Aggregate existing logs from the ones generated by flipper-server

Summary:
This change aggregates/redirects flipper-server logs with logs generated by the app.

This is a great approach, why:

As we tail the file, we deserialise the logs, and re-log them using console. This means, that they will be intercepted by the logging infrastructure flipper already has in place which will make these logs go to scribe, error reporting, etc.

Reviewed By: passy

Differential Revision: D36473790

fbshipit-source-id: a3547c5c8733217c61bb2d9b94990626bbf0a492

desktop/app/src/init.tsx

@@ -23,10 +23,12 @@ import {
   loadProcessConfig,
   loadSettings,
   setupPrefetcher,
+  Tail,
 } from 'flipper-server-core';
 import {
   FlipperServer,
   getLogger,
+  LoggerInfo,
   isTest,
   Logger,
   parseEnvironmentVariables,
@@ -103,7 +105,16 @@ async function getEmbeddedFlipperServer(
 }
 
 // eslint-disable-next-line @typescript-eslint/no-unused-vars
-async function getFlipperServer(_logger: Logger): Promise<FlipperServer> {
+async function getFlipperServer(
+  _logger: Logger,
+  electronIpcClient: ElectronIpcClientRenderer,
+): Promise<FlipperServer> {
+  const appPath = await electronIpcClient.send('getPath', 'app');
+  const staticPath = getStaticDir(appPath);
+
+  const loggerOutputFile = 'flipper-server-log.out';
+  tailServerLogs(path.join(staticPath, loggerOutputFile));
+
   const flipperServer = await createFlipperServer(
     'localhost',
     52342,
@@ -169,6 +180,18 @@ function getStaticDir(appPath: string) {
   return _staticPath;
 }
 
+function tailServerLogs(logsPath: string) {
+  console.info('flipper-server logs located at: ', logsPath);
+  const tail = new Tail(logsPath);
+  tail.on('line', (line: any) => {
+    try {
+      const loggerInfo: LoggerInfo = JSON.parse(line);
+      console[loggerInfo.type](loggerInfo.msg);
+    } catch (_) {}
+  });
+  tail.watch();
+}
+
 // getLogger() is not  yet created when the electron app starts.
 // we can't create it here yet, as the real logger is wired up to
 // the redux store and the rest of the world. So we create a delegating logger