ADFA-5514: plot the Gradle daemon, the process that actually holds the build

app/src/main/java/com/itsaky/androidide/activities/editor/BaseEditorActivity.kt

@@ -1038,6 +1038,34 @@ abstract class BaseEditorActivity :
 		resetMemUsageChart()
 	}
 
+	/**
+	 * Plots the Gradle daemon, reported by the tooling server once a build has spawned it.
+	 *
+	 * The daemon is the largest of the three watched processes -- larger than the IDE and the
+	 * tooling server together on a Compose project -- and it is the likeliest reason a build is slow
+	 * or is killed on a small device. Until ADFA-5514 it was the one process the chart did not show.
+	 */
+	fun watchGradleDaemon(pid: Int) {
+		memoryUsageWatcher.watchProcess(pid, PROC_GRADLE_DAEMON)
+		resetMemUsageChart()
+	}
+
+	/**
+	 * Stops plotting the Gradle daemon [pid], which has exited.
+	 *
+	 * Not on build finish: a daemon outlives the build that spawned it and goes on holding its heap
+	 * while idle, which is the number worth showing on a device that is short of memory.
+	 *
+	 * By pid rather than by name, so a late exit cannot take out its successor's line. Removing "the
+	 * Gradle daemon" would: a daemon that dies as the next build starts one is two reports racing
+	 * over one row, and [watchProcess]'s `unique` has already dropped the old pid by then, so this
+	 * is a no-op in exactly the case where the name would have been wrong.
+	 */
+	fun unwatchGradleDaemon(pid: Int) {
+		memoryUsageWatcher.unwatchProcess(pid)
+		resetMemUsageChart()
+	}
+
 	protected fun resetMemUsageChart() {
 		val processes = memoryUsageWatcher.getMemoryUsages()
 		val datasets =

app/src/main/java/com/itsaky/androidide/activities/editor/ProjectHandlerActivity.kt

@@ -690,13 +690,36 @@ abstract class ProjectHandlerActivity : BaseEditorActivity() {
 		}
 	}
 
+	/**
+	 * Re-adds the processes the service already knows about to this activity's memory watcher.
+	 *
+	 * A configuration change replaces the activity and its [MemoryUsageWatcher] but not the service
+	 * or the processes it is driving, and both pids are reported on one-shot callbacks that a
+	 * replacement listener has already missed -- the tooling server's on the start it did not
+	 * request, the daemon's on the build that spawned it. Without this the chart came back after a
+	 * rotation plotting the IDE alone, which is the smallest of the three.
+	 */
+	private fun readoptWatchedProcesses(service: GradleBuildService) {
+		val tooling = service.toolingServerPid
+		val daemon = service.gradleDaemonPid
+		if (tooling == null && daemon == null) {
+			return
+		}
+
+		logger.info("Re-adopting watched processes: tooling server {}, Gradle daemon {}", tooling, daemon)
+		tooling?.let { memoryUsageWatcher.watchProcess(it, PROC_GRADLE_TOOLING) }
+		daemon?.let { memoryUsageWatcher.watchProcess(it, PROC_GRADLE_DAEMON) }
+		resetMemUsageChart()
+	}
+
 	protected fun onGradleBuildServiceConnected(service: GradleBuildService) {
 		log.info("Connected to Gradle build service")
 
 		buildServiceConnection.onConnected = null
 		editorViewModel.isBoundToBuildSerice = true
 		Lookup.getDefault().update(BuildService.KEY_BUILD_SERVICE, service)
 		service.setEventListener(mBuildEventListener)
+		readoptWatchedProcesses(service)
 
 		if (service.isToolingServerStarted()) {
 			if (service.isBuildInProgress) {

app/src/main/java/com/itsaky/androidide/handlers/EditorBuildEventListener.kt

@@ -77,6 +77,16 @@ class EditorBuildEventListener : GradleBuildService.EventListener {
 		this.enabled = false
 	}
 
+	override fun onGradleDaemonStarted(pid: Int) {
+		checkActivity("onGradleDaemonStarted") ?: return
+		activity.watchGradleDaemon(pid)
+	}
+
+	override fun onGradleDaemonExited(pid: Int) {
+		checkActivity("onGradleDaemonExited") ?: return
+		activity.unwatchGradleDaemon(pid)
+	}
+
 	override fun prepareBuild(buildInfo: BuildInfo) {
 		checkActivity("prepareBuild") ?: return
 

app/src/main/java/com/itsaky/androidide/services/builder/GradleBuildService.kt

@@ -119,6 +119,33 @@ class GradleBuildService :
 	 */
 	private var toolingApiClient: ForwardingToolingApiClient? = null
 	private var toolingServerRunner: ToolingServerRunner? = null
+
+	/**
+	 * The Gradle daemon's pid, or `null` when no daemon is known to be running.
+	 *
+	 * Remembered here and not merely forwarded, because the listener is an activity. A daemon is
+	 * reported once, when a build spawns it, and then outlives that build; an activity recreated
+	 * after that -- a rotation, a font-scale change -- gets a listener that hears about new daemons
+	 * only, so its memory chart silently loses the largest of the three processes. It reads this
+	 * instead. See [onGradleDaemonStarted].
+	 *
+	 * Volatile because the two ends are on different threads: the tooling API's client callbacks
+	 * write it on the RPC reader thread, and [ProjectHandlerActivity] reads it on the main thread
+	 * while binding. Without it a recreated activity can read a stale `null` and quietly leave the
+	 * daemon off the chart -- the very failure this field exists to prevent.
+	 */
+	@Volatile
+	var gradleDaemonPid: Int? = null
+		private set
+
+	/**
+	 * The tooling server's pid, or `null` while no started server has one.
+	 *
+	 * Same reason as [gradleDaemonPid]: [startToolingServer] reports the pid to whoever asked for
+	 * the start, so an activity that finds the server already up never hears it.
+	 */
+	val toolingServerPid: Int?
+		get() = toolingServerRunner?.takeIf { it.isStarted }?.pid
 	private var outputReaderJob: Job? = null
 	private var notificationManager: NotificationManager? = null
 	private var server: IToolingApiServer? = null
@@ -420,6 +447,20 @@ class GradleBuildService :
 			)
 		}
 
+	override fun onGradleDaemonStarted(pid: Int) {
+		log.info("Gradle daemon started: pid {}", pid)
+		gradleDaemonPid = pid
+		eventListener?.onGradleDaemonStarted(pid)
+	}
+
+	override fun onGradleDaemonExited(pid: Int) {
+		log.info("Gradle daemon exited: pid {}", pid)
+		if (gradleDaemonPid == pid) {
+			gradleDaemonPid = null
+		}
+		eventListener?.onGradleDaemonExited(pid)
+	}
+
 	override fun onBuildSuccessful(result: BuildResult) {
 		updateNotification(getString(R.string.build_status_sucess), false)
 
@@ -760,6 +801,14 @@ class GradleBuildService :
 					runOnUiThread { listener.onBuildSuccessful(tasks) }
 				}
 
+				override fun onGradleDaemonStarted(pid: Int) {
+					runOnUiThread { listener.onGradleDaemonStarted(pid) }
+				}
+
+				override fun onGradleDaemonExited(pid: Int) {
+					runOnUiThread { listener.onGradleDaemonExited(pid) }
+				}
+
 				override fun onProgressEvent(event: ProgressEvent) {
 					runOnUiThread { listener.onProgressEvent(event) }
 				}
@@ -823,6 +872,25 @@ class GradleBuildService :
 		 */
 		fun onBuildSuccessful(tasks: List<String?>)
 
+		/**
+		 * Called when the Gradle daemon has been identified by the tooling server.
+		 *
+		 * Defaulted, because a daemon is only of interest to a listener that plots it and every
+		 * other implementer would otherwise gain two empty methods.
+		 *
+		 * @param pid The process id of the Gradle daemon.
+		 * @see IToolingApiClient.onGradleDaemonStarted
+		 */
+		fun onGradleDaemonStarted(pid: Int) = Unit
+
+		/**
+		 * Called when the Gradle daemon has exited.
+		 *
+		 * @param pid The process id of the daemon that exited.
+		 * @see IToolingApiClient.onGradleDaemonExited
+		 */
+		fun onGradleDaemonExited(pid: Int) = Unit
+
 		/**
 		 * Called when a progress event is received from the Tooling API server.
 		 *

app/src/main/java/com/itsaky/androidide/services/builder/ToolingServerRunner.kt

@@ -48,6 +48,14 @@ internal class ToolingServerRunner(
 	private var listener: OnServerStartListener?,
 	private var observer: Observer?,
 ) {
+	/**
+	 * The server process's pid, or `null` before it has started.
+	 *
+	 * Volatile for the same reason as [GradleBuildService.gradleDaemonPid]: [startAsync] writes it
+	 * from a coroutine on [runnerScope], and the editor reads it on the main thread when it
+	 * re-adopts the watched processes after being recreated.
+	 */
+	@Volatile
 	internal var pid: Int? = null
 	private var job: Job? = null
 	private var _isStarted = AtomicBoolean(false)

app/src/main/java/com/itsaky/androidide/utils/MemoryUsageWatcher.kt

@@ -20,6 +20,7 @@ package com.itsaky.androidide.utils
 import android.app.ActivityManager
 import android.os.Debug
 import android.os.Debug.MemoryInfo
+import androidx.annotation.VisibleForTesting
 import androidx.collection.IntObjectMap
 import androidx.collection.MutableIntObjectMap
 import androidx.core.content.getSystemService
@@ -36,6 +37,7 @@ import kotlinx.coroutines.launch
 import kotlinx.coroutines.newSingleThreadContext
 import kotlinx.coroutines.withContext
 import org.slf4j.LoggerFactory
+import java.io.File
 import java.util.concurrent.ConcurrentHashMap
 import java.util.concurrent.atomic.AtomicBoolean
 
@@ -115,7 +117,8 @@ class MemoryUsageWatcher(
 		}
 	}
 
-	private fun readUsages() {
+	@VisibleForTesting
+	internal fun readUsages() {
 		val activityManager = BaseApplication.baseInstance.getSystemService<ActivityManager>()
 		if (activityManager == null) {
 			log.error("ActivityManager is null")
@@ -134,16 +137,28 @@ class MemoryUsageWatcher(
 					return@forEach
 				}
 
-			ReflectionUtils.invokeMethod(android_os_Debug_getMemoryInfo, null, pid, proc.memInfo)
-
-			// From https://developer.android.com/tools/dumpsys#meminfo
-			// "PSS is a good measure for the actual RAM weight of a process and for comparison against
-			// the RAM use of other processes and the total available RAM."
-			val usage = proc.memInfo.totalPss
-
-			// values are in kB, convert to bytes
-			val usageBytes = usage * 1024L
-			memoryUsage[pid]!!.apply {
+			// A dead process still has an entry here until whoever is watching it says otherwise, and
+			// Debug.getMemoryInfo leaves memInfo untouched for one -- so sampling it again would
+			// repeat the last reading forever and draw a flat line for a process that no longer
+			// exists. The Gradle daemon made this reachable: unlike the IDE and the tooling server it
+			// comes and goes, and it is the largest of the three (ADFA-5514). Plot a zero instead,
+			// which is both true and visibly the end of that process.
+			val usageBytes =
+				if (!isProcessAlive(pid)) {
+					0L
+				} else {
+					ReflectionUtils.invokeMethod(android_os_Debug_getMemoryInfo, null, pid, proc.memInfo)
+
+					// From https://developer.android.com/tools/dumpsys#meminfo
+					// "PSS is a good measure for the actual RAM weight of a process and for comparison against
+					// the RAM use of other processes and the total available RAM."
+					// values are in kB, convert to bytes
+					proc.memInfo.totalPss * 1024L
+				}
+			// [proc], not a second lookup: unwatchProcess runs on the main thread and can drop the
+			// entry between the two, and the Gradle daemon is unwatched from a build event
+			// (ADFA-5514), so the window is real rather than theoretical.
+			proc.apply {
 				// we insert the usage entry at the start of the array, then increment the shift amount by 1
 				// this makes the newly inserted usage entry the last element in the array
 				// and the oldest usage entry the first element in the array
@@ -160,6 +175,15 @@ class MemoryUsageWatcher(
 		}
 	}
 
+	/**
+	 * Whether [pid] still names a live process.
+	 *
+	 * `/proc` rather than `ProcessHandle`, which Android only gained recently, or a signal probe,
+	 * which needs a permission this does not have.
+	 */
+	@VisibleForTesting
+	internal var isProcessAlive: (Int) -> Boolean = { pid -> File("/proc/$pid").exists() }
+
 	/**
 	 * Watches the memory usage of the given process.
 	 *