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roundtrip.go
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/
roundtrip.go
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// Copyright 2016 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// Mostly lifted from prometheus/web/api/v1/api.go.
package queryrangebase
import (
"context"
"flag"
"io"
"io/ioutil"
"net/http"
"time"
"github.com/grafana/dskit/flagext"
"github.com/opentracing/opentracing-go"
"github.com/pkg/errors"
"github.com/weaveworks/common/httpgrpc"
"github.com/weaveworks/common/user"
)
const day = 24 * time.Hour
// PassthroughMiddleware is a noop middleware
var PassthroughMiddleware = MiddlewareFunc(func(next Handler) Handler {
return next
})
// Config for query_range middleware chain.
type Config struct {
// Deprecated: SplitQueriesByInterval will be removed in the next major release
SplitQueriesByInterval time.Duration `yaml:"split_queries_by_interval"`
AlignQueriesWithStep bool `yaml:"align_queries_with_step"`
ResultsCacheConfig `yaml:"results_cache"`
CacheResults bool `yaml:"cache_results"`
MaxRetries int `yaml:"max_retries"`
ShardedQueries bool `yaml:"parallelise_shardable_queries"`
// List of headers which query_range middleware chain would forward to downstream querier.
ForwardHeaders flagext.StringSlice `yaml:"forward_headers_list"`
}
// RegisterFlags adds the flags required to config this to the given FlagSet.
func (cfg *Config) RegisterFlags(f *flag.FlagSet) {
f.IntVar(&cfg.MaxRetries, "querier.max-retries-per-request", 5, "Maximum number of retries for a single request; beyond this, the downstream error is returned.")
f.BoolVar(&cfg.AlignQueriesWithStep, "querier.align-querier-with-step", false, "Mutate incoming queries to align their start and end with their step.")
f.BoolVar(&cfg.CacheResults, "querier.cache-results", false, "Cache query results.")
f.BoolVar(&cfg.ShardedQueries, "querier.parallelise-shardable-queries", true, "Perform query parallelisations based on storage sharding configuration and query ASTs. This feature is supported only by the chunks storage engine.")
f.Var(&cfg.ForwardHeaders, "frontend.forward-headers-list", "List of headers forwarded by the query Frontend to downstream querier.")
cfg.ResultsCacheConfig.RegisterFlags(f)
}
// Validate validates the config.
func (cfg *Config) Validate() error {
if cfg.SplitQueriesByInterval != 0 {
return errors.New("the yaml flag `split_queries_by_interval` must now be set in the `limits_config` section instead of the `query_range` config section")
}
if cfg.CacheResults {
if err := cfg.ResultsCacheConfig.Validate(); err != nil {
return errors.Wrap(err, "invalid ResultsCache config")
}
}
return nil
}
// HandlerFunc is like http.HandlerFunc, but for Handler.
type HandlerFunc func(context.Context, Request) (Response, error)
// Do implements Handler.
func (q HandlerFunc) Do(ctx context.Context, req Request) (Response, error) {
return q(ctx, req)
}
// Handler is like http.Handle, but specifically for Prometheus query_range calls.
type Handler interface {
Do(context.Context, Request) (Response, error)
}
// MiddlewareFunc is like http.HandlerFunc, but for Middleware.
type MiddlewareFunc func(Handler) Handler
// Wrap implements Middleware.
func (q MiddlewareFunc) Wrap(h Handler) Handler {
return q(h)
}
// Middleware is a higher order Handler.
type Middleware interface {
Wrap(Handler) Handler
}
// MergeMiddlewares produces a middleware that applies multiple middleware in turn;
// ie Merge(f,g,h).Wrap(handler) == f.Wrap(g.Wrap(h.Wrap(handler)))
func MergeMiddlewares(middleware ...Middleware) Middleware {
return MiddlewareFunc(func(next Handler) Handler {
for i := len(middleware) - 1; i >= 0; i-- {
next = middleware[i].Wrap(next)
}
return next
})
}
// Tripperware is a signature for all http client-side middleware.
type Tripperware func(http.RoundTripper) http.RoundTripper
// RoundTripFunc is to http.RoundTripper what http.HandlerFunc is to http.Handler.
type RoundTripFunc func(*http.Request) (*http.Response, error)
// RoundTrip implements http.RoundTripper.
func (f RoundTripFunc) RoundTrip(r *http.Request) (*http.Response, error) {
return f(r)
}
type roundTripper struct {
next http.RoundTripper
handler Handler
codec Codec
headers []string
}
// NewRoundTripper merges a set of middlewares into an handler, then inject it into the `next` roundtripper
// using the codec to translate requests and responses.
func NewRoundTripper(next http.RoundTripper, codec Codec, headers []string, middlewares ...Middleware) http.RoundTripper {
transport := roundTripper{
next: next,
codec: codec,
headers: headers,
}
transport.handler = MergeMiddlewares(middlewares...).Wrap(&transport)
return transport
}
func (q roundTripper) RoundTrip(r *http.Request) (*http.Response, error) {
// include the headers specified in the roundTripper during decoding the request.
request, err := q.codec.DecodeRequest(r.Context(), r, q.headers)
if err != nil {
return nil, err
}
if span := opentracing.SpanFromContext(r.Context()); span != nil {
request.LogToSpan(span)
}
response, err := q.handler.Do(r.Context(), request)
if err != nil {
return nil, err
}
return q.codec.EncodeResponse(r.Context(), response)
}
// Do implements Handler.
func (q roundTripper) Do(ctx context.Context, r Request) (Response, error) {
request, err := q.codec.EncodeRequest(ctx, r)
if err != nil {
return nil, err
}
if err := user.InjectOrgIDIntoHTTPRequest(ctx, request); err != nil {
return nil, httpgrpc.Errorf(http.StatusBadRequest, err.Error())
}
response, err := q.next.RoundTrip(request)
if err != nil {
return nil, err
}
defer func() {
_, _ = io.Copy(ioutil.Discard, io.LimitReader(response.Body, 1024)) //nolint:errcheck
response.Body.Close()
}()
return q.codec.DecodeResponse(ctx, response, r)
}