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retry.go
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retry.go
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/*
* Copyright (C) 2023 Intergral GmbH
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
package frontend
import (
"fmt"
"net/http"
"github.com/opentracing/opentracing-go"
"github.com/opentracing/opentracing-go/ext"
ot_log "github.com/opentracing/opentracing-go/log"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/prometheus/promauto"
"github.com/weaveworks/common/httpgrpc"
)
func newRetryWare(maxRetries int, registerer prometheus.Registerer) Middleware {
retriesCount := promauto.With(registerer).NewHistogram(prometheus.HistogramOpts{
Namespace: "deep",
Subsystem: "query_frontend",
Name: "retries",
Help: "Number of times a request is retried.",
Buckets: []float64{0, 1, 2, 3, 4, 5},
})
return MiddlewareFunc(func(next http.RoundTripper) http.RoundTripper {
return retryWare{
next: next,
maxRetries: maxRetries,
retriesCount: retriesCount,
}
})
}
type retryWare struct {
next http.RoundTripper
maxRetries int
retriesCount prometheus.Histogram
}
// RoundTrip implements http.RoundTripper
func (r retryWare) RoundTrip(req *http.Request) (*http.Response, error) {
ctx := req.Context()
span, ctx := opentracing.StartSpanFromContext(ctx, "frontend.Retry")
defer span.Finish()
ext.SpanKindRPCClient.Set(span)
// context propagation
req = req.WithContext(ctx)
tries := 0
defer func() { r.retriesCount.Observe(float64(tries)) }()
for {
if ctx.Err() != nil {
return nil, ctx.Err()
}
resp, err := r.next.RoundTrip(req)
// do not retry if no error and response is not HTTP 5xx
if err == nil && !shouldRetry(resp.StatusCode) {
return resp, nil
}
// do not retry if GRPC error contains response that is not HTTP 5xx
httpResp, ok := httpgrpc.HTTPResponseFromError(err)
if ok && !shouldRetry(int(httpResp.Code)) {
return resp, err
}
// reached max retries
tries++
if tries >= r.maxRetries {
return resp, err
}
statusCode := 0
if resp != nil {
statusCode = resp.StatusCode
}
if httpResp != nil {
statusCode = int(httpResp.Code)
}
// avoid calling err.Error() on an error returned by frontend middleware
// https://github.com/intergral/deep/issues/857
errMsg := fmt.Sprint(err)
span.LogFields(
ot_log.String("msg", "error processing request. retrying"),
ot_log.Int("try", tries),
ot_log.Int("status_code", statusCode),
ot_log.String("errMsg", errMsg),
)
}
}
func shouldRetry(statusCode int) bool {
return statusCode/100 == 5
}