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Module containing Observation related code
/*
* Copyright 2022 VMware, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package io.micrometer.observation;
import io.micrometer.common.lang.Nullable;
import io.micrometer.observation.Observation.Context;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
/**
* Handler for an {@link Observation}. Hooks in to the lifecycle of an observation.
* Example of handler implementations can create metrics, spans or logs.
*
* @param type of context
* @author Jonatan Ivanov
* @author Tommy Ludwig
* @author Marcin Grzejszczak
* @since 1.10.0
*/
public interface ObservationHandler {
/**
* Reacts to starting of an {@link Observation}.
* @param context an {@link Observation.Context}
*/
default void onStart(T context) {
}
/**
* Reacts to an error during an {@link Observation}.
* @param context an {@link Observation.Context}
*/
default void onError(T context) {
}
/**
* Reacts to arbitrary {@link Observation.Event}.
* @param event the {@link Observation.Event} that was signaled
* @param context an {@link Observation.Context}
*/
default void onEvent(Observation.Event event, T context) {
}
/**
* Reacts to opening of an {@link Observation.Scope}.
* @param context an {@link Observation.Context}
*/
default void onScopeOpened(T context) {
}
/**
* Reacts to closing of an {@link Observation.Scope}.
* @param context an {@link Observation.Context}
*/
default void onScopeClosed(T context) {
}
/**
* Reacts to resetting of scopes. If your handler uses a {@link ThreadLocal} value,
* this method should clear that {@link ThreadLocal} or any other scoped variable.
* @param context an {@link Observation.Context}
* @since 1.10.4
*/
default void onScopeReset(T context) {
}
/**
* Reacts to stopping of an {@link Observation}.
* @param context an {@link Observation.Context}
*/
default void onStop(T context) {
}
/**
* Tells the registry whether this handler should be applied for a given
* {@link Observation.Context}.
* @param context an {@link Observation.Context}
* @return {@code true} when this handler should be used
*/
boolean supportsContext(Observation.Context context);
/**
* Handler wrapping other handlers.
*/
interface CompositeObservationHandler extends ObservationHandler {
/**
* Returns the registered handlers.
* @return registered handlers
*/
List> getHandlers();
}
/**
* Handler picking the first matching handler from the list.
*/
class FirstMatchingCompositeObservationHandler implements CompositeObservationHandler {
private final List> handlers;
/**
* Creates a new instance of {@code FirstMatchingCompositeObservationHandler}.
* @param handlers the handlers that are registered under the composite
*/
@SafeVarargs
public FirstMatchingCompositeObservationHandler(ObservationHandler... handlers) {
this(Arrays.asList(handlers));
}
/**
* Creates a new instance of {@code FirstMatchingCompositeObservationHandler}.
* @param handlers the handlers that are registered under the composite
*/
@SuppressWarnings("unchecked")
public FirstMatchingCompositeObservationHandler(
List> handlers) {
List> castedHandlers = new ArrayList<>(handlers.size());
for (ObservationHandler handler : handlers) {
castedHandlers.add((ObservationHandler) handler);
}
this.handlers = castedHandlers;
}
@Override
public List> getHandlers() {
return this.handlers;
}
@Override
public void onStart(Observation.Context context) {
ObservationHandler handler = getFirstApplicableHandler(context);
if (handler != null) {
handler.onStart(context);
}
}
@Override
public void onError(Observation.Context context) {
ObservationHandler handler = getFirstApplicableHandler(context);
if (handler != null) {
handler.onError(context);
}
}
@Override
public void onEvent(Observation.Event event, Observation.Context context) {
ObservationHandler handler = getFirstApplicableHandler(context);
if (handler != null) {
handler.onEvent(event, context);
}
}
@Override
public void onScopeOpened(Observation.Context context) {
ObservationHandler handler = getFirstApplicableHandler(context);
if (handler != null) {
handler.onScopeOpened(context);
}
}
@Override
public void onScopeClosed(Observation.Context context) {
ObservationHandler handler = getFirstApplicableHandler(context);
if (handler != null) {
handler.onScopeClosed(context);
}
}
@Override
public void onScopeReset(Observation.Context context) {
ObservationHandler handler = getFirstApplicableHandler(context);
if (handler != null) {
handler.onScopeReset(context);
}
}
@Override
public void onStop(Observation.Context context) {
ObservationHandler handler = getFirstApplicableHandler(context);
if (handler != null) {
handler.onStop(context);
}
}
@Override
public boolean supportsContext(Observation.Context context) {
ObservationHandler handler = getFirstApplicableHandler(context);
return handler != null;
}
@Nullable
private ObservationHandler getFirstApplicableHandler(Observation.Context context) {
for (ObservationHandler handler : this.handlers) {
if (handler.supportsContext(context)) {
return handler;
}
}
return null;
}
}
/**
* Handler picking all matching handlers from the list.
*/
class AllMatchingCompositeObservationHandler implements CompositeObservationHandler {
private final List> handlers;
/**
* Creates a new instance of {@code AllMatchingCompositeObservationHandler}.
* @param handlers the handlers that are registered under the composite
*/
@SafeVarargs
public AllMatchingCompositeObservationHandler(ObservationHandler... handlers) {
this(Arrays.asList(handlers));
}
/**
* Creates a new instance of {@code AllMatchingCompositeObservationHandler}.
* @param handlers the handlers that are registered under the composite
*/
@SuppressWarnings("unchecked")
public AllMatchingCompositeObservationHandler(
List> handlers) {
List> castedHandlers = new ArrayList<>(handlers.size());
for (ObservationHandler handler : handlers) {
castedHandlers.add((ObservationHandler) handler);
}
this.handlers = castedHandlers;
}
@Override
public List> getHandlers() {
return this.handlers;
}
@Override
public void onStart(Observation.Context context) {
for (ObservationHandler handler : this.handlers) {
if (handler.supportsContext(context)) {
handler.onStart(context);
}
}
}
@Override
public void onError(Observation.Context context) {
for (ObservationHandler handler : this.handlers) {
if (handler.supportsContext(context)) {
handler.onError(context);
}
}
}
@Override
public void onEvent(Observation.Event event, Observation.Context context) {
for (ObservationHandler handler : this.handlers) {
if (handler.supportsContext(context)) {
handler.onEvent(event, context);
}
}
}
@Override
public void onScopeOpened(Observation.Context context) {
for (ObservationHandler handler : this.handlers) {
if (handler.supportsContext(context)) {
handler.onScopeOpened(context);
}
}
}
@Override
public void onScopeClosed(Observation.Context context) {
for (ObservationHandler handler : this.handlers) {
if (handler.supportsContext(context)) {
handler.onScopeClosed(context);
}
}
}
@Override
public void onScopeReset(Observation.Context context) {
for (ObservationHandler handler : this.handlers) {
if (handler.supportsContext(context)) {
handler.onScopeReset(context);
}
}
}
@Override
public void onStop(Observation.Context context) {
for (ObservationHandler handler : this.handlers) {
if (handler.supportsContext(context)) {
handler.onStop(context);
}
}
}
@Override
public boolean supportsContext(Observation.Context context) {
for (ObservationHandler handler : this.handlers) {
if (handler.supportsContext(context)) {
return true;
}
}
return false;
}
}
}