序
本文主要研究一下golang的zap的hook
实例
func hookDemo() {
count := &atomic.Int64{}
logger, _ := zap.NewProduction(zap.Hooks(func(entry zapcore.Entry) error {
fmt.Println("count:", count.Inc(), "msg:", entry.Message)
return nil
}))
defer logger.Sync() // flushes buffer, if any
sugar := logger.Sugar()
sugar.Infow("failed to fetch URL",
// Structured context as loosely typed key-value pairs.
"url", "#34;,
"attempt", 3,
"backoff", time.Second,
)
sugar.Info("hello world")
}
输出
{"level":"info","ts":1608045721.769727,"caller":"zap/zap_demo.go:29","msg":"failed to fetch URL","url":"#34;,"attempt":3,"backoff":1}
count: 1 msg: failed to fetch URL
{"level":"info","ts":1608045721.769826,"caller":"zap/zap_demo.go:35","msg":"hello world"}
count: 2 msg: hello world
Hooks
zap@v1.16.0/options.go
func Hooks(hooks ...func(zapcore.Entry) error) Option {
return optionFunc(func(log *Logger) {
log.core = zapcore.RegisterHooks(log.core, hooks...)
})
}
zapcore.RegisterHooks
zap@v1.16.0/zapcore/hook.go
func RegisterHooks(core Core, hooks ...func(Entry) error) Core {
funcs := append([]func(Entry) error{}, hooks...)
return &hooked{
Core: core,
funcs: funcs,
}
}
RegisterHooks方法创建hooked，hooks赋值给hooked的funcs属性
hook
zap@v1.16.0/zapcore/hook.go
type hooked struct {
Core
funcs []func(Entry) error
}
func (h *hooked) Check(ent Entry, ce *CheckedEntry) *CheckedEntry {
// Let the wrapped Core decide whether to log this message or not. This
// also gives the downstream a chance to register itself directly with the
// CheckedEntry.
if downstream := h.Core.Check(ent, ce); downstream != nil {
return downstream.AddCore(ent, h)
}
return ce
}
func (h *hooked) With(fields []Field) Core {
return &hooked{
Core: h.Core.With(fields),
funcs: h.funcs,
}
}
func (h *hooked) Write(ent Entry, _ []Field) error {
// Since our downstream had a chance to register itself directly with the
// CheckedMessage, we don't need to call it here.
var err error
for i := range h.funcs {
err = multierr.Append(err, h.funcs[i](ent))
}
return err
}
hooked内嵌了Core，它覆盖了Check、With、Write方法；Check方法将hooked添加到downstream；Write方法遍历hooks，执行回调
小结
Hooks方法将log的core使用zapcore.RegisterHooks包装了一下；RegisterHooks方法创建hooked，hooks赋值给hooked的funcs属性；hooked包装了core，因而需要在Check的时候把自己注册进去，然后在Write的时候就可以执行到自己注册的hooks。一般可以将metrics等简单的操作通过hook来实现，而复杂的逻辑则最好通过实现zapcore.Core来做。
doc
- zap
