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0e8e8f0f31
Allows for a plugin type that can be used to scrape metrics. This is useful because metrics are not neccessarily at a standard location... `--metrics-addr` must be set, and must currently be a TCP socket. Even if metrics are done via a unix socket, there's no guarentee where the socket may be located on the system, making bind-mounting such a socket into a container difficult (and racey, failure-prone on daemon restart). Metrics plugins side-step this issue by always listening on a unix socket and then bind-mounting that into a known path in the plugin container. Note there has been similar work in the past (and ultimately punted at the time) for consistent access to the Docker API from within a container. Why not add metrics to the Docker API and just provide a plugin with access to the Docker API? Certainly this can be useful, but gives a lot of control/access to a plugin that may only need the metrics. We can look at supporting API plugins separately for this reason. Signed-off-by: Brian Goff <cpuguy83@gmail.com>
86 lines
2.4 KiB
Go
86 lines
2.4 KiB
Go
// +build !windows
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package daemon
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import (
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"net"
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"net/http"
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"os"
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"path/filepath"
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"syscall"
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"github.com/Sirupsen/logrus"
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"github.com/docker/docker/pkg/mount"
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"github.com/docker/docker/pkg/plugingetter"
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"github.com/docker/docker/pkg/plugins"
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metrics "github.com/docker/go-metrics"
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"github.com/pkg/errors"
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)
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func (daemon *Daemon) listenMetricsSock() (string, error) {
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path := filepath.Join(daemon.configStore.ExecRoot, "metrics.sock")
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syscall.Unlink(path)
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l, err := net.Listen("unix", path)
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if err != nil {
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return "", errors.Wrap(err, "error setting up metrics plugin listener")
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}
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mux := http.NewServeMux()
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mux.Handle("/metrics", metrics.Handler())
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go func() {
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http.Serve(l, mux)
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}()
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daemon.metricsPluginListener = l
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return path, nil
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}
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func registerMetricsPluginCallback(getter plugingetter.PluginGetter, sockPath string) {
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getter.Handle(metricsPluginType, func(name string, client *plugins.Client) {
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// Use lookup since nothing in the system can really reference it, no need
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// to protect against removal
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p, err := getter.Get(name, metricsPluginType, plugingetter.Lookup)
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if err != nil {
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return
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}
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mp := metricsPlugin{p}
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sockBase := mp.sockBase()
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if err := os.MkdirAll(sockBase, 0755); err != nil {
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logrus.WithError(err).WithField("name", name).WithField("path", sockBase).Error("error creating metrics plugin base path")
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return
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}
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defer func() {
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if err != nil {
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os.RemoveAll(sockBase)
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}
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}()
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pluginSockPath := filepath.Join(sockBase, mp.sock())
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_, err = os.Stat(pluginSockPath)
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if err == nil {
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mount.Unmount(pluginSockPath)
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} else {
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logrus.WithField("path", pluginSockPath).Debugf("creating plugin socket")
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f, err := os.OpenFile(pluginSockPath, os.O_CREATE, 0600)
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if err != nil {
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return
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}
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f.Close()
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}
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if err := mount.Mount(sockPath, pluginSockPath, "none", "bind,ro"); err != nil {
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logrus.WithError(err).WithField("name", name).Error("could not mount metrics socket to plugin")
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return
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}
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if err := pluginStartMetricsCollection(p); err != nil {
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if err := mount.Unmount(pluginSockPath); err != nil {
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if mounted, _ := mount.Mounted(pluginSockPath); mounted {
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logrus.WithError(err).WithField("sock_path", pluginSockPath).Error("error unmounting metrics socket from plugin during cleanup")
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}
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}
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logrus.WithError(err).WithField("name", name).Error("error while initializing metrics plugin")
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}
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})
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}
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