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Add guards around structures to prevent racing. #74

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@antihax antihax commented Mar 17, 2017

@wing328 From what I can tell, there are races around the data structures here when hit concurrently.

Please review and make sure my use of Collections.synchronizedList and synchronized are correct. I have not written anything in Java for some time.

I have these changes running locally with go test on a loop and beefed up the concurrency significantly in the go tests. Running 30 minutes with no failures now. This should resolve swagger-codegen #5102.

static List<Category> categories = new ArrayList<Category>();

static List<Pet> pets = Collections.synchronizedList(new ArrayList<Pet>());
static List<Category> categories = Collections.synchronizedList(new ArrayList<Category>());
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I guess you don't need to synchronize this, as it is not used anywhere outside the static initializer.

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Removed. Thanks.


public class StoreData {
static List<Order> orders = new ArrayList<Order>();
static List<Order> orders = Collections.synchronizedList(new ArrayList<Order>());
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If you always access this in a synchronized block, there is no need for the additional synchronizedList.

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Removed. Thanks,

@@ -68,11 +69,13 @@ public Pet getPetById(long petId) {

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@ePaul ePaul Mar 17, 2017

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So you in almost all methods synchronize on pets, just not in getPetById (some lines up from here). Intentionally?
I'm not sure if this here could create some issue ...

The iterator is not synchronized, but checks for concurrent modifications (in an unsynchronized way).
So if any other request gets in between with deletion/addition, this could throw an exception.

On the other hand, if you synchronize everything anyways, you could get rid of the synchronizedList.

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I missed the iterator around it. I also removed the synchronizedLists since all the operations are within sync {}.

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wing328 commented Mar 17, 2017

@antihax thanks for the PR. Can you submit it against my repo instead: https://github.com/wing328/swagger-samples ? That way we can more easily test and deploy.

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antihax commented Mar 17, 2017

updated based on review. I will see if i can figure out to submit to your repo.

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3 participants