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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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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,72 @@ | ||
| // 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. | ||
|
|
||
| package processors | ||
|
|
||
| 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) | ||
| } | ||
|
|
||
| // 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 | ||
| } | ||
|
|
||
| // 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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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,97 @@ | ||
| // 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. | ||
|
|
||
| package processors | ||
|
|
||
| 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 | ||
| }) | ||
| } |