1 files changed, 169 insertions, 0 deletions
diff --git a/modules/log/event_writer_base.go b/modules/log/event_writer_base.go
new file mode 100644
index 00000000..c327c48c
--- /dev/null
+++ b/modules/log/event_writer_base.go
@@ -0,0 +1,169 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package log
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"regexp"
+	"runtime/pprof"
+	"time"
+)
+
+// EventWriterBase is the base interface for most event writers
+// It provides default implementations for most methods
+type EventWriterBase interface {
+	Base() *EventWriterBaseImpl
+	GetWriterType() string
+	GetWriterName() string
+	GetLevel() Level
+
+	Run(ctx context.Context)
+}
+
+type EventWriterBaseImpl struct {
+	writerType string
+
+	Name  string
+	Mode  *WriterMode
+	Queue chan *EventFormatted
+
+	FormatMessage     EventFormatter // format the Event to a message and write it to output
+	OutputWriteCloser io.WriteCloser // it will be closed when the event writer is stopped
+	GetPauseChan      func() chan struct{}
+
+	shared  bool
+	stopped chan struct{}
+}
+
+var _ EventWriterBase = (*EventWriterBaseImpl)(nil)
+
+func (b *EventWriterBaseImpl) Base() *EventWriterBaseImpl {
+	return b
+}
+
+func (b *EventWriterBaseImpl) GetWriterType() string {
+	return b.writerType
+}
+
+func (b *EventWriterBaseImpl) GetWriterName() string {
+	return b.Name
+}
+
+func (b *EventWriterBaseImpl) GetLevel() Level {
+	return b.Mode.Level
+}
+
+// Run is the default implementation for EventWriter.Run
+func (b *EventWriterBaseImpl) Run(ctx context.Context) {
+	defer b.OutputWriteCloser.Close()
+
+	var exprRegexp *regexp.Regexp
+	if b.Mode.Expression != "" {
+		var err error
+		if exprRegexp, err = regexp.Compile(b.Mode.Expression); err != nil {
+			FallbackErrorf("unable to compile expression %q for writer %q: %v", b.Mode.Expression, b.Name, err)
+		}
+	}
+
+	handlePaused := func() {
+		if pause := b.GetPauseChan(); pause != nil {
+			select {
+			case <-pause:
+			case <-ctx.Done():
+			}
+		}
+	}
+
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case event, ok := <-b.Queue:
+			if !ok {
+				return
+			}
+
+			handlePaused()
+
+			if exprRegexp != nil {
+				fileLineCaller := fmt.Sprintf("%s:%d:%s", event.Origin.Filename, event.Origin.Line, event.Origin.Caller)
+				matched := exprRegexp.MatchString(fileLineCaller) || exprRegexp.MatchString(event.Origin.MsgSimpleText)
+				if !matched {
+					continue
+				}
+			}
+
+			var err error
+			switch msg := event.Msg.(type) {
+			case string:
+				_, err = b.OutputWriteCloser.Write([]byte(msg))
+			case []byte:
+				_, err = b.OutputWriteCloser.Write(msg)
+			case io.WriterTo:
+				_, err = msg.WriteTo(b.OutputWriteCloser)
+			default:
+				_, err = b.OutputWriteCloser.Write([]byte(fmt.Sprint(msg)))
+			}
+			if err != nil {
+				FallbackErrorf("unable to write log message of %q (%v): %v", b.Name, err, event.Msg)
+			}
+		}
+	}
+}
+
+func NewEventWriterBase(name, writerType string, mode WriterMode) *EventWriterBaseImpl {
+	if mode.BufferLen == 0 {
+		mode.BufferLen = 1000
+	}
+	if mode.Level == UNDEFINED {
+		mode.Level = INFO
+	}
+	if mode.StacktraceLevel == UNDEFINED {
+		mode.StacktraceLevel = NONE
+	}
+	b := &EventWriterBaseImpl{
+		writerType: writerType,
+
+		Name:  name,
+		Mode:  &mode,
+		Queue: make(chan *EventFormatted, mode.BufferLen),
+
+		GetPauseChan:  GetManager().GetPauseChan, // by default, use the global pause channel
+		FormatMessage: EventFormatTextMessage,
+	}
+	return b
+}
+
+// eventWriterStartGo use "go" to start an event worker's Run method
+func eventWriterStartGo(ctx context.Context, w EventWriter, shared bool) {
+	if w.Base().stopped != nil {
+		return // already started
+	}
+	w.Base().shared = shared
+	w.Base().stopped = make(chan struct{})
+
+	ctxDesc := "Logger: EventWriter: " + w.GetWriterName()
+	if shared {
+		ctxDesc = "Logger: EventWriter (shared): " + w.GetWriterName()
+	}
+	writerCtx, writerCancel := newProcessTypedContext(ctx, ctxDesc)
+	go func() {
+		defer writerCancel()
+		defer close(w.Base().stopped)
+		pprof.SetGoroutineLabels(writerCtx)
+		w.Run(writerCtx)
+	}()
+}
+
+// eventWriterStopWait stops an event writer and waits for it to finish flushing (with a timeout)
+func eventWriterStopWait(w EventWriter) {
+	close(w.Base().Queue)
+	select {
+	case <-w.Base().stopped:
+	case <-time.After(2 * time.Second):
+		FallbackErrorf("unable to stop log writer %q in time, skip", w.GetWriterName())
+	}
+}