noproc error on Map/Reduce

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noproc error on Map/Reduce

Matt Black
Hello list,

I've written a large map/reduce query using the Python bindings - basically it's an expanded version of the users/tags example in this post:


When I run the query it fails with this error, with which I am unfamiliar.. Any thoughts on how to diagnose?

Exception: Error running MapReduce operation. Headers: {'date': 'Thu, 11 Oct 2012 03:57:39 GMT', 'content-length': '1211', 'content-type': 'application/json', 'http_code': 500, 'server': 'MochiWeb/1.1 WebMachine/1.9.0 (someone had painted it blue)'} Body: '{"phase":0,"error":"{noproc,{gen_server,call,[riak_kv_js_map,{reserve_vm,<0.23487.1151>},infinity]}}","input":"{ok,{r_object,<<\\"carts\\">>,<<\\"1284510f1d9013cf43d44cce3fde7847\\">>,[{r_content,{dict,6,16,16,8,80,48,{[],[],[],[],[],[],[],[],[],[],[],[],[],[],[],[]},{{[],[],[[<<\\"Links\\">>,{{<<\\"cart-products\\">>,<<\\"1284510f1d9013cf43d44cce3fde7847-0\\">>},<<\\"cart-products\\">>},{{<<\\"users\\">>,<<\\"1284510f1d9013cf43d44cce3fde7847\\">>},<<\\"user\\">>}]],[],[],[],[],[],[],[],[[<<\\"content-type\\">>,97,112,112,108,105,99,97,116,105,111,110,47,106,115,111,110],[<<\\"X-Riak-VT...\\">>,...]],...}}},...}],...},...}","type":"exit","stack":"[{gen_server,call,3,[{file,\\"gen_server.erl\\"},{line,188}]},{riak_kv_js_manager,blocking_dispatch,4,[{file,\\"src/riak_kv_js_manager.erl\\"},{line,250}]},{riak_kv_mrc_map,map_js,3,[{file,\\"src/riak_kv_mrc_map.erl\\"},{line,192}]},{riak_kv_mrc_map,process,3,[{file,\\"src/riak_kv_mrc_map.erl\\"},{line,140}]},{riak_pipe_vnode_worker,process_input,3,[{file,\\"src/riak_pipe_vnode_worker.erl\\"},{line,445}]},{riak_pipe_vnode_worker,wait_for_input,2,[{file,\\"src/riak_pipe_vnode_worker.erl\\"},{line,377}]},{gen_fsm,handle_msg,...},...]"}'

Thanks

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Re: noproc error on Map/Reduce

bryan-basho
Administrator
On Thu, Oct 11, 2012 at 12:12 AM, Matt Black <[hidden email]> wrote:
> When I run the query it fails with this error, with which I am unfamiliar..
> Any thoughts on how to diagnose?

Hi, Matt. The interesting part of that error is:

> '{"phase":0,"error":"{noproc,{gen_server,call,[riak_kv_js_map,{reserve_vm,<0.23487.1151>},infinity]}}"

That `noproc` is saying that the process that gen_server:call/3 was
trying to contact wasn't there. The arguments indicate that it was
calling the riak_kv_js_map process, which is the riak_kv_js_manager of
the Javascript VMs used in evaluating map functions. If it's not
there, it must have crashed, which should have left a message in your
Riak node's logs. If it's there, you'll probably find it by searching
for riak_kv_js_manager, together with the phrase "initial call".

It's also possible that it was not the manager, but instead the VM
process that was absent. This particular error can bubble up in this
way. If this is the problem, there may be a race condition in the
checkin/checkout of those VMs. We did fix one such condition earlier
this year … which Riak version are you using? If this is the problem,
you'll probably see errors in your Riak node's logs about
riak_kv_js_vm crashing/exiting.

I've opened a new issue to track this problem here:
https://github.com/basho/riak_kv/issues/403 . If you learn more about
the root cause, please reply either here or there.

Thank you,
Bryan

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