Benson Wong
6cf1317341
- make concurrency limiting the scheduler.Scheduler's responsibility - eliminate the separate concurrency limit middleware - move concurrencyLimit logic into scheduler.FIFO to maintain backwards compatibility - add HTTPError from #834 Updates #834
64 lines
1.7 KiB
Go
64 lines
1.7 KiB
Go
package shared
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import (
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"encoding/json"
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"net/http"
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"strconv"
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)
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// HTTPError is an error that carries a complete HTTP response. A producer (e.g.
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// a scheduler shedding a request) returns one of these; a renderer (e.g.
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// router.SendError) writes the status, headers, and body verbatim instead of
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// mapping the error to a generic status. It is the seam that lets a component
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// shed a request with a rich response (e.g. a 429 with rate-limit headers and a
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// JSON hint body) without the renderer knowing the producer's internals.
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type HTTPError interface {
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error
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StatusCode() int
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Header() http.Header
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Body() []byte
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}
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// ConcurrencyLimitError is an HTTPError for a 429 concurrency-limit rejection.
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// Zero-value fields fall back to sensible defaults: a 1-second Retry-After and a
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// JSON hint body.
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type ConcurrencyLimitError struct {
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// RetryAfter, when > 0, is sent as the Retry-After header (in seconds).
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// Defaults to 1.
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RetryAfter int
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// Message overrides the JSON body's "error" field. Defaults to
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// "Too many requests".
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Message string
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}
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func (e ConcurrencyLimitError) Error() string { return "concurrency limit reached" }
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func (e ConcurrencyLimitError) StatusCode() int { return http.StatusTooManyRequests }
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func (e ConcurrencyLimitError) Header() http.Header {
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h := http.Header{}
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h.Set("Content-Type", "application/json")
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h.Set("Retry-After", e.retryAfter())
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return h
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}
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func (e ConcurrencyLimitError) Body() []byte {
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b, _ := json.Marshal(map[string]string{"error": e.message()})
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return b
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}
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func (e ConcurrencyLimitError) retryAfter() string {
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if e.RetryAfter > 0 {
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return strconv.Itoa(e.RetryAfter)
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}
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return "1"
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}
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func (e ConcurrencyLimitError) message() string {
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if e.Message != "" {
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return e.Message
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}
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return "Too many requests"
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}
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