open-consul/agent/checks/docker.go

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package checks
import (
"bytes"
"encoding/json"
"fmt"
"io"
"io/ioutil"
"net/http"
"net/url"
"strings"
"github.com/armon/circbuf"
"github.com/docker/go-connections/sockets"
)
// DockerClient is a simplified client for the Docker Engine API
// to execute the health checks and avoid significant dependencies.
// It also consumes all data returned from the Docker API through
// a ring buffer with a fixed limit to avoid excessive resource
// consumption.
type DockerClient struct {
host string
scheme string
proto string
addr string
basepath string
maxbuf int64
client *http.Client
}
func NewDockerClient(host string, maxbuf int64) (*DockerClient, error) {
if host == "" {
host = DefaultDockerHost
}
proto, addr, basepath, err := ParseHost(host)
if err != nil {
return nil, err
}
transport := new(http.Transport)
sockets.ConfigureTransport(transport, proto, addr)
client := &http.Client{Transport: transport}
return &DockerClient{
host: host,
scheme: "http",
proto: proto,
addr: addr,
basepath: basepath,
maxbuf: maxbuf,
client: client,
}, nil
}
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func (c *DockerClient) Close() error {
if t, ok := c.client.Transport.(*http.Transport); ok {
t.CloseIdleConnections()
}
return nil
}
func (c *DockerClient) Host() string {
return c.host
}
// ParseHost verifies that the given host strings is valid.
// copied from github.com/docker/docker/client.go
func ParseHost(host string) (string, string, string, error) {
protoAddrParts := strings.SplitN(host, "://", 2)
if len(protoAddrParts) == 1 {
return "", "", "", fmt.Errorf("unable to parse docker host `%s`", host)
}
var basePath string
proto, addr := protoAddrParts[0], protoAddrParts[1]
if proto == "tcp" {
parsed, err := url.Parse("tcp://" + addr)
if err != nil {
return "", "", "", err
}
addr = parsed.Host
basePath = parsed.Path
}
return proto, addr, basePath, nil
}
func (c *DockerClient) call(method, uri string, v interface{}) (*circbuf.Buffer, int, error) {
req, err := http.NewRequest(method, uri, nil)
if err != nil {
return nil, 0, err
}
if c.proto == "unix" || c.proto == "npipe" {
// For local communications, it doesn't matter what the host is. We just
// need a valid and meaningful host name. (See #189)
req.Host = "docker"
}
req.URL.Host = c.addr
req.URL.Scheme = c.scheme
if v != nil {
var b bytes.Buffer
if err := json.NewEncoder(&b).Encode(v); err != nil {
return nil, 0, err
}
req.Body = ioutil.NopCloser(&b)
req.Header.Set("Content-Type", "application/json")
}
resp, err := c.client.Do(req)
if err != nil {
return nil, 0, err
}
defer resp.Body.Close()
b, err := circbuf.NewBuffer(c.maxbuf)
if err != nil {
return nil, 0, err
}
_, err = io.Copy(b, resp.Body)
return b, resp.StatusCode, err
}
func (c *DockerClient) CreateExec(containerID string, cmd []string) (string, error) {
data := struct {
AttachStdin bool
AttachStdout bool
AttachStderr bool
Tty bool
Cmd []string
}{
AttachStderr: true,
AttachStdout: true,
Cmd: cmd,
}
uri := fmt.Sprintf("/containers/%s/exec", url.QueryEscape(containerID))
b, code, err := c.call("POST", uri, data)
switch {
case err != nil:
return "", fmt.Errorf("create exec failed for container %s: %v", containerID, err)
case code == 201:
var resp struct{ Id string }
if err = json.NewDecoder(bytes.NewReader(b.Bytes())).Decode(&resp); err != nil {
return "", fmt.Errorf("create exec response for container %s cannot be parsed: %s", containerID, err)
}
return resp.Id, nil
case code == 404:
return "", fmt.Errorf("create exec failed for unknown container %s", containerID)
case code == 409:
return "", fmt.Errorf("create exec failed since container %s is paused or stopped", containerID)
default:
return "", fmt.Errorf("create exec failed for container %s with status %d: %s", containerID, code, b)
}
}
func (c *DockerClient) StartExec(containerID, execID string) (*circbuf.Buffer, error) {
data := struct{ Detach, Tty bool }{Detach: false, Tty: true}
uri := fmt.Sprintf("/exec/%s/start", execID)
b, code, err := c.call("POST", uri, data)
switch {
// todo(fs): https://github.com/hashicorp/consul/pull/3621
// todo(fs): for some reason the docker agent closes the connection during the
// todo(fs): io.Copy call in c.call which causes a "connection reset by peer" error
// todo(fs): even though both body and status code have been received. My current is
// todo(fs): that the docker agent closes this prematurely but I don't understand why.
// todo(fs): the code below ignores this error.
case err != nil && !strings.Contains(err.Error(), "connection reset by peer"):
return nil, fmt.Errorf("start exec failed for container %s: %v", containerID, err)
case code == 200:
return b, nil
case code == 404:
return nil, fmt.Errorf("start exec failed for container %s: invalid exec id %s", containerID, execID)
case code == 409:
return nil, fmt.Errorf("start exec failed since container %s is paused or stopped", containerID)
default:
return nil, fmt.Errorf("start exec failed for container %s with status %d: body: %s err: %v", containerID, code, b, err)
}
}
func (c *DockerClient) InspectExec(containerID, execID string) (int, error) {
uri := fmt.Sprintf("/exec/%s/json", execID)
b, code, err := c.call("GET", uri, nil)
switch {
case err != nil:
return 0, fmt.Errorf("inspect exec failed for container %s: %s", containerID, err)
case code == 200:
var resp struct{ ExitCode int }
if err := json.NewDecoder(bytes.NewReader(b.Bytes())).Decode(&resp); err != nil {
return 0, fmt.Errorf("inspect exec response for container %s cannot be parsed: %v", containerID, err)
}
return resp.ExitCode, nil
case code == 404:
return 0, fmt.Errorf("inspect exec failed for container %s: invalid exec id %s", containerID, execID)
default:
return 0, fmt.Errorf("inspect exec failed for container %s with status %d: %s", containerID, code, b)
}
}