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本文主要研究一下dubbo-go的tracingFilter
tracingFilter
dubbo-go-v1.4.2/filter/filter_impl/tracing_filter.go
const (
tracingFilterName = "tracing"
)
// this should be executed before users set their own Tracer
func init() {
extension.SetFilter(tracingFilterName, newTracingFilter)
opentracing.SetGlobalTracer(opentracing.NoopTracer{})
}
var (
errorKey = "ErrorMsg"
successKey = "Success"
)
// if you wish to using opentracing, please add the this filter into your filter attribute in your configure file.
// notice that this could be used in both client-side and server-side.
type tracingFilter struct {
}
- tracingFilter的init方法设置了newTracingFilter
newTracingFilter
dubbo-go-v1.4.2/filter/filter_impl/tracing_filter.go
func newTracingFilter() filter.Filter {
if tracingFilterInstance == nil {
tracingFilterInstance = &tracingFilter{}
}
return tracingFilterInstance
}
- newTracingFilter方法实例化tracingFilter
Invoke
dubbo-go-v1.4.2/filter/filter_impl/tracing_filter.go
func (tf *tracingFilter) Invoke(ctx context.Context, invoker protocol.Invoker, invocation protocol.Invocation) protocol.Result {
var (
spanCtx context.Context
span opentracing.Span
)
operationName := invoker.GetUrl().ServiceKey() + "#" + invocation.MethodName()
wiredCtx := ctx.Value(constant.TRACING_REMOTE_SPAN_CTX)
preSpan := opentracing.SpanFromContext(ctx)
if preSpan != nil {
// it means that someone already create a span to trace, so we use the span to be the parent span
span = opentracing.StartSpan(operationName, opentracing.ChildOf(preSpan.Context()))
spanCtx = opentracing.ContextWithSpan(ctx, span)
} else if wiredCtx != nil {
// it means that there has a remote span, usually from client side. so we use this as the parent
span = opentracing.StartSpan(operationName, opentracing.ChildOf(wiredCtx.(opentracing.SpanContext)))
spanCtx = opentracing.ContextWithSpan(ctx, span)
} else {
// it means that there is not any span, so we create a span as the root span.
span, spanCtx = opentracing.StartSpanFromContext(ctx, operationName)
}
defer func() {
span.Finish()
}()
result := invoker.Invoke(spanCtx, invocation)
span.SetTag(successKey, result.Error() != nil)
if result.Error() != nil {
span.LogFields(log.String(errorKey, result.Error().Error()))
}
return result
}
- Invoke方法首先构建operationName,然后使用opentracing.StartSpan开启span,之后defer执行span.Finish(),然后执行invoker.Invoke(spanCtx, invocation),最后设置span.SetTag及span.LogFields
OnResponse
dubbo-go-v1.4.2/filter/filter_impl/tracing_filter.go
func (tf *tracingFilter) OnResponse(ctx context.Context, result protocol.Result,
invoker protocol.Invoker, invocation protocol.Invocation) protocol.Result {
return result
}
- OnResponse方法直接返回result
小结
tracingFilter的Invoke方法首先构建operationName,然后使用opentracing.StartSpan开启span,之后defer执行span.Finish(),然后执行invoker.Invoke(spanCtx, invocation),最后设置span.SetTag及span.LogFields
doc
来源:oschina
链接:https://my.oschina.net/go4it/blog/4422322