| ### Debugging |
| |
| Debugging java agent can be a challenging task since some instrumentation |
| code is directly inlined into target classes. |
| |
| #### Advice methods |
| |
| Breakpoints do not work in advice methods, because their code is directly inlined |
| by ByteBuddy into the target class. It is good to keep these methods as small as possible. |
| The advice methods are annotated with: |
| |
| ```java |
| @net.bytebuddy.asm.Advice.OnMethodEnter |
| @net.bytebuddy.asm.Advice.OnMethodExit |
| ``` |
| |
| The best approach to debug advice methods and agent initialization is to use the following statements: |
| |
| ```java |
| System.out.println() |
| Thread.dumpStack() |
| ``` |
| |
| #### Agent initialization code |
| |
| If you want to debug agent initialization code (e.g. `OpenTelemetryAgent`, `AgentInitializer`, |
| `AgentInstaller`, `OpenTelemetryInstaller`, etc.) then it's important to specify the `-agentlib:` JVM arg |
| before the `-javaagent:` JVM arg and use `suspend=y` (see full example below). |
| |
| #### Enabling debugging |
| |
| The following example shows remote debugger configuration. The breakpoints |
| should work in any code except ByteBuddy advice methods. |
| |
| ```bash |
| java -agentlib:jdwp="transport=dt_socket,server=y,suspend=y,address=5000" -javaagent:opentelemetry-javaagent-<version>-all.jar -jar app.jar |
| ``` |
