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Add a file lock to the data directory on startup to prevent multiple …
…agents. (elastic#18483) * Add a file lock to the data directory on startup to prevent multiple agents. * Add export comments to AppLocker. * Fix periodic to not block startup.
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// Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one | ||
// or more contributor license agreements. Licensed under the Elastic License; | ||
// you may not use this file except in compliance with the Elastic License. | ||
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package application | ||
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import ( | ||
"fmt" | ||
"os" | ||
"path/filepath" | ||
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"github.com/gofrs/flock" | ||
) | ||
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const lockFileName = "agent.lock" | ||
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// ErrAppAlreadyRunning error returned when another elastic-agent is already holding the lock. | ||
var ErrAppAlreadyRunning = fmt.Errorf("another elastic-agent is already running") | ||
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// AppLocker locks the agent.lock file inside the provided directory. | ||
type AppLocker struct { | ||
lock *flock.Flock | ||
} | ||
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// NewAppLocker creates an AppLocker that locks the agent.lock file inside the provided directory. | ||
func NewAppLocker(dir string) *AppLocker { | ||
if _, err := os.Stat(dir); os.IsNotExist(err) { | ||
_ = os.Mkdir(dir, 0755) | ||
} | ||
return &AppLocker{ | ||
lock: flock.New(filepath.Join(dir, lockFileName)), | ||
} | ||
} | ||
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// TryLock tries to grab the lock file and returns error if it cannot. | ||
func (a *AppLocker) TryLock() error { | ||
locked, err := a.lock.TryLock() | ||
if err != nil { | ||
return err | ||
} | ||
if !locked { | ||
return ErrAppAlreadyRunning | ||
} | ||
return nil | ||
} | ||
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// Unlock releases the lock file. | ||
func (a *AppLocker) Unlock() error { | ||
return a.lock.Unlock() | ||
} |
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Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,29 @@ | ||
// Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one | ||
// or more contributor license agreements. Licensed under the Elastic License; | ||
// you may not use this file except in compliance with the Elastic License. | ||
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package application | ||
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import ( | ||
"io/ioutil" | ||
"os" | ||
"testing" | ||
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"github.com/stretchr/testify/assert" | ||
"github.com/stretchr/testify/require" | ||
) | ||
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func TestAppLocker(t *testing.T) { | ||
tmp, _ := ioutil.TempDir("", "locker") | ||
defer os.RemoveAll(tmp) | ||
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locker1 := NewAppLocker(tmp) | ||
locker2 := NewAppLocker(tmp) | ||
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require.NoError(t, locker1.TryLock()) | ||
assert.Error(t, locker2.TryLock()) | ||
require.NoError(t, locker1.Unlock()) | ||
require.NoError(t, locker2.TryLock()) | ||
assert.Error(t, locker1.TryLock()) | ||
require.NoError(t, locker2.Unlock()) | ||
} |
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