CODEWITHSUNDEEP
javamemory-leakswhile-loop
chnet
chnet

Reputation: 2033

java while loop memory leak

I used a while loop to fetch message from Amazon SQS. Partial code is as follows:

ReceiveMessageRequest receiveMessageRequest = new ReceiveMessageRequest(myQueueUrl);
while (true) {
    List<Message> messages = sqs.receiveMessage(receiveMessageRequest).getMessages();

     if (messages.size() > 0) {

             MemcachedClient c = new MemcachedClient(new BinaryConnectionFactory(), AddrUtil.getAddresses(memAddress));

             for (Message message : messages) {

                 // get message from aws sqs
                 String messageid = message.getBody();
                 String messageRecieptHandle = message.getReceiptHandle();
                 sqs.deleteMessage(new DeleteMessageRequest(myQueueUrl, messageRecieptHandle));

                 // get details info from memcache 
                 String result = null;
                 String key = null;
                 key = "message-"+messageid;
                 result = c.get(key);

             }
             c.shutdown();
          }
       }

Will it cause memory leak in such case? I checked using "ps aux". What I found is that the RSS (resident set size, the non-swapped physical memory that a task used) is growing slowly.

Upvotes: 0

Views: 1867

Answers (2)

Andrey Krot
Andrey Krot

Reputation: 62

Sorry, but I don't see here code to remove message from the message queue. Did you clean the message list? In case that DeleteRequest removes message from the queue then you try to modify message list which you itereate.

Also you can get better memory usage statistic with visualvm tool which is part of JDK now.

Upvotes: 1

Mark Peters
Mark Peters

Reputation: 81154

You can't evaluate whether your Java application has a memory leak simply based on the RSS of the process. Most JVMs are pretty greedy, they would rather take more memory from the OS than spend a lot of work on Garbage Collection.

That said your while loop doesn't seem like it has any obvious memory "leaks" either, but that depends on what some of the method calls do (which isn't included above). If you are storing things in static variables, that can be a cause of concern but if the only references are within the scope of the loop you're probably fine.

The simplest way to know if you have a memory leak in a certain area of code is to rigorously exercise that code within a single run of your application (potentially set with a relatively low maximum heap size). If you get an OutOfMemoryError, you probably have a memory leak.

Upvotes: 2

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