tracinglib: new helper for naming flow scopes am: 32ce2d935d (625faabe) · Commits · e / os / android_frameworks_libs_systemui

tracinglib/README.md

+13 −14

Original line number	Diff line number	Diff line
		# Coroutine Tracing

		This library contains utilities for tracing coroutines. Coroutines cannot normally be traced using
		the `android.os.Trace` APIs because it will often lead to malformed trace sections. This is because
		each `Trace.beginSection` must have a matching `Trace.endSection` on the same thread before the
		scope is finished, so if they are used around a suspend point, the trace section will remain open
		while other unrelated work executes. It could even remain open indefinitely if the coroutine is
		canceled.

		To address this, we introduce a function `traceCoroutine("name") {}` that can be used for tracing
		sections of coroutine code. When invoked, a trace section with the given name will start
		This library contains utilities for tracing coroutines. Coroutines cannot be traced using the
		`android.os.Trace` APIs because suspension points will lead to malformed trace sections. This is
		because each `Trace.beginSection` must have a matching `Trace.endSection`; if a coroutine suspends
		before `Trace.endSection` is called, the trace section will remain open while other unrelated work
		executes.

		To address this, we introduce a function `traceCoroutine("name") { ... }` that can be used for
		tracing sections of coroutine code. When invoked, a trace section with the given name will start
		immediately, and its name will also be written to an object in the current `CoroutineContext` used
		for coroutine-local storage. When the coroutine suspends, all trace sections will end immediately.
		When resumed, the coroutine will read the names of the previous sections from coroutine-local
		@@ -61,19 +60,19 @@ val coldFlow = flow {
		emit(1)
		emit(2)
		emit(3)
		}.withTraceName("my-flow")
		}

		coldFlow.collect {
		coldFlow.collect("F") {
		println(it)
		delay(10)
		yield()
		}
		```

		Would be traced as follows:

		```
		Thread #1 \| [=== my-flow:collect ===] [=== my-flow:collect ===] [=== my-flow:collect ===]
		\| [== my-flow:emit ==] [== my-flow:emit ==] [== my-flow:emit ==]
		Thread #1 \| [====== collect:F ======] [==== collect:F =====] [====== collect:F ======]
		\| [== collect:F:emit ==] [== collect:F:emit ==] [== collect:F:emit ==]
		```

		# Building and Running

tracinglib/core/src/coroutines/CoroutineTracing.kt

+40 −46

Original line number	Diff line number	Diff line
		@@ -32,17 +32,15 @@ import kotlinx.coroutines.launch
		import kotlinx.coroutines.runBlocking
		import kotlinx.coroutines.withContext

		const val DEFAULT_TRACK_NAME = "Coroutines"

		@OptIn(ExperimentalContracts::class)
		suspend inline fun <R> coroutineScope(
		suspend inline fun <R> coroutineScopeTraced(
		traceName: String,
		crossinline block: suspend CoroutineScope.() -> R,
		): R {
		contract { callsInPlace(block, InvocationKind.EXACTLY_ONCE) }
		return traceCoroutine(traceName) {
		return@traceCoroutine coroutineScope wrappedCoroutineScope@{
		return@wrappedCoroutineScope block()
		return coroutineScope {
		traceCoroutine(traceName) {
		return@coroutineScope block()
		}
		}
		}
		@@ -52,31 +50,33 @@ suspend inline fun <R> coroutineScope(
		*
		* @see traceCoroutine
		*/
		inline fun CoroutineScope.launch(
		inline fun CoroutineScope.launchTraced(
		crossinline spanName: () -> String,
		context: CoroutineContext = EmptyCoroutineContext,
		start: CoroutineStart = CoroutineStart.DEFAULT,
		noinline block: suspend CoroutineScope.() -> Unit,
		): Job = launch(nameCoroutine(spanName) + context, start, block)
		): Job {
		return launch(nameCoroutine(spanName) + context, start, block)
		}

		/**
		* Convenience function for calling [CoroutineScope.launch] with [traceCoroutine] to enable tracing.
		*
		* @see traceCoroutine
		*/
		fun CoroutineScope.launch(
		spanName: String,
		fun CoroutineScope.launchTraced(
		spanName: String? = null,
		context: CoroutineContext = EmptyCoroutineContext,
		start: CoroutineStart = CoroutineStart.DEFAULT,
		block: suspend CoroutineScope.() -> Unit,
		): Job = launch(nameCoroutine(spanName) + context, start, block)
		): Job = launchTraced({ spanName ?: block::class.simpleName ?: "launch" }, context, start, block)

		/**
		* Convenience function for calling [CoroutineScope.async] with [traceCoroutine] enable tracing
		*
		* @see traceCoroutine
		*/
		inline fun <T> CoroutineScope.async(
		inline fun <T> CoroutineScope.asyncTraced(
		spanName: () -> String,
		context: CoroutineContext = EmptyCoroutineContext,
		start: CoroutineStart = CoroutineStart.DEFAULT,
		@@ -88,19 +88,20 @@ inline fun <T> CoroutineScope.async(
		*
		* @see traceCoroutine
		*/
		fun <T> CoroutineScope.async(
		spanName: String,
		fun <T> CoroutineScope.asyncTraced(
		spanName: String? = null,
		context: CoroutineContext = EmptyCoroutineContext,
		start: CoroutineStart = CoroutineStart.DEFAULT,
		block: suspend CoroutineScope.() -> T,
		): Deferred<T> = async(nameCoroutine(spanName) + context, start, block)
		): Deferred<T> =
		asyncTraced({ spanName ?: block::class.simpleName ?: "async" }, context, start, block)

		/**
		* Convenience function for calling [runBlocking] with [traceCoroutine] to enable tracing.
		*
		* @see traceCoroutine
		*/
		inline fun <T> runBlocking(
		inline fun <T> runBlockingTraced(
		spanName: () -> String,
		context: CoroutineContext,
		noinline block: suspend CoroutineScope.() -> T,
		@@ -111,29 +112,29 @@ inline fun <T> runBlocking(
		*
		* @see traceCoroutine
		*/
		fun <T> runBlocking(
		spanName: String,
		fun <T> runBlockingTraced(
		spanName: String? = null,
		context: CoroutineContext,
		block: suspend CoroutineScope.() -> T,
		): T = runBlocking(nameCoroutine(spanName) + context, block)
		): T = runBlockingTraced({ spanName ?: block::class.simpleName ?: "runBlocking" }, context, block)

		/**
		* Convenience function for calling [withContext] with [traceCoroutine] to enable tracing.
		*
		* @see traceCoroutine
		*/
		suspend fun <T> withContext(
		spanName: String,
		suspend fun <T> withContextTraced(
		spanName: String? = null,
		context: CoroutineContext,
		block: suspend CoroutineScope.() -> T,
		): T = withContext(nameCoroutine(spanName) + context, block)
		): T = withContextTraced({ spanName ?: block::class.simpleName ?: "withContext" }, context, block)

		/**
		* Convenience function for calling [withContext] with [traceCoroutine] to enable tracing.
		*
		* @see traceCoroutine
		*/
		suspend inline fun <T> withContext(
		suspend inline fun <T> withContextTraced(
		spanName: () -> String,
		context: CoroutineContext,
		noinline block: suspend CoroutineScope.() -> T,
		@@ -143,37 +144,30 @@ suspend inline fun <T> withContext(
		* Traces a section of work of a `suspend` [block]. The trace sections will appear on the thread
		* that is currently executing the [block] of work. If the [block] is suspended, all trace sections
		* added using this API will end until the [block] is resumed, which could happen either on this
		* thread or on another thread. If a child coroutine is started, it will inherit the trace sections
		* of its parent. The child will continue to print these trace sections whether or not the parent
		* coroutine is still running them.
		* thread or on another thread. If a child coroutine is started, it will NOT inherit the trace
		* sections of its parent; however, it will include metadata in the trace section pointing to the
		* parent.
		*
		* The current [CoroutineContext] must have a [TraceContextElement] for this API to work. Otherwise,
		* the trace sections will be dropped.
		*
		* For example, in the following trace, Thread #1 ran some work, suspended, then continued working
		* on Thread #2. Meanwhile, Thread #2 created a new child coroutine which inherited its trace
		* sections. Then, the original coroutine resumed on Thread #1 before ending. Meanwhile Thread #3 is
		* still printing trace sections from its parent because they were copied when it was created. There
		* is no way for the parent to communicate to the child that it marked these slices as completed.
		* While this might seem counterintuitive, it allows us to pinpoint the origin of the child
		* coroutine's work.
		* For example, in the following trace, Thread #1 starts a coroutine, suspends, and continues the
		* coroutine on Thread #2. Next, Thread #2 start a child coroutine in an unconfined manner. Then,
		* still on Thread #2, the original coroutine suspends, the child resumes, and the child suspends.
		* Then, the original coroutine resumes on Thread#1.
		*
		* ```
		* Thread #1 \| [==== Slice A ====] [==== Slice A ====]
		* \| [==== B ====] [=== B ===]
		* --------------------------------------------------------------------------------------
		* Thread #2 \| [====== Slice A ======]
		* \| [========= B =========]
		* \| [===== C ======]
		* --------------------------------------------------------------------------------------
		* Thread #3 \| [== Slice A ==] [== Slice A ==]
		* \| [===== B =====] [===== B =====]
		* \| [===== C =====] [===== C =====]
		* \| [=== D ===]
		* -----------------------------------------------------------------------------------------------\|
		* Thread #1 \| [== Slice A ==] [==== Slice A ====]
		* \| [== B ==] [=== B ===]
		* -----------------------------------------------------------------------------------------------\|
		* Thread #2 \| [==== Slice A ====] [=== C ====]
		* \| [======= B =======]
		* \| [=== C ====]
		* -----------------------------------------------------------------------------------------------\|
		* ```
		*
		* @param name The name of the code section to appear in the trace
		* @see endSlice
		* @param spanName The name of the code section to appear in the trace
		* @see traceCoroutine
		*/
		@OptIn(ExperimentalContracts::class)

tracinglib/core/src/coroutines/TraceContextElement.kt

+48 −92

Original line number	Diff line number	Diff line
		@@ -28,11 +28,8 @@ import java.util.stream.Stream
		import kotlin.contracts.ExperimentalContracts
		import kotlin.contracts.InvocationKind
		import kotlin.contracts.contract
		import kotlin.coroutines.AbstractCoroutineContextKey
		import kotlin.coroutines.CoroutineContext
		import kotlin.coroutines.EmptyCoroutineContext
		import kotlin.coroutines.getPolymorphicElement
		import kotlin.coroutines.minusPolymorphicKey
		import kotlinx.coroutines.CopyableThreadContextElement
		import kotlinx.coroutines.CoroutineScope
		import kotlinx.coroutines.DelicateCoroutinesApi
		@@ -92,19 +89,30 @@ val traceThreadLocal = TraceDataThreadLocal()
		* names.
		* @param strictMode whether to add additional checks to coroutine tracing machinery. These checks
		* are expensive and should only be used for testing.
		* @param shouldIgnoreClassName lambda that takes binary class name (as returned from
		* [StackFrame.getClassName] and returns true if it should be ignored (e.g. search for relevant
		* class name should continue) or false otherwise
		*/
		fun createCoroutineTracingContext(
		name: String = "UnnamedScope",
		walkStackForDefaultNames: Boolean = false,
		includeParentNames: Boolean = false,
		strictMode: Boolean = false,
		shouldIgnoreClassName: (String) -> Boolean = { false },
		): CoroutineContext =
		if (Flags.coroutineTracing()) {
		TraceContextElement(
		scopeName = name,
		name = name,
		// Minor perf optimization: no need to create TraceData() for root scopes since all
		// launches require creation of child via [copyForChild] or [mergeForChild].
		contextTraceData = null,
		inheritedTracePrefix = "",
		coroutineDepth = 0,
		parentId = -1,
		walkStackForDefaultNames = walkStackForDefaultNames,
		includeParentNames = includeParentNames,
		strictMode = strictMode,
		shouldIgnoreClassName = shouldIgnoreClassName,
		)
		} else {
		EmptyCoroutineContext
		@@ -141,29 +149,21 @@ inline fun nameCoroutine(name: () -> String): CoroutineContext {
		*
		* @property name the name of the current coroutine
		*/
		/**
		* A coroutine context element that can be used for naming the child coroutine under construction.
		*
		* @property name the name to be used for the child under construction
		* @see nameCoroutine
		*/
		@VisibleForTesting(otherwise = VisibleForTesting.PACKAGE_PRIVATE)
		open class BaseTraceElement(val name: String) : CoroutineContext.Element {
		companion object Key : CoroutineContext.Key<BaseTraceElement>
		open class CoroutineTraceName(val name: String) : CoroutineContext.Element {
		companion object Key : CoroutineContext.Key<CoroutineTraceName>

		override val key: CoroutineContext.Key<*>
		get() = Key

		protected val currentId = ThreadLocalRandom.current().nextInt(1, Int.MAX_VALUE)

		@OptIn(ExperimentalStdlibApi::class)
		override fun <E : CoroutineContext.Element> get(key: CoroutineContext.Key<E>): E? {
		val rv = getPolymorphicElement(key)
		debug { "#get($key)=$rv" }
		return rv
		}

		@OptIn(ExperimentalStdlibApi::class)
		override fun minusKey(key: CoroutineContext.Key<*>): CoroutineContext {
		val rv = minusPolymorphicKey(key)
		debug { "#minusKey($key)=$rv" }
		return rv
		}

		@Deprecated(
		message =
		"""
		@@ -175,7 +175,7 @@ open class BaseTraceElement(val name: String) : CoroutineContext.Element {
		""",
		level = DeprecationLevel.ERROR,
		)
		operator fun plus(other: BaseTraceElement): BaseTraceElement {
		operator fun plus(other: CoroutineTraceName): CoroutineTraceName {
		debug { "#plus(${other.currentId})" }
		return other
		}
		@@ -187,26 +187,6 @@ open class BaseTraceElement(val name: String) : CoroutineContext.Element {
		}
		}

		/**
		* A coroutine context element that can be used for naming the child coroutine under construction.
		*
		* @property name the name to be used for the child under construction
		* @see nameCoroutine
		*/
		@VisibleForTesting(otherwise = VisibleForTesting.PACKAGE_PRIVATE)
		class CoroutineTraceName(name: String) : BaseTraceElement(name) {
		@OptIn(ExperimentalStdlibApi::class)
		companion object Key :
		AbstractCoroutineContextKey<BaseTraceElement, CoroutineTraceName>(
		BaseTraceElement,
		{ it as? CoroutineTraceName },
		)

		init {
		debug { "#init: name=$name" }
		}
		}

		/**
		* Used for tracking parent-child relationship of coroutines and persisting [TraceData] when
		* coroutines are suspended and resumed.
		@@ -231,14 +211,17 @@ class CoroutineTraceName(name: String) : BaseTraceElement(name) {
		* the child. This should only be used for testing because it can result in extremely long trace
		* names.
		* @param strictMode whether to add additional checks to coroutine machinery. These checks are
		* expensive and should only be used for testing. * @see createCoroutineTracingContext
		* expensive and should only be used for testing.
		* @param shouldIgnoreClassName lambda that takes binary class name (as returned from
		* [StackFrame.getClassName] and returns true if it should be ignored (e.g. search for relevant
		* class name should continue) or false otherwise
		* @see createCoroutineTracingContext
		* @see nameCoroutine
		* @see traceCoroutine
		*/
		@OptIn(DelicateCoroutinesApi::class, ExperimentalCoroutinesApi::class)
		@VisibleForTesting(otherwise = VisibleForTesting.PACKAGE_PRIVATE)
		class TraceContextElement
		private constructor(
		class TraceContextElement(
		name: String,
		@get:VisibleForTesting(otherwise = VisibleForTesting.PACKAGE_PRIVATE)
		val contextTraceData: TraceData?,
		@@ -248,37 +231,8 @@ private constructor(
		private val walkStackForDefaultNames: Boolean,
		private val includeParentNames: Boolean,
		private val strictMode: Boolean,
		) : CopyableThreadContextElement<TraceData?>, BaseTraceElement(name) {

		@OptIn(ExperimentalStdlibApi::class)
		companion object Key :
		AbstractCoroutineContextKey<BaseTraceElement, TraceContextElement>(
		BaseTraceElement,
		{ it as? TraceContextElement },
		) {
		override fun toString(): String {
		return "TraceContextElement.Key"
		}
		}

		@VisibleForTesting(otherwise = VisibleForTesting.PRIVATE)
		constructor(
		scopeName: String,
		walkStackForDefaultNames: Boolean = false,
		includeParentNames: Boolean = false,
		strictMode: Boolean = false,
		) : this(
		name = scopeName,
		// Minor perf optimization: no need to create TraceData() for root scopes since all launches
		// require creation of child via [copyForChild] or [mergeForChild].
		contextTraceData = null,
		inheritedTracePrefix = "",
		coroutineDepth = 0,
		parentId = -1,
		walkStackForDefaultNames = walkStackForDefaultNames,
		includeParentNames = includeParentNames,
		strictMode = strictMode,
		)
		private val shouldIgnoreClassName: (String) -> Boolean,
		) : CopyableThreadContextElement<TraceData?>, CoroutineTraceName(name) {

		private var childCoroutineCount = AtomicInteger(0)

		@@ -371,7 +325,7 @@ private constructor(
		override fun mergeForChild(overwritingElement: CoroutineContext.Element): CoroutineContext {
		debug { "#mergeForChild" }
		if (DEBUG) {
		overwritingElement[TraceContextElement]?.let {
		(overwritingElement as? TraceContextElement)?.let {
		Log.e(
		TAG,
		"${this::class.java.simpleName}@$currentId#mergeForChild(@${it.currentId}): " +
		@@ -380,15 +334,13 @@ private constructor(
		)
		}
		}
		val nameForChild =
		overwritingElement[CoroutineTraceName]?.name
		?: overwritingElement[TraceContextElement]?.name
		?: ""
		val nameForChild = (overwritingElement as CoroutineTraceName).name
		return createChildContext(nameForChild)
		}

		private fun createChildContext(
		name: String = if (walkStackForDefaultNames) walkStackForClassName() else ""
		name: String =
		if (walkStackForDefaultNames) walkStackForClassName(shouldIgnoreClassName) else ""
		): TraceContextElement {
		debug { "#createChildContext: \"$name\" has new child with name \"${name}\"" }
		val childCount = childCoroutineCount.incrementAndGet()
		@@ -402,26 +354,31 @@ private constructor(
		walkStackForDefaultNames = walkStackForDefaultNames,
		includeParentNames = includeParentNames,
		strictMode = strictMode,
		shouldIgnoreClassName = shouldIgnoreClassName,
		)
		}
		}

		/** Get a name for the trace section include the name of the call site. */
		private fun walkStackForClassName(): String {
		/**
		* Get a name for the trace section include the name of the call site.
		*
		* @param additionalDropPredicate additional checks for whether class should be ignored
		*/
		private fun walkStackForClassName(
		additionalDropPredicate: (String) -> Boolean = { false }
		): String {
		Trace.traceBegin(Trace.TRACE_TAG_APP, "walkStackForClassName")
		try {
		var frame = ""
		StackWalker.getInstance().walk { s: Stream<StackFrame> ->
		s.dropWhile { f: StackFrame ->
		with(f.className) {
		startsWith("kotlin") \|\|
		startsWith("android") \|\|
		startsWith("com.android.internal.") \|\|
		startsWith("com.android.app.tracing.")
		}
		val className = f.className
		className.startsWith("kotlin") \|\|
		className.startsWith("com.android.app.tracing.") \|\|
		additionalDropPredicate(className)
		}
		.findFirst()
		.ifPresent { frame = it.className.substringAfterLast(".") }
		.ifPresent { frame = it.className.substringAfterLast(".") + "." + it.methodName }
		}
		return frame
		} catch (e: Exception) {
		@@ -435,6 +392,5 @@ private fun walkStackForClassName(): String {
		private const val UNEXPECTED_TRACE_DATA_ERROR_MESSAGE =
		"Overwriting context element with non-empty trace data. There should only be one " +
		"TraceContextElement per coroutine, and it should be installed in the root scope. "

		internal val TAG = "CoroutineTracing"
		internal const val TAG = "CoroutineTracing"
		internal const val DEBUG = false

tracinglib/core/src/coroutines/flow/FlowExt.kt

+146 −84

File changed.

Preview size limit exceeded, changes collapsed.

tracinglib/demo/src/ApplicationComponent.kt

+12 −3

Original line number	Diff line number	Diff line
		@@ -52,6 +52,8 @@ import kotlinx.coroutines.android.asCoroutineDispatcher

		@Qualifier @MustBeDocumented @Retention(RUNTIME) annotation class FixedThreadC

		@Qualifier @MustBeDocumented @Retention(RUNTIME) annotation class FixedThreadD

		@Module
		class ConcurrencyModule {

		@@ -80,21 +82,28 @@ class ConcurrencyModule {
		@Singleton
		@FixedThreadA
		fun provideDispatcherA(): CoroutineDispatcher {
		return startThreadWithLooper("Thread A").threadHandler.asCoroutineDispatcher()
		return startThreadWithLooper("Thread:A").threadHandler.asCoroutineDispatcher()
		}

		@Provides
		@Singleton
		@FixedThreadB
		fun provideDispatcherB(): CoroutineDispatcher {
		return startThreadWithLooper("Thread B").threadHandler.asCoroutineDispatcher()
		return startThreadWithLooper("Thread:B").threadHandler.asCoroutineDispatcher()
		}

		@Provides
		@Singleton
		@FixedThreadC
		fun provideDispatcherC(): CoroutineDispatcher {
		return startThreadWithLooper("Thread C").threadHandler.asCoroutineDispatcher()
		return startThreadWithLooper("Thread:C").threadHandler.asCoroutineDispatcher()
		}

		@Provides
		@Singleton
		@FixedThreadD
		fun provideDispatcherD(): CoroutineDispatcher {
		return startThreadWithLooper("Thread:D").threadHandler.asCoroutineDispatcher()
		}
		}