Plugin is spawning multiple flow server processes in different projects

[michalkvasnicak]

When I run eslint configuration with this plugin in different projects there are multiple flow processes running as a result.

Only way to get rid of these processes is to stop them manually.

This is screenshot when I run linting in 2 projects.

Is there a mechanism to stop them automatically? I know that it is hard because you start server on first run and then use flow check-contents to keep this plugin performant.

[michalkvasnicak]

I've tried to add the following line to collect.js#executeFlow

process.on('exit', () => childProcess.spawnSync(getFlowBin(), ['stop']));

This works nice with webpack in watching mode but is not good if you are using eslint in your editor because it kills flow server everytime lint process is done.

[amilajack]

What version are you using? Try both 1.2.0 and 1.3.0 separately. Do you get the same issues with both? From the code, it looks like you're using 1.2.0. 1.3.0 has huge performance improvements.

[michalkvasnicak]

I am using 1.3.0. It works good as expected. But problem with multiple servers starts if I open another project where I am using this plugin too. Then it will start another flow server for given project.

I don't see any nice solution to this because we can't detect if you've stopped your work on project. So flow server will stay running.

So how many separate projects you start, that many flow servers you will have running.

For example:

I am working on project A (/path/a), start npm run lint. This plugin starts flow server and validates source files.
Then I decide to not work on this project and move on separate project B (/path/b), start npm run lint. This plugin starts flow server for this directory too. There are 2 flow servers running as a result of this operations (each spawning multiple child processes as on screenshot from first post).

Only way to stop server from A is by running flow stop in this directory.

[amilajack]

What if the servers could have some kind of timeout option where they will automatically be killed after a certain time, say 1 hour? Also how impactful is the instantiation of new flow servers on your machine? I haven't noticed much one mine (but this is still an issue that i'm going to fix)

[michalkvasnicak]

I haven't noticed any impact on my machine. I came across it when I was debugging my app. It is just eating memory even if it is not used. Timeouts would be good but how should they work?

For example: I am using webpack in watch mode with eslint-loader which runs your plugin. So I can easily detect termination of process and kill flow server too.

Perhaps mentioning it in readme is enough so user will know that they need to stop flow server manually.

[amilajack]

I think that this module should be responsible for handling servers that it instantiates. I think the timeout method is a good one.

[amilajack]

@jdmota Would be great if you could look into this. I think it can be solved by small json object of when flow was last run on the project and killing the processes if flow hasn't been run on the project in an hour or so?

{
  '/Users/foo/project-1': '1490553978', // <- unix timestamp?
  '/Users/foo/project-2': '1490554013'
}

[jdmota]

I will take a look. I just need to understand how the flow server works. Maybe trying to start a flow server ahead of time can help... eslint-plugin-flow-check does that actually.

[jdmota]

I am working on project A (/path/a), start npm run lint. This plugin starts flow server and validates source files.
Then I decide to not work on this project and move on separate project B (/path/b), start npm run lint. This plugin starts flow server for this directory too. There are 2 flow servers running as a result of this operations (each spawning multiple child processes as on screenshot from first post).
Only way to stop server from A is by running flow stop in this directory.

Probably I'm not understanding the issue correctly... because when I run flow, there are processes that stay on the background, but they close immediately when I close the terminal. So I don't know if there is really a problem that needs to be fixed here...

[amilajack]

but they close immediately when I close the terminal

They actually stay open. This is good because flow can cache. The downside is that we have to kill them after a certain time period