ghproxy.go

/*
Copyright 2018 The Kubernetes 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 main

import (
	"errors"
	"flag"
	"fmt"
	"net/http"
	"net/http/httputil"
	"net/url"
	"strconv"
	"time"

	"github.com/prometheus/client_golang/prometheus"
	"github.com/sirupsen/logrus"

	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"

	"k8s.io/test-infra/ghproxy/ghcache"
	"k8s.io/test-infra/greenhouse/diskutil"
	"k8s.io/test-infra/prow/config"
	"k8s.io/test-infra/prow/interrupts"
	"k8s.io/test-infra/prow/logrusutil"
	"k8s.io/test-infra/prow/metrics"
	"k8s.io/test-infra/prow/pjutil"
)

var (
	diskFree = prometheus.NewGauge(prometheus.GaugeOpts{
		Name: "ghcache_disk_free",
		Help: "Free gb on github-cache disk",
	})
	diskUsed = prometheus.NewGauge(prometheus.GaugeOpts{
		Name: "ghcache_disk_used",
		Help: "Used gb on github-cache disk",
	})
	diskTotal = prometheus.NewGauge(prometheus.GaugeOpts{
		Name: "ghcache_disk_total",
		Help: "Total gb on github-cache disk",
	})
)

func init() {
	prometheus.MustRegister(diskFree)
	prometheus.MustRegister(diskUsed)
	prometheus.MustRegister(diskTotal)
}

// GitHub reverse proxy HTTP cache RoundTripper stack:
//  v -   <Client(s)>
//  v ^ reverse proxy
//  v ^ ghcache: downstreamTransport (coalescing, instrumentation)
//  v ^ ghcache: httpcache layer
//  v ^ ghcache: upstreamTransport (cache-control, instrumentation)
//  v ^ http.DefaultTransport
//  > ^   <Upstream>

type options struct {
	dir    string
	sizeGB int

	redisAddress string

	port           int
	upstream       string
	upstreamParsed *url.URL

	maxConcurrency int

	// pushGateway fields are used to configure pushing prometheus metrics.
	pushGateway         string
	pushGatewayInterval time.Duration

	logLevel string

	serveMetrics bool
}

func (o *options) validate() error {
	level, err := logrus.ParseLevel(o.logLevel)
	if err != nil {
		return fmt.Errorf("invalid log level specified: %v", err)
	}
	logrus.SetLevel(level)

	if (o.dir == "") != (o.sizeGB == 0) {
		return errors.New("--cache-dir and --cache-sizeGB must be specified together to enable the disk cache (otherwise a memory cache is used)")
	}
	upstreamURL, err := url.Parse(o.upstream)
	if err != nil {
		return fmt.Errorf("failed to parse upstream URL: %v", err)
	}
	o.upstreamParsed = upstreamURL
	return nil
}

func flagOptions() *options {
	o := &options{}
	flag.StringVar(&o.dir, "cache-dir", "", "Directory to cache to if using a disk cache.")
	flag.IntVar(&o.sizeGB, "cache-sizeGB", 0, "Cache size in GB if using a disk cache.")
	flag.StringVar(&o.redisAddress, "redis-address", "", "Redis address if using a redis cache e.g. localhost:6379.")
	flag.IntVar(&o.port, "port", 8888, "Port to listen on.")
	flag.StringVar(&o.upstream, "upstream", "https://api.github.com", "Scheme, host, and base path of reverse proxy upstream.")
	flag.IntVar(&o.maxConcurrency, "concurrency", 25, "Maximum number of concurrent in-flight requests to GitHub.")
	flag.StringVar(&o.pushGateway, "push-gateway", "", "If specified, push prometheus metrics to this endpoint.")
	flag.DurationVar(&o.pushGatewayInterval, "push-gateway-interval", time.Minute, "Interval at which prometheus metrics are pushed.")
	flag.StringVar(&o.logLevel, "log-level", "debug", fmt.Sprintf("Log level is one of %v.", logrus.AllLevels))
	flag.BoolVar(&o.serveMetrics, "serve-metrics", false, "If true, it serves prometheus metrics")
	return o
}

func main() {
	logrusutil.ComponentInit("ghproxy")

	o := flagOptions()
	flag.Parse()
	if err := o.validate(); err != nil {
		logrus.WithError(err).Fatal("Invalid arguments.")
	}

	var cache http.RoundTripper
	if o.redisAddress != "" {
		cache = ghcache.NewRedisCache(http.DefaultTransport, o.redisAddress, o.maxConcurrency)
	} else if o.dir == "" {
		cache = ghcache.NewMemCache(http.DefaultTransport, o.maxConcurrency)
	} else {
		cache = ghcache.NewDiskCache(http.DefaultTransport, o.dir, o.sizeGB, o.maxConcurrency)
		go diskMonitor(o.pushGatewayInterval, o.dir)
	}

	pjutil.ServePProf()
	defer interrupts.WaitForGracefulShutdown()
	metrics.ExposeMetrics("ghproxy", config.PushGateway{
		Endpoint: o.pushGateway, Interval: &metav1.Duration{Duration: o.pushGatewayInterval}, ServeMetrics: o.serveMetrics})

	proxy := newReverseProxy(o.upstreamParsed, cache, 30*time.Second)
	server := &http.Server{Addr: ":" + strconv.Itoa(o.port), Handler: proxy}
	interrupts.ListenAndServe(server, 30*time.Second)
}

func newReverseProxy(upstreamURL *url.URL, transport http.RoundTripper, timeout time.Duration) http.Handler {
	proxy := httputil.NewSingleHostReverseProxy(upstreamURL)
	// Wrap the director to change the upstream request 'Host' header to the
	// target host.
	director := proxy.Director
	proxy.Director = func(req *http.Request) {
		director(req)
		req.Host = req.URL.Host
	}
	proxy.Transport = transport

	return http.TimeoutHandler(proxy, timeout, fmt.Sprintf("ghproxy timed out after %v", timeout))
}

// helper to update disk metrics (copied from greenhouse)
func diskMonitor(interval time.Duration, diskRoot string) {
	logger := logrus.WithField("sync-loop", "disk-monitor")
	ticker := time.NewTicker(interval)
	for ; true; <-ticker.C {
		logger.Info("tick")
		_, bytesFree, bytesUsed, err := diskutil.GetDiskUsage(diskRoot)
		if err != nil {
			logger.WithError(err).Error("Failed to get disk metrics")
		} else {
			diskFree.Set(float64(bytesFree) / 1e9)
			diskUsed.Set(float64(bytesUsed) / 1e9)
			diskTotal.Set(float64(bytesFree+bytesUsed) / 1e9)
		}
	}
}