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handler.go
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handler.go
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/*
Copyright 2018 The Knative 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.
*/
package handler
import (
"context"
"net/http"
"net/http/httputil"
"net/url"
"go.opencensus.io/plugin/ochttp"
"go.opencensus.io/trace"
"go.uber.org/zap"
"knative.dev/pkg/logging"
pkgnet "knative.dev/pkg/network"
tracingconfig "knative.dev/pkg/tracing/config"
"knative.dev/serving/pkg/activator"
activatorconfig "knative.dev/serving/pkg/activator/config"
activatornet "knative.dev/serving/pkg/activator/net"
"knative.dev/serving/pkg/activator/util"
"knative.dev/serving/pkg/network"
"knative.dev/serving/pkg/queue"
)
// Throttler is the interface that Handler calls to Try to proxy the user request.
type Throttler interface {
Try(context.Context, func(string) error) error
}
// activationHandler will wait for an active endpoint for a revision
// to be available before proxying the request
type activationHandler struct {
transport http.RoundTripper
tracingTransport http.RoundTripper
throttler Throttler
bufferPool httputil.BufferPool
}
// New constructs a new http.Handler that deals with revision activation.
func New(ctx context.Context, t Throttler) http.Handler {
defaultTransport := pkgnet.AutoTransport
return &activationHandler{
transport: defaultTransport,
tracingTransport: &ochttp.Transport{Base: defaultTransport},
throttler: t,
bufferPool: network.NewBufferPool(),
}
}
func (a *activationHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
logger := logging.FromContext(r.Context())
tracingEnabled := activatorconfig.FromContext(r.Context()).Tracing.Backend != tracingconfig.None
tryContext, trySpan := r.Context(), (*trace.Span)(nil)
if tracingEnabled {
tryContext, trySpan = trace.StartSpan(r.Context(), "throttler_try")
}
if err := a.throttler.Try(tryContext, func(dest string) error {
trySpan.End()
proxyCtx, proxySpan := r.Context(), (*trace.Span)(nil)
if tracingEnabled {
proxyCtx, proxySpan = trace.StartSpan(r.Context(), "proxy")
}
a.proxyRequest(logger, w, r.WithContext(proxyCtx), &url.URL{
Scheme: "http",
Host: dest,
}, tracingEnabled)
proxySpan.End()
return nil
}); err != nil {
// Set error on our capacity waiting span and end it
trySpan.Annotate([]trace.Attribute{trace.StringAttribute("activator.throttler.error", err.Error())}, "ThrottlerTry")
trySpan.End()
logger.Errorw("Throttler try error", zap.Error(err))
switch err {
case activatornet.ErrActivatorOverload, context.DeadlineExceeded, queue.ErrRequestQueueFull:
http.Error(w, err.Error(), http.StatusServiceUnavailable)
default:
w.WriteHeader(http.StatusInternalServerError)
}
}
}
func (a *activationHandler) proxyRequest(logger *zap.SugaredLogger, w http.ResponseWriter, r *http.Request, target *url.URL, tracingEnabled bool) {
network.RewriteHostIn(r)
r.Header.Set(network.ProxyHeaderName, activator.Name)
// Setup the reverse proxy.
proxy := httputil.NewSingleHostReverseProxy(target)
proxy.BufferPool = a.bufferPool
proxy.Transport = a.transport
if tracingEnabled {
proxy.Transport = a.tracingTransport
}
proxy.FlushInterval = -1
proxy.ErrorHandler = pkgnet.ErrorHandler(logger)
util.SetupHeaderPruning(proxy)
proxy.ServeHTTP(w, r)
}