feat: Try to restart once mongod on shutdown

`mongodb-prebuilt` on "addr in use" error returns "Mongod shutting down"
error. So we can not be exactly sure that problem was in busy port.
That's why we try only one time more to start mongo.

Author: nodkz

src/index.js

@@ -46,46 +46,29 @@ export default class MongoDBMemoryServer {
     }
   }
 
+  debug(msg: string) {
+    if (this.opts.debug) {
+      console.log(msg);
+    }
+  }
+
   async start(): Promise<boolean> {
     if (this.runningInstance) {
       throw new Error(
         'MongoDB instance already in status startup/running/error. Use opts.debug = true for more info.'
       );
     }
 
-    this.runningInstance = Promise.resolve().then(async () => {
-      const data = {};
-      let tmpDir;
-
-      data.port = await getport(this.opts.port);
-      data.uri = await generateConnectionString(data.port);
-      data.storageEngine = this.opts.storageEngine || 'ephemeralForTest';
-      if (this.opts.dbPath) {
-        data.dbPath = this.opts.dbPath;
-      } else {
-        tmpDir = tmp.dirSync({ prefix: 'mongo-mem-', unsafeCleanup: true });
-        data.dbPath = tmpDir.name;
-      }
-
-      if (this.opts.debug) {
-        console.log(`Starting MongoDB instance with following options: ${JSON.stringify(data)}`);
-      }
-
-      const mongodCli = new MongodHelper([
-        '--port',
-        data.port,
-        '--storageEngine',
-        data.storageEngine,
-        '--dbpath',
-        data.dbPath,
-        '--noauth',
-      ]);
-
-      mongodCli.debug.enabled = this.opts.debug;
-
-      // Download if not exists mongo binaries in ~/.mongodb-prebuilt
-      // After that startup MongoDB instance
-      await mongodCli.run().catch(err => {
+    this.runningInstance = this._startUpInstance()
+      .catch(err => {
+        if (err.message === 'Mongod shutting down' || err === 'Mongod shutting down') {
+          this.debug(`Mongodb does not started. Trying to start on another port one more time...`);
+          this.opts.port = null;
+          return this._startUpInstance();
+        }
+        throw err;
+      })
+      .catch(err => {
         if (!this.opts.debug) {
           throw new Error(
             `${err.message}\n\nUse debug option for more info: new MongoMemoryServer({ debug: true })`
@@ -94,32 +77,60 @@ export default class MongoDBMemoryServer {
         throw err;
       });
 
-      data.mongodCli = mongodCli;
-      data.tmpDir = tmpDir;
+    return this.runningInstance.then(() => true);
+  }
 
-      return data;
-    });
+  async _startUpInstance(): Promise<MongoInstanceDataT> {
+    const data = {};
+    let tmpDir;
+
+    data.port = await getport(this.opts.port);
+    data.uri = await generateConnectionString(data.port);
+    data.storageEngine = this.opts.storageEngine || 'ephemeralForTest';
+    if (this.opts.dbPath) {
+      data.dbPath = this.opts.dbPath;
+    } else {
+      tmpDir = tmp.dirSync({ prefix: 'mongo-mem-', unsafeCleanup: true });
+      data.dbPath = tmpDir.name;
+    }
 
-    return this.runningInstance.then(() => true);
+    this.debug(`Starting MongoDB instance with following options: ${JSON.stringify(data)}`);
+
+    const mongodCli = new MongodHelper([
+      '--port',
+      data.port,
+      '--storageEngine',
+      data.storageEngine,
+      '--dbpath',
+      data.dbPath,
+      '--noauth',
+    ]);
+
+    mongodCli.debug.enabled = this.opts.debug;
+
+    // Download if not exists mongo binaries in ~/.mongodb-prebuilt
+    // After that startup MongoDB instance
+    await mongodCli.run();
+
+    data.mongodCli = mongodCli;
+    data.tmpDir = tmpDir;
+
+    return data;
   }
 
   async stop(): Promise<boolean> {
     const { mongodCli, port, tmpDir } = await this.getInstanceData();
 
     if (mongodCli && mongodCli.mongoBin.childProcess) {
       // .mongoBin.childProcess.connected
-      if (this.opts.debug) {
-        console.log(
-          `Shutdown MongoDB server on port ${port} with pid ${mongodCli.mongoBin.childProcess.pid}`
-        );
-      }
+      this.debug(
+        `Shutdown MongoDB server on port ${port} with pid ${mongodCli.mongoBin.childProcess.pid}`
+      );
       mongodCli.mongoBin.childProcess.kill();
     }
 
     if (tmpDir) {
-      if (this.opts.debug) {
-        console.log(`Removing tmpDir ${tmpDir.name}`);
-      }
+      this.debug(`Removing tmpDir ${tmpDir.name}`);
       tmpDir.removeCallback();
     }