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package client // import "github.com/docker/docker/client"
import (
"bytes"
"context"
"encoding/json"
"errors"
"io"
"net/url"
"github.com/docker/docker/api/types/container"
"github.com/docker/docker/api/types/versions"
)
const containerWaitErrorMsgLimit = 2 * 1024 /* Max: 2KiB */
// ContainerWait waits until the specified container is in a certain state
// indicated by the given condition, either "not-running" (default),
// "next-exit", or "removed".
//
// If this client's API version is before 1.30, condition is ignored and
// ContainerWait will return immediately with the two channels, as the server
// will wait as if the condition were "not-running".
//
// If this client's API version is at least 1.30, ContainerWait blocks until
// the request has been acknowledged by the server (with a response header),
// then returns two channels on which the caller can wait for the exit status
// of the container or an error if there was a problem either beginning the
// wait request or in getting the response. This allows the caller to
// synchronize ContainerWait with other calls, such as specifying a
// "next-exit" condition before issuing a ContainerStart request.
func (cli *Client) ContainerWait(ctx context.Context, containerID string, condition container.WaitCondition) (<-chan container.WaitResponse, <-chan error) {
if versions.LessThan(cli.ClientVersion(), "1.30") {
return cli.legacyContainerWait(ctx, containerID)
}
resultC := make(chan container.WaitResponse)
errC := make(chan error, 1)
query := url.Values{}
if condition != "" {
query.Set("condition", string(condition))
}
resp, err := cli.post(ctx, "/containers/"+containerID+"/wait", query, nil, nil)
if err != nil {
defer ensureReaderClosed(resp)
errC <- err
return resultC, errC
}
go func() {
defer ensureReaderClosed(resp)
body := resp.body
responseText := bytes.NewBuffer(nil)
stream := io.TeeReader(body, responseText)
var res container.WaitResponse
if err := json.NewDecoder(stream).Decode(&res); err != nil {
// NOTE(nicks): The /wait API does not work well with HTTP proxies.
// At any time, the proxy could cut off the response stream.
//
// But because the HTTP status has already been written, the proxy's
// only option is to write a plaintext error message.
//
// If there's a JSON parsing error, read the real error message
// off the body and send it to the client.
_, _ = io.ReadAll(io.LimitReader(stream, containerWaitErrorMsgLimit))
errC <- errors.New(responseText.String())
return
}
resultC <- res
}()
return resultC, errC
}
// legacyContainerWait returns immediately and doesn't have an option to wait
// until the container is removed.
func (cli *Client) legacyContainerWait(ctx context.Context, containerID string) (<-chan container.WaitResponse, <-chan error) {
resultC := make(chan container.WaitResponse)
errC := make(chan error)
go func() {
resp, err := cli.post(ctx, "/containers/"+containerID+"/wait", nil, nil, nil)
if err != nil {
errC <- err
return
}
defer ensureReaderClosed(resp)
var res container.WaitResponse
if err := json.NewDecoder(resp.body).Decode(&res); err != nil {
errC <- err
return
}
resultC <- res
}()
return resultC, errC
}
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