aboutsummaryrefslogtreecommitdiff
path: root/src/server/Session/session.ts
diff options
context:
space:
mode:
Diffstat (limited to 'src/server/Session/session.ts')
-rw-r--r--src/server/Session/session.ts867
1 files changed, 557 insertions, 310 deletions
diff --git a/src/server/Session/session.ts b/src/server/Session/session.ts
index a3e6c4e16..ec3d46ac1 100644
--- a/src/server/Session/session.ts
+++ b/src/server/Session/session.ts
@@ -1,439 +1,686 @@
-import { red, cyan, green, yellow, magenta, blue } from "colors";
-import { on, fork, setupMaster, Worker, isMaster } from "cluster";
+import { red, cyan, green, yellow, magenta, blue, white, Color, grey, gray, black } 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";
import { readFileSync } from "fs";
import { validate, ValidationError } from "jsonschema";
import { configurationSchema } from "./session_config_schema";
+import { exec, ExecOptions } from "child_process";
/**
- * 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 {
+ type ColorLabel = "yellow" | "red" | "cyan" | "green" | "blue" | "magenta" | "grey" | "gray" | "white" | "black";
+ const colorMapping: Map<ColorLabel, Color> = new Map([
+ ["yellow", yellow],
+ ["red", red],
+ ["cyan", cyan],
+ ["green", green],
+ ["blue", blue],
+ ["magenta", magenta],
+ ["grey", grey],
+ ["gray", gray],
+ ["white", white],
+ ["black", black]
+ ]);
+
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;
- protected sessionMonitorRef: Session.Monitor | undefined;
+ public killSession = (reason: string, graceful = true, errorCode = 0) => {
+ const target = isMaster ? this.sessionMonitor : this.serverWorker;
+ target.killSession(reason, graceful, errorCode);
+ }
+
+ 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");
+ this.serverWorker.sendMonitorAction("kill", {
+ graceful: false,
+ reason: "Cannot access the session monitor directly from the server worker thread.",
+ errorCode: 1
+ });
+ throw new Error();
}
return this.sessionMonitorRef!;
}
- public set sessionMonitor(monitor: Session.Monitor) {
- if (!isMaster) {
- throw new Error("Cannot set the session monitor directly from the server worker thread");
- }
- this.sessionMonitorRef = monitor;
- }
- protected serverWorkerRef: Session.ServerWorker | undefined;
+ 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 set serverWorker(worker: Session.ServerWorker) {
- if (isMaster) {
- throw new Error("Cannot set the server worker directly from the session monitor thread");
- }
- this.serverWorkerRef = worker;
- }
public async launch(): Promise<void> {
if (!this.launched) {
this.launched = true;
- await this.launchImplementation();
+ 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.");
}
}
- protected abstract async launchImplementation(): Promise<void>;
+ }
+
+ interface Identifier {
+ text: string;
+ color: ColorLabel;
+ }
+ interface Identifiers {
+ master: Identifier;
+ worker: Identifier;
+ exec: Identifier;
}
interface Configuration {
showServerOutput: boolean;
- masterIdentifier: string;
- workerIdentifier: string;
+ identifiers: Identifiers;
ports: { [description: string]: number };
- pollingRoute: string;
- pollingIntervalSeconds: number;
- pollingFailureTolerance: number;
- [key: string]: any;
+ polling: {
+ route: string;
+ intervalSeconds: number;
+ failureTolerance: number;
+ };
}
- const defaultConfiguration: Configuration = {
+ const defaultConfig: Configuration = {
showServerOutput: false,
- masterIdentifier: yellow("__monitor__:"),
- workerIdentifier: magenta("__server__:"),
+ identifiers: {
+ master: {
+ text: "__monitor__",
+ color: "yellow"
+ },
+ worker: {
+ text: "__server__",
+ color: "magenta"
+ },
+ exec: {
+ text: "__exec__",
+ color: "green"
+ }
+ },
ports: { server: 3000 },
- pollingRoute: "/",
- pollingIntervalSeconds: 30,
- pollingFailureTolerance: 1
+ polling: {
+ route: "/",
+ intervalSeconds: 30,
+ failureTolerance: 0
+ }
};
- export interface Monitor {
- log: (...optionalParams: any[]) => void;
- restartServer: () => void;
- setPort: (port: "server" | "socket" | string, value: number, immediateRestart: boolean) => void;
- killSession: (graceful?: boolean) => never;
- addReplCommand: (basename: string, argPatterns: (RegExp | string)[], action: ReplAction) => void;
- addChildMessageHandler: (message: string, handler: ActionHandler) => void;
- }
+ export type ExitHandler = (reason: Error | boolean) => void | Promise<void>;
- export interface ServerWorker {
- killSession: () => void;
- addExitHandler: (handler: ExitHandler) => void;
- }
+ export namespace Monitor {
- export interface MonitorNotifierHooks {
- key?: (key: string, masterLog: (...optionalParams: any[]) => void) => boolean | Promise<boolean>;
- crash?: (error: Error, masterLog: (...optionalParams: any[]) => void) => boolean | Promise<boolean>;
- }
+ export interface NotifierHooks {
+ key?: (key: string) => (boolean | Promise<boolean>);
+ crash?: (error: Error) => (boolean | Promise<boolean>);
+ }
- export interface SessionAction {
- message: string;
- args: any;
- }
+ export interface Action {
+ message: string;
+ args: any;
+ }
+
+ export type ServerMessageHandler = (action: Action) => void | Promise<void>;
- export type ExitHandler = (reason: Error | null) => void | Promise<void>;
- export type ActionHandler = (action: SessionAction) => 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;
+ /**
+ * 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 config: 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) {
+ process.send?.({
+ action: {
+ message: "kill",
+ args: {
+ reason: "cannot create a monitor on the worker process.",
+ graceful: false,
+ errorCode: 1
+ }
}
- configuration[property] = defaultConfiguration[property];
- }
+ });
+ process.exit(1);
+ } else if (++Monitor.count > 1) {
+ console.error(red("cannot create more than one monitor."));
+ process.exit(1);
+ } else {
+ return new Monitor(notifiers);
+ }
+ }
+
+ /**
+ * 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 (reason: string, graceful = true, errorCode = 0) => {
+ this.mainLog(cyan(`exiting session ${graceful ? "clean" : "immediate"}ly`));
+ this.mainLog(`session exit reason: ${(red(reason))}`);
+ await this.executeExitHandlers(true);
+ this.killActiveWorker(graceful, true);
+ process.exit(errorCode);
+ }
+
+ /**
+ * 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);
+ }
+
+ public exec = (command: string, options?: ExecOptions) => {
+ return new Promise<void>(resolve => {
+ exec(command, { ...options, encoding: "utf8" }, (error, stdout, stderr) => {
+ if (error) {
+ this.execLog(red(`unable to execute ${white(command)}`));
+ error.message.split("\n").forEach(line => line.length && this.execLog(red(`(error) ${line}`)));
+ } else {
+ let outLines: string[], errorLines: string[];
+ if ((outLines = stdout.split("\n").filter(line => line.length)).length) {
+ outLines.forEach(line => line.length && this.execLog(cyan(`(stdout) ${line}`)));
+ }
+ if ((errorLines = stderr.split("\n").filter(line => line.length)).length) {
+ errorLines.forEach(line => line.length && this.execLog(yellow(`(stderr) ${line}`)));
+ }
+ }
+ resolve();
+ });
});
- if (formatMaster) {
- configuration.masterIdentifier = yellow(configuration.masterIdentifier + ":");
+ }
+
+ /**
+ * Add a listener at this message. When the monitor process
+ * receives a message, it will invoke all registered functions.
+ */
+ public addServerMessageListener = (message: string, handler: Monitor.ServerMessageHandler) => {
+ const handlers = this.onMessage[message];
+ if (handlers) {
+ handlers.push(handler);
+ } else {
+ this.onMessage[message] = [handler];
}
- if (formatWorker) {
- configuration.workerIdentifier = magenta(configuration.workerIdentifier + ":");
+ }
+
+ /**
+ * Unregister a given listener at this message.
+ */
+ public removeServerMessageListener = (message: string, handler: Monitor.ServerMessageHandler) => {
+ const handlers = this.onMessage[message];
+ if (handlers) {
+ const index = handlers.indexOf(handler);
+ if (index > -1) {
+ handlers.splice(index, 1);
+ }
}
- return configuration;
- } catch (error) {
- if (error instanceof ValidationError) {
- console.log(red("\nSession configuration failed."));
- console.log("The given session.config.json configuration file is invalid.");
- console.log(`${error.instance}: ${error.stack}`);
- process.exit(0);
- } else if (error.code === "ENOENT" && error.path === "./session.config.json") {
- console.log(cyan("Loading default session parameters..."));
- console.log("Consider including a session.config.json configuration file in your project root for customization.");
- return defaultConfiguration;
- } else {
- console.log(red("\nSession configuration failed."));
- console.log("The following unknown error occurred during configuration.");
- console.log(error.stack);
- process.exit(0);
+ }
+
+ /**
+ * Unregister all listeners at this message.
+ */
+ public clearServerMessageListeners = (message: string) => this.onMessage[message] = undefined;
+
+ private constructor(notifiers?: Monitor.NotifierHooks) {
+ this.notifiers = notifiers;
+
+ console.log(this.timestamp(), cyan("initializing session..."));
+
+ this.config = this.loadAndValidateConfiguration();
+
+ this.initializeSessionKey();
+ // determines whether or not we see the compilation / initialization / runtime output of each child server process
+ const output = this.config.showServerOutput ? "inherit" : "ignore";
+ setupMaster({ stdio: ["ignore", output, output, "ipc"] });
+
+ // handle exceptions in the master thread - there shouldn't be many of these
+ // the IPC (inter process communication) channel closed exception can't seem
+ // to be caught in a try catch, and is inconsequential, so it is ignored
+ process.on("uncaughtException", ({ message, stack }): void => {
+ if (message !== "Channel closed") {
+ this.mainLog(red(message));
+ if (stack) {
+ this.mainLog(`uncaught exception\n${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 ${signal}`}.`;
+ this.mainLog(cyan(prompt));
+ // to make this a robust, continuous session, every time a child process dies, we immediately spawn a new one
+ this.spawn();
+ });
+
+ this.repl = this.initializeRepl();
+ this.spawn();
+ }
+
+ /**
+ * Generates a blue UTC string associated with the time
+ * of invocation.
+ */
+ private timestamp = () => blue(`[${new Date().toUTCString()}]`);
+
+ /**
+ * A formatted, identified and timestamped log in color
+ */
+ public mainLog = (...optionalParams: any[]) => {
+ console.log(this.timestamp(), this.config.identifiers.master.text, ...optionalParams);
+ }
+
+ /**
+ * A formatted, identified and timestamped log in color for non-
+ */
+ private execLog = (...optionalParams: any[]) => {
+ console.log(this.timestamp(), this.config.identifiers.exec.text, ...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.mainLog(statement);
}
}
- }
- function timestamp() {
- return blue(`[${new Date().toUTCString()}]`);
- }
+ /**
+ * At any arbitrary layer of nesting within the configuration objects, any single value that
+ * is not specified by the configuration is given the default counterpart. If, within an object,
+ * one peer is given by configuration and two are not, the one is preserved while the two are given
+ * the default value.
+ * @returns the composition of all of the assigned objects, much like Object.assign(), but with more
+ * granularity in the overwriting of nested objects
+ */
+ private preciseAssign = (target: any, ...sources: any[]): any => {
+ for (const source of sources) {
+ this.preciseAssignHelper(target, source);
+ }
+ return target;
+ }
- /**
- * 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?: MonitorNotifierHooks): Promise<Monitor> {
- 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 log = (...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, log);
- const statement = success ? green("distributed session key to recipients") : red("distribution of session key failed");
- log(statement);
+ private preciseAssignHelper = (target: any, source: any) => {
+ Array.from(new Set([...Object.keys(target), ...Object.keys(source)])).map(property => {
+ let targetValue: any, sourceValue: any;
+ if (sourceValue = source[property]) {
+ if (typeof sourceValue === "object" && typeof (targetValue = target[property]) === "object") {
+ this.preciseAssignHelper(targetValue, sourceValue);
+ } else {
+ target[property] = sourceValue;
+ }
+ }
+ });
}
- // 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") {
- log(red(message));
- if (stack) {
- log(`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 => {
+ let config: Configuration;
+ try {
+ console.log(this.timestamp(), cyan("validating configuration..."));
+ config = 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(config, configurationSchema, options);
+ config = this.preciseAssign({}, defaultConfig, config);
+ } 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}: ${error.stack}`);
+ process.exit(0);
+ } else if (error.code === "ENOENT" && error.path === "./session.config.json") {
+ console.log(cyan("Loading default session parameters..."));
+ console.log("Consider including a session.config.json configuration file in your project root for customization.");
+ config = this.preciseAssign({}, defaultConfig);
+ } else {
+ console.log(red("\nSession configuration failed."));
+ console.log("The following unknown error occurred during configuration.");
+ console.log(error.stack);
+ process.exit(0);
}
+ } finally {
+ const { identifiers } = config!;
+ Object.keys(identifiers).forEach(key => {
+ const resolved = key as keyof Identifiers;
+ const { text, color } = identifiers[resolved];
+ identifiers[resolved].text = (colorMapping.get(color) || white)(`${text}:`);
+ });
+ return config!;
}
- });
+ }
- // determines whether or not we see the compilation / initialization / runtime output of each child server process
- setupMaster({ silent: !showServerOutput });
+ /**
+ * 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.config.identifiers.master.text}` });
+ const boolean = /true|false/;
+ const number = /\d+/;
+ const letters = /[a-zA-Z]+/;
+ repl.registerCommand("exit", [/clean|force/], args => this.killSession("manual exit requested by repl", args[0] === "clean", 0));
+ repl.registerCommand("restart", [/clean|force/], args => this.killActiveWorker(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.mainLog(red("the polling interval must be a non-negative integer"));
+ } else {
+ if (newPollingIntervalSeconds !== this.config.polling.intervalSeconds) {
+ this.config.polling.intervalSeconds = newPollingIntervalSeconds;
+ if (args[3] === "true") {
+ this.activeWorker?.send({ newPollingIntervalSeconds });
+ }
+ }
+ }
+ });
+ return repl;
+ }
+
+ private executeExitHandlers = async (reason: Error | boolean) => Promise.all(this.exitHandlers.map(handler => handler(reason)));
- // attempts to kills the active worker ungracefully, unless otherwise specified
- const tryKillActiveWorker = (graceful = false): boolean => {
- if (activeWorker && !activeWorker.isDead()) {
+ /**
+ * Attempts to kill the active worker gracefully, unless otherwise specified.
+ */
+ private killActiveWorker = (graceful = true, isSessionEnd = false): void => {
+ if (this.activeWorker && !this.activeWorker.isDead()) {
if (graceful) {
- activeWorker.kill();
+ this.activeWorker.send({ manualExit: { isSessionEnd } });
} else {
- activeWorker.process.kill();
+ this.activeWorker.process.kill();
}
- return true;
}
- return false;
- };
-
- const restartServer = (): void => {
- // indicate to the worker that we are 'expecting' this restart
- activeWorker.send({ setResponsiveness: false });
- tryKillActiveWorker(true);
- };
-
- const killSession = (graceful = true): never => {
- log(cyan(`exiting session ${graceful ? "clean" : "immediate"}ly`));
- tryKillActiveWorker(graceful);
- process.exit(0);
- };
+ }
- const setPort = (port: "server" | "socket" | string, value: number, immediateRestart: boolean): void => {
+ /**
+ * Allows the caller to set the port at which the target (be it the server,
+ * the websocket, some other custom port) is listening. If an immediate restart
+ * is specified, this monitor will kill the active child and re-launch the server
+ * at the port. Otherwise, the updated port won't be used until / unless the child
+ * dies on its own and triggers a restart.
+ */
+ private setPort = (port: "server" | "socket" | string, value: number, immediateRestart: boolean): void => {
if (value > 1023 && value < 65536) {
- ports[port] = value;
+ this.config.ports[port] = value;
if (immediateRestart) {
- restartServer();
+ this.killActiveWorker();
}
} else {
- log(red(`${port} is an invalid port number`));
+ this.mainLog(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({
- pollingRoute,
- pollingFailureTolerance,
+ /**
+ * Kills the current active worker and proceeds to spawn a new worker,
+ * feeding in configuration information as environment variables.
+ */
+ private spawn = (): void => {
+ const {
+ polling: {
+ route,
+ failureTolerance,
+ intervalSeconds
+ },
+ ports
+ } = this.config;
+ this.killActiveWorker();
+ this.activeWorker = fork({
+ pollingRoute: route,
+ pollingFailureTolerance: failureTolerance,
serverPort: ports.server,
socketPort: ports.socket,
- pollingIntervalSeconds,
- session_key: key,
+ pollingIntervalSeconds: intervalSeconds,
+ session_key: this.key,
DB: process.env.DB
});
- log(cyan(`spawned new server worker with process id ${activeWorker.process.pid}`));
+ this.mainLog(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.config.identifiers.worker.text} action requested (${cyan(message)})`);
switch (message) {
case "kill":
- log(red("an authorized user has manually ended the server session"));
- killSession();
+ const { reason, graceful, errorCode } = args;
+ this.killSession(reason, graceful, errorCode);
+ break;
case "notify_crash":
- if (notifiers && notifiers.crash) {
+ if (this.notifiers?.crash) {
const { error } = args;
- const success = await notifiers.crash(error, log);
+ const success = await this.notifiers.crash(error);
const statement = success ? green("distributed crash notification to recipients") : red("distribution of crash notification failed");
- log(statement);
+ this.mainLog(statement);
}
+ break;
case "set_port":
const { port, value, immediateRestart } = args;
- setPort(port, value, immediateRestart);
- default:
- const handler = childMessageHandlers[message];
- if (handler) {
- handler({ message, args });
- }
+ this.setPort(port, value, immediateRestart);
+ break;
+ }
+ const handlers = this.onMessage[message];
+ if (handlers) {
+ handlers.forEach(handler => handler({ message, args }));
}
- } else if (lifecycle) {
- console.log(timestamp(), `${workerIdentifier} lifecycle phase (${lifecycle})`);
+ }
+ if (lifecycle) {
+ console.log(this.timestamp(), `${this.config.identifiers.worker.text} 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 ${signal}`}.`;
- log(cyan(prompt));
- // to make this a robust, continuous session, every time a child process dies, we immediately spawn a new one
- spawn();
- });
-
- // builds the repl that allows the following commands to be typed into stdin of the master thread
- const repl = new Repl({ identifier: () => `${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) {
- log(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; },
- restartServer,
- killSession,
- setPort,
- log
- };
}
/**
* 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<ServerWorker> {
- let shouldServerBeResponsive = false;
- const exitHandlers: ExitHandler[] = [];
- let pollingFailureCount = 0;
-
- const lifecycleNotification = (lifecycle: string) => process.send?.({ lifecycle });
-
- // notify master thread (which will log update in the console) of initialization via IPC
- lifecycleNotification(green("compiling and initializing..."));
-
- // 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;
+ 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) {
+ console.error(red("cannot create a worker on the monitor process."));
+ process.exit(1);
+ } else if (++ServerWorker.count > 1) {
+ process.send?.({
+ action: {
+ message: "kill", args: {
+ reason: "cannot create more than one worker on a given worker process.",
+ graceful: false,
+ errorCode: 1
+ }
+ }
+ });
+ process.exit(1);
+ } else {
+ return new ServerWorker(work);
}
- });
+ }
- const executeExitHandlers = async (reason: Error | null) => Promise.all(exitHandlers.map(handler => handler(reason)));
+ /**
+ * 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 = (reason: string, graceful = true, errorCode = 0) => this.sendMonitorAction("kill", { reason, graceful, errorCode });
+
+ /**
+ * 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();
+ }
- // 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;
- // communicates via IPC to the master thread that it should dispatch a crash notification email
- process.send?.({
- action: {
- message: "notify_crash",
- args: { error }
+ /**
+ * 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) {
+ const { isSessionEnd } = manualExit;
+ await this.executeExitHandlers(isSessionEnd);
+ process.exit(0);
+ }
+ });
+
+ // one reason to exit, as the process might be in an inconsistent state after such an exception
+ process.on('uncaughtException', this.proactiveUnplannedExit);
+ process.on('unhandledRejection', reason => {
+ const appropriateError = reason instanceof Error ? reason : new Error(`unhandled rejection: ${reason}`);
+ this.proactiveUnplannedExit(appropriateError);
});
- await executeExitHandlers(error);
+ }
+
+ /**
+ * Execute the list of functions registered to be called
+ * whenever the process exits.
+ */
+ private executeExitHandlers = async (reason: Error | boolean) => Promise.all(this.exitHandlers.map(handler => handler(reason)));
+
+ /**
+ * Notify master thread (which will log update in the console) of initialization via IPC.
+ */
+ public 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
+ 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;
- resolve();
+ this.shouldServerBeResponsive = true;
} 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`));
}
}
+ } finally {
+ resolve();
}
- }, 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 {
- addExitHandler: (handler: ExitHandler) => exitHandlers.push(handler),
- killSession: () => process.send!({ action: { message: "kill" } })
- };
}
}
generated by cgit v1.2.3-70-g09d2 (git 2.46.0) at 2025-10-10 03:07:22 +0000