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[Suggestion] Use File based logger #15
Description
Hi, thanks for bringing us Python Language Server!
I'm using it with LanguageClient_neovim. And I'm debugging some issue with PLS.
Usually, the server is opened by language client. Users cannot control where language server can log.
PLS now logs to stderr by default. It would be helpful if PLS can log to a file. So editor users can inspect log independent of language client's behavior. For example, logging to /tmp/LanguageServer.log by default and file path can be configured by command line argument.
Thank you!
Activity
gatesn commentedon Mar 5, 2017
Will look to implement something similar to here: https://fangpenlin.com/posts/2012/08/26/good-logging-practice-in-python/
Sensible defaults but read logging config from file if it's available
HerringtonDarkholme commentedon Mar 7, 2017
Actually this problem is more serious. autozimu/LanguageClient-neovim#21
It seems writing to stderr blocks writing to stdout.
gatesn commentedon Mar 7, 2017
So the problem, as you pointed out, is that languageClient-neovim sets
stderr=PIPE. What is happening is the client blocks waiting to read from stdout, Pyls fills up stderr buffer and blocks waiting to write to stderr and we end up in deadlock.See here for more explanation:
http://stackoverflow.com/questions/1180606/using-subprocess-popen-for-process-with-large-output
What languageClient-neovim should be doing is use select to read off both stdout and stderr and then throwing away stderr if it doesn't think its relevant. Alternatively it could set stderr=None to just drop it entirely, it could redirect it to appear on the client's stderr, or it could pass in a file object to redirect stderr to disk.
I agree that Pyls should have more configurable logging and will work on implementing that, but it's not in any language server contract that logs cannot be written to stderr.
Equally changing the log level isn't sufficient as in the case there is a lot of
ERRORmessages it will still hang! Just happening less frequently.So I think the solution here is for us to support configurable logging, and to make things easy for clients maybe a command line switch to redirect stderr to a file, but also for languageClient-neovim to properly handle stderr.
HerringtonDarkholme commentedon Mar 7, 2017
I don't think LanguageClient is the same as the stackoverflow question.
Actually PYLS blocks at writing to stdout, not stderr. Recorded here autozimu/LanguageClient-neovim#21
Source:
https://github.com/palantir/python-language-server/blob/master/pyls/jsonrpc.py#L155
gatesn commentedon Mar 7, 2017
@HerringtonDarkholme would be great to get your thoughts on this PR as a solution: #19
PR: Update pyflakes and pycodestyle dependency versions (palantir#15)