WRLGS-11: Generic function for timestamp in stderr

index.js

@@ -1,4 +1,5 @@
 const API = require('./lib/api.js');
+const stderrUtils = require('./lib/stderrUtils');
 
 /*
  * For convenience purposes, we provide an already instanciated API; so that
@@ -11,4 +12,40 @@ module.exports = {
     Logger: werelogs.Logger,
     configure: werelogs.reconfigure.bind(werelogs),
     Werelogs: API,
+    /**
+     * Log to stderr with timestamp
+     *
+     * @example <caption>Simplest usage</caption>
+     * ```
+     * const { stderrUtils } = require('werelogs');
+     * stderrUtils.catchAndTimestampStderr();
+     * ```
+     *
+     * @example <caption>Manage process exit</caption>
+     * ```
+     * const { stderrUtils } = require('werelogs');
+     * // set exitCode to null to keep process running on uncaughtException
+     * stderrUtils.catchAndTimestampStderr(undefined, null);
+     * // application code
+     * process.on('uncaughtException', (err) => {
+     *     // custom handling, close connections, files
+     *     this.worker.kill(); // or process.exit(1);
+     * });
+     * // Note you could use prependListener to execute your callback first
+     * // and then let stderrUtils exit the process.
+     * ```
+     *
+     * @example <caption>Custom listener</caption>
+     * ```
+     * const { stderrUtils } = require('werelogs');
+     * stderrUtils.catchAndTimestampWarning();
+     * // application code
+     * process.on('uncaughtException', (err, origin) => {
+     *     stderrUtils.printErrorWithTimestamp(err, origin);
+     *     // close and stop everything
+     *     process.exit(1);
+     * });
+     * ```
+     */
+    stderrUtils,
 };

lib/stderrUtils.js

@@ -0,0 +1,97 @@
+/** Returns a timestamp in ISO format YYYY-MM-DDThh:mm:ss.sssZ */
+const defaultTimestamp = () => new Date().toISOString()
+
+/**
+ * Prints on stderr a timestamp, the origin and the error
+ *
+ * If no other instructions are needed on uncaughtException,
+ * consider using `catchAndTimestampStderr` directly.
+ *
+ * @example
+ * process.on('uncaughtException', (err, origin) => {
+ *   printErrorWithTimestamp(err, origin);
+ *   // server.close();
+ *   // file.close();
+ *   process.nextTick(() => process.exit(1));
+ * });
+ * // Don't forget to timestamp warning
+ * catchAndTimestampWarning();
+ * @param {Error} err see process event uncaughtException
+ * @param {uncaughtException|unhandledRejection} origin see process event
+ * @param {string} [date=`defaultTimestamp()`] Date to print
+ */
+function printErrorWithTimestamp(
+    err, origin, date = defaultTimestamp()
+) {
+    process.stderr.write(`${date}: ${origin}:\n${err.stack}\n`)
+}
+
+/**
+ * Prefer using `catchAndTimestampStderr` instead of this function.
+ *
+ * Adds listener for uncaughtException to print with timestamp.
+ *
+ * If you want to manage the end of the process, you can set exitCode to null.
+ * Or you can use `printErrorWithTimestamp` in your own uncaughtException listener.
+ *
+ * @param {Function} [dateFct=`defaultTimestamp`] Function returning a formatted date
+ * @param {*} [exitCode=1] On uncaughtException, if not null, `process.exit` will
+ *                         be called with this value
+ */
+function catchAndTimestampUncaughtException(
+    date = defaultTimestamp, exitCode = 1
+) {
+    process.on('uncaughtException', function timestampUncaughtException (err, origin) {
+        printErrorWithTimestamp(err, origin, date());
+        if (exitCode !== null) {
+            process.nextTick(() => process.exit(exitCode));
+        }
+    })
+}
+
+/**
+ * Forces the use of `--trace-warnings` and adds a date in warning detail
+ * The warning will be printed by the default `onWarning`
+ *
+ * @param {string} [date=`defaultTimestamp`] Function returning a formatted date
+ */
+function catchAndTimestampWarning(date = defaultTimestamp) {
+    process.traceProcessWarnings = true;
+    // must be executed first, before the default `onWarning`
+    process.prependListener('warning', function timestampWarning (warning) {
+        if (warning.detail)
+            warning.detail += `\nAbove Warning Date: ${defaultTimestamp()}`
+        else
+            warning.detail = `Above Warning Date: ${defaultTimestamp()}`
+    });
+}
+
+/**
+ * Adds listener for uncaughtException and warning to print them with timestamp.
+ *
+ * If you want to manage the end of the process, you can set exitCode to null.
+ * Or you can use `printErrorWithTimestamp` in your own uncaughtException listener.
+ *
+ * @example
+ * const { stderrUtils } = require('werelogs');
+ * // first instruction in your index.js or entrypoint
+ * stderrUtils.catchAndTimestampStderr();
+ *
+ * @param {Function} [date=`defaultTimestamp`] Function returning a formatted date
+ * @param {*} [exitCode=1] On uncaughtException, if not null, `process.exit` will
+ *                         be called with this value
+ */
+function catchAndTimestampStderr(
+    date = defaultTimestamp, exitCode = 1
+) {
+    catchAndTimestampUncaughtException(date, exitCode);
+    catchAndTimestampWarning(date);
+}
+
+module.exports = {
+    defaultTimestamp,
+    printErrorWithTimestamp,
+    catchAndTimestampUncaughtException,
+    catchAndTimestampWarning,
+    catchAndTimestampStderr
+}