Do you have a default query memory limit set? Admission control does not generally work well if it's relying on the estimated memory requirement - you really need to have query memory limits set. If you have the default query memory limit set to 25GB, then admission control assumes that the query will use that amount on each node. I assume you mean 700GB memory total across all nodes - how much memory do you have per node?
On Tue, Jan 31, 2017 at 7:31 AM, Jeszy <[email protected]> wrote: > That would be good. If they eventually run successfully, a query profile > would also be welcome. > > Thanks > > On Tue, Jan 31, 2017 at 4:28 PM, William Cox <william.cox@distilnetworks. > com> wrote: > >> Jeszy, >> >> Thanks for the suggestion. We also have a 25GB per-query limit set up. >> Queries that estimate a large size are rejected with an error stating they >> exceeded the memory limit. The queries I'm having trouble with are ones >> that have no such error but simply wait in the CREATED state. Next time it >> happens I'll see if I can grab the memory estimates and check. >> Thanks. >> -William >> >> >> On Tue, Jan 31, 2017 at 7:08 AM, Jeszy <[email protected]> wrote: >> >>> Hey William, >>> >>> IIUC you have configured both a memory-based upper bound and a # queries >>> upper bound for the default pool. A query can get queued if it would exceed >>> either of these limits. If you're not hitting the number of queries one, >>> then it's probably memory, which can happen even if not fully utilized - >>> unless you specify a mem_limit for the query, the estimated memory >>> requirement will be used for deciding whether the query should be admitted. >>> This can get out of hand when the cardinality estimation is off, either due >>> to a very complex query or because of missing / old stats. >>> >>> This is about memory-based admission control exclusively, but I think it >>> will be helpful: http://www.cloudera.com/docume >>> ntation/enterprise/latest/topics/impala_admission.html#admission_memory >>> >>> HTH >>> >>> On Mon, Jan 30, 2017 at 8:31 PM, William Cox < >>> [email protected]> wrote: >>> >>>> I'm running CDH CDH-5.8.0-1 and Impala =version 2.6.0-cdh5.8.0 RELEASE >>>> (build 8d8652f69461f0dd8d5f474573fb5de7ceb0ee6b). We have enabled >>>> resource management and allocated ~700Gb of memory with 30 running queries >>>> for the default. Our background data jobs are Unlimited. >>>> >>>> >>>> In spite of this setup, we still encounter times where queries will be >>>> marked as CREATED and waiting for allocation when the number of running >>>> queries is well below 30 and the amount of used memory, as listed in the >>>> CDH UI, is well below 700GB. >>>> >>>> This is seemingly unpredicable. We've created extensive monitors to >>>> track # of running queries and memory usage but there seems to be no >>>> pattern to why/when these queries won't be submitted to the cluster. >>>> >>>> Is there some key metric that I might be missing or is there any >>>> suggestions folks have for tracking down these queries that won't be >>>> submitted? >>>> Thanks. >>>> -William >>>> >>>> >>> >> >
