Split child and parent wrappers

I think having them combined and relying on if statements was getting
confusing especially if we want to add additional messages with
different payloads (which will soon be the case).

src/node/entry.ts

@@ -19,7 +19,7 @@ import { coderCloudBind } from "./coder-cloud"
 import { commit, version } from "./constants"
 import { register } from "./routes"
 import { humanPath, isFile, open } from "./util"
-import { ipcMain, WrapperProcess } from "./wrapper"
+import { isChild, wrapper } from "./wrapper"
 
 export const runVsCodeCli = (args: DefaultedArgs): void => {
   logger.debug("forking vs code cli...")
@@ -137,7 +137,7 @@ const main = async (args: DefaultedArgs): Promise<void> => {
       logger.info("  - Connected to cloud agent")
     } catch (err) {
       logger.error(err.message)
-      ipcMain.exit(1)
+      wrapper.exit(1)
     }
   }
 
@@ -161,9 +161,9 @@ async function entry(): Promise<void> {
   // There's no need to check flags like --help or to spawn in an existing
   // instance for the child process because these would have already happened in
   // the parent and the child wouldn't have been spawned.
-  if (ipcMain.isChild) {
+  if (isChild(wrapper)) {
-    await ipcMain.handshake()
+    await wrapper.handshake()
-    ipcMain.preventExit()
+    wrapper.preventExit()
     return main(args)
   }
 
@@ -201,11 +201,10 @@ async function entry(): Promise<void> {
     return openInExistingInstance(args, socketPath)
   }
 
-  const wrapper = new WrapperProcess(require("../../package.json").version)
   return wrapper.start()
 }
 
 entry().catch((error) => {
   logger.error(error.message)
-  ipcMain.exit(error)
+  wrapper.exit(error)
 })

src/node/vscode.ts

@@ -8,7 +8,7 @@ import { rootPath } from "./constants"
 import { settings } from "./settings"
 import { SocketProxyProvider } from "./socket"
 import { isFile } from "./util"
-import { ipcMain } from "./wrapper"
+import { wrapper } from "./wrapper"
 
 export class VscodeProvider {
   public readonly serverRootPath: string
@@ -20,7 +20,7 @@ export class VscodeProvider {
   public constructor() {
     this.vsRootPath = path.resolve(rootPath, "lib/vscode")
     this.serverRootPath = path.join(this.vsRootPath, "out/vs/server")
-    ipcMain.onDispose(() => this.dispose())
+    wrapper.onDispose(() => this.dispose())
   }
 
   public async dispose(): Promise<void> {

src/node/wrapper.ts

@@ -1,4 +1,4 @@
-import { field, logger } from "@coder/logger"
+import { Logger, field, logger } from "@coder/logger"
 import * as cp from "child_process"
 import * as path from "path"
 import * as rfs from "rotating-file-stream"
@@ -14,9 +14,9 @@ interface RelaunchMessage {
   version: string
 }
 
-export type Message = RelaunchMessage | HandshakeMessage
+type Message = RelaunchMessage | HandshakeMessage
 
-export class ProcessError extends Error {
+class ProcessError extends Error {
   public constructor(message: string, public readonly code: number | undefined) {
     super(message)
     this.name = this.constructor.name
@@ -25,16 +25,26 @@ export class ProcessError extends Error {
 }
 
 /**
- * Allows the wrapper and inner processes to communicate.
+ * Wrapper around a process that tries to gracefully exit when a process exits
+ * and provides a way to prevent `process.exit`.
  */
-export class IpcMain {
+abstract class Process {
-  private readonly _onMessage = new Emitter<Message>()
+  /**
-  public readonly onMessage = this._onMessage.event
+   * Emit this to trigger a graceful exit.
-  private readonly _onDispose = new Emitter<NodeJS.Signals | undefined>()
+   */
-  public readonly onDispose = this._onDispose.event
+  protected readonly _onDispose = new Emitter<NodeJS.Signals | undefined>()
-  public readonly processExit: (code?: number) => never = process.exit
 
-  public constructor(private readonly parentPid?: number) {
+  /**
+   * Emitted when the process is about to be disposed.
+   */
+  public readonly onDispose = this._onDispose.event
+
+  /**
+   * Uniquely named logger for the process.
+   */
+  public abstract logger: Logger
+
+  public constructor() {
     process.on("SIGINT", () => this._onDispose.emit("SIGINT"))
     process.on("SIGTERM", () => this._onDispose.emit("SIGTERM"))
     process.on("exit", () => this._onDispose.emit(undefined))
@@ -43,42 +53,27 @@ export class IpcMain {
       // Remove listeners to avoid possibly triggering disposal again.
       process.removeAllListeners()
 
-      // Try waiting for other handlers run first then exit.
+      // Try waiting for other handlers to run first then exit.
-      logger.debug(`${parentPid ? "inner process" : "wrapper"} ${process.pid} disposing`, field("code", signal))
+      this.logger.debug("disposing", field("code", signal))
       wait.then(() => this.exit(0))
       setTimeout(() => this.exit(0), 5000)
     })
-
-    // Kill the inner process if the parent dies. This is for the case where the
-    // parent process is forcefully terminated and cannot clean up.
-    if (parentPid) {
-      setInterval(() => {
-        try {
-          // process.kill throws an exception if the process doesn't exist.
-          process.kill(parentPid, 0)
-        } catch (_) {
-          // Consider this an error since it should have been able to clean up
-          // the child process unless it was forcefully killed.
-          logger.error(`parent process ${parentPid} died`)
-          this._onDispose.emit(undefined)
-        }
-      }, 5000)
-    }
   }
 
   /**
-   * Ensure we control when the process exits.
+   * Ensure control over when the process exits.
    */
   public preventExit(): void {
-    process.exit = function (code?: number) {
+    ;(process.exit as any) = (code?: number) => {
-      logger.warn(`process.exit() was prevented: ${code || "unknown code"}.`)
+      this.logger.warn(`process.exit() was prevented: ${code || "unknown code"}.`)
-    } as (code?: number) => never
+    }
   }
 
-  public get isChild(): boolean {
+  private readonly processExit: (code?: number) => never = process.exit
-    return typeof this.parentPid !== "undefined"
-  }
 
+  /**
+   * Will always exit even if normal exit is being prevented.
+   */
   public exit(error?: number | ProcessError): never {
     if (error && typeof error !== "number") {
       this.processExit(typeof error.code === "number" ? error.code : 1)
@@ -86,47 +81,61 @@ export class IpcMain {
       this.processExit(error)
     }
   }
+}
 
-  public handshake(child?: cp.ChildProcess): Promise<void> {
+/**
-    return new Promise((resolve, reject) => {
+ * Child process that will clean up after itself if the parent goes away and can
-      const target = child || process
+ * perform a handshake with the parent and ask it to relaunch.
+ */
+class ChildProcess extends Process {
+  public logger = logger.named(`child:${process.pid}`)
+
+  public constructor(private readonly parentPid: number) {
+    super()
+
+    // Kill the inner process if the parent dies. This is for the case where the
+    // parent process is forcefully terminated and cannot clean up.
+    setInterval(() => {
+      try {
+        // process.kill throws an exception if the process doesn't exist.
+        process.kill(this.parentPid, 0)
+      } catch (_) {
+        // Consider this an error since it should have been able to clean up
+        // the child process unless it was forcefully killed.
+        this.logger.error(`parent process ${parentPid} died`)
+        this._onDispose.emit(undefined)
+      }
+    }, 5000)
+  }
+
+  /**
+   * Initiate the handshake and wait for a response from the parent.
+   */
+  public handshake(): Promise<void> {
+    return new Promise((resolve) => {
       const onMessage = (message: Message): void => {
-        logger.debug(
+        logger.debug(`received message from ${this.parentPid}`, field("message", message))
-          `${child ? "wrapper" : "inner process"} ${process.pid} received message from ${
-            child ? child.pid : this.parentPid
-          }`,
-          field("message", message),
-        )
         if (message.type === "handshake") {
-          target.removeListener("message", onMessage)
+          process.removeListener("message", onMessage)
-          target.on("message", (msg) => this._onMessage.emit(msg))
-          // The wrapper responds once the inner process starts the handshake.
-          if (child) {
-            if (!target.send) {
-              throw new Error("child not spawned with IPC")
-            }
-            target.send({ type: "handshake" })
-          }
           resolve()
         }
       }
-      target.on("message", onMessage)
+      // Initiate the handshake and wait for the reply.
-      if (child) {
+      process.on("message", onMessage)
-        child.once("error", reject)
-        child.once("exit", (code) => {
-          reject(new ProcessError(`Unexpected exit with code ${code}`, code !== null ? code : undefined))
-        })
-      } else {
-        // The inner process initiates the handshake.
       this.send({ type: "handshake" })
-      }
     })
   }
 
+  /**
+   * Notify the parent process that it should relaunch the child.
+   */
   public relaunch(version: string): void {
     this.send({ type: "relaunch", version })
   }
 
+  /**
+   * Send a message to the parent.
+   */
   private send(message: Message): void {
     if (!process.send) {
       throw new Error("not spawned with IPC")
@@ -135,29 +144,30 @@ export class IpcMain {
   }
 }
 
-/**
- * Channel for communication between the child and parent processes.
- */
-export const ipcMain = new IpcMain(
-  typeof process.env.CODE_SERVER_PARENT_PID !== "undefined" ? parseInt(process.env.CODE_SERVER_PARENT_PID) : undefined,
-)
-
 export interface WrapperOptions {
   maxMemory?: number
   nodeOptions?: string
 }
 
 /**
- * Provides a way to wrap a process for the purpose of updating the running
+ * Parent process wrapper that spawns the child process and performs a handshake
- * instance.
+ * with it. Will relaunch the child if it receives a SIGUSR1 or is asked to by
+ * the child. If the child otherwise exits the parent will also exit.
  */
-export class WrapperProcess {
+export class ParentProcess extends Process {
-  private process?: cp.ChildProcess
+  public logger = logger.named(`parent:${process.pid}`)
+
+  private child?: cp.ChildProcess
   private started?: Promise<void>
   private readonly logStdoutStream: rfs.RotatingFileStream
   private readonly logStderrStream: rfs.RotatingFileStream
 
+  protected readonly _onChildMessage = new Emitter<Message>()
+  protected readonly onChildMessage = this._onChildMessage.event
+
   public constructor(private currentVersion: string, private readonly options?: WrapperOptions) {
+    super()
+
     const opts = {
       size: "10M",
       maxFiles: 10,
@@ -165,19 +175,19 @@ export class WrapperProcess {
     this.logStdoutStream = rfs.createStream(path.join(paths.data, "coder-logs", "code-server-stdout.log"), opts)
     this.logStderrStream = rfs.createStream(path.join(paths.data, "coder-logs", "code-server-stderr.log"), opts)
 
-    ipcMain.onDispose(() => {
+    this.onDispose(() => {
       this.disposeChild()
     })
 
-    ipcMain.onMessage((message) => {
+    this.onChildMessage((message) => {
       switch (message.type) {
         case "relaunch":
-          logger.info(`Relaunching: ${this.currentVersion} -> ${message.version}`)
+          this.logger.info(`Relaunching: ${this.currentVersion} -> ${message.version}`)
           this.currentVersion = message.version
           this.relaunch()
           break
         default:
-          logger.error(`Unrecognized message ${message}`)
+          this.logger.error(`Unrecognized message ${message}`)
           break
       }
     })
@@ -185,9 +195,9 @@ export class WrapperProcess {
 
   private disposeChild(): void {
     this.started = undefined
-    if (this.process) {
+    if (this.child) {
-      this.process.removeAllListeners()
+      this.child.removeAllListeners()
-      this.process.kill()
+      this.child.kill()
     }
   }
 
@@ -196,16 +206,16 @@ export class WrapperProcess {
     try {
       await this.start()
     } catch (error) {
-      logger.error(error.message)
+      this.logger.error(error.message)
-      ipcMain.exit(typeof error.code === "number" ? error.code : 1)
+      this.exit(typeof error.code === "number" ? error.code : 1)
     }
   }
 
   public start(): Promise<void> {
     // If we have a process then we've already bound this.
-    if (!this.process) {
+    if (!this.child) {
       process.on("SIGUSR1", async () => {
-        logger.info("Received SIGUSR1; hotswapping")
+        this.logger.info("Received SIGUSR1; hotswapping")
         this.relaunch()
       })
     }
@@ -217,7 +227,7 @@ export class WrapperProcess {
 
   private async _start(): Promise<void> {
     const child = this.spawn()
-    this.process = child
+    this.child = child
 
     // Log both to stdout and to the log directory.
     if (child.stdout) {
@@ -229,13 +239,13 @@ export class WrapperProcess {
       child.stderr.pipe(process.stderr)
     }
 
-    logger.debug(`spawned inner process ${child.pid}`)
+    this.logger.debug(`spawned inner process ${child.pid}`)
 
-    await ipcMain.handshake(child)
+    await this.handshake(child)
 
     child.once("exit", (code) => {
-      logger.debug(`inner process ${child.pid} exited unexpectedly`)
+      this.logger.debug(`inner process ${child.pid} exited unexpectedly`)
-      ipcMain.exit(code || 0)
+      this.exit(code || 0)
     })
   }
 
@@ -256,18 +266,52 @@ export class WrapperProcess {
       stdio: ["ipc"],
     })
   }
+
+  /**
+   * Wait for a handshake from the child then reply.
+   */
+  private handshake(child: cp.ChildProcess): Promise<void> {
+    return new Promise((resolve, reject) => {
+      const onMessage = (message: Message): void => {
+        logger.debug(`received message from ${child.pid}`, field("message", message))
+        if (message.type === "handshake") {
+          child.removeListener("message", onMessage)
+          child.on("message", (msg) => this._onChildMessage.emit(msg))
+          child.send({ type: "handshake" })
+          resolve()
+        }
+      }
+      child.on("message", onMessage)
+      child.once("error", reject)
+      child.once("exit", (code) => {
+        reject(new ProcessError(`Unexpected exit with code ${code}`, code !== null ? code : undefined))
+      })
+    })
+  }
+}
+
+/**
+ * Process wrapper.
+ */
+export const wrapper =
+  typeof process.env.CODE_SERVER_PARENT_PID !== "undefined"
+    ? new ChildProcess(parseInt(process.env.CODE_SERVER_PARENT_PID))
+    : new ParentProcess(require("../../package.json").version)
+
+export function isChild(proc: ChildProcess | ParentProcess): proc is ChildProcess {
+  return proc instanceof ChildProcess
 }
 
 // It's possible that the pipe has closed (for example if you run code-server
 // --version | head -1). Assume that means we're done.
 if (!process.stdout.isTTY) {
-  process.stdout.on("error", () => ipcMain.exit())
+  process.stdout.on("error", () => wrapper.exit())
 }
 
 // Don't let uncaught exceptions crash the process.
 process.on("uncaughtException", (error) => {
-  logger.error(`Uncaught exception: ${error.message}`)
+  wrapper.logger.error(`Uncaught exception: ${error.message}`)
   if (typeof error.stack !== "undefined") {
-    logger.error(error.stack)
+    wrapper.logger.error(error.stack)
   }
 })