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-rw-r--r--src/server/Session/session.ts722
1 files changed, 455 insertions, 267 deletions
diff --git a/src/server/Session/session.ts b/src/server/Session/session.ts
index 2a483fbab..936357364 100644
--- a/src/server/Session/session.ts
+++ b/src/server/Session/session.ts
@@ -1,5 +1,5 @@
-import { red, cyan, green, yellow, magenta, blue } from "colors";
-import { on, fork, setupMaster, Worker } from "cluster";
+import { red, cyan, green, yellow, magenta, blue, white } from "colors";
+import { on, fork, setupMaster, Worker, isMaster, isWorker } from "cluster";
import { get } from "request-promise";
import { Utils } from "../../Utils";
import Repl, { ReplAction } from "../repl";
@@ -8,18 +8,64 @@ import { validate, ValidationError } from "jsonschema";
import { configurationSchema } from "./session_config_schema";
/**
- * This namespace relies on NodeJS's cluster module, which allows a parent (master) process to share
- * code with its children (workers). A simple `isMaster` flag indicates who is trying to access
- * the code, and thus determines the functionality that actually gets invoked (checked by the caller, not internally).
- *
- * Think of the master thread as a factory, and the workers as the helpers that actually run the server.
- *
- * So, when we run `npm start`, given the appropriate check, initializeMaster() is called in the parent process
- * This will spawn off its own child process (by default, mirrors the execution path of its parent),
- * in which initializeWorker() is invoked.
- */
+ * This namespace relies on NodeJS's cluster module, which allows a parent (master) process to share
+ * code with its children (workers). A simple `isMaster` flag indicates who is trying to access
+ * the code, and thus determines the functionality that actually gets invoked (checked by the caller, not internally).
+ *
+ * Think of the master thread as a factory, and the workers as the helpers that actually run the server.
+ *
+ * So, when we run `npm start`, given the appropriate check, initializeMaster() is called in the parent process
+ * This will spawn off its own child process (by default, mirrors the execution path of its parent),
+ * in which initializeWorker() is invoked.
+ */
export namespace Session {
+ export abstract class AppliedSessionAgent {
+
+ // the following two methods allow the developer to create a custom
+ // session and use the built in customization options for each thread
+ protected abstract async launchMonitor(): Promise<Session.Monitor>;
+ protected abstract async launchServerWorker(): Promise<Session.ServerWorker>;
+
+ private launched = false;
+
+ public killSession(graceful = true) {
+ const target = isMaster ? this.sessionMonitor : this.serverWorker;
+ target.killSession(graceful);
+ }
+
+
+ private sessionMonitorRef: Session.Monitor | undefined;
+ public get sessionMonitor(): Session.Monitor {
+ if (!isMaster) {
+ throw new Error("Cannot access the session monitor directly from the server worker thread");
+ }
+ return this.sessionMonitorRef!;
+ }
+
+ private serverWorkerRef: Session.ServerWorker | undefined;
+ public get serverWorker(): Session.ServerWorker {
+ if (isMaster) {
+ throw new Error("Cannot access the server worker directly from the session monitor thread");
+ }
+ return this.serverWorkerRef!;
+ }
+
+ public async launch(): Promise<void> {
+ if (!this.launched) {
+ this.launched = true;
+ if (isMaster) {
+ this.sessionMonitorRef = await this.launchMonitor();
+ } else {
+ this.serverWorkerRef = await this.launchServerWorker();
+ }
+ } else {
+ throw new Error("Cannot launch a session thread more than once per process.");
+ }
+ }
+
+ }
+
interface Configuration {
showServerOutput: boolean;
masterIdentifier: string;
@@ -38,344 +84,486 @@ export namespace Session {
ports: { server: 3000 },
pollingRoute: "/",
pollingIntervalSeconds: 30,
- pollingFailureTolerance: 1
+ pollingFailureTolerance: 0
};
- interface MasterExtensions {
- addReplCommand: (basename: string, argPatterns: (RegExp | string)[], action: ReplAction) => void;
- addChildMessageHandler: (message: string, handler: ActionHandler) => void;
- }
+ export type ExitHandler = (reason: Error | null) => void | Promise<void>;
- export interface NotifierHooks {
- key?: (key: string, masterLog: (...optionalParams: any[]) => void) => boolean | Promise<boolean>;
- crash?: (error: Error, masterLog: (...optionalParams: any[]) => void) => boolean | Promise<boolean>;
- }
+ export namespace Monitor {
- export interface SessionAction {
- message: string;
- args: any;
- }
+ export interface NotifierHooks {
+ key?: (key: string) => (boolean | Promise<boolean>);
+ crash?: (error: Error) => (boolean | Promise<boolean>);
+ }
- export interface SessionHooks {
- masterLog: (...optionalParams: any[]) => void;
- killSession: (graceful?: boolean) => never;
- restartServer: () => void;
- }
+ export interface Action {
+ message: string;
+ args: any;
+ }
+
+ export type ServerMessageHandler = (action: Action) => void | Promise<void>;
- export type ExitHandler = (error: Error) => void | Promise<void>;
- export type ActionHandler = (action: SessionAction, hooks: SessionHooks) => void | Promise<void>;
- export interface EmailTemplate {
- subject: string;
- body: string;
}
- function loadAndValidateConfiguration(): Configuration {
- try {
- console.log(timestamp(), cyan("validating configuration..."));
- const configuration: Configuration = JSON.parse(readFileSync('./session.config.json', 'utf8'));
- const options = {
- throwError: true,
- allowUnknownAttributes: false
- };
- // ensure all necessary and no excess information is specified by the configuration file
- validate(configuration, configurationSchema, options);
- let formatMaster = true;
- let formatWorker = true;
- Object.keys(defaultConfiguration).forEach(property => {
- if (!configuration[property]) {
- if (property === "masterIdentifier") {
- formatMaster = false;
- } else if (property === "workerIdentifier") {
- formatWorker = false;
- }
- configuration[property] = defaultConfiguration[property];
- }
- });
- if (formatMaster) {
- configuration.masterIdentifier = yellow(configuration.masterIdentifier + ":");
- }
- if (formatWorker) {
- configuration.workerIdentifier = magenta(configuration.workerIdentifier + ":");
+ /**
+ * Validates and reads the configuration file, accordingly builds a child process factory
+ * and spawns off an initial process that will respawn as predecessors die.
+ */
+ export class Monitor {
+
+ private static count = 0;
+ private exitHandlers: ExitHandler[] = [];
+ private readonly notifiers: Monitor.NotifierHooks | undefined;
+ private readonly configuration: Configuration;
+ private onMessage: { [message: string]: Monitor.ServerMessageHandler[] | undefined } = {};
+ private activeWorker: Worker | undefined;
+ private key: string | undefined;
+ private repl: Repl;
+
+ public static Create(notifiers?: Monitor.NotifierHooks) {
+ if (isWorker) {
+ console.error(red("Monitor must be on the master process."));
+ process.exit(1);
+ } else if (++Monitor.count > 1) {
+ console.error(("Cannot create more than one monitor."));
+ process.exit(1);
+ } else {
+ return new Monitor(notifiers);
}
- return configuration;
- } catch (error) {
- if (error instanceof ValidationError) {
- console.log(red("\nSession configuration failed."));
- console.log("The given session.config.json configuration file is invalid.");
- console.log(`${error.instance}: ${error.stack}`);
- process.exit(0);
- } else if (error.code === "ENOENT" && error.path === "./session.config.json") {
- console.log(cyan("Loading default session parameters..."));
- console.log("Consider including a session.config.json configuration file in your project root for customization.");
- return defaultConfiguration;
+ }
+
+ /**
+ * Kill this session and its active child
+ * server process, either gracefully (may wait
+ * indefinitely, but at least allows active networking
+ * requests to complete) or immediately.
+ */
+ public killSession = async (graceful = true) => {
+ this.log(cyan(`exiting session ${graceful ? "clean" : "immediate"}ly`));
+ await this.executeExitHandlers(null);
+ this.tryKillActiveWorker(graceful);
+ process.exit(0);
+ }
+
+ /**
+ * Execute the list of functions registered to be called
+ * whenever the process exits.
+ */
+ public addExitHandler = (handler: ExitHandler) => this.exitHandlers.push(handler);
+
+ /**
+ * Extend the default repl by adding in custom commands
+ * that can invoke application logic external to this module
+ */
+ public addReplCommand = (basename: string, argPatterns: (RegExp | string)[], action: ReplAction) => {
+ this.repl.registerCommand(basename, argPatterns, action);
+ }
+
+ /**
+ * Add a listener at this message. When the monitor process
+ * receives a message, it will invoke all registered functions.
+ */
+ public addServerMessageListener = (message: string, handler: Monitor.ServerMessageHandler) => {
+ const handlers = this.onMessage[message];
+ if (handlers) {
+ handlers.push(handler);
} else {
- console.log(red("\nSession configuration failed."));
- console.log("The following unknown error occurred during configuration.");
- console.log(error.stack);
- process.exit(0);
+ this.onMessage[message] = [handler];
}
}
- }
- function timestamp() {
- return blue(`[${new Date().toUTCString()}]`);
- }
+ /**
+ * Unregister a given listener at this message.
+ */
+ public removeServerMessageListener = (message: string, handler: Monitor.ServerMessageHandler) => {
+ const handlers = this.onMessage[message];
+ if (handlers) {
+ const index = handlers.indexOf(handler);
+ if (index > -1) {
+ handlers.splice(index, 1);
+ }
+ }
+ }
- /**
- * Validates and reads the configuration file, accordingly builds a child process factory
- * and spawns off an initial process that will respawn as predecessors die.
- */
- export async function initializeMonitorThread(notifiers?: NotifierHooks): Promise<MasterExtensions> {
- console.log(timestamp(), cyan("initializing session..."));
- let activeWorker: Worker;
- const childMessageHandlers: { [message: string]: ActionHandler } = {};
-
- // read in configuration .json file only once, in the master thread
- // pass down any variables the pertinent to the child processes as environment variables
- const configuration = loadAndValidateConfiguration();
- const {
- masterIdentifier,
- workerIdentifier,
- ports,
- pollingRoute,
- showServerOutput,
- pollingFailureTolerance
- } = configuration;
- let { pollingIntervalSeconds } = configuration;
-
- const masterLog = (...optionalParams: any[]) => console.log(timestamp(), masterIdentifier, ...optionalParams);
-
- // this sends a pseudorandomly generated guid to the configuration's recipients, allowing them alone
- // to kill the server via the /kill/:key route
- let key: string | undefined;
- if (notifiers && notifiers.key) {
- key = Utils.GenerateGuid();
- const success = await notifiers.key(key, masterLog);
- const statement = success ? green("distributed session key to recipients") : red("distribution of session key failed");
- masterLog(statement);
+ /**
+ * Unregister all listeners at this message.
+ */
+ public clearServerMessageListeners = (message: string) => this.onMessage[message] = undefined;
+
+ private constructor(notifiers?: Monitor.NotifierHooks) {
+ this.notifiers = notifiers;
+
+ console.log(this.timestamp(), cyan("initializing session..."));
+
+ this.configuration = this.loadAndValidateConfiguration();
+ this.initializeSessionKey();
+ // determines whether or not we see the compilation / initialization / runtime output of each child server process
+ setupMaster({ silent: !this.configuration.showServerOutput });
+
+ // handle exceptions in the master thread - there shouldn't be many of these
+ // the IPC (inter process communication) channel closed exception can't seem
+ // to be caught in a try catch, and is inconsequential, so it is ignored
+ process.on("uncaughtException", ({ message, stack }): void => {
+ if (message !== "Channel closed") {
+ this.log(red(message));
+ if (stack) {
+ this.log(`uncaught exception\n${red(stack)}`);
+ }
+ }
+ });
+
+ // a helpful cluster event called on the master thread each time a child process exits
+ on("exit", ({ process: { pid } }, code, signal) => {
+ const prompt = `server worker with process id ${pid} has exited with code ${code}${signal === null ? "" : `, having encountered signal ${signal}`}.`;
+ this.log(cyan(prompt));
+ // to make this a robust, continuous session, every time a child process dies, we immediately spawn a new one
+ this.spawn();
+ });
+
+ this.repl = this.initializeRepl();
+ this.spawn();
+ }
+
+
+ /**
+ * Generates a blue UTC string associated with the time
+ * of invocation.
+ */
+ private timestamp = () => blue(`[${new Date().toUTCString()}]`);
+
+ /**
+ * A formatted, identified and timestamped log in color
+ */
+ public log = (...optionalParams: any[]) => {
+ console.log(this.timestamp(), this.configuration.masterIdentifier, ...optionalParams);
+ }
+
+ /**
+ * If the caller has indicated an interest
+ * in being notified of this feature, creates
+ * a GUID for this session that can, for example,
+ * be used as authentication for killing the server
+ * (checked externally).
+ */
+ private initializeSessionKey = async (): Promise<void> => {
+ if (this.notifiers?.key) {
+ this.key = Utils.GenerateGuid();
+ const success = await this.notifiers.key(this.key);
+ const statement = success ? green("distributed session key to recipients") : red("distribution of session key failed");
+ this.log(statement);
+ }
+ }
+
+ /**
+ * Builds the repl that allows the following commands to be typed into stdin of the master thread.
+ */
+ private initializeRepl = (): Repl => {
+ const repl = new Repl({ identifier: () => `${this.timestamp()} ${this.configuration.masterIdentifier}` });
+ const boolean = /true|false/;
+ const number = /\d+/;
+ const letters = /[a-zA-Z]+/;
+ repl.registerCommand("exit", [/clean|force/], args => this.killSession(args[0] === "clean"));
+ repl.registerCommand("restart", [/clean|force/], args => this.tryKillActiveWorker(args[0] === "clean"));
+ repl.registerCommand("set", [letters, "port", number, boolean], args => this.setPort(args[0], Number(args[2]), args[3] === "true"));
+ repl.registerCommand("set", [/polling/, number, boolean], args => {
+ const newPollingIntervalSeconds = Math.floor(Number(args[2]));
+ if (newPollingIntervalSeconds < 0) {
+ this.log(red("the polling interval must be a non-negative integer"));
+ } else {
+ if (newPollingIntervalSeconds !== this.configuration.pollingIntervalSeconds) {
+ this.configuration.pollingIntervalSeconds = newPollingIntervalSeconds;
+ if (args[3] === "true") {
+ this.activeWorker?.send({ newPollingIntervalSeconds });
+ }
+ }
+ }
+ });
+ return repl;
}
- // handle exceptions in the master thread - there shouldn't be many of these
- // the IPC (inter process communication) channel closed exception can't seem
- // to be caught in a try catch, and is inconsequential, so it is ignored
- process.on("uncaughtException", ({ message, stack }) => {
- if (message !== "Channel closed") {
- masterLog(red(message));
- if (stack) {
- masterLog(`uncaught exception\n${red(stack)}`);
+ /**
+ * Reads in configuration .json file only once, in the master thread
+ * and pass down any variables the pertinent to the child processes as environment variables.
+ */
+ private loadAndValidateConfiguration = (): Configuration => {
+ try {
+ console.log(this.timestamp(), cyan("validating configuration..."));
+ const configuration: Configuration = JSON.parse(readFileSync('./session.config.json', 'utf8'));
+ const options = {
+ throwError: true,
+ allowUnknownAttributes: false
+ };
+ // ensure all necessary and no excess information is specified by the configuration file
+ validate(configuration, configurationSchema, options);
+ let formatMaster = true;
+ let formatWorker = true;
+ Object.keys(defaultConfiguration).forEach(property => {
+ if (!configuration[property]) {
+ if (property === "masterIdentifier") {
+ formatMaster = false;
+ } else if (property === "workerIdentifier") {
+ formatWorker = false;
+ }
+ configuration[property] = defaultConfiguration[property];
+ }
+ });
+ if (formatMaster) {
+ configuration.masterIdentifier = yellow(configuration.masterIdentifier + ":");
+ }
+ if (formatWorker) {
+ configuration.workerIdentifier = magenta(configuration.workerIdentifier + ":");
+ }
+ return configuration;
+ } catch (error) {
+ if (error instanceof ValidationError) {
+ console.log(red("\nSession configuration failed."));
+ console.log("The given session.config.json configuration file is invalid.");
+ console.log(`${error.instance}: ${error.stack}`);
+ process.exit(0);
+ } else if (error.code === "ENOENT" && error.path === "./session.config.json") {
+ console.log(cyan("Loading default session parameters..."));
+ console.log("Consider including a session.config.json configuration file in your project root for customization.");
+ return defaultConfiguration;
+ } else {
+ console.log(red("\nSession configuration failed."));
+ console.log("The following unknown error occurred during configuration.");
+ console.log(error.stack);
+ process.exit(0);
}
}
- });
+ }
- // determines whether or not we see the compilation / initialization / runtime output of each child server process
- setupMaster({ silent: !showServerOutput });
- // attempts to kills the active worker ungracefully, unless otherwise specified
- const tryKillActiveWorker = (graceful = false): boolean => {
- if (activeWorker && !activeWorker.isDead()) {
+ private executeExitHandlers = async (reason: Error | null) => Promise.all(this.exitHandlers.map(handler => handler(reason)));
+
+ /**
+ * Attempts to kill the active worker gracefully, unless otherwise specified.
+ */
+ private tryKillActiveWorker = (graceful = true): boolean => {
+ if (!this.activeWorker?.isDead()) {
if (graceful) {
- activeWorker.kill();
+ this.activeWorker?.send({ manualExit: true });
} else {
- activeWorker.process.kill();
+ this.activeWorker?.process.kill();
}
return true;
}
return false;
- };
-
- const restartServer = () => {
- // indicate to the worker that we are 'expecting' this restart
- activeWorker.send({ setResponsiveness: false });
- tryKillActiveWorker(true);
- };
-
- const killSession = (graceful = true) => {
- masterLog(cyan(`exiting session ${graceful ? "clean" : "immediate"}ly`));
- tryKillActiveWorker(graceful);
- process.exit(0);
- };
+ }
- const setPort = (port: string, value: number, immediateRestart: boolean) => {
+ /**
+ * Allows the caller to set the port at which the target (be it the server,
+ * the websocket, some other custom port) is listening. If an immediate restart
+ * is specified, this monitor will kill the active child and re-launch the server
+ * at the port. Otherwise, the updated port won't be used until / unless the child
+ * dies on its own and triggers a restart.
+ */
+ private setPort = (port: "server" | "socket" | string, value: number, immediateRestart: boolean): void => {
if (value > 1023 && value < 65536) {
- ports[port] = value;
+ this.configuration.ports[port] = value;
if (immediateRestart) {
- restartServer();
+ this.tryKillActiveWorker();
}
} else {
- masterLog(red(`${port} is an invalid port number`));
+ this.log(red(`${port} is an invalid port number`));
}
- };
+ }
- // kills the current active worker and proceeds to spawn a new worker,
- // feeding in configuration information as environment variables
- const spawn = (): void => {
- tryKillActiveWorker();
- activeWorker = fork({
+ /**
+ * Kills the current active worker and proceeds to spawn a new worker,
+ * feeding in configuration information as environment variables.
+ */
+ private spawn = (): void => {
+ const {
+ pollingRoute,
+ pollingFailureTolerance,
+ pollingIntervalSeconds,
+ ports
+ } = this.configuration;
+ this.tryKillActiveWorker();
+ this.activeWorker = fork({
pollingRoute,
pollingFailureTolerance,
serverPort: ports.server,
socketPort: ports.socket,
pollingIntervalSeconds,
- session_key: key
+ session_key: this.key
});
- masterLog(cyan(`spawned new server worker with process id ${activeWorker.process.pid}`));
+ this.log(cyan(`spawned new server worker with process id ${this.activeWorker.process.pid}`));
// an IPC message handler that executes actions on the master thread when prompted by the active worker
- activeWorker.on("message", async ({ lifecycle, action }) => {
+ this.activeWorker.on("message", async ({ lifecycle, action }) => {
if (action) {
- const { message, args } = action as SessionAction;
- console.log(timestamp(), `${workerIdentifier} action requested (${cyan(message)})`);
+ const { message, args } = action as Monitor.Action;
+ console.log(this.timestamp(), `${this.configuration.workerIdentifier} action requested (${cyan(message)})`);
switch (message) {
case "kill":
- masterLog(red("an authorized user has manually ended the server session"));
- killSession();
+ this.log(red("an authorized user has manually ended the server session"));
+ this.killSession(args.graceful);
+ break;
case "notify_crash":
- if (notifiers && notifiers.crash) {
+ if (this.notifiers?.crash) {
const { error } = args;
- const success = await notifiers.crash(error, masterLog);
+ const success = await this.notifiers.crash(error);
const statement = success ? green("distributed crash notification to recipients") : red("distribution of crash notification failed");
- masterLog(statement);
+ this.log(statement);
}
+ break;
case "set_port":
const { port, value, immediateRestart } = args;
- setPort(port, value, immediateRestart);
- default:
- const handler = childMessageHandlers[message];
- if (handler) {
- handler({ message, args }, { restartServer, killSession, masterLog });
- }
+ this.setPort(port, value, immediateRestart);
+ break;
+ }
+ const handlers = this.onMessage[message];
+ if (handlers) {
+ handlers.forEach(handler => handler({ message, args }));
}
} else if (lifecycle) {
- console.log(timestamp(), `${workerIdentifier} lifecycle phase (${lifecycle})`);
+ console.log(this.timestamp(), `${this.configuration.workerIdentifier} lifecycle phase (${lifecycle})`);
}
});
- };
-
- // a helpful cluster event called on the master thread each time a child process exits
- on("exit", ({ process: { pid } }, code, signal) => {
- const prompt = `server worker with process id ${pid} has exited with code ${code}${signal === null ? "" : `, having encountered signal ${signal}`}.`;
- masterLog(cyan(prompt));
- // to make this a robust, continuous session, every time a child process dies, we immediately spawn a new one
- spawn();
- });
-
- // builds the repl that allows the following commands to be typed into stdin of the master thread
- const repl = new Repl({ identifier: () => `${timestamp()} ${masterIdentifier}` });
- const boolean = /true|false/;
- const number = /\d+/;
- const letters = /[a-zA-Z]+/;
- repl.registerCommand("exit", [/clean|force/], args => killSession(args[0] === "clean"));
- repl.registerCommand("restart", [], restartServer);
- repl.registerCommand("set", [letters, "port", number, boolean], args => setPort(args[0], Number(args[2]), args[3] === "true"));
- repl.registerCommand("set", [/polling/, number, boolean], args => {
- const newPollingIntervalSeconds = Math.floor(Number(args[2]));
- if (newPollingIntervalSeconds < 0) {
- masterLog(red("the polling interval must be a non-negative integer"));
- } else {
- if (newPollingIntervalSeconds !== pollingIntervalSeconds) {
- pollingIntervalSeconds = newPollingIntervalSeconds;
- if (args[3] === "true") {
- activeWorker.send({ newPollingIntervalSeconds });
- }
- }
- }
- });
- // finally, set things in motion by spawning off the first child (server) process
- spawn();
-
- // returned to allow the caller to add custom commands
- return {
- addReplCommand: repl.registerCommand,
- addChildMessageHandler: (message: string, handler: ActionHandler) => { childMessageHandlers[message] = handler; }
- };
+ }
+
}
/**
* Effectively, each worker repairs the connection to the server by reintroducing a consistent state
* if its predecessor has died. It itself also polls the server heartbeat, and exits with a notification
* email if the server encounters an uncaught exception or if the server cannot be reached.
- * @param work the function specifying the work to be done by each worker thread
*/
- export async function initializeWorkerThread(work: Function): Promise<(handler: ExitHandler) => void> {
- let shouldServerBeResponsive = false;
- const exitHandlers: ExitHandler[] = [];
- let pollingFailureCount = 0;
+ export class ServerWorker {
+
+ private static count = 0;
+ private shouldServerBeResponsive = false;
+ private exitHandlers: ExitHandler[] = [];
+ private pollingFailureCount = 0;
+ private pollingIntervalSeconds: number;
+ private pollingFailureTolerance: number;
+ private pollTarget: string;
+ private serverPort: number;
+
+ public static Create(work: Function) {
+ if (isMaster) {
+ throw new Error("Worker must be launched on a worker process.");
+ } else if (++ServerWorker.count > 1 || isMaster) {
+ process.send?.({ action: { message: "kill", args: { graceful: false } } });
+ process.exit(1);
+ } else {
+ return new ServerWorker(work);
+ }
+ }
- const lifecycleNotification = (lifecycle: string) => process.send?.({ lifecycle });
+ /**
+ * Allows developers to invoke application specific logic
+ * by hooking into the exiting of the server process.
+ */
+ public addExitHandler = (handler: ExitHandler) => this.exitHandlers.push(handler);
+
+ /**
+ * Kill the session monitor (parent process) from this
+ * server worker (child process). This will also kill
+ * this process (child process).
+ */
+ public killSession = (graceful = true) => this.sendMonitorAction("kill", { graceful });
+
+ /**
+ * A convenience wrapper to tell the session monitor (parent process)
+ * to carry out the action with the specified message and arguments.
+ */
+ public sendMonitorAction = (message: string, args?: any) => process.send!({ action: { message, args } });
+
+ private constructor(work: Function) {
+ this.lifecycleNotification(green(`initializing process... (${white(`${process.execPath} ${process.execArgv.join(" ")}`)})`));
+
+ const { pollingRoute, serverPort, pollingIntervalSeconds, pollingFailureTolerance } = process.env;
+ this.serverPort = Number(serverPort);
+ this.pollingIntervalSeconds = Number(pollingIntervalSeconds);
+ this.pollingFailureTolerance = Number(pollingFailureTolerance);
+ this.pollTarget = `http://localhost:${serverPort}${pollingRoute}`;
+
+ this.configureProcess();
+ work();
+ this.pollServer();
+ }
- // notify master thread (which will log update in the console) of initialization via IPC
- lifecycleNotification(green("compiling and initializing..."));
+ /**
+ * Set up message and uncaught exception handlers for this
+ * server process.
+ */
+ private configureProcess = () => {
+ // updates the local values of variables to the those sent from master
+ process.on("message", async ({ newPollingIntervalSeconds, manualExit }) => {
+ if (newPollingIntervalSeconds !== undefined) {
+ this.pollingIntervalSeconds = newPollingIntervalSeconds;
+ }
+ if (manualExit !== undefined) {
+ await this.executeExitHandlers(null);
+ process.exit(0);
+ }
+ });
- // updates the local value of listening to the value sent from master
- process.on("message", ({ setResponsiveness, newPollingIntervalSeconds }) => {
- if (setResponsiveness) {
- shouldServerBeResponsive = setResponsiveness;
- }
- if (newPollingIntervalSeconds) {
- pollingIntervalSeconds = newPollingIntervalSeconds;
- }
- });
+ // one reason to exit, as the process might be in an inconsistent state after such an exception
+ process.on('uncaughtException', this.proactiveUnplannedExit);
+ }
- // called whenever the process has a reason to terminate, either through an uncaught exception
- // in the process (potentially inconsistent state) or the server cannot be reached
- const activeExit = async (error: Error): Promise<void> => {
- shouldServerBeResponsive = false;
+ /**
+ * Execute the list of functions registered to be called
+ * whenever the process exits.
+ */
+ private executeExitHandlers = async (reason: Error | null) => Promise.all(this.exitHandlers.map(handler => handler(reason)));
+
+ /**
+ * Notify master thread (which will log update in the console) of initialization via IPC.
+ */
+ private lifecycleNotification = (event: string) => process.send?.({ lifecycle: event });
+
+ /**
+ * Called whenever the process has a reason to terminate, either through an uncaught exception
+ * in the process (potentially inconsistent state) or the server cannot be reached.
+ */
+ private proactiveUnplannedExit = async (error: Error): Promise<void> => {
+ this.shouldServerBeResponsive = false;
// communicates via IPC to the master thread that it should dispatch a crash notification email
- process.send?.({
- action: {
- message: "notify_crash",
- args: { error }
- }
- });
- await Promise.all(exitHandlers.map(handler => handler(error)));
+ this.sendMonitorAction("notify_crash", { error });
+ await this.executeExitHandlers(error);
// notify master thread (which will log update in the console) of crash event via IPC
- lifecycleNotification(red(`crash event detected @ ${new Date().toUTCString()}`));
- lifecycleNotification(red(error.message));
+ this.lifecycleNotification(red(`crash event detected @ ${new Date().toUTCString()}`));
+ this.lifecycleNotification(red(error.message));
process.exit(1);
- };
-
- // one reason to exit, as the process might be in an inconsistent state after such an exception
- process.on('uncaughtException', activeExit);
-
- const { env } = process;
- const { pollingRoute, serverPort } = env;
- let pollingIntervalSeconds = Number(env.pollingIntervalSeconds);
- const pollingFailureTolerance = Number(env.pollingFailureTolerance);
- // this monitors the health of the server by submitting a get request to whatever port / route specified
- // by the configuration every n seconds, where n is also given by the configuration.
- const pollTarget = `http://localhost:${serverPort}${pollingRoute}`;
- const pollServer = async (): Promise<void> => {
+ }
+
+ /**
+ * This monitors the health of the server by submitting a get request to whatever port / route specified
+ * by the configuration every n seconds, where n is also given by the configuration.
+ */
+ private pollServer = async (): Promise<void> => {
await new Promise<void>(resolve => {
setTimeout(async () => {
try {
- await get(pollTarget);
- if (!shouldServerBeResponsive) {
- // notify master thread (which will log update in the console) via IPC that the server is up and running
- process.send?.({ lifecycle: green(`listening on ${serverPort}...`) });
+ await get(this.pollTarget);
+ if (!this.shouldServerBeResponsive) {
+ // notify monitor thread that the server is up and running
+ this.lifecycleNotification(green(`listening on ${this.serverPort}...`));
}
- shouldServerBeResponsive = true;
+ this.shouldServerBeResponsive = true;
resolve();
} catch (error) {
// if we expect the server to be unavailable, i.e. during compilation,
// the listening variable is false, activeExit will return early and the child
// process will continue
- if (shouldServerBeResponsive) {
- if (++pollingFailureCount > pollingFailureTolerance) {
- activeExit(error);
+ if (this.shouldServerBeResponsive) {
+ if (++this.pollingFailureCount > this.pollingFailureTolerance) {
+ this.proactiveUnplannedExit(error);
} else {
- lifecycleNotification(yellow(`the server has encountered ${pollingFailureCount} of ${pollingFailureTolerance} tolerable failures`));
+ this.lifecycleNotification(yellow(`the server has encountered ${this.pollingFailureCount} of ${this.pollingFailureTolerance} tolerable failures`));
}
}
}
- }, 1000 * pollingIntervalSeconds);
+ }, 1000 * this.pollingIntervalSeconds);
});
// controlled, asynchronous infinite recursion achieves a persistent poll that does not submit a new request until the previous has completed
- pollServer();
- };
-
- work();
- pollServer(); // begin polling
+ this.pollServer();
+ }
- return (handler: ExitHandler) => exitHandlers.push(handler);
}
} \ No newline at end of file
generated by cgit v1.2.3-70-g09d2 (git 2.46.0) at 2025-11-22 01:18:01 +0000