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When Postfix is running in a Docker container, it's most useful to use the built-in Docker logging (as with Systemd). Setting `--docker.enable` allows that. The log source is using `client.NewEnvClient`, which reads environment variables to determine which Docker to connect to, and how TLS is handled.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,96 @@ | ||
| // +build !nodocker | ||
|
|
||
| package main | ||
|
|
||
| import ( | ||
| "bufio" | ||
| "context" | ||
| "io" | ||
| "log" | ||
| "strings" | ||
|
|
||
| "github.com/alecthomas/kingpin" | ||
| "github.com/docker/docker/api/types" | ||
| "github.com/docker/docker/client" | ||
| ) | ||
|
|
||
| // A DockerLogSource reads log records from the given Docker | ||
| // journal. | ||
| type DockerLogSource struct { | ||
| client DockerClient | ||
| containerID string | ||
| reader *bufio.Reader | ||
| } | ||
|
|
||
| // A DockerClient is the client interface that client.Client | ||
| // provides. See https://pkg.go.dev/github.com/docker/docker/client | ||
| type DockerClient interface { | ||
| io.Closer | ||
| ContainerLogs(context.Context, string, types.ContainerLogsOptions) (io.ReadCloser, error) | ||
| } | ||
|
|
||
| // NewDockerLogSource returns a log source for reading Docker logs. | ||
| func NewDockerLogSource(ctx context.Context, c DockerClient, containerID string) (*DockerLogSource, error) { | ||
| r, err := c.ContainerLogs(ctx, containerID, types.ContainerLogsOptions{ | ||
| ShowStdout: true, | ||
| ShowStderr: true, | ||
| Follow: true, | ||
| Tail: "0", | ||
| }) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
|
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| logSrc := &DockerLogSource{ | ||
| client: c, | ||
| containerID: containerID, | ||
| reader: bufio.NewReader(r), | ||
| } | ||
|
|
||
| return logSrc, nil | ||
| } | ||
|
|
||
| func (s *DockerLogSource) Close() error { | ||
| return s.client.Close() | ||
| } | ||
|
|
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| func (s *DockerLogSource) Path() string { | ||
| return "docker:" + s.containerID | ||
| } | ||
|
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| func (s *DockerLogSource) Read(ctx context.Context) (string, error) { | ||
| line, err := s.reader.ReadString('\n') | ||
| if err != nil { | ||
| return "", err | ||
| } | ||
| return strings.TrimSpace(line), nil | ||
| } | ||
|
|
||
| // A dockerLogSourceFactory is a factory that can create | ||
| // DockerLogSources from command line flags. | ||
| type dockerLogSourceFactory struct { | ||
| enable bool | ||
| containerID string | ||
| } | ||
|
|
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| func (f *dockerLogSourceFactory) Init(app *kingpin.Application) { | ||
| app.Flag("docker.enable", "Read from Docker logs. Environment variable DOCKER_HOST can be used to change the address. See https://pkg.go.dev/github.com/docker/docker/client?tab=doc#NewEnvClient for more information.").Default("false").BoolVar(&f.enable) | ||
| app.Flag("docker.container.id", "ID/name of the Postfix Docker container.").Default("postfix").StringVar(&f.containerID) | ||
| } | ||
|
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| func (f *dockerLogSourceFactory) New(ctx context.Context) (LogSourceCloser, error) { | ||
| if !f.enable { | ||
| return nil, nil | ||
| } | ||
|
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||
| log.Println("Reading log events from Docker") | ||
| c, err := client.NewEnvClient() | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| return NewDockerLogSource(ctx, c, f.containerID) | ||
| } | ||
|
|
||
| func init() { | ||
| RegisterLogSourceFactory(&dockerLogSourceFactory{}) | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,79 @@ | ||
| // +build !nodocker | ||
|
|
||
| package main | ||
|
|
||
| import ( | ||
| "context" | ||
| "io" | ||
| "io/ioutil" | ||
| "strings" | ||
| "testing" | ||
|
|
||
| "github.com/docker/docker/api/types" | ||
| "github.com/stretchr/testify/assert" | ||
| ) | ||
|
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| func TestNewDockerLogSource(t *testing.T) { | ||
| ctx := context.Background() | ||
| c := &fakeDockerClient{} | ||
| src, err := NewDockerLogSource(ctx, c, "acontainer") | ||
| if err != nil { | ||
| t.Fatalf("NewDockerLogSource failed: %v", err) | ||
| } | ||
|
|
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| assert.Equal(t, []string{"acontainer"}, c.containerLogsCalls, "A call to ContainerLogs should be made.") | ||
|
|
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| if err := src.Close(); err != nil { | ||
| t.Fatalf("Close failed: %v", err) | ||
| } | ||
|
|
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| assert.Equal(t, 1, c.closeCalls, "A call to Close should be made.") | ||
| } | ||
|
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| func TestDockerLogSource_Path(t *testing.T) { | ||
| ctx := context.Background() | ||
| c := &fakeDockerClient{} | ||
| src, err := NewDockerLogSource(ctx, c, "acontainer") | ||
| if err != nil { | ||
| t.Fatalf("NewDockerLogSource failed: %v", err) | ||
| } | ||
| defer src.Close() | ||
|
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| assert.Equal(t, "docker:acontainer", src.Path(), "Path should be set by New.") | ||
| } | ||
|
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| func TestDockerLogSource_Read(t *testing.T) { | ||
| ctx := context.Background() | ||
|
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| c := &fakeDockerClient{ | ||
| logsReader: ioutil.NopCloser(strings.NewReader("Feb 13 23:31:30 ahost anid[123]: aline\n")), | ||
| } | ||
| src, err := NewDockerLogSource(ctx, c, "acontainer") | ||
| if err != nil { | ||
| t.Fatalf("NewDockerLogSource failed: %v", err) | ||
| } | ||
| defer src.Close() | ||
|
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| s, err := src.Read(ctx) | ||
| if err != nil { | ||
| t.Fatalf("Read failed: %v", err) | ||
| } | ||
| assert.Equal(t, "Feb 13 23:31:30 ahost anid[123]: aline", s, "Read should get data from the journal entry.") | ||
| } | ||
|
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| type fakeDockerClient struct { | ||
| logsReader io.ReadCloser | ||
|
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| containerLogsCalls []string | ||
| closeCalls int | ||
| } | ||
|
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| func (c *fakeDockerClient) ContainerLogs(ctx context.Context, containerID string, opts types.ContainerLogsOptions) (io.ReadCloser, error) { | ||
| c.containerLogsCalls = append(c.containerLogsCalls, containerID) | ||
| return c.logsReader, nil | ||
| } | ||
|
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| func (c *fakeDockerClient) Close() error { | ||
| c.closeCalls++ | ||
| return nil | ||
| } |
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