Fix: TypeError: Cannot read property 'level' of undefined

Feature: dump unfinished log into a file while exiting

metro/index.js

@@ -4,8 +4,26 @@ const split = require('split2');
 const logCollector = require('./log-collector');
 const metricsCollector = require('./metrics-collector');
 
-process.stdin
-    .pipe(split())
-    .pipe(logCollector())
-    .pipe(metricsCollector())
-    .pipe(process.stdout);
+const streams = [process.stdin, split(), logCollector(), metricsCollector(), process.stdout]
+
+pipeline('pipe', streams);
+
+process.on('SIGINT', exitProcess(0));
+process.on('SIGTERM', exitProcess(0));
+process.on('uncaughtException', exitProcess(1));
+process.on('unhandledRejection', exitProcess(1));
+
+function pipeline (action, streams) {
+    for (let index = 0; index < streams.length - 1; index++) {
+        const source = streams[index];
+        const destination = streams[index + 1];
+        source[action](destination);
+    }
+}
+
+function exitProcess (code = 0) {
+    return function exitProcess (signal) {
+        pipeline('unpipe', streams);
+        process.exit(code);
+    };
+}

metro/log-collector.js

@@ -1,10 +1,13 @@
 'use strict'
 
+const fs = require('fs');
 const split = require('split2');
 const assingDeep = require('assign-deep');
 const { Transform } = require('stream');
 const DEV_ENVS = ['test', 'development'];
-const logs = new Map();
+const dumpPath = `${__dirname}/dump.json`;
+
+let logs;
 
 const LEVELS = {
     10: 'trace',
@@ -16,7 +19,7 @@ const LEVELS = {
 }
 
 module.exports = function logCollector () {
-    return new Transform({
+    const stream = new Transform({
         transform (chunk, enc, callback) {
             let entry;
 
@@ -34,7 +37,7 @@ module.exports = function logCollector () {
                 return callback();
             }
 
-            const { id, end } = entry;
+            const { id } = entry;
 
             if (id === undefined) {
                 entry.level = LEVELS[entry.level];
@@ -42,17 +45,17 @@ module.exports = function logCollector () {
                 return callback();
             }
 
-            if (end === true) {
-                const accEntry = logs.get(id);
-                accEntry.level = LEVELS[accEntry.level];
-                accEntry.time = entry.time;
-                this.push(`${JSON.stringify(accEntry)}\n`);
-                logs.delete(id);
-                return callback();
-            }
-
             if (logs.has(id)) {
                 const accEntry = logs.get(id);
+                const { end } = entry;
+
+                if (end === true) {
+                    accEntry.level = LEVELS[accEntry.level];
+                    accEntry.time = entry.time;
+                    this.push(`${JSON.stringify(accEntry)}\n`);
+                    logs.delete(id);
+                    return callback();
+                }
 
                 if (accEntry.level > entry.level) {
                     delete entry.level
@@ -70,7 +73,32 @@ module.exports = function logCollector () {
 
             callback();
         }
-    })
+    });
+
+    stream.on('pipe', () => {
+        if (!fs.existsSync(dumpPath)) {
+            logs = new Map();
+            return;
+        }
+
+        try {
+            const dump = require(dumpPath);
+            logs = new Map(dump);
+        } catch (err) {
+            console.error(`Cannot read the dump for unfinished logs: ${err}`);
+            logs = new Map();
+        }
+    });
+
+    stream.on('unpipe', () => {
+        try {
+            fs.writeFileSync(dumpPath, JSON.stringify([...logs]));
+        } catch (err) {
+            console.error(`Cannot create a dump for unfinished logs: ${err}`);
+        }
+    });
+
+    return stream;
 }
 
 function hasProperty(obj, prop) {