumentation.java:108)
	at co.elastic.apm.agent.bci.ElasticApmAgent.applyAdvice(ElasticApmAgent.java:250)
	at co.elastic.apm.agent.bci.ElasticApmAgent.initAgentBuilder(ElasticApmAgent.java:212)
	at co.elastic.apm.agent.bci.ElasticApmAgent.initInstrumentation(ElasticApmAgent.java:160)
	at co.elastic.apm.agent.bci.ElasticApmAgent.initialize(ElasticApmAgent.java:121)
	... 12 more

The problem is that grpc specific classes are referenced in the method matcher that are executed in the bootstrap classloader where these types are not available:

apm-agent-java/apm-agent-plugins/apm-grpc/apm-grpc-plugin/src/main/java/co/elastic/apm/agent/grpc/ClientCallImplInstrumentation.java

Lines 107 to 109 in b2ac746

	public ElementMatcher<? super MethodDescription> getMethodMatcher() {
	return isConstructor().and(takesArgument(0, MethodDescriptor.class));
	}

[codecov-io]

Codecov Report

Merging #1162 into master will increase coverage by 3.34%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #1162      +/-   ##
============================================
+ Coverage     60.48%   63.83%   +3.34%     
- Complexity       85     2782    +2697     
============================================
  Files           330      284      -46     
  Lines         16284    13589    -2695     
  Branches       2411     1865     -546     
============================================
- Hits           9849     8674    -1175     
+ Misses         5801     4326    -1475     
+ Partials        634      589      -45     

Impacted Files	Coverage Δ	Complexity Δ
...pm/agent/profiler/ProfilingActivationListener.java	57.14% <0.00%> (-7.86%)	3.00% <0.00%> (+3.00%)	⬇️
.../agent/plugin/api/AbstractSpanInstrumentation.java	48.31% <0.00%> (-7.40%)	3.00% <0.00%> (+3.00%)	⬇️
...o/elastic/apm/agent/profiler/SamplingProfiler.java	77.93% <0.00%> (-7.16%)	46.00% <0.00%> (+46.00%)	⬇️
...va/co/elastic/apm/agent/impl/transaction/Span.java	78.72% <0.00%> (-6.09%)	33.00% <0.00%> (+33.00%)	⬇️
...va/co/elastic/apm/agent/impl/ElasticApmTracer.java	69.89% <0.00%> (-5.74%)	84.00% <0.00%> (+84.00%)	⬇️
...ic/apm/agent/plugin/api/TracedInstrumentation.java	26.47% <0.00%> (-5.45%)	6.00% <0.00%> (+6.00%)	⬇️
...lastic/apm/agent/objectpool/ObjectPoolFactory.java	87.50% <0.00%> (-5.36%)	9.00% <0.00%> (+9.00%)	⬇️
...bci/methodmatching/TraceMethodInstrumentation.java	57.14% <0.00%> (-4.77%)	9.00% <0.00%> (+9.00%)	⬇️
...astic/apm/agent/impl/transaction/AbstractSpan.java	74.24% <0.00%> (-4.56%)	39.00% <0.00%> (+39.00%)	⬇️
...astic/apm/agent/impl/transaction/TraceContext.java	77.53% <0.00%> (-4.52%)	77.00% <0.00%> (+77.00%)	⬇️
... and 63 more

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