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Each processor might end up in multiple processor groups. Every group has its own `Close` that calls `Close` on each processor of that group which leads to multiple `Close` calls on the same processor. If the `SafeProcessor` wrapper was not used, the processor would have to handle multiple `Close` calls with adding `sync.Once` in its `Close` function. We make it easer for processor developers and take care of it in the processor registry instead. (cherry picked from commit 5007b58)
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// Licensed to Elasticsearch B.V. under one or more contributor | ||
// license agreements. See the NOTICE file distributed with | ||
// this work for additional information regarding copyright | ||
// ownership. Elasticsearch B.V. licenses this file to you 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 processors | ||
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import ( | ||
"errors" | ||
"sync/atomic" | ||
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"github.com/elastic/beats/v7/libbeat/beat" | ||
"github.com/elastic/elastic-agent-libs/config" | ||
) | ||
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var ErrClosed = errors.New("attempt to use a closed processor") | ||
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type SafeProcessor struct { | ||
Processor | ||
closed uint32 | ||
} | ||
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// Run allows to run processor only when `Close` was not called prior | ||
func (p *SafeProcessor) Run(event *beat.Event) (*beat.Event, error) { | ||
if atomic.LoadUint32(&p.closed) == 1 { | ||
return nil, ErrClosed | ||
} | ||
return p.Processor.Run(event) | ||
} | ||
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// Close makes sure the underlying `Close` function is called only once. | ||
func (p *SafeProcessor) Close() (err error) { | ||
if atomic.CompareAndSwapUint32(&p.closed, 0, 1) { | ||
return Close(p.Processor) | ||
} | ||
return nil | ||
} | ||
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// SafeWrap makes sure that the processor handles all the required edge-cases. | ||
// | ||
// Each processor might end up in multiple processor groups. | ||
// Every group has its own `Close` that calls `Close` on each | ||
// processor of that group which leads to multiple `Close` calls | ||
// on the same processor. | ||
// | ||
// If `SafeWrap` is not used, the processor must handle multiple | ||
// `Close` calls by using `sync.Once` in its `Close` function. | ||
// We make it easer for processor developers and take care of it | ||
// in the processor registry instead. | ||
func SafeWrap(constructor Constructor) Constructor { | ||
return func(config *config.C) (Processor, error) { | ||
processor, err := constructor(config) | ||
if err != nil { | ||
return nil, err | ||
} | ||
return &SafeProcessor{ | ||
Processor: processor, | ||
}, nil | ||
} | ||
} |
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// Licensed to Elasticsearch B.V. under one or more contributor | ||
// license agreements. See the NOTICE file distributed with | ||
// this work for additional information regarding copyright | ||
// ownership. Elasticsearch B.V. licenses this file to you 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 processors | ||
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import ( | ||
"testing" | ||
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"github.com/stretchr/testify/require" | ||
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"github.com/elastic/beats/v7/libbeat/beat" | ||
"github.com/elastic/elastic-agent-libs/config" | ||
) | ||
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var mockEvent = &beat.Event{} | ||
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type mockProcessor struct { | ||
runCount int | ||
closeCount int | ||
} | ||
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func newMockConstructor() (Constructor, *mockProcessor) { | ||
p := mockProcessor{} | ||
constructor := func(config *config.C) (Processor, error) { | ||
return &p, nil | ||
} | ||
return constructor, &p | ||
} | ||
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func (p *mockProcessor) Run(event *beat.Event) (*beat.Event, error) { | ||
p.runCount++ | ||
return mockEvent, nil | ||
} | ||
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func (p *mockProcessor) Close() error { | ||
p.closeCount++ | ||
return nil | ||
} | ||
func (p *mockProcessor) String() string { | ||
return "mock-processor" | ||
} | ||
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func TestSafeProcessor(t *testing.T) { | ||
cons, p := newMockConstructor() | ||
var ( | ||
sp Processor | ||
err error | ||
) | ||
t.Run("creates a wrapped processor", func(t *testing.T) { | ||
sw := SafeWrap(cons) | ||
sp, err = sw(nil) | ||
require.NoError(t, err) | ||
}) | ||
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t.Run("propagates Run to a processor", func(t *testing.T) { | ||
e, err := sp.Run(nil) | ||
require.NoError(t, err) | ||
require.Equal(t, e, mockEvent) | ||
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e, err = sp.Run(nil) | ||
require.NoError(t, err) | ||
require.Equal(t, e, mockEvent) | ||
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require.Equal(t, 2, p.runCount) | ||
}) | ||
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t.Run("propagates Close to a processor only once", func(t *testing.T) { | ||
err := Close(sp) | ||
require.NoError(t, err) | ||
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err = Close(sp) | ||
require.NoError(t, err) | ||
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require.Equal(t, 1, p.closeCount) | ||
}) | ||
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t.Run("does not propagate Run when closed", func(t *testing.T) { | ||
e, err := sp.Run(nil) | ||
require.Nil(t, e) | ||
require.ErrorIs(t, err, ErrClosed) | ||
require.Equal(t, 2, p.runCount) // still 2 from the previous test case | ||
}) | ||
} |