chore: add debugging log when error occurs in Accept()

[hellodudu]

---

name: Pull request
about: wrap errors description
title: 'wrap errors'
labels: ''
assignees: ''

1. Are you opening this pull request for bug-fixs, optimizations or new feature?

optimizations

2. Please describe how these code changes achieve your intention.

acceptNewConnection sometimes return a simple ErrAcceptSocket error with no exactly description. It will cost so much time to figure out where the problem is. For example, if the connection number achieved system's fd limit, I just got an error message like Main reactor is exiting due to error: accept a new connection error. After errors wrapped, the error message is like Main reactor is exiting due to error: accept a new connection error: too many open files.

3. Please link to the relevant issues (if any).

4. Which documentation changes (if any) need to be made/updated because of this PR?

4. Checklist

• I have squashed all insignificant commits.
• I have commented my code for explaining package types, values, functions, and non-obvious lines.
• I have written unit tests and verified that all tests passes (if needed).
• I have documented feature info on the README (only when this PR is adding a new feature).
• (optional) I am willing to help maintain this change if there are issues with it later.

[panjf2000]

Sorry, I don't see any value from this code change, what's the point of this PR?

[hellodudu]

I got an accept a new connection error when benchmark gnet, but I don't know how it comes until adding logs into acceptNewConnection
I think wrapping all returned errors into err and use errors.Is() to check if it contains any error is benefit for positioning problem, though it's less graceful.

[panjf2000]

If you're just doing this only for debugging purposes, I'd suggest you add a debug log under this:

gnet/reactor_linux.go

Line 39 in b4a9840

logging.Infof("Main reactor is exiting due to error: %v", err)

[hellodudu]

gnet/reactor_linux.go

Line 39 in b4a9840

logging.Infof("Main reactor is exiting due to error: %v", err)

I'm afraid this err just returns errors.ErrAcceptSocket with no more details when unix.Accept(fd) failed. And we won't know why acceptNewConnection fails unless adding some logs before return errors.ErrAcceptSocket.

gnet/acceptor_unix.go

Lines 34 to 40 in b4a9840

	nfd, sa, err := unix.Accept(fd)
	if err != nil {
	if err == unix.EAGAIN {
	return nil
	}
	return errors.ErrAcceptSocket
	}

[panjf2000]

gnet/reactor_linux.go

Line 39 in b4a9840

logging.Infof("Main reactor is exiting due to error: %v", err)

I'm afraid this err just returns errors.ErrAcceptSocket with no more details when unix.Accept(fd) failed. And we won't know why acceptNewConnection fails unless adding some logs before return errors.ErrAcceptSocket.

gnet/acceptor_unix.go

Lines 34 to 40 in b4a9840

	nfd, sa, err := unix.Accept(fd)
	if err != nil {
	if err == unix.EAGAIN {
	return nil
	}
	return errors.ErrAcceptSocket
	}

Make senses, then could you take a look across acceptor_unix.go, connection_unix.go and eventloop_unix.go and add logging.Debugf or logging.Warnf for those critical errors?
@hellodudu

[hellodudu]

You mean adding logs instead of wrap errors? sure, that's better.

[panjf2000]

I just refactored the logging logic in 8837a92, please rebase your branch on it.
@hellodudu

[hellodudu]

Done.

[codecov]

Codecov Report

Merging #222 (3861b6e) into master (8837a92) will increase coverage by 1.83%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #222      +/-   ##
==========================================
+ Coverage   83.83%   85.67%   +1.83%     
==========================================
  Files          18       18              
  Lines        1231     1410     +179     
==========================================
+ Hits         1032     1208     +176     
- Misses        148      151       +3     
  Partials       51       51              

Flag	Coverage Δ
unittests	85.67% <0.00%> (+1.83%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
acceptor_unix.go	41.66% <0.00%> (+0.75%)	⬆️
loop_bsd.go	100.00% <0.00%> (ø)
listener_unix.go	100.00% <0.00%> (ø)
acceptor_windows.go	100.00% <0.00%> (ø)
options.go	88.67% <0.00%> (+0.10%)	⬆️
server_windows.go	98.05% <0.00%> (+0.20%)	⬆️
reactor_bsd.go	87.50% <0.00%> (+0.83%)	⬆️
server_unix.go	88.95% <0.00%> (+0.95%)	⬆️
listener_windows.go	93.33% <0.00%> (+1.02%)	⬆️
eventloop_windows.go	90.78% <0.00%> (+1.23%)	⬆️
... and 9 more

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[panjf2000]

Thanks~