97 lines
3.3 KiB
Markdown
97 lines
3.3 KiB
Markdown
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# HTTP Server-Timing for Go
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[](https://godoc.org/github.com/mitchellh/go-server-timing)
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This is a library including middleware for using
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[HTTP Server-Timing](https://www.w3.org/TR/server-timing) with Go. This header
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allows a server to send timing information from the backend, such as database
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access time, file reads, etc. The timing information can be then be inspected
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in the standard browser developer tools:
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## Features
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* Middleware for injecting the server timing struct into the request `Context`
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and writing the `Server-Timing` header.
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* Concurrency-safe structures for easily recording timings of multiple
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concurrency tasks.
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* Parse `Server-Timing` headers as a client.
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* Note: No browser properly supports sending the Server-Timing header as
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an [HTTP Trailer](https://tools.ietf.org/html/rfc7230#section-4.4) so
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the Middleware only supports a normal header currently.
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## Browser Support
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Browser support is required to **view** server timings easily. Because server
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timings are sent as an HTTP header, there is no negative impact to sending
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the header to unsupported browsers.
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* **Chrome 65 or higher** is required to properly display server timings
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in the devtools.
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* **Firefox is pending** with an [open bug report (ID 1403051)](https://bugzilla.mozilla.org/show_bug.cgi?id=1403051)
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* IE, Opera, and others are unknown at this time.
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## Usage
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Example usage is shown below. A fully runnable example is available in
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the `example/` directory.
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```go
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func main() {
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// Our handler. In a real application this might be your root router,
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// or some subset of your router. Wrapping this ensures that all routes
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// handled by this handler have access to the server timing header struct.
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var h http.Handler = http.HandlerFunc(handler)
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// Wrap our handler with the server timing middleware
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h = servertiming.Middleware(h, nil)
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// Start!
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http.ListenAndServe(":8080", h)
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}
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func handler(w http.ResponseWriter, r *http.Request) {
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// Get our timing header builder from the context
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timing := servertiming.FromContext(r.Context())
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// Imagine your handler performs some tasks in a goroutine, such as
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// accessing some remote service. timing is concurrency safe so we can
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// record how long that takes. Let's simulate making 5 concurrent requests
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// to various servicse.
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var wg sync.WaitGroup
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for i := 0; i < 5; i++ {
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wg.Add(1)
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name := fmt.Sprintf("service-%d", i)
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go func(name string) {
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// This creats a new metric and starts the timer. The Stop is
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// deferred so when the function exits it'll record the duration.
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defer timing.NewMetric(name).Start().Stop()
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time.Sleep(random(25, 75))
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wg.Done()
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}(name)
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}
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// Imagine this is just some blocking code in your main handler such
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// as a SQL query. Let's record that.
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m := timing.NewMetric("sql").WithDesc("SQL query").Start()
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time.Sleep(random(20, 50))
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m.Stop()
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// Wait for the goroutine to end
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wg.Wait()
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// You could continue recording more metrics, but let's just return now
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w.WriteHeader(200)
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w.Write([]byte("Done. Check your browser inspector timing details."))
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}
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func random(min, max int) time.Duration {
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return (time.Duration(rand.Intn(max-min) + min)) * time.Millisecond
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}
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```
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