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fix(agent): Work around lumberjack reopening log file after close #5941

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Merged
merged 1 commit into from
Feb 1, 2023
Merged

fix(agent): Work around lumberjack reopening log file after close #5941

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34 changes: 33 additions & 1 deletion cli/agent.go
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Original file line number Diff line number Diff line change
Expand Up @@ -3,13 +3,15 @@ package cli
import (
"context"
"fmt"
"io"
"net/http"
"net/http/pprof"
"net/url"
"os"
"os/signal"
"path/filepath"
"runtime"
"sync"
"time"

"cloud.google.com/go/compute/metadata"
Expand Down Expand Up @@ -91,11 +93,14 @@ func workspaceAgent() *cobra.Command {
// reaper.
go dumpHandler(ctx)

logWriter := &lumberjack.Logger{
ljLogger := &lumberjack.Logger{
Filename: filepath.Join(logDir, "coder-agent.log"),
MaxSize: 5, // MB
}
defer ljLogger.Close()
logWriter := &closeWriter{w: ljLogger}
defer logWriter.Close()

logger := slog.Make(sloghuman.Sink(cmd.ErrOrStderr()), sloghuman.Sink(logWriter)).Leveled(slog.LevelDebug)

version := buildinfo.Version()
Expand Down Expand Up @@ -229,3 +234,30 @@ func serveHandler(ctx context.Context, logger slog.Logger, handler http.Handler,
_ = srv.Close()
}
}

// closeWriter is a wrapper around an io.WriteCloser that prevents
// writes after Close. This is necessary because lumberjack will
// re-open the file on write.
type closeWriter struct {
w io.WriteCloser
mu sync.Mutex // Protects following.
closed bool
}

func (c *closeWriter) Close() error {
c.mu.Lock()
defer c.mu.Unlock()

c.closed = true
return c.w.Close()
}

func (c *closeWriter) Write(p []byte) (int, error) {
c.mu.Lock()
defer c.mu.Unlock()

if c.closed {
return 0, io.ErrClosedPipe
}
return c.w.Write(p)
}