Bug 1607259 - Allow configuring the maximum number of running processes, r=jlast.

Differential Revision: https://phabricator.services.mozilla.com/D58817

--HG--
extra : moz-landing-system : lando

devtools/server/actors/replay/control.js

@@ -150,14 +150,17 @@ function ChildProcess(rootId, forkId, recording, recordingLength, startPoint) {
   // run forward to the first checkpoint.
   this.manifests = [
     {
-      manifest: { kind: "initial" },
-      onFinished: ({ point }) => {
+      manifest: { kind: "primordial" },
+      onFinished: ({ point, maxRunningProcesses }) => {
         if (this == gMainChild) {
           getCheckpointInfo(FirstCheckpointId).point = point;
           Services.tm.dispatchToMainThread(
             recording ? maybeResumeRecording : setMainChild
           );
         }
+        if (maxRunningProcesses) {
+          gMaxRunningLeafChildren = maxRunningProcesses;
+        }
       },
     },
   ];
@@ -477,7 +480,7 @@ function newLeafChild(endpoint, onFinished = () => {}) {
 }
 
 // How many leaf children we can have running simultaneously.
-const MaxRunningLeafChildren = 4;
+let gMaxRunningLeafChildren = 4;
 
 // How many leaf children are currently running.
 let gNumRunningLeafChildren = 0;
@@ -489,7 +492,7 @@ const gChildWaiters = [[], [], []];
 // the limits on the maximum number of running leaves and returning the new
 // child when it reaches the endpoint.
 async function ensureLeafChild(endpoint, priority = Priority.HIGH) {
-  if (gNumRunningLeafChildren < MaxRunningLeafChildren) {
+  if (gNumRunningLeafChildren < gMaxRunningLeafChildren) {
     gNumRunningLeafChildren++;
   } else {
     await new Promise(resolve => gChildWaiters[priority].push(resolve));
@@ -505,7 +508,7 @@ async function ensureLeafChild(endpoint, priority = Priority.HIGH) {
 function stopRunningLeafChild() {
   gNumRunningLeafChildren--;
 
-  if (gNumRunningLeafChildren < MaxRunningLeafChildren) {
+  if (gNumRunningLeafChildren < gMaxRunningLeafChildren) {
     for (const waiters of gChildWaiters) {
       if (waiters.length) {
         const resolve = waiters.shift();
@@ -617,14 +620,14 @@ function respawnCrashedChild(child) {
   }
 
   for (const manifest of processedManifests) {
-    if (manifest.kind != "initial" && manifest.kind != "fork") {
+    if (manifest.kind != "primordial" && manifest.kind != "fork") {
       child.sendManifest(manifest);
     }
   }
 
   for (const { manifest, onFinished } of manifests) {
     if (
-      manifest.kind != "initial" &&
+      manifest.kind != "primordial" &&
       (manifest.kind != "fork" || manifest != manifests[0].manifest)
     ) {
       child.sendManifest(manifest, onFinished);

devtools/server/actors/replay/replay.js

@@ -1132,10 +1132,10 @@ function finishResume(point) {
 // finished. This does not need to be specified for all manifests.
 const gManifestFinishedAfterCheckpointHandlers = {
   primordial(_, point) {
-    // The primordial manifest runs forward to the first checkpoint, saves it,
-    // and then finishes.
+    // The primordial manifest runs forward to the first checkpoint.
     assert(point.checkpoint == FirstCheckpointId);
-    RecordReplayControl.manifestFinished({ point });
+    const maxRunningProcesses = RecordReplayControl.maxRunningProcesses();
+    RecordReplayControl.manifestFinished({ point, maxRunningProcesses });
   },
 
   resume(_, point) {

toolkit/recordreplay/ipc/JSControl.cpp

@@ -996,6 +996,28 @@ static bool RecordReplay_Repaint(JSContext* aCx, unsigned aArgc, Value* aVp) {
   return true;
 }
 
+static bool RecordReplay_MaxRunningProcesses(JSContext* aCx, unsigned aArgc,
+                                             Value* aVp) {
+  CallArgs args = CallArgsFromVp(aArgc, aVp);
+  args.rval().setUndefined();
+
+  // The number of processes we can run at a time is supplied via an environment
+  // variable. This is normally set by the translation layer when we are running
+  // in the cloud.
+  if (IsReplaying()) {
+    AutoEnsurePassThroughThreadEvents pt;
+    const char* env = getenv("MOZ_REPLAYING_MAX_RUNNING_PROCESSES");
+    if (env) {
+      int numProcesses = atoi(env);
+      if (numProcesses > 0) {
+        args.rval().setInt32(numProcesses);
+      }
+    }
+  }
+
+  return true;
+}
+
 static bool RecordReplay_Dump(JSContext* aCx, unsigned aArgc, Value* aVp) {
   // This method is an alternative to dump() that can be used in places where
   // thread events are disallowed.
@@ -1479,6 +1501,7 @@ static const JSFunctionSpec gRecordReplayMethods[] = {
           0),
     JS_FN("findScriptHits", RecordReplay_FindScriptHits, 3, 0),
     JS_FN("findChangeFrames", RecordReplay_FindChangeFrames, 3, 0),
+    JS_FN("maxRunningProcesses", RecordReplay_MaxRunningProcesses, 0, 0),
     JS_FN("dump", RecordReplay_Dump, 1, 0),
     JS_FS_END};