check if the agentArgs are null during bootstrap

[sergekh42]

Fixes #

PR #910 broke the ability to use the standard Java agnet OPTS:
JAVA_OPTS="-javaagent:grafana-opentelemetry-java.jar"

it requires us now to use:
JAVA_OPTS="-javaagent:grafana-opentelemetry-java.jar="

Notice the equal symbol at the end. The agentArgs are null if the equal symbol is not entered. Causing the isEmpty check to fail.

Exception in thread "main" java.lang.reflect.InvocationTargetException
	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(Unknown Source)
	at java.base/java.lang.reflect.Method.invoke(Unknown Source)
	at java.instrument/sun.instrument.InstrumentationImpl.loadClassAndStartAgent(Unknown Source)
	at java.instrument/sun.instrument.InstrumentationImpl.loadClassAndCallPremain(Unknown Source)
Caused by: java.lang.NullPointerException: Cannot invoke "String.isEmpty()" because "agentArgs" is null
	at com.grafana.AgentStarted.run(AgentStarted.java:12)
	at com.grafana.GrafanaOpenTelemetryAgent.startAgent(GrafanaOpenTelemetryAgent.java:53)
	at com.grafana.GrafanaOpenTelemetryAgent.premain(GrafanaOpenTelemetryAgent.java:45)
	... 4 more
*** java.lang.instrument ASSERTION FAILED ***: "result" with message agent load/premain call failed at src/java.instrument/share/native/libinstrument/JPLISAgent.c line: 422
FATAL ERROR in native method: processing of -javaagent failed, processJavaStart failed

Changes

Check if agentArgs is not null AND the string is not empty.

Merge requirement checklist

• Unit tests added/updated
• CHANGELOG.md file updated for non-trivial changes
• Changes in public API reviewed (if applicable)

[CLAassistant]

All committers have signed the CLA.

[sergekh42]

We use Grafana at our org. Requiring us to go to each app to update the JAVA_OPTS to have an equal symbol at the end is a real pain. We use environment variables to configure our agents, not agent arguments. Please consider making this change.

[sergekh42]

Closing, just saw there is already a PR open - #917