Merge branch 'master' of https://github.com/browngraphicslab/Dash-Web into pen

1 files changed, 0 insertions, 592 deletions

diff --git a/src/server/Session/session.ts b/src/server/Session/session.ts
deleted file mode 100644
index 06a076ae4..000000000
--- a/src/server/Session/session.ts
+++ /dev/null
@@ -1,592 +0,0 @@
-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";
-import { readFileSync } from "fs";
-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.
- */
-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 = (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) {
-                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!;
-        }
-
-        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;
-        workerIdentifier: string;
-        ports: { [description: string]: number };
-        pollingRoute: string;
-        pollingIntervalSeconds: number;
-        pollingFailureTolerance: number;
-        [key: string]: any;
-    }
-
-    const defaultConfiguration: Configuration = {
-        showServerOutput: false,
-        masterIdentifier: yellow("__monitor__:"),
-        workerIdentifier: magenta("__server__:"),
-        ports: { server: 3000 },
-        pollingRoute: "/",
-        pollingIntervalSeconds: 30,
-        pollingFailureTolerance: 0
-    };
-
-    export type ExitHandler = (reason: Error | null) => void | Promise<void>;
-
-    export namespace Monitor {
-
-        export interface NotifierHooks {
-            key?: (key: string) => (boolean | Promise<boolean>);
-            crash?: (error: Error) => (boolean | Promise<boolean>);
-        }
-
-        export interface Action {
-            message: string;
-            args: any;
-        }
-
-        export type ServerMessageHandler = (action: Action) => void | Promise<void>;
-
-    }
-
-    /**
-     * 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) {
-                process.send?.({
-                    action: {
-                        message: "kill",
-                        args: {
-                            reason: "cannot create a monitor on the worker process.",
-                            graceful: false,
-                            errorCode: 1
-                        }
-                    }
-                });
-                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.log(cyan(`exiting session ${graceful ? "clean" : "immediate"}ly`));
-            this.log(`reason: ${(red(reason))}`);
-            await this.executeExitHandlers(null);
-            this.tryKillActiveWorker(graceful);
-            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);
-        }
-
-        /**
-         * 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];
-            }
-        }
-
-        /**
-         * 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);
-                }
-            }
-        }
-
-        /**
-         * 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("manual exit requested by repl", args[0] === "clean", 0));
-            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;
-        }
-
-        /**
-         * 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);
-                }
-            }
-        }
-
-
-        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) {
-                    this.activeWorker?.send({ manualExit: true });
-                } else {
-                    this.activeWorker?.process.kill();
-                }
-                return true;
-            }
-            return false;
-        }
-
-        /**
-         * 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) {
-                this.configuration.ports[port] = value;
-                if (immediateRestart) {
-                    this.tryKillActiveWorker();
-                }
-            } else {
-                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.
-         */
-        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: this.key
-            });
-            this.log(cyan(`spawned new server worker with process id ${this.activeWorker.process.pid}`));
-            // an IPC message handler that executes actions on the master thread when prompted by the active worker
-            this.activeWorker.on("message", async ({ lifecycle, action }) => {
-                if (action) {
-                    const { message, args } = action as Monitor.Action;
-                    console.log(this.timestamp(), `${this.configuration.workerIdentifier} action requested (${cyan(message)})`);
-                    switch (message) {
-                        case "kill":
-                            const { reason, graceful, errorCode } = args;
-                            this.killSession(reason, graceful, errorCode);
-                            break;
-                        case "notify_crash":
-                            if (this.notifiers?.crash) {
-                                const { error } = args;
-                                const success = await this.notifiers.crash(error);
-                                const statement = success ? green("distributed crash notification to recipients") : red("distribution of crash notification failed");
-                                this.log(statement);
-                            }
-                            break;
-                        case "set_port":
-                            const { port, value, immediateRestart } = args;
-                            this.setPort(port, value, immediateRestart);
-                            break;
-                    }
-                    const handlers = this.onMessage[message];
-                    if (handlers) {
-                        handlers.forEach(handler => handler({ message, args }));
-                    }
-                } else if (lifecycle) {
-                    console.log(this.timestamp(), `${this.configuration.workerIdentifier} lifecycle phase (${lifecycle})`);
-                }
-            });
-        }
-
-    }
-
-    /**
-     * 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.
-     */
-    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);
-            }
-        }
-
-        /**
-         * 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();
-        }
-
-        /**
-         * 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);
-                }
-            });
-
-            // one reason to exit, as the process might be in an inconsistent state after such an exception
-            process.on('uncaughtException', this.proactiveUnplannedExit);
-        }
-
-        /**
-         * 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.
-         */
-        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
-            this.lifecycleNotification(red(`crash event detected @ ${new Date().toUTCString()}`));
-            this.lifecycleNotification(red(error.message));
-            process.exit(1);
-        }
-
-        /**
-         * 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(this.pollTarget);
-                        if (!this.shouldServerBeResponsive) {
-                            // notify monitor thread that the server is up and running
-                            this.lifecycleNotification(green(`listening on ${this.serverPort}...`));
-                        }
-                        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 (this.shouldServerBeResponsive) {
-                            if (++this.pollingFailureCount > this.pollingFailureTolerance) {
-                                this.proactiveUnplannedExit(error);
-                            } else {
-                                this.lifecycleNotification(yellow(`the server has encountered ${this.pollingFailureCount} of ${this.pollingFailureTolerance} tolerable failures`));
-                            }
-                        }
-                    }
-                }, 1000 * this.pollingIntervalSeconds);
-            });
-            // controlled, asynchronous infinite recursion achieves a persistent poll that does not submit a new request until the previous has completed
-            this.pollServer();
-        }
-
-    }
-
-}
\ No newline at end of file