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events_utils.go
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events_utils.go
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package main
import (
"bufio"
"bytes"
"fmt"
"io"
"os/exec"
"strconv"
"github.com/go-check/check"
)
// eventMatcher is a function that tries to match an event input.
type eventMatcher func(text string)
// eventObserver runs an events commands and observes its output.
type eventObserver struct {
buffer *bytes.Buffer
command *exec.Cmd
stdout io.Reader
}
// newEventObserver creates the observer and initializes the command
// without running it. Users must call `eventObserver.Start` to start the command.
func newEventObserver(c *check.C, args ...string) (*eventObserver, error) {
since := daemonTime(c).Unix()
cmdArgs := []string{"events", "--since", strconv.FormatInt(since, 10)}
if len(args) > 0 {
cmdArgs = append(cmdArgs, args...)
}
eventsCmd := exec.Command(dockerBinary, cmdArgs...)
stdout, err := eventsCmd.StdoutPipe()
if err != nil {
return nil, err
}
return &eventObserver{
buffer: new(bytes.Buffer),
command: eventsCmd,
stdout: stdout,
}, nil
}
// Start starts the events command.
func (e *eventObserver) Start() error {
return e.command.Start()
}
// Stop stops the events command.
func (e *eventObserver) Stop() {
e.command.Process.Kill()
}
// Match tries to match the events output with a given matcher.
func (e *eventObserver) Match(match eventMatcher) {
scanner := bufio.NewScanner(e.stdout)
for scanner.Scan() {
text := scanner.Text()
e.buffer.WriteString(text)
e.buffer.WriteString("\n")
match(text)
}
}
// TimeoutError generates an error for a given containerID and event type.
// It attaches the events command output to the error.
func (e *eventObserver) TimeoutError(id, event string) error {
return fmt.Errorf("failed to observe event `%s` for %s\n%v", event, id, e.output())
}
// output returns the events command output read until now by the Match goroutine.
func (e *eventObserver) output() string {
return e.buffer.String()
}