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moby--moby/client/events.go
Brian Goff 47585996bf Fixes a race condition in client events monitoring
In cases where there is high latency (ie, not-local network)
`waitExitOrRemoved` was not receiving events for short-lived containers.
This caused the client to hang while waiting for a notification that the
container has stopped.

This happens because `client.Events()` returns immediately and spins a
goroutine up to process events. The problem here is it returns before
the request to the events endpoint is even made.
Even without high-latency issues, there is no guarantee that the
goroutine is even scheduled by the time the function returns.

Signed-off-by: Brian Goff <cpuguy83@gmail.com>
2016-12-16 10:11:53 -05:00

102 lines
2.2 KiB
Go

package client
import (
"encoding/json"
"net/url"
"time"
"golang.org/x/net/context"
"github.com/docker/docker/api/types"
"github.com/docker/docker/api/types/events"
"github.com/docker/docker/api/types/filters"
timetypes "github.com/docker/docker/api/types/time"
)
// Events returns a stream of events in the daemon. It's up to the caller to close the stream
// by cancelling the context. Once the stream has been completely read an io.EOF error will
// be sent over the error channel. If an error is sent all processing will be stopped. It's up
// to the caller to reopen the stream in the event of an error by reinvoking this method.
func (cli *Client) Events(ctx context.Context, options types.EventsOptions) (<-chan events.Message, <-chan error) {
messages := make(chan events.Message)
errs := make(chan error, 1)
started := make(chan struct{})
go func() {
defer close(errs)
query, err := buildEventsQueryParams(cli.version, options)
if err != nil {
close(started)
errs <- err
return
}
resp, err := cli.get(ctx, "/events", query, nil)
if err != nil {
close(started)
errs <- err
return
}
defer resp.body.Close()
decoder := json.NewDecoder(resp.body)
close(started)
for {
select {
case <-ctx.Done():
errs <- ctx.Err()
return
default:
var event events.Message
if err := decoder.Decode(&event); err != nil {
errs <- err
return
}
select {
case messages <- event:
case <-ctx.Done():
errs <- ctx.Err()
return
}
}
}
}()
<-started
return messages, errs
}
func buildEventsQueryParams(cliVersion string, options types.EventsOptions) (url.Values, error) {
query := url.Values{}
ref := time.Now()
if options.Since != "" {
ts, err := timetypes.GetTimestamp(options.Since, ref)
if err != nil {
return nil, err
}
query.Set("since", ts)
}
if options.Until != "" {
ts, err := timetypes.GetTimestamp(options.Until, ref)
if err != nil {
return nil, err
}
query.Set("until", ts)
}
if options.Filters.Len() > 0 {
filterJSON, err := filters.ToParamWithVersion(cliVersion, options.Filters)
if err != nil {
return nil, err
}
query.Set("filters", filterJSON)
}
return query, nil
}