Cache.query with ScanQuery Hangs forever

[Timay <to...@trustwave.com>]

Hey all, using Ignite 2.1 we are trying to use an IgniteCache.query to
retrieve records that match our query. We attempt this query on a timed
basis and it gets executed  when their may be no records on the cache.
Example below. 

       ScanQuery<String,SessionData> query = new ScanQuery<>(new
MatchingPredicate(name));
       List<Data> matches = _cache.query(query, Entry::getValue).getAll();


From the thread dump (below) it looks like in
GridCacheQueryFutureAdapter.internalIterator we get put into a
wait(Long.MAX_VAL). Which will just hang until i am long gone. I am
guessing, since i am not sure of all the uses cases, that their is a bug
when a cache is empty and a query is run we may end up in the wait. So my
questions are:

    1) Whats the point of such a long wait?
    2) Can we adjust the timeout on a ScanQuery basis? 
 

"Thread-15" - Thread t@79
   java.lang.Thread.State: TIMED_WAITING
        at java.lang.Object.wait(Native Method)
        - waiting on <46b8b561> (a
org.apache.ignite.internal.processors.cache.query.GridCacheDistributedQueryFuture)
        at
org.apache.ignite.internal.processors.cache.query.GridCacheQueryFutureAdapter.internalIterator(GridCacheQueryFutureAdapter.java:304)
        at
org.apache.ignite.internal.processors.cache.query.GridCacheQueryFutureAdapter.next(GridCacheQueryFutureAdapter.java:161)
        at
org.apache.ignite.internal.processors.cache.query.GridCacheDistributedQueryManager$5.onHasNext(GridCacheDistributedQueryManager.java:635)
        at
org.apache.ignite.internal.util.GridCloseableIteratorAdapter.hasNextX(GridCloseableIteratorAdapter.java:53)
        at
org.apache.ignite.internal.processors.cache.IgniteCacheProxy$1$1.onHasNext(IgniteCacheProxy.java:579)
        at
org.apache.ignite.internal.util.GridCloseableIteratorAdapter.hasNextX(GridCloseableIteratorAdapter.java:53)
        at
org.apache.ignite.internal.util.lang.GridIteratorAdapter.hasNext(GridIteratorAdapter.java:45)
        at
org.apache.ignite.internal.processors.cache.QueryCursorImpl.getAll(QueryCursorImpl.java:114)


Ease of viewing code 

GridCacheQueryFutureAdapter.java 
 
    private Iterator<R> internalIterator() throws IgniteCheckedException {
        checkError();

        Iterator<R> it = null;

        while (it == null || !it.hasNext()) {
            Collection<R> c;

            synchronized (this) {
                it = iter;

                if (it != null && it.hasNext())
                    break;

                c = queue.poll();

                if (c != null)
                    it = iter = c.iterator();

                if (isDone() && queue.peek() == null)
                    break;
            }

 
 
if (c == null && !isDone()) {
    loadPage();

    long timeout = qry.query().timeout();

    long waitTime = timeout == 0 ? Long.MAX_VALUE : timeout -
(U.currentTimeMillis() - startTime);  

    if (waitTime <= 0) {
        it = Collections.<R>emptyList().iterator();

        break;
    }
 
synchronized (this) {
    try {
        if (queue.isEmpty() && !isDone())
           * wait(waitTime);   *                                                  
//line 304 
    }
    catch (InterruptedException e) {
        Thread.currentThread().interrupt();

        throw new IgniteCheckedException("Query was interrupted: " + qry,
e);
    }
}






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Re: Cache.query with ScanQuery Hangs forever

[vkulichenko <va...@gmail.com>]

Tim,

Can you try replacing lambda with a static class? Does it help?

-Val



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Re: Cache.query with ScanQuery Hangs forever

[Timay <to...@trustwave.com>]

it looks like it was classpath loading issue with "Entry::getValue". Since
this is a lambda it will try to serialize the containing class which is not
expected at the cluster nor necessary. When i killed the process I got stack
trace(below) point to that. So i assume some issue with around the class
path loading.

/class org.apache.ignite.IgniteCheckedException: Query execution failed:
GridCacheQueryBean [qry=GridCacheQueryAdapter [type=SCAN, clsName=null,
clause=null, filter=ManagerServiceImpl$InactivePredicate@220fd437,
transform=*ManagerServiceImpl$$Lambda$32/1251084807@7b343e3*/


This is something i have seen before during a compute operation, during an
exception handling we had a library that was not supplied to the cluster get
referenced and it failed silently but would not release the thread. Are any
issues known around that? I may take a look if i can, but any info would me
begin. 

Thanks. 
Tim



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Re: Cache.query with ScanQuery Hangs forever

[vkulichenko <va...@gmail.com>]

I can't reproduce this behavior and actually it sounds very weird that scan
query can hang with empty cache. Do you have a complete test reproducing the
problem that you can share with us?

-Val



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