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Moonchild
117 lines
3.9 KiB
Markdown
117 lines
3.9 KiB
Markdown
Lazy Actor Modules and E10S setup
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---------------------------------
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The **DebuggerServer** loads and creates most of the actors lazily to keep
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the initial memory usage down (which is extremely important on lower end devices).
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## Register a lazy global/tab actor module
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register a global actor:
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```js
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DebuggerServer.registerModule("devtools/server/actors/webapps", {
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prefix: "webapps",
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constructor: "WebappsActor",
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type: { global: true }
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});
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```
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register a tab actor:
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```js
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DebuggerServer.registerModule("devtools/server/actors/webconsole", {
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prefix: "console",
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constructor: "WebConsoleActor",
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type: { tab: true }
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});
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```
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## E10S Setup
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Some of the actor modules needs to exchange messages between the parent and child processes.
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E.g. the **director-manager** needs to ask the list installed **director scripts** from
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the **director-registry** running in the parent process) and the parent/child setup
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is lazily directed by the **DebuggerServer**.
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When the actor is loaded for the first time in the the **DebuggerServer** running in the
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child process, it has the chances to run its setup procedure, e.g. in the **director-registry**:
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```js
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...
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const {DebuggerServer} = require("devtools/server/main");
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...
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// skip child setup if this actor module is not running in a child process
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if (DebuggerServer.isInChildProcess) {
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setupChildProcess();
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}
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...
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```
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The above setupChildProcess helper will use the **DebuggerServer.setupInParent**
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to start a setup process in the parent process Debugger Server, e.g. in the the **director-registry**:
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```js
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function setupChildProcess() {
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const { sendSyncMessage } = DebuggerServer.parentMessageManager;
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DebuggerServer.setupInParent({
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module: "devtools/server/actors/director-registry",
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setupParent: "setupParentProcess"
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});
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...
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```
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in the parent process, the **DebuggerServer** will require the requested module
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and call the **setupParent** exported helper with the **MessageManager**
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connected to the child process as parameter, e.g. in the **director-registry**:
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```js
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/**
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* E10S parent/child setup helpers
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*/
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let gTrackedMessageManager = new Set();
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exports.setupParentProcess = function setupParentProcess({ mm, childID }) {
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if (gTrackedMessageManager.has(mm)) { return; }
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gTrackedMessageManager.add(mm);
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// listen for director-script requests from the child process
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mm.addMessageListener("debug:director-registry-request", handleChildRequest);
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// time to unsubscribe from the disconnected message manager
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DebuggerServer.once("disconnected-from-child:" + childID, handleMessageManagerDisconnected);
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function handleMessageManagerDisconnected(evt, { mm: disconnected_mm }) {
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...
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}
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```
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The DebuggerServer emits "disconnected-from-child:CHILDID" events to give the actor modules
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the chance to cleanup their handlers registered on the disconnected message manager.
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## E10S setup flow
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In the child process:
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- DebuggerServer loads an actor module
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- the actor module check DebuggerServer.isInChildProcess
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- the actor module calls the DebuggerServer.setupInParent helper
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- the DebuggerServer.setupInParent helper asks to the parent process
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to run the required setup
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- the actor module use the DebuggerServer.parentMessageManager.sendSyncMessage,
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DebuggerServer.parentMessageManager.addMessageListener helpers to send requests
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or to subscribe message handlers
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In the parent process:
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- The DebuggerServer receives the DebuggerServer.setupInParent request
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- it tries to load the required module
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- it tries to call the **mod[setupParent]** method with the frame message manager and the childID
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in the json parameter **{ mm, childID }**
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- the module setupParent helper use the mm to subscribe the messagemanager events
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- the module setupParent helper use the DebuggerServer object to subscribe *once* the
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**"disconnected-from-child:CHILDID"** event (needed to unsubscribe the messagemanager events)
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