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/*
* Copyright 2019 Google LLC
*
* 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
*
* http://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 org.apache.ratis.thirdparty.io.perfmark;
import com.google.errorprone.annotations.DoNotCall;
import com.google.errorprone.annotations.MustBeClosed;
import java.lang.reflect.Method;
/**
* PerfMark is a very low overhead tracing library. To use PerfMark, annotate the code that needs to
* be traced using the start and stop methods. For example:
*
* {@code
* PerfMark.startTask("parseMessage");
* try {
* message = parse(bytes);
* } finally {
* PerfMark.stopTask("parseMessage");
* }
* }
*
* When PerfMark is enabled, these tracing calls will record the start and stop times of the
* given task. When disabled, PerfMark disables these tracing calls, resulting in no additional
* tracing overhead. PerfMark can be enabled or disabled using the {@link #setEnabled(boolean)}. By
* default, PerfMark starts off disabled. PerfMark can be automatically enabled by setting the
* System property {@code org.apache.ratis.thirdparty.io.perfmark.PerfMark.startEnabled} to true.
*
*
Tasks represent the span of work done by some code, starting and stopping in the same thread.
* Each task is started using one of the {@code startTask} methods, and ended using one of
* {@code stopTask} methods. Each start must have a corresponding stop. While not required,
* it is good practice for the start and stop calls have matching arguments for clarity. Tasks
* form a "tree", with each child task starting after the parent has started, and stopping before
* the parent has stopped. The most recently started (and not yet stopped) task is used by the
* tagging and linking commands described below.
*
*
Tags are metadata about the task. Each {@code Tag} contains a String and/or a long that
* describes the task, such as an RPC name, or request ID. When PerfMark is disabled, the Tag
* objects are not created, avoiding overhead. Tags are useful for keeping track of metadata
* about a task(s) that doesn't change frequently, or needs to be applied at multiple layers.
* In addition to Tag objects, named-tags can be added to the current task using the
* {@code attachTag} methods. These allow including key-value like metadata with the task.
*
*
Links allow the code to represent relationships between different threads. When one thread
* initiates work for another thread (such as a callback), Links express the control flow. For
* example:
*
*
{@code
* PerfMark.startTask("handleMessage");
* try {
* Link link = PerfMark.linkOut();
* message = parse(bytes);
* executor.execute(() -> {
* PerfMark.startTask("processMessage");
* try {
* PerfMark.linkIn(link);
* handle(message);
* } finally {
* PerfMark.stopTask("processMessage");
* }
* });
* } finally {
* PerfMark.stopTask("handleMessage");
* }
* }
*
* Links are created inside the scope of the current task and are linked into the scope of
* another task. PerfMark will represent the causal relationship between these two tasks. Links
* have a many-many relationship, and can be reused. Like Tasks and Tags, when PerfMark is
* disabled, the Links returned are no-op implementations.
*
*
Events are a special kind of Task, which do not have a duration. In effect, they only have
* a single timestamp the represents a particular occurrence. Events are slightly more efficient
* than tasks while PerfMark is enabled, but cannot be used with Links or named-tags.
*
* @author Carl Mastrangelo
*/
public final class PerfMark {
/**
* Turns on or off PerfMark recording. Don't call this method too frequently; while neither on nor
* off have very high overhead, transitioning between the two may be slow.
*
* @param value {@code true} to enable PerfMark recording, or {@code false} to disable it.
*/
public static void setEnabled(boolean value) {
impl.setEnabled(value);
}
/**
* Marks the beginning of a task. If PerfMark is disabled, this method is a no-op. The name of the
* task should be a runtime-time constant, usually a string literal. Tasks with the same name can
* be grouped together for analysis later, so avoid using too many unique task names.
*
*
The tag is a run-time identifier for the task. It represents the dynamic part of the task,
* while the task name is the constant part of the task. While not always enforced, tags should
* not be {@code null}.
*
* @param taskName the name of the task.
* @param tag a user provided tag for the task.
*/
public static void startTask(String taskName, Tag tag) {
impl.startTask(taskName, tag);
}
/**
* Marks the beginning of a task. If PerfMark is disabled, this method is a no-op. The name of the
* task should be a runtime-time constant, usually a string literal. Tasks with the same name can
* be grouped together for analysis later, so avoid using too many unique task names.
*
* @param taskName the name of the task.
*/
public static void startTask(String taskName) {
impl.startTask(taskName);
}
/**
* Marks the beginning of a task. If PerfMark is disabled, this method is a no-op. The name of the
* task should be a runtime-time constant, usually a string literal. Tasks with the same name can
* be grouped together for analysis later, so avoid using too many unique task names.
*
*
This function has many more caveats than the {@link #startTask(String)} that accept a
* string. See the docs at {@link #attachTag(String, Object, StringFunction)} for a list of risks
* associated with passing a function.
*
* @param taskNameObject the name of the task.
* @param taskNameFunction the function that will convert the taskNameObject to a taskName
* @param the object type to be stringified
* @since 0.22.0
*/
public static void startTask(T taskNameObject, StringFunction taskNameFunction) {
impl.startTask(taskNameObject, taskNameFunction);
}
/**
* Marks the beginning of a task. If PerfMark is disabled, this method is a no-op. The names of
* the task and subtask should be runtime-time constants, usually a string literal. Tasks with the
* same name can be grouped together for analysis later, so avoid using too many unique task
* names.
*
* @param taskName the name of the task.
* @param subTaskName the name of the sub task
* @since 0.20.0
*/
public static void startTask(String taskName, String subTaskName) {
impl.startTask(taskName, subTaskName);
}
/**
* Marks the beginning of a task. If PerfMark is disabled, this method is a no-op. The name of the
* task should be a runtime-time constant, usually a string literal. Tasks with the same name can
* be grouped together for analysis later, so avoid using too many unique task names.
*
* The returned closeable is meant to be used in a try-with-resources block. Callers should not
* allow the returned closeable to be used outside of the try block that initiated the call.
* Unlike other closeables, it is not safe to call close() more than once.
*
* @param taskName the name of the task.
* @return a closeable that must be closed at the end of the task
* @since 0.23.0
*/
@MustBeClosed
public static TaskCloseable traceTask(String taskName) {
impl.startTask(taskName);
return TaskCloseable.INSTANCE;
}
/**
* Marks the beginning of a task. If PerfMark is disabled, this method is a no-op. The name of the
* task should be a runtime-time constant, usually a string literal. Tasks with the same name can
* be grouped together for analysis later, so avoid using too many unique task names.
*
*
This function has many more caveats than the {@link #traceTask(String)} that accept a
* string. See the docs at {@link #attachTag(String, Object, StringFunction)} for a list of risks
* associated with passing a function. Unlike other closeables, it is not safe to call close()
* more than once.
*
* @param taskNameObject the name of the task.
* @param taskNameFunction the function that will convert the taskNameObject to a taskName
* @param the object type to be stringified
* @return a closeable that must be closed at the end of the task
* @since 0.23.0
*/
@MustBeClosed
public static TaskCloseable traceTask(
T taskNameObject, StringFunction taskNameFunction) {
impl.startTask(taskNameObject, taskNameFunction);
return TaskCloseable.INSTANCE;
}
/**
* Marks an event. Events are logically both a task start and a task end. Events have no duration
* associated. Events still represent the instant something occurs. If PerfMark is disabled, this
* method is a no-op.
*
* The tag is a run-time identifier for the event. It represents the dynamic part of the event,
* while the event name is the constant part of the event. While not always enforced, tags should
* not be {@code null}.
*
* @param eventName the name of the event.
* @param tag a user provided tag for the event.
*/
public static void event(String eventName, Tag tag) {
impl.event(eventName, tag);
}
/**
* Marks an event. Events are logically both a task start and a task end. Events have no duration
* associated. Events still represent the instant something occurs. If PerfMark is disabled, this
* method is a no-op.
*
* @param eventName the name of the event.
*/
public static void event(String eventName) {
impl.event(eventName);
}
/**
* Marks an event. Events are logically both a task start and a task end. Events have no duration
* associated. Events still represent the instant something occurs. If PerfMark is disabled, this
* method is a no-op.
*
* @param eventName the name of the event.
* @param subEventName the name of the sub event.
* @since 0.20.0
*/
public static void event(String eventName, String subEventName) {
impl.event(eventName, subEventName);
}
/**
* Marks the end of a task. If PerfMark is disabled, this method is a no-op.
*
*
It is important that {@link #stopTask} always be called after starting a task, even in case
* of exceptions. Failing to do so may result in corrupted results.
*
* @since 0.22.0
*/
public static void stopTask() {
impl.stopTask();
}
/**
* Marks the end of a task. If PerfMark is disabled, this method is a no-op. The task name and tag
* should match the ones provided to the corresponding {@link #startTask(String, Tag)}, if
* provided. If the task name or tag do not match, the implementation will prefer the starting
* name and tag. The name and tag help identify the task if PerfMark is enabled mid way through
* the task, or if the previous results have been overwritten. The name of the task should be a
* runtime-time constant, usually a string literal. Consider using {@link #stopTask()} instead.
*
*
It is important that {@link #stopTask} always be called after starting a task, even in case
* of exceptions. Failing to do so may result in corrupted results.
*
* @param taskName the name of the task being ended.
* @param tag the tag of the task being ended.
*/
public static void stopTask(String taskName, Tag tag) {
impl.stopTask(taskName, tag);
}
/**
* Marks the end of a task. If PerfMark is disabled, this method is a no-op. The task name should
* match the ones provided to the corresponding {@link #startTask(String)}, if provided. If the
* task name does not match, the implementation will prefer the starting name. The name helps
* identify the task if PerfMark is enabled mid way through the task, or if the previous results
* have been overwritten. The name of the task should be a runtime-time constant, usually a string
* literal. Consider using {@link #stopTask()} instead.
*
*
It is important that {@link #stopTask} always be called after starting a task, even in case
* of exceptions. Failing to do so may result in corrupted results.
*
* @param taskName the name of the task being ended.
*/
public static void stopTask(String taskName) {
impl.stopTask(taskName);
}
/**
* Marks the end of a task. If PerfMark is disabled, this method is a no-op. The task name should
* match the ones provided to the corresponding {@link #startTask(String, String)}, if provided.
* If the task name does not match, the implementation will prefer the starting name. The name
* helps identify the task if PerfMark is enabled mid way through the task, or if the previous
* results have been overwritten. The name of the task should be a runtime-time constant, usually
* a string literal. Consider using {@link #stopTask()} instead.
*
*
It is important that {@link #stopTask} always be called after starting a task, even in case
* of exceptions. Failing to do so may result in corrupted results.
*
* @param taskName the name of the task being ended.
* @param subTaskName the name of the sub task being ended.
* @since 0.20.0
*/
public static void stopTask(String taskName, String subTaskName) {
impl.stopTask(taskName, subTaskName);
}
/**
* Creates a tag with no name or numeric identifier. The returned instance is different based on
* if PerfMark is enabled or not.
*
*
This method is seldomly useful; users should generally prefer to use the overloads of
* methods that don't need a tag. An empty tag may be useful though when the tag of a group of
* tasks may change over time.
*
* @return a Tag that has no name or id.
*/
public static Tag createTag() {
return Impl.NO_TAG;
}
/**
* Creates a tag with no name. The returned instance is different based on if PerfMark is enabled
* or not. The provided id does not have to be globally unique, but is instead meant to give
* context to a task.
*
* @param id a user provided identifier for this Tag.
* @return a Tag that has no name.
*/
public static Tag createTag(long id) {
return impl.createTag(Impl.NO_TAG_NAME, id);
}
/**
* Creates a tag with no numeric identifier. The returned instance is different based on if
* PerfMark is enabled or not. The provided name does not have to be globally unique, but is
* instead meant to give context to a task.
*
* @param name a user provided name for this Tag.
* @return a Tag that has no numeric identifier.
*/
public static Tag createTag(String name) {
return impl.createTag(name, Impl.NO_TAG_ID);
}
/**
* Creates a tag with both a name and a numeric identifier. The returned instance is different
* based on if PerfMark is enabled or not. Neither the provided name nor id has to be globally
* unique, but are instead meant to give context to a task.
*
* @param id a user provided identifier for this Tag.
* @param name a user provided name for this Tag.
* @return a Tag that has both a name and id.
*/
public static Tag createTag(String name, long id) {
return impl.createTag(name, id);
}
/**
* DO NOT CALL, no longer implemented. Use {@link #linkOut} instead.
*
* @return a no-op link that
*/
@Deprecated
@DoNotCall
public static Link link() {
return Impl.NO_LINK;
}
/**
* A link connects between two tasks that start asynchronously. When {@link #linkOut()} is called,
* an association between the most recently started task and a yet-to-be named task on another
* thread, is created. Links are a one-to-many relationship. A single started task can have
* multiple associated tasks on other threads.
*
* @since 0.17.0
* @return A Link to be used in other tasks.
*/
public static Link linkOut() {
return impl.linkOut();
}
/**
* Associate this link with the most recently started task. There may be at most one inbound
* linkage per task: the first call to {@link #linkIn} decides which outbound task is the origin.
*
* @param link a link created inside of another task.
* @since 0.17.0
*/
public static void linkIn(Link link) {
impl.linkIn(link);
}
/**
* Attaches an additional tag to the current active task. The tag provided is independent of the
* tag used with {@link #startTask(String, Tag)} and {@link #stopTask(String, Tag)}. Unlike the
* two previous two task overloads, the tag provided to {@link #attachTag(Tag)} does not have to
* match any other tags in use. This method is useful for when you have the tag information after
* the task is started.
*
*
Here are some example usages:
*
*
Recording the amount of work done in a task:
*
*
* PerfMark.startTask("read");
* byte[] data = file.read();
* PerfMark.attachTag(PerfMark.createTag("bytes read", data.length));
* PerfMark.stopTask("read");
*
*
* Recording a tag which may be absent on an exception:
*
*
* Socket s;
* Tag remoteTag = PerfMark.createTag(remoteAddress.toString());
* PerfMark.startTask("connect", remoteTag);
* try {
* s = connect(remoteAddress);
* PerfMark.attachTag(PerfMark.createTag(s.getLocalAddress().toString());
* } finally {
* PerfMark.stopTask("connect", remoteTag);
* }
*
*
* @since 0.18.0
* @param tag the Tag to attach.
*/
public static void attachTag(Tag tag) {
impl.attachTag(tag);
}
/**
* Attaches an additional keyed tag to the current active task. The tag provided is independent of
* the tag used with {@code startTask} and {@code stopTask}. This tag operation is different than
* {@link Tag} in that the tag value has an associated name (also called a key). The tag name and
* value are attached to the most recently started task, and don't have to match any other tags.
* This method is useful for when you have the tag information after the task is started.
*
* @param tagName The name of the value being attached
* @param tagValue The value to attach to the current task.
* @since 0.20.0
*/
public static void attachTag(String tagName, String tagValue) {
impl.attachTag(tagName, tagValue);
}
/**
* Attaches an additional keyed tag to the current active task. The tag provided is independent of
* the tag used with {@code startTask} and {@code stopTask}. This tag operation is different than
* {@link Tag} in that the tag value has an associated name (also called a key). The tag name and
* value are attached to the most recently started task, and don't have to match any other tags.
* This method is useful for when you have the tag information after the task is started.
*
* @param tagName The name of the value being attached
* @param tagValue The value to attach to the current task.
* @since 0.20.0
*/
public static void attachTag(String tagName, long tagValue) {
impl.attachTag(tagName, tagValue);
}
/**
* Attaches an additional keyed tag to the current active task. The tag provided is independent of
* the tag used with {@code startTask} and {@code stopTask}. This tag operation is different than
* {@link Tag} in that the tag values have an associated name (also called a key). The tag name
* and values are attached to the most recently started task, and don't have to match any other
* tags. This method is useful for when you have the tag information after the task is started.
*
* This method may treat the given two longs as special. If the tag name contains the string
* "uuid" (case insensitive), the value may be treated as a single 128 bit value. An example
* usage:
*
*
* RPC rpc = ...
* PerfMark.startTask("sendRPC");
* try {
* UUID u = rpc.uuid();
* PerfMark.attachTag("rpc uuid", u.getMostSignificantBits(), u.getLeastSignificantBits());
* send(rpc);
* } finally {
* PerfMark.stopTask("sendRPC");
* }
*
*
* @param tagName The name of the value being attached
* @param tagValue0 The first value to attach to the current task.
* @param tagValue1 The second value to attach to the current task.
* @since 0.20.0
*/
public static void attachTag(String tagName, long tagValue0, long tagValue1) {
impl.attachTag(tagName, tagValue0, tagValue1);
}
/**
* Attaches an additional keyed tag to the current active task. The tag provided is independent of
* the tag used with {@code startTask} and {@code stopTask}. This tag operation is different than
* {@link Tag} in that the tag value has an associated name (also called a key). The tag name and
* value are attached to the most recently started task, and don't have to match any other tags.
* This method is useful for when you have the tag information after the task is started.
*
* Unlike {@link #attachTag(String, String)}, this defers constructing the tagValue String
* until later, and avoids doing any work while PerfMark is disabled. Callers are expected to
* provide a method handle that can consume the {@code tagObject}, and produce a tagValue. For
* example:
*
*
{@code
* Response resp = client.makeCall(request);
* PerfMark.attachTag("httpServerHeader", resp, r -> r.getHeaders().get("Server"));
* }
*
* Also unlike {@link #attachTag(String, String)}, this function is easier to misuse. Prefer
* using the other attachTag methods unless you are confident you need this one. Be familiar with
* following issues:
*
*
* - Callers should be careful to not capture the {@code tagObject}, and instead use the
* argument to {@code stringFunction}. This avoids a memory allocation and possibly holding
* the tagObject alive longer than necessary.
*
- The {@code stringFunction} should be idempotent, have no side effects, and be safe to
* invoke from other threads. If the string function references state that may be changed,
* callers must synchronize access. The string function may be called multiple times for the
* same tag object. Additionally, if {@code attachTag()} is called with the same tag object
* and string function multiple times, PerfMark may invoke the function only once.
*
- The tag object may kept alive longer than normal, and prevent garbage collection from
* reclaiming it. If the tag object retains a large amount of resources, this may appear as
* a memory leak. The risk of this memory increase will need to be balanced with the cost of
* eagerly constructing the tag value string. Additionally, if the string function is a
* capturing lambda (refers to local or global state), the function itself may appear as a
* leak.
*
- If the stringFunction is {@code null}, or if it throws an exception when called, the tag
* value will not be attached. It is implementation defined if such problems are reported
* (e.g. logged). Note that exceptions are expensive compared to PerfMark calls, and thus
* may slow down tracing. If an exception is thrown, or if the stringFunction is {@code
* null}, PerfMark may invoke other methods on the tag object or string function, such as
* {@code toString()} and {@code getClass()}.
*
*
* @param tagName The name of the value being attached
* @param tagObject The tag object which will passed to the stringFunction.
* @param stringFunction The function that will convert the object to
* @param the type of tag object to be stringified
* @since 0.22.0
*/
public static void attachTag(
String tagName, T tagObject, StringFunction stringFunction) {
impl.attachTag(tagName, tagObject, stringFunction);
}
private static final Impl impl;
static {
Impl instance = null;
Throwable err = null;
Class clz = null;
try {
clz = Class.forName("org.apache.ratis.thirdparty.io.perfmark.impl.SecretPerfMarkImpl$PerfMarkImpl");
} catch (Throwable t) {
err = t;
}
if (clz != null) {
try {
instance = clz.asSubclass(Impl.class).getConstructor(Tag.class).newInstance(Impl.NO_TAG);
} catch (Throwable t) {
err = t;
}
}
if (instance != null) {
impl = instance;
} else {
impl = new Impl(Impl.NO_TAG);
}
if (err != null) {
try {
if (Boolean.getBoolean("org.apache.ratis.thirdparty.io.perfmark.PerfMark.debug")) {
// We need to be careful here, as it's easy to accidentally cause a class load. Logger is loaded
// reflectively to avoid accidentally pulling it in.
// TODO(carl-mastrangelo): Maybe make this load SLF4J instead?
Class logClass = Class.forName("java.util.logging.Logger");
Object logger = logClass.getMethod("getLogger", String.class).invoke(null, PerfMark.class.getName());
Class levelClass = Class.forName("java.util.logging.Level");
Object level = levelClass.getField("FINE").get(null);
Method logMethod = logClass.getMethod("log", levelClass, String.class, Throwable.class);
logMethod.invoke(logger, level, "Error during PerfMark.", err);
}
} catch (Throwable e) {
// ignored.
}
}
}
private PerfMark() {}
}