Apache Flink: Is MapState automatically updated when I modify a stored object?
Is it necessary to use MapState.put() to manually update the state or whether is the state automatically updated when I modify an object?
private transient MapState<String, Word> words;
.......
Word w = words.get(word);
if (w == null)
w = new Word(word);
//words.put(word, w); //A
if (....)
w.countBad(1); // countXXX modifies a the private variable in a Word object
else
w.countGood(1);
//words.put(word, w); //B
Q: If I use the A method, will the next count calculation automatically update the corresponding Mapstate state? Or do I need to use the B method to manually update the state after the calculation is complete?
apache-flink flink-streaming
edited Nov 12 '18 at 11:02
Fabian Hueske
11.9k12027
asked Nov 12 '18 at 7:00
Cheng JiangCheng Jiang
436
add a comment |
Is it necessary to use MapState.put() to manually update the state or whether is the state automatically updated when I modify an object?
private transient MapState<String, Word> words;
.......
Word w = words.get(word);
if (w == null)
w = new Word(word);
//words.put(word, w); //A
if (....)
w.countBad(1); // countXXX modifies a the private variable in a Word object
else
w.countGood(1);
//words.put(word, w); //B
Q: If I use the A method, will the next count calculation automatically update the corresponding Mapstate state? Or do I need to use the B method to manually update the state after the calculation is complete?
apache-flink flink-streaming
edited Nov 12 '18 at 11:02
Fabian Hueske
11.9k12027
asked Nov 12 '18 at 7:00
Cheng JiangCheng Jiang
436
add a comment |
Is it necessary to use MapState.put() to manually update the state or whether is the state automatically updated when I modify an object?
private transient MapState<String, Word> words;
.......
Word w = words.get(word);
if (w == null)
w = new Word(word);
//words.put(word, w); //A
if (....)
w.countBad(1); // countXXX modifies a the private variable in a Word object
else
w.countGood(1);
//words.put(word, w); //B
Q: If I use the A method, will the next count calculation automatically update the corresponding Mapstate state? Or do I need to use the B method to manually update the state after the calculation is complete?
apache-flink flink-streaming
edited Nov 12 '18 at 11:02
Fabian Hueske
11.9k12027
asked Nov 12 '18 at 7:00
Cheng JiangCheng Jiang
436
Is it necessary to use MapState.put() to manually update the state or whether is the state automatically updated when I modify an object?
private transient MapState<String, Word> words;
.......
Word w = words.get(word);
if (w == null)
w = new Word(word);
//words.put(word, w); //A
if (....)
w.countBad(1); // countXXX modifies a the private variable in a Word object
else
w.countGood(1);
//words.put(word, w); //B
Q: If I use the A method, will the next count calculation automatically update the corresponding Mapstate state? Or do I need to use the B method to manually update the state after the calculation is complete?
apache-flink flink-streaming
apache-flink flink-streaming
edited Nov 12 '18 at 11:02
Fabian Hueske
11.9k12027
asked Nov 12 '18 at 7:00
Cheng JiangCheng Jiang
436
edited Nov 12 '18 at 11:02
Fabian Hueske
11.9k12027
asked Nov 12 '18 at 7:00
Cheng JiangCheng Jiang
436
edited Nov 12 '18 at 11:02
Fabian Hueske
11.9k12027
edited Nov 12 '18 at 11:02
Fabian Hueske
11.9k12027
edited Nov 12 '18 at 11:02
Fabian Hueske
11.9k12027
11.9k12027
asked Nov 12 '18 at 7:00
Cheng JiangCheng Jiang
436
asked Nov 12 '18 at 7:00
Cheng JiangCheng Jiang
436
asked Nov 12 '18 at 7:00
Cheng JiangCheng Jiang
436
436
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
From an API point of view, you always need to manually update the state.
However, the actual behavior depends on the state backend. If the application uses the InMemoryStateBackend or the FsStateBackend, all local state is stored on the JVM heap of the worker process, i.e., the state backend just holds a reference to the object. Hence, the state is directly modified when you modify the object.
If you use the RocksDBStateBackend all state accesses are de/serialized and read from / written to RocksDB. In this case modifying the object does not have an effect on the state.
I recommend to always explicitly update the state because this will ensure that you can switch the state backend without adjusting the logic of your application.
answered Nov 12 '18 at 10:57
Fabian HueskeFabian Hueske
11.9k12027
add a comment |
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
From an API point of view, you always need to manually update the state.
However, the actual behavior depends on the state backend. If the application uses the InMemoryStateBackend or the FsStateBackend, all local state is stored on the JVM heap of the worker process, i.e., the state backend just holds a reference to the object. Hence, the state is directly modified when you modify the object.
If you use the RocksDBStateBackend all state accesses are de/serialized and read from / written to RocksDB. In this case modifying the object does not have an effect on the state.
I recommend to always explicitly update the state because this will ensure that you can switch the state backend without adjusting the logic of your application.
answered Nov 12 '18 at 10:57
Fabian HueskeFabian Hueske
11.9k12027
add a comment |
From an API point of view, you always need to manually update the state.
However, the actual behavior depends on the state backend. If the application uses the InMemoryStateBackend or the FsStateBackend, all local state is stored on the JVM heap of the worker process, i.e., the state backend just holds a reference to the object. Hence, the state is directly modified when you modify the object.
If you use the RocksDBStateBackend all state accesses are de/serialized and read from / written to RocksDB. In this case modifying the object does not have an effect on the state.
I recommend to always explicitly update the state because this will ensure that you can switch the state backend without adjusting the logic of your application.
answered Nov 12 '18 at 10:57
Fabian HueskeFabian Hueske
11.9k12027
add a comment |
From an API point of view, you always need to manually update the state.
However, the actual behavior depends on the state backend. If the application uses the InMemoryStateBackend or the FsStateBackend, all local state is stored on the JVM heap of the worker process, i.e., the state backend just holds a reference to the object. Hence, the state is directly modified when you modify the object.
If you use the RocksDBStateBackend all state accesses are de/serialized and read from / written to RocksDB. In this case modifying the object does not have an effect on the state.
I recommend to always explicitly update the state because this will ensure that you can switch the state backend without adjusting the logic of your application.
answered Nov 12 '18 at 10:57
Fabian HueskeFabian Hueske
11.9k12027
From an API point of view, you always need to manually update the state.
However, the actual behavior depends on the state backend. If the application uses the InMemoryStateBackend or the FsStateBackend, all local state is stored on the JVM heap of the worker process, i.e., the state backend just holds a reference to the object. Hence, the state is directly modified when you modify the object.
If you use the RocksDBStateBackend all state accesses are de/serialized and read from / written to RocksDB. In this case modifying the object does not have an effect on the state.
I recommend to always explicitly update the state because this will ensure that you can switch the state backend without adjusting the logic of your application.
answered Nov 12 '18 at 10:57
Fabian HueskeFabian Hueske
11.9k12027
answered Nov 12 '18 at 10:57
Fabian HueskeFabian Hueske
11.9k12027
answered Nov 12 '18 at 10:57
Fabian HueskeFabian Hueske
11.9k12027
answered Nov 12 '18 at 10:57
Fabian HueskeFabian Hueske
11.9k12027
11.9k12027
add a comment |
add a comment |
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