Micrometer Mastery: Unleash Advanced Observability In Your JVM Apps

Observation observation = Observation.start("talk", registry);
try { // TODO: Scope
    doSomething(); // This is what we're observing.
} catch (Exception exception) {
    observation.error(exception); // This is signaling an error
    throw exception;
} finally { // TODO: Attach tags (key-value)
    observation.stop();
}

public class ObservedTeaService implements TeaService {

    // Boilerplate.

    private final TeaService delegate; // Delegate to the business implementatino.

    @Override
    public TeaResponse make(String name, String size) {
        return Observation.createNotStarted("make.tea", registry)
            .lowCardinalityKeyValue("tea.name", name)
            .highCardinalityKeyValue("tea.size", size)
            .observe(() -> delegate.make(name, size);
    }
}

@Bean
ObservationPredicate noActuatorServerObservations() {
    return (name, context) -> {
        if (name.equals("http.server.requests") && context instanceof ServerRequestObservationContext server Context) {
            return !serverContext.getCarrier().getRequestURI().startsWith("/actuator");
        } else {
            return true;
        }
    };
}

@Configuration(proxyBeanMethods = false)
@ConditionalOnClass(DataSourceBaseContext.class)
static class DataSourceActuatorConfig {

    @Bean
    ObservationFilter tempoServiceGraphFilter() {
        // TODO: remove this once Tempo is fixed: https://github.com/grafana/tempo/issues/2212
        return context -> {
            if (context instanceof DataSourceBaseContext dataSourceBaseContext && dataSourceBaseContext.getRemoteServiceName() != null) {
                context.addHighCardinalityKeyValue(KeyValue.of("db.name", dataSourceBaseContext.getRemoteServiceName()));
            }
            return context;
        }
    }
}

private static final MakeTeaConvention DEFAULT_CONVENTION = new DefaultMakeTeaConvention();
private final MakeTeaConvention customConvention;
...

return Observation.createNotStarted(
        customConvention,
        DEFAULT_CONVENTION,
        () -> new MakeTeaContext(name, size),
        registry)
    .observe(() -> delegate.make(name, size));

public class MakeTeaContext extends Observation.Context {

    private final String teaName;
    private final String teaSize;

    // Required-args constructor, and getters
}

public class DefaultMakeTeaConvention implements MakeTeaConvention {

    @Nullable
    @Override
    public String getName() {
        return "make.tea"
    }

    @NonNull
    @Override
    public KeyValues getLowCardinalityKeyValues(MakeTeaContext context) {
        return KeyValues.of(
            "tea.name", context.getTeaName(),
            "tea.size", context.getTeaSize()
        );
    }
}

return MakeTeaDocumentation.Make_TEA.observation(
        customConvention,
        DEFAULT_CONVENTION,
        () -> new MakeTeaContext(name, size),
        registry)
    .observe(() -> delegate.make(name, size));
)

public class MakeTeaDocumentation implements ObservationDocumentation {

    /**
     * Make some tea.
     */
    MAKE_TEA {

        @Override
        public Class<? extends ObservationConvention<? extends Observation.Context>> getDefaultConvention() {
            return DefaultMakeTeaConvention.class;
        }

        @NonNull
        @Override
        public KeyName[] getLowCardinalityKeyNames() {
            return LowCardinalityKeyNames.values();
        }
    };

    enum LowCardinalityKeyNames implements KeyName {

        TEA_NAME {

            @NonNull
            @Override
            public String asString() {
                return "tea.name";
            }
        },

        TEA_Size {

            @NonNull
            @Override
            public String asString() {
                return "tea.size";
            }
        }
    }
}

@Override
public KeyValues getLowCardinalityKeyValues(MakeTeaContext context) {
    return KeyValues.of(
        MakeTeaDocumentation.LowCardinalityKeyNames.TEA_NAME.withValue(context.getTeaName));
        MakeTeaDocumentation.LowCardinalityKeyNames.TEA_SIZE.withValue(context.getTeaSize));
    );
}