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Diffstat (limited to 'Godeps/_workspace/src/gopkg.in/throttled/throttled.v1/rate.go')
-rw-r--r-- | Godeps/_workspace/src/gopkg.in/throttled/throttled.v1/rate.go | 116 |
1 files changed, 116 insertions, 0 deletions
diff --git a/Godeps/_workspace/src/gopkg.in/throttled/throttled.v1/rate.go b/Godeps/_workspace/src/gopkg.in/throttled/throttled.v1/rate.go new file mode 100644 index 000000000..d7a7de6d7 --- /dev/null +++ b/Godeps/_workspace/src/gopkg.in/throttled/throttled.v1/rate.go @@ -0,0 +1,116 @@ +package throttled + +import ( + "math" + "net/http" + "strconv" + "time" +) + +// Static check to ensure that rateLimiter implements Limiter. +var _ Limiter = (*rateLimiter)(nil) + +// RateLimit creates a throttler that limits the number of requests allowed +// in a certain time window defined by the Quota q. The q parameter specifies +// the requests per time window, and it is silently set to at least 1 request +// and at least a 1 second window if it is less than that. The time window +// starts when the first request is made outside an existing window. Fractions +// of seconds are not supported, they are truncated. +// +// The vary parameter indicates what criteria should be used to group requests +// for which the limit must be applied (ex.: rate limit based on the remote address). +// See varyby.go for the various options. +// +// The specified store is used to keep track of the request count and the +// time remaining in the window. The throttled package comes with some stores +// in the throttled/store package. Custom stores can be created too, by implementing +// the Store interface. +// +// Requests that bust the rate limit are denied access and go through the denied handler, +// which may be specified on the Throttler and that defaults to the package-global +// variable DefaultDeniedHandler. +// +// The rate limit throttler sets the following headers on the response: +// +// X-RateLimit-Limit : quota +// X-RateLimit-Remaining : number of requests remaining in the current window +// X-RateLimit-Reset : seconds before a new window +// +// Additionally, if the request was denied access, the following header is added: +// +// Retry-After : seconds before the caller should retry +// +func RateLimit(q Quota, vary *VaryBy, store Store) *Throttler { + // Extract requests and window + reqs, win := q.Quota() + + // Create and return the throttler + return &Throttler{ + limiter: &rateLimiter{ + reqs: reqs, + window: win, + vary: vary, + store: store, + }, + } +} + +// The rate limiter implements limiting the request to a certain quota +// based on the vary-by criteria. State is saved in the store. +type rateLimiter struct { + reqs int + window time.Duration + vary *VaryBy + store Store +} + +// Start initializes the limiter for execution. +func (r *rateLimiter) Start() { + if r.reqs < 1 { + r.reqs = 1 + } + if r.window < time.Second { + r.window = time.Second + } +} + +// Limit is called for each request to the throttled handler. It checks if +// the request can go through and signals it via the returned channel. +// It returns an error if the operation fails. +func (r *rateLimiter) Limit(w http.ResponseWriter, req *http.Request) (<-chan bool, error) { + // Create return channel and initialize + ch := make(chan bool, 1) + ok := true + key := r.vary.Key(req) + + // Get the current count and remaining seconds + cnt, secs, err := r.store.Incr(key, r.window) + // Handle the possible situations: error, begin new window, or increment current window. + switch { + case err != nil && err != ErrNoSuchKey: + // An unexpected error occurred + return nil, err + case err == ErrNoSuchKey || secs <= 0: + // Reset counter + if err := r.store.Reset(key, r.window); err != nil { + return nil, err + } + cnt = 1 + secs = int(r.window.Seconds()) + default: + // If the limit is reached, deny access + if cnt > r.reqs { + ok = false + } + } + // Set rate-limit headers + w.Header().Add("X-RateLimit-Limit", strconv.Itoa(r.reqs)) + w.Header().Add("X-RateLimit-Remaining", strconv.Itoa(int(math.Max(float64(r.reqs-cnt), 0)))) + w.Header().Add("X-RateLimit-Reset", strconv.Itoa(secs)) + if !ok { + w.Header().Add("Retry-After", strconv.Itoa(secs)) + } + // Send response via the return channel + ch <- ok + return ch, nil +} |