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70 lines
1.6 KiB
70 lines
1.6 KiB
package middleware
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import (
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"crypto/rand"
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"encoding/base64"
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"fmt"
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"net/http"
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"os"
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"strings"
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"sync/atomic"
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"github.com/zenazn/goji/web"
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)
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// Key to use when setting the request ID.
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const RequestIdKey = "reqId"
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var prefix string
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var reqid uint64
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func init() {
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hostname, err := os.Hostname()
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if hostname == "" || err != nil {
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hostname = "localhost"
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}
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var buf [12]byte
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rand.Read(buf[:])
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b64 := base64.StdEncoding.EncodeToString(buf[:])
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// Strip out annoying characters. We have something like a billion to
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// one chance of having enough from 12 bytes of entropy
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b64 = strings.NewReplacer("+", "", "/", "").Replace(b64)
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prefix = fmt.Sprintf("%s/%s", hostname, b64[0:8])
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}
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// RequestId is a middleware that injects a request ID into the context of each
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// request. A request ID is a string of the form "host.example.com/random-0001",
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// where "random" is a base62 random string that uniquely identifies this go
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// process, and where the last number is an atomically incremented request
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// counter.
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func RequestId(c *web.C, h http.Handler) http.Handler {
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fn := func(w http.ResponseWriter, r *http.Request) {
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if c.Env == nil {
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c.Env = make(map[string]interface{})
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}
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myid := atomic.AddUint64(&reqid, 1)
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c.Env[RequestIdKey] = fmt.Sprintf("%s-%06d", prefix, myid)
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h.ServeHTTP(w, r)
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}
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return http.HandlerFunc(fn)
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}
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// Get a request ID from the given context if one is present. Returns the empty
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// string if a request ID cannot be found.
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func GetReqId(c web.C) string {
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if c.Env == nil {
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return ""
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}
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v, ok := c.Env[RequestIdKey]
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if !ok {
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return ""
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}
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if reqId, ok := v.(string); ok {
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return reqId
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} else {
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return ""
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}
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}
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