You might see an error in the log, but there are a lot of things about the JS 
VM that are too opaque. It's on our list of things to improve, for sure.

Sean Cribbs <[email protected]>
Developer Advocate
Basho Technologies, Inc.
http://basho.com/

On May 10, 2011, at 9:30 AM, Jeremy Raymond wrote:

> Okay thanks. I figure something like this was going on. Besides the timeout 
> return value is there any way to tell what happened or at what phase of some 
> chained map reduce operations things failed? Would I see errors in the logs 
> that indicated a crash of the Javascript engine or something along those 
> lines?
> 
> - Jeremy
> 
> 
> On Tue, May 10, 2011 at 9:27 AM, Sean Cribbs <[email protected]> wrote:
> For large numbers of objects, your JavaScript functions will become 
> bottlenecks, largely because the data has to be converted to and from JSON 
> for every application of the function. If your reduce function isn't actually 
> coalescing a value (e.g. sort doesn't), then you will run into this problem.  
> See if you can reimplement the functions in Erlang or decrease the quantity 
> of values being passed to and returned from the reduce functions.
> 
> Sean Cribbs <[email protected]>
> Developer Advocate
> Basho Technologies, Inc.
> http://basho.com/
> 
> On May 10, 2011, at 9:20 AM, Jeremy Raymond wrote:
> 
>> Hello,
>>  
>> In a MapReduce job I have filtering through about 6500 items if I filter out 
>> enough items my m/r job completes successfully. If I loosen the filtering 
>> such that a large number of items would be included in the results the m/r 
>> fails with error {error,javascript_reduce_timeout}. This error occurs after 
>> about 10 seconds of processing. Would Javascript errors such as the 
>> Javascript process running out of memory and crashing result in this timeout 
>> error? I also noticed that after this error is returned, the riak node I 
>> made the request on chugs along at ~100% CPU for about another minute but 
>> the other two nodes quite down almost immediately after the error is 
>> returned. How might I go about debugging this?
>>  
>> - Jeremy
>>  
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