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Background with serial not working #1775
Description
Activity
- changed the title
[-]Serial not working when called from a Background thread[/-][+]Background with serial not working[/+]on May 19, 2016 Hi,
Thank you for the notification.
My first thought, is that sometimes the executor starts to run the task immediately, which in it's first line calls
managed.getAndSet(true), so in BackgroundExecutor.execute(Task task), in the second if, the task is not added to the TASKS field.I just read the current version of the
BackgroundExecutor(not tested), I agree with your analysis.If two tasks are executed in the wrong order, then they have both been submitted to the executor. As you said, the reason is that
hasSerialRunning(task.serial)returnsfalsethe second time, because the tasks has not been added toTASKS.IMO this has been introduced by 99a5170 (#1689) (cc @guitcastro).
However,
org.androidannotations.test.ThreadActivityTest.serializedBackgroundTasks()should have catched the problem.Could you improve the test (or add another one) to make it fail like in your case, please?
Hey guys,
Thanks for managing this issue. Sorry for the inconvenience caused by this bug.
TheBackgroundExecutoris one of the most complex classes in AA, due to heavy concurrent
code. I try to review the PRs carefully, but i also make mistakes in this area. 😢
I would be very happy if you could provide a fix.I would be very happy if you could provide a fix.
I got some time today to work on the problem: #1803.
@himamis @guitcastro, could you check if it works for you, please?
Sorry guys, I am complete out time right now.
Also sorry for break the serial executor.ps: My wife just had a kid, that's why I didn't answer the previous mention and is also why I am out of time.
=)
Also sorry for break the serial executor.
Thanks for having spotted the issue with a synchronous executor.
That's unfortunate that the problem was not catched by unit tests. I tried to write a unit test to reproduce it, but I didn't manage to observe a wrong behavior due to the race condition from there. I only reproduced it on Android from your sample.
My wife just had a kid
Concrats! And good luck 😛 😫
Hi everyone!
I have a really similar issue I originally posted as a duplicate in #1806
I don't have good news, but I have something that may help you! The sample you'll find below may help for reproducing the issue (happens all the time) and for writing unit tests!I am using the
@Backgroundannotation in an app to perform network requests. I added aserialin the annotation parameters, but my backend developer and me discovered that multiple requests are made at once.I then discovered that this part of the doc:
If you want execute some background methods SEQUENTIALLY, you should simply use
serial()field. All task with the same serial key will be executed sequentially.is not respected. Any running
@Backroundannotated method will make them run in PARALLEL.I made sample, which didn't reproduce the issue at first. I then added another background job, and I saw tasks with same serial starting concurrently from the logs.
You can look at
MainActivity.classwhere there's a dummy Background job, which disturbs the one inMyBean.classwhich is started as soon as you press the pink Floating Action Button.The implementation is absolutely straightforward, and the short classes I quoted are the only classes that matters.
Expected output:
Hello from 1282! Goodbye from 1282! Hello from 1279! Goodbye from 1279! Hello from 1279! Goodbye from 1279! Hello from 1279! Goodbye from 1279! Hello from 1278! Goodbye from 1278! Hello from 1281! Goodbye from 1281! Hello from 1277! Goodbye from 1277! Hello from 1274! Goodbye from 1274! Hello from 1283! Goodbye from 1283! Hello from 1280! Goodbye from 1280!
Actual output:
Hello from 1314! Hello from 1307! Hello from 1315! Hello from 1311! Hello from 1316! Hello from 1313! Hello from 1317! Hello from 1312! Goodbye from 1314! Goodbye from 1307! Goodbye from 1315! Goodbye from 1316! Goodbye from 1313! Goodbye from 1317! Goodbye from 1311! Hello from 1307! Hello from 1315! Goodbye from 1312! Goodbye from 1315! Goodbye from 1307!
The Background annotation with serial does not work always as expected, in the case, when it's called from another background thread.
It is expected that methods annotated with the @background(serial = X) annotation (provided X is the same for all of them) will run in the order that they were called.
Example
In the above example, we expect that first the backgroundSerialLong method then the second backgroundSerialShort method prints it's log message.
But sometimes it's the other way around, resulting in the following log:
My first thought, is that sometimes the executor starts to run the task immediately, which in it's first line calls
managed.getAndSet(true), so in BackgroundExecutor.execute(Task task), in the second if, the task is not added to the TASKS field.Because of this, the second background task, doesn't know about the first one.
UPDATE
I've tested this by calling the aforementioned two methods from the myButtonClicked method (which runs on the main thread) and the same thing happens. Sometimes it works, sometimes it doesn't. Around 2 out of 5 times it fails.