logging: Buffer the logs before config is loaded (#7245)

internal/logbuffer.go

@@ -0,0 +1,72 @@
+// Copyright 2015 Matthew Holt and The Caddy Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package internal
+
+import (
+	"sync"
+
+	"go.uber.org/zap"
+	"go.uber.org/zap/zapcore"
+)
+
+// LogBufferCore is a zapcore.Core that buffers log entries in memory.
+type LogBufferCore struct {
+	mu      sync.Mutex
+	entries []zapcore.Entry
+	fields  [][]zapcore.Field
+	level   zapcore.LevelEnabler
+}
+
+func NewLogBufferCore(level zapcore.LevelEnabler) *LogBufferCore {
+	return &LogBufferCore{
+		level: level,
+	}
+}
+
+func (c *LogBufferCore) Enabled(lvl zapcore.Level) bool {
+	return c.level.Enabled(lvl)
+}
+
+func (c *LogBufferCore) With(fields []zapcore.Field) zapcore.Core {
+	return c
+}
+
+func (c *LogBufferCore) Check(entry zapcore.Entry, ce *zapcore.CheckedEntry) *zapcore.CheckedEntry {
+	if c.Enabled(entry.Level) {
+		return ce.AddCore(entry, c)
+	}
+	return ce
+}
+
+func (c *LogBufferCore) Write(entry zapcore.Entry, fields []zapcore.Field) error {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	c.entries = append(c.entries, entry)
+	c.fields = append(c.fields, fields)
+	return nil
+}
+
+func (c *LogBufferCore) Sync() error { return nil }
+
+// FlushTo flushes buffered logs to the given zap.Logger.
+func (c *LogBufferCore) FlushTo(logger *zap.Logger) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	for idx, entry := range c.entries {
+		logger.WithOptions().Check(entry.Level, entry.Message).Write(c.fields[idx]...)
+	}
+	c.entries = nil
+	c.fields = nil
+}