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docker_cache.go
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docker_cache.go
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package main
import (
"flag"
"fmt"
"github.com/samalba/dockerclient"
"log"
"math/rand"
"os"
"strings"
"time"
)
type Config struct {
Id string
HttpApiAddress string
CacheURL string
DockerURL string
UpdateInterval time.Duration
}
type RuntimeInfo struct {
Id string
Cache *Cache
Docker *dockerclient.DockerClient
Ttl time.Duration
}
// Callback used to listen to Docker's events
func dockerEventCallback(event *dockerclient.Event, args ...interface{}) {
rtInfo := args[0].(*RuntimeInfo)
eventName := strings.ToLower(event.Status)
eventErr := func(err error) {
log.Println("Cannot process event:", eventName, event.Id, err)
}
if eventName == "start" || eventName == "restart" {
containerInfo, err := rtInfo.Docker.InspectContainer(event.Id)
if err != nil {
eventErr(err)
return
}
err = rtInfo.Cache.AddContainer(containerInfo)
if err != nil {
eventErr(err)
}
log.Println("Reported 1 new container to the Cache:", event.Id)
return
}
if eventName == "die" {
containerInfo, err := rtInfo.Docker.InspectContainer(event.Id)
if err != nil {
eventErr(err)
return
}
err = rtInfo.Cache.DeleteContainer(containerInfo)
if err != nil {
eventErr(err)
}
log.Println("Removed 1 container from the Cache:", event.Id)
return
}
}
func update(rtInfo *RuntimeInfo) {
containers, err := rtInfo.Docker.ListContainers(false)
if err != nil {
log.Println("Cannot list Docker containers:", err,
"(will retry later)")
return
}
for _, container := range containers {
containerInfo, err := rtInfo.Docker.InspectContainer(container.Id)
if err != nil {
// If we cannot get the info of the container, it may have been
// removed already. Ignoring to avoid race condition.
continue
}
err = rtInfo.Cache.SetContainerInfo(containerInfo)
if err != nil {
log.Println("Cannot write in the Cache (SetContainerInfo):", err)
return
}
}
err = rtInfo.Cache.SetContainersList(containers)
if err != nil {
log.Println("Cannot write in the Cache (SetContainersList):", err)
return
}
log.Println("Reported", len(containers), "containers to the Cache")
version, err := rtInfo.Docker.Version()
if err != nil {
log.Println("Cannot get Docker's version:", err)
return
}
versionString := fmt.Sprintf("%s;git-%s;%s", version.Version,
version.GitCommit, version.GoVersion)
rtInfo.Cache.SetHostParam("docker_version", versionString)
}
func getHostname() string {
hostname, err := os.Hostname()
if err != nil {
log.Fatal(err)
}
return hostname
}
func parseFlags() *Config {
config := &Config{}
flag.StringVar(&config.Id, "id", getHostname(),
"Id that will identify this host on the Cache (it should be unique to avoid conflicts)")
flag.StringVar(&config.HttpApiAddress, "listen", ":8000",
"Listen address for the HTTP API server")
flag.StringVar(&config.CacheURL, "cache", "redis://localhost:6379",
"Cache URL which will receive the data")
flag.StringVar(&config.DockerURL, "docker", "unix:///var/run/docker.sock",
"Docker daemon URL to read the data")
flag.DurationVar(&config.UpdateInterval, "updateInterval",
time.Duration(120)*time.Second,
"Interval for polling data from Docker")
flag.Parse()
return config
}
func main() {
random := rand.New(rand.NewSource(int64(int(time.Now().UnixNano()) * os.Getpid())))
config := parseFlags()
ttl := time.Duration(float64(config.UpdateInterval) * 1.5)
cache, err := NewCache(config.CacheURL, config.Id, ttl)
if err != nil {
log.Fatalf("Cannot init the cache: %s", err)
}
docker, err := dockerclient.NewDockerClient(config.DockerURL, nil)
if err != nil {
log.Fatalf("Cannot init the docker client: %s", err)
}
rtInfo := &RuntimeInfo{config.Id, cache, docker, ttl}
log.Printf("Started monitoring Docker events (%s)\n", config.Id)
docker.StartMonitorEvents(dockerEventCallback, rtInfo)
go func() {
// Start the HTTP API
log.Printf("Starting API HTTP server on %s", config.HttpApiAddress)
err := StartHttpApi(cache, config.HttpApiAddress)
if err != nil {
log.Fatalf("Cannot start the HTTP API: %s", err)
}
}()
go func() {
// Garbage collect expired hosts at random interval
for {
cache.ClearExpiredHosts()
offset := random.Intn(int(config.UpdateInterval.Seconds()))
time.Sleep(config.UpdateInterval + (time.Duration(offset) * time.Second))
}
}()
func() {
for {
update(rtInfo)
time.Sleep(config.UpdateInterval)
}
}()
}