go io_error ai_generated true

panic: runtime error: too many open files (in goroutine)

ID: go/too-many-open-files-in-goroutine

Also available as: JSON · Markdown · 中文
80%Fix Rate
85%Confidence
0Evidence
2024-09-12First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
1.0 active — — —
1.1 active — — —
1.2 active — — —

Root Cause

A goroutine is opening many file descriptors without closing them, exhausting the system limit. This can happen in concurrent programs that handle many connections or files.

generic

中文

goroutine 打开了大量文件描述符但没有关闭，耗尽了系统限制。这可能在处理大量连接或文件的并发程序中发生。

Workarounds

  1. 90% success Use a semaphore to limit concurrent file operations 
    sem := make(chan struct{}, 10) // limit 10 concurrent opens
for i := 0; i < 100; i++ {
    go func() {
        sem <- struct{}{}
        defer func() { <-sem }()
        f, err := os.Open("file.txt")
        if err != nil {
            log.Fatal(err)
        }
        defer f.Close()
        // process file
    }()
}
  2. 95% success Ensure all files are closed in a timely manner 
    f, err := os.Open("file.txt")
if err != nil {
    return err
}
defer f.Close()
// use f

Dead Ends

Common approaches that don't work:

  1. Increasing the system ulimit without fixing the code 80% fail

    This only delays the problem; if the code doesn't close files properly, the new limit will also be exhausted eventually.

  2. Using defer to close files but not handling errors 70% fail

    defer ensures close is called, but if multiple goroutines open files concurrently, the defer may not execute quickly enough, leading to file descriptor exhaustion.