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journal: add StderrIsJournalStream function
This function can be used for automatic protocol upgrade described in [1]. Both unit tests and runnable example are included. Only the latter requires systemd, as unit tests are self-sufficient, and only test that JOURNAL_STREAM environment variable is checked properly. [1] https://systemd.io/JOURNAL_NATIVE_PROTOCOL/#automatic-protocol-upgrading
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// Copyright 2022 CoreOS, Inc. | ||
// | ||
// Licensed under the Apache License, Version 2.0 (the "License"); | ||
// you may not use this file except in compliance with the License. | ||
// You may obtain a copy of the License at | ||
// | ||
// http://www.apache.org/licenses/LICENSE-2.0 | ||
// | ||
// Unless required by applicable law or agreed to in writing, software | ||
// distributed under the License is distributed on an "AS IS" BASIS, | ||
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
// See the License for the specific language governing permissions and | ||
// limitations under the License | ||
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package main | ||
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import ( | ||
"fmt" | ||
"os" | ||
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"github.com/coreos/go-systemd/v22/journal" | ||
) | ||
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func main() { | ||
ok, err := journal.StderrIsJournalStream() | ||
if err != nil { | ||
panic(err) | ||
} | ||
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if ok { | ||
// use journal native protocol | ||
journal.Send("this is a message logged through the native protocol", journal.PriInfo, nil) | ||
} else { | ||
// use stderr | ||
fmt.Fprintln(os.Stderr, "this is a message logged through stderr") | ||
} | ||
} |
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#!/bin/bash | ||
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set -e | ||
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go build | ||
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echo "Running directly" | ||
./journal | ||
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echo "Running through systemd" | ||
unit_name="run-$(systemd-id128 new)" | ||
systemd-run -u "$unit_name" --user --wait --quiet ./journal | ||
journalctl --user -u "$unit_name" |
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// Copyright 2022 CoreOS, Inc. | ||
// | ||
// Licensed under the Apache License, Version 2.0 (the "License"); | ||
// you may not use this file except in compliance with the License. | ||
// You may obtain a copy of the License at | ||
// | ||
// http://www.apache.org/licenses/LICENSE-2.0 | ||
// | ||
// Unless required by applicable law or agreed to in writing, software | ||
// distributed under the License is distributed on an "AS IS" BASIS, | ||
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
// See the License for the specific language governing permissions and | ||
// limitations under the License. | ||
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//go:build unix | ||
// +build unix | ||
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package journal_test | ||
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import ( | ||
"fmt" | ||
"os" | ||
"syscall" | ||
"testing" | ||
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"github.com/coreos/go-systemd/v22/journal" | ||
) | ||
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func TestStderrIsJournalStream(t *testing.T) { | ||
if _, ok := os.LookupEnv("JOURNAL_STREAM"); ok { | ||
t.Fatal("unset JOURNAL_STREAM before running this test") | ||
} | ||
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t.Run("Missing", func(t *testing.T) { | ||
ok, err := journal.StderrIsJournalStream() | ||
if err != nil { | ||
t.Fatal(err) | ||
} | ||
if ok { | ||
t.Error("stderr shouldn't be connected to journal stream") | ||
} | ||
}) | ||
t.Run("Present", func(t *testing.T) { | ||
f, stat := getUnixStreamSocket(t) | ||
defer f.Close() | ||
os.Setenv("JOURNAL_STREAM", fmt.Sprintf("%d:%d", stat.Dev, stat.Ino)) | ||
defer os.Unsetenv("JOURNAL_STREAM") | ||
replaceStderr(int(f.Fd()), func() { | ||
ok, err := journal.StderrIsJournalStream() | ||
if err != nil { | ||
t.Fatal(err) | ||
} | ||
if !ok { | ||
t.Error("stderr should've been connected to journal stream") | ||
} | ||
}) | ||
}) | ||
t.Run("NotMatching", func(t *testing.T) { | ||
f, stat := getUnixStreamSocket(t) | ||
defer f.Close() | ||
os.Setenv("JOURNAL_STREAM", fmt.Sprintf("%d:%d", stat.Dev+1, stat.Ino)) | ||
defer os.Unsetenv("JOURNAL_STREAM") | ||
replaceStderr(int(f.Fd()), func() { | ||
ok, err := journal.StderrIsJournalStream() | ||
if err != nil { | ||
t.Fatal(err) | ||
} | ||
if ok { | ||
t.Error("stderr shouldn't be connected to journal stream") | ||
} | ||
}) | ||
}) | ||
t.Run("Malformed", func(t *testing.T) { | ||
f, stat := getUnixStreamSocket(t) | ||
defer f.Close() | ||
os.Setenv("JOURNAL_STREAM", fmt.Sprintf("%d-%d", stat.Dev, stat.Ino)) | ||
defer os.Unsetenv("JOURNAL_STREAM") | ||
replaceStderr(int(f.Fd()), func() { | ||
_, err := journal.StderrIsJournalStream() | ||
if err == nil { | ||
t.Fatal("JOURNAL_STREAM is malformed, but no error returned") | ||
} | ||
}) | ||
}) | ||
} | ||
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func ExampleStderrIsJournalStream() { | ||
// NOTE: this is just an example. Production code | ||
// will likely use this to setup a logging library | ||
// to write messages to either journal or stderr. | ||
ok, err := journal.StderrIsJournalStream() | ||
if err != nil { | ||
panic(err) | ||
} | ||
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if ok { | ||
// use journal native protocol | ||
journal.Send("this is a message logged through the native protocol", journal.PriInfo, nil) | ||
} else { | ||
// use stderr | ||
fmt.Fprintln(os.Stderr, "this is a message logged through stderr") | ||
} | ||
} | ||
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func replaceStderr(fd int, cb func()) { | ||
savedStderr, err := syscall.Dup(syscall.Stderr) | ||
if err != nil { | ||
panic(err) | ||
} | ||
defer syscall.Close(savedStderr) | ||
err = syscall.Dup2(fd, syscall.Stderr) | ||
if err != nil { | ||
panic(err) | ||
} | ||
defer func() { | ||
err := syscall.Dup2(savedStderr, syscall.Stderr) | ||
if err != nil { | ||
panic(err) | ||
} | ||
}() | ||
cb() | ||
} | ||
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// getUnixStreamSocket returns a unix stream socket obtained with | ||
// socketpair(2), and its fstat result. Only one end of the socket pair | ||
// is returned, and the other end is closed immediately: we don't need | ||
// it for our purposes. | ||
func getUnixStreamSocket(t *testing.T) (*os.File, *syscall.Stat_t) { | ||
fds, err := syscall.Socketpair(syscall.AF_UNIX, syscall.SOCK_STREAM, 0) | ||
if err != nil { | ||
t.Fatal(os.NewSyscallError("socketpair", err)) | ||
} | ||
// we don't need the remote end for our tests | ||
syscall.Close(fds[1]) | ||
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file := os.NewFile(uintptr(fds[0]), "unix-stream") | ||
stat, err := file.Stat() | ||
if err != nil { | ||
t.Fatal(err) | ||
} | ||
return file, stat.Sys().(*syscall.Stat_t) | ||
} |
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