RE: CPU consumption of Cassandra
I tried to run cassandra-stress on some of my table as proposed by Jake Luciani. For a simple table, this tool is able to perform 8 read op/s with a few CPU consumption if I request the table by the PK(name, tenanted) Ex : TABLE : CREATE TABLE IF NOT EXISTS buckets (tenantid varchar, name varchar, owner varchar, location varchar, description varchar, codeQuota varchar, creationDate timestamp, updateDate timestamp, PRIMARY KEY (name, tenantid)); QUERY : select * from buckets where name = ? and tenantid = ? limit 1; TOP output for 900 threads on cassandra-stress : top - 13:17:09 up 173 days, 21:54, 4 users, load average: 11.88, 4.30, 2.76 Tasks: 272 total, 1 running, 270 sleeping, 0 stopped, 1 zombie Cpu(s): 71.4%us, 14.0%sy, 0.0%ni, 13.1%id, 0.0%wa, 0.0%hi, 1.5%si, 0.0%st Mem: 98894704k total, 96367436k used, 2527268k free,15440k buffers Swap:0k total,0k used,0k free, 88194556k cached PID USER PR NI VIRT RES SHR S %CPU %MEMTIME+ COMMAND 25857 root 20 0 29.7g 1.5g 12m S 693.0 1.6 38:45.58 java == Cassandra-stress 29160 cassandr 20 0 16.3g 4.8g 10m S 1.3 5.0 44:46.89 java == Cassandra Now, If I run another query on a table that provides a list of buckets according to the owner, the number of op/s is divided by 2 (42000 op/s) and CPU consumption grow UP. Ex : TABLE : CREATE TABLE IF NOT EXISTS owner_to_buckets (tenantid varchar, name varchar, owner varchar, location varchar, description varchar, codeQuota varchar, creationDate timestamp, updateDate timestamp, PRIMARY KEY ((owner, tenantid), name)); QUERY : select * from owner_to_buckets where owner = ? and tenantid = ? limit 10; TOP output for 4 threads on cassandra-stress: top - 13:49:16 up 173 days, 22:26, 4 users, load average: 1.76, 1.48, 1.17 Tasks: 273 total, 1 running, 271 sleeping, 0 stopped, 1 zombie Cpu(s): 26.3%us, 8.0%sy, 0.0%ni, 64.7%id, 0.0%wa, 0.0%hi, 1.0%si, 0.0%st Mem: 98894704k total, 97512156k used, 1382548k free,14580k buffers Swap:0k total,0k used,0k free, 90413772k cached PID USER PR NI VIRT RES SHR S %CPU %MEMTIME+ COMMAND 29160 cassandr 20 0 13.6g 4.8g 37m S 186.7 5.1 62:26.77 java == Cassandra 50622 root 20 0 28.8g 469m 12m S 102.5 0.5 0:45.84 java == Cassandra-stress TOP output for 271 threads on cassandra-stress: top - 13:57:03 up 173 days, 22:34, 4 users, load average: 4.67, 1.76, 1.25 Tasks: 272 total, 1 running, 270 sleeping, 0 stopped, 1 zombie Cpu(s): 81.5%us, 14.0%sy, 0.0%ni, 3.1%id, 0.0%wa, 0.0%hi, 1.3%si, 0.0%st Mem: 98894704k total, 94955936k used, 3938768k free,15892k buffers Swap:0k total,0k used,0k free, 85993676k cached PID USER PR NI VIRT RES SHR S %CPU %MEMTIME+ COMMAND 29160 cassandr 20 0 13.6g 4.8g 38m S 430.0 5.1 82:31.80 java == Cassandra 50622 root 20 0 29.1g 2.3g 12m S 343.4 2.4 17:51.22 java == Cassandra-stress I have 4 tables with a composed PRIMARY KEY (two of them has 4 entries : 2 for the partition key, one for cluster column and one for sort column) Two of these tables are frequently read with the partition key because we want to list data of a given user, this should explain my CPU load according to the simple test done with Cassandra-stress ... How can I avoid this? Collections could be an option but the number of data per user is not limited and can easily exceed 200 entries. According to the Cassandra documentation, collections have a size limited to 64KB. So it is probably not a solution in my case. :( Regards, Eric De : Chris Lohfink [mailto:clohf...@blackbirdit.com] Envoyé : lundi 22 septembre 2014 22:03 À : user@cassandra.apache.org Objet : Re: CPU consumption of Cassandra Its going to depend a lot on your data model but 5-6k is on the low end of what I would expect. N=RF=2 is not really something I would recommend. That said 93GB is not much data so the bottleneck may exist more in your data model, queries, or client. What profiler are you using? The cpu on the select/read is marked as RUNNABLE but its really more of a wait state that may throw some profilers off, it may be a red haring. --- Chris Lohfink On Sep 22, 2014, at 11:39 AM, Leleu Eric eric.le...@worldline.commailto:eric.le...@worldline.com wrote: Hi, I'm currently testing Cassandra 2.0.9 (and since the last week 2.1) under some read heavy load... I have 2 cassandra nodes (RF : 2) running under CentOS 6 with 16GB of RAM and 8 Cores. I have around 93GB of data per node (one Disk of 300GB with SAS interface and a Rotational Speed of 10500) I have 300 active client threads and they request the C* nodes with a Consitency level set to ONE (I'm using the CQL datastax driver). During my tests I saw a lot of CPU consumption (70% user / 6%sys / 4% iowait / 20%idle). C* nodes respond to around 5000 op/s (sometime up to 6000op/s) I try to profile
Re: CPU consumption of Cassandra
Well, first off you shouldn't run stress tool on the node your testing. Give it its own box. With RF=N=2 your essentially testing a single machine locally which isnt the best indicator long term (optimizations available when reading data thats local to the node). 80k/sec on a system is pretty good though, your probably seeing slower on the 2nd query since its returning 10x the data and there will be more to go through within the partition. 42k/sec is still acceptable imho since these are smaller boxes. You are probably seeing high CPU because the system is doing a lot :) If you want to get more out of these systems can do some tuning probably, enable trace to see whats actually the bottleneck. Collections will very likely hurt more then help. --- Chris Lohfink On Sep 23, 2014, at 9:39 AM, Leleu Eric eric.le...@worldline.com wrote: I tried to run “cassandra-stress” on some of my table as proposed by Jake Luciani. For a simple table, this tool is able to perform 8 read op/s with a few CPU consumption if I request the table by the PK(name, tenanted) Ex : TABLE : CREATE TABLE IF NOT EXISTS buckets (tenantid varchar, name varchar, owner varchar, location varchar, description varchar, codeQuota varchar, creationDate timestamp, updateDate timestamp, PRIMARY KEY (name, tenantid)); QUERY : select * from buckets where name = ? and tenantid = ? limit 1; TOP output for 900 threads on cassandra-stress : top - 13:17:09 up 173 days, 21:54, 4 users, load average: 11.88, 4.30, 2.76 Tasks: 272 total, 1 running, 270 sleeping, 0 stopped, 1 zombie Cpu(s): 71.4%us, 14.0%sy, 0.0%ni, 13.1%id, 0.0%wa, 0.0%hi, 1.5%si, 0.0%st Mem: 98894704k total, 96367436k used, 2527268k free,15440k buffers Swap:0k total,0k used,0k free, 88194556k cached PID USER PR NI VIRT RES SHR S %CPU %MEMTIME+ COMMAND 25857 root 20 0 29.7g 1.5g 12m S 693.0 1.6 38:45.58 java ç Cassandra-stress 29160 cassandr 20 0 16.3g 4.8g 10m S 1.3 5.0 44:46.89 java ç Cassandra Now, If I run another query on a table that provides a list of buckets according to the owner, the number of op/s is divided by 2 (42000 op/s) and CPU consumption grow UP. Ex : TABLE : CREATE TABLE IF NOT EXISTS owner_to_buckets (tenantid varchar, name varchar, owner varchar, location varchar, description varchar, codeQuota varchar, creationDate timestamp, updateDate timestamp, PRIMARY KEY ((owner, tenantid), name)); QUERY : select * from owner_to_buckets where owner = ? and tenantid = ? limit 10; TOP output for 4 threads on cassandra-stress: top - 13:49:16 up 173 days, 22:26, 4 users, load average: 1.76, 1.48, 1.17 Tasks: 273 total, 1 running, 271 sleeping, 0 stopped, 1 zombie Cpu(s): 26.3%us, 8.0%sy, 0.0%ni, 64.7%id, 0.0%wa, 0.0%hi, 1.0%si, 0.0%st Mem: 98894704k total, 97512156k used, 1382548k free,14580k buffers Swap:0k total,0k used,0k free, 90413772k cached PID USER PR NI VIRT RES SHR S %CPU %MEMTIME+ COMMAND 29160 cassandr 20 0 13.6g 4.8g 37m S 186.7 5.1 62:26.77 java ç Cassandra 50622 root 20 0 28.8g 469m 12m S 102.5 0.5 0:45.84 java ç Cassandra-stress TOP output for 271 threads on cassandra-stress: top - 13:57:03 up 173 days, 22:34, 4 users, load average: 4.67, 1.76, 1.25 Tasks: 272 total, 1 running, 270 sleeping, 0 stopped, 1 zombie Cpu(s): 81.5%us, 14.0%sy, 0.0%ni, 3.1%id, 0.0%wa, 0.0%hi, 1.3%si, 0.0%st Mem: 98894704k total, 94955936k used, 3938768k free,15892k buffers Swap:0k total,0k used,0k free, 85993676k cached PID USER PR NI VIRT RES SHR S %CPU %MEMTIME+ COMMAND 29160 cassandr 20 0 13.6g 4.8g 38m S 430.0 5.1 82:31.80 java ç Cassandra 50622 root 20 0 29.1g 2.3g 12m S 343.4 2.4 17:51.22 java ç Cassandra-stress I have 4 tables with a composed PRIMARY KEY (two of them has 4 entries : 2 for the partition key, one for cluster column and one for sort column) Two of these tables are frequently read with the partition key because we want to list data of a given user, this should explain my CPU load according to the simple test done with Cassandra-stress … How can I avoid this? Collections could be an option but the number of data per user is not limited and can easily exceed 200 entries. According to the Cassandra documentation, collections have a size limited to 64KB. So it is probably not a solution in my case. L Regards, Eric De : Chris Lohfink [mailto:clohf...@blackbirdit.com] Envoyé : lundi 22 septembre 2014 22:03 À : user@cassandra.apache.org Objet : Re: CPU consumption of Cassandra Its going to depend a lot on your data model but 5-6k is on the low end of what I would expect. N=RF=2 is not really something I would recommend. That said 93GB is not much
Is there harm from having all the nodes in the seed list?
Is there any harm from having all the nodes listed in the seeds list in cassandra.yaml? Donald A. Smith | Senior Software Engineer P: 425.201.3900 x 3866 C: (206) 819-5965 F: (646) 443-2333 dona...@audiencescience.commailto:dona...@audiencescience.com [AudienceScience]
Cassandra sometimes times out on write queries and it spends majority amount of the CPU time on method org.apache.cassandra.db.marshal.AbstractCompositeType.compare()
Hi, I am running some load test in a 5 node Cassandra cluster (EC2, single region, each node has 15 GB RAM, Cassandra version 2.0.6, replication factor 3). My Java program uses Java driver version 2.0.6 and it does 2000 rounds of batch write queries, each with 8 inserts, 8 updates and 8 deletes. When I run the test, I usually see really high CPU usage on some of the nodes. And sometimes I get a time out indicated by com.datastax.driver.core.exceptions.WriteTimeoutException: Cassandra timeout during write query at consistency ONE (1 replica were required but only 0 acknowledged the write). My cluster has 1 ms write timeout limit. I used VisualVM and did some CPU sampling. What I noticed is that CPU spends majority of the time inside method org.apache.cassandra.db.marshal.AbstractCompositeType.compare() and the snapshot indicates that the call tree is most of the time like this: java.lang.Thread.State: RUNNABLE at org.apache.cassandra.db.marshal.AbstractCompositeType.compare(AbstractCompositeType.java:98) at org.apache.cassandra.db.marshal.AbstractCompositeType.compare(AbstractCompositeType.java:35) at java.util.Arrays.binarySearch0(Arrays.java:1585) at java.util.Arrays.binarySearch(Arrays.java:1570) at org.apache.cassandra.db.RangeTombstoneList.searchInternal(RangeTombstoneList.java:236) at org.apache.cassandra.db.RangeTombstoneList.isDeleted(RangeTombstoneList.java:210) at org.apache.cassandra.db.DeletionInfo.isDeleted(DeletionInfo.java:136) at org.apache.cassandra.db.DeletionInfo.isDeleted(DeletionInfo.java:123) at org.apache.cassandra.db.AtomicSortedColumns.addAllWithSizeDelta(AtomicSortedColumns.java:193) at org.apache.cassandra.db.Memtable.resolve(Memtable.java:194) at org.apache.cassandra.db.Memtable.put(Memtable.java:158) at org.apache.cassandra.db.ColumnFamilyStore.apply(ColumnFamilyStore.java:891) at org.apache.cassandra.db.Keyspace.apply(Keyspace.java:368) at org.apache.cassandra.db.Keyspace.apply(Keyspace.java:333) at org.apache.cassandra.db.RowMutation.apply(RowMutation.java:206) at org.apache.cassandra.db.RowMutationVerbHandler.doVerb(RowMutationVerbHandler.java:56) at org.apache.cassandra.net.MessageDeliveryTask.run(MessageDeliveryTask.java:60) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) at java.lang.Thread.run(Thread.java:745) So it looks like it is tombstone search related even though I am not seeing tombstone warning message in Cassandra's system log. Per http://www.datastax.com/dev/blog/how-cassandra-deals-with-replica-failure, write timeout is not really an error. But with my load and 10 seconds write timeout limit, getting timeout seems to be problematic. Do you guys have some hint or pointer what I should go about this issue? Thanks.
RE : CPU consumption of Cassandra
First of all, Thanks for your help ! :) Here is some details : With RF=N=2 your essentially testing a single machine locally which isnt the best indicator long term I will test with more nodes, (4 with RF = 2) but for now I'm limited to 2 nodes for non technical reason ... Well, first off you shouldn't run stress tool on the node your testing. Give it its own box. I performed the test in a new Keyspace in order to have a clear dataset. the 2nd query since its returning 10x the data and there will be more to go through within the partition I configured cassandra-stress in a way of each user has only one bucket so the amount of data is the same in the both case. (select * from buckets where name = ? and tenantid = ? limit 1 and select * from owner_to_buckets where owner = ? and tenantid = ? limit 10). Does cassandra perform extra read when the limit is bigger than the available data (even if the partition key contains only one single value in the clustering column) ? If the amount of data is the same, how can we explain the difference of CPU consumption? Regards, Eric De : Chris Lohfink [clohf...@blackbirdit.com] Date d'envoi : mardi 23 septembre 2014 19:23 À : user@cassandra.apache.org Objet : Re: CPU consumption of Cassandra Well, first off you shouldn't run stress tool on the node your testing. Give it its own box. With RF=N=2 your essentially testing a single machine locally which isnt the best indicator long term (optimizations available when reading data thats local to the node). 80k/sec on a system is pretty good though, your probably seeing slower on the 2nd query since its returning 10x the data and there will be more to go through within the partition. 42k/sec is still acceptable imho since these are smaller boxes. You are probably seeing high CPU because the system is doing a lot :) If you want to get more out of these systems can do some tuning probably, enable trace to see whats actually the bottleneck. Collections will very likely hurt more then help. --- Chris Lohfink On Sep 23, 2014, at 9:39 AM, Leleu Eric eric.le...@worldline.commailto:eric.le...@worldline.com wrote: I tried to run “cassandra-stress” on some of my table as proposed by Jake Luciani. For a simple table, this tool is able to perform 8 read op/s with a few CPU consumption if I request the table by the PK(name, tenanted) Ex : TABLE : CREATE TABLE IF NOT EXISTS buckets (tenantid varchar, name varchar, owner varchar, location varchar, description varchar, codeQuota varchar, creationDate timestamp, updateDate timestamp, PRIMARY KEY (name, tenantid)); QUERY : select * from buckets where name = ? and tenantid = ? limit 1; TOP output for 900 threads on cassandra-stress : top - 13:17:09 up 173 days, 21:54, 4 users, load average: 11.88, 4.30, 2.76 Tasks: 272 total, 1 running, 270 sleeping, 0 stopped, 1 zombie Cpu(s): 71.4%us, 14.0%sy, 0.0%ni, 13.1%id, 0.0%wa, 0.0%hi, 1.5%si, 0.0%st Mem: 98894704k total, 96367436k used, 2527268k free,15440k buffers Swap:0k total,0k used,0k free, 88194556k cached PID USER PR NI VIRT RES SHR S %CPU %MEMTIME+ COMMAND 25857 root 20 0 29.7g 1.5g 12m S 693.0 1.6 38:45.58 java == Cassandra-stress 29160 cassandr 20 0 16.3g 4.8g 10m S 1.3 5.0 44:46.89 java == Cassandra Now, If I run another query on a table that provides a list of buckets according to the owner, the number of op/s is divided by 2 (42000 op/s) and CPU consumption grow UP. Ex : TABLE : CREATE TABLE IF NOT EXISTS owner_to_buckets (tenantid varchar, name varchar, owner varchar, location varchar, description varchar, codeQuota varchar, creationDate timestamp, updateDate timestamp, PRIMARY KEY ((owner, tenantid), name)); QUERY : select * from owner_to_buckets where owner = ? and tenantid = ? limit 10; TOP output for 4 threads on cassandra-stress: top - 13:49:16 up 173 days, 22:26, 4 users, load average: 1.76, 1.48, 1.17 Tasks: 273 total, 1 running, 271 sleeping, 0 stopped, 1 zombie Cpu(s): 26.3%us, 8.0%sy, 0.0%ni, 64.7%id, 0.0%wa, 0.0%hi, 1.0%si, 0.0%st Mem: 98894704k total, 97512156k used, 1382548k free,14580k buffers Swap:0k total,0k used,0k free, 90413772k cached PID USER PR NI VIRT RES SHR S %CPU %MEMTIME+ COMMAND 29160 cassandr 20 0 13.6g 4.8g 37m S 186.7 5.1 62:26.77 java == Cassandra 50622 root 20 0 28.8g 469m 12m S 102.5 0.5 0:45.84 java == Cassandra-stress TOP output for 271 threads on cassandra-stress: top - 13:57:03 up 173 days, 22:34, 4 users, load average: 4.67, 1.76, 1.25 Tasks: 272 total, 1 running, 270 sleeping, 0 stopped, 1 zombie Cpu(s): 81.5%us, 14.0%sy, 0.0%ni, 3.1%id, 0.0%wa, 0.0%hi, 1.3%si, 0.0%st Mem: 98894704k total, 94955936k used, 3938768k free,15892k buffers Swap:0k total,0k used,0k free, 85993676k cached PID
Re: Is there harm from having all the nodes in the seed list?
Well, having all nodes in the seed list does not compromise any correctness of gossip protocol. However there will be extra network traffic when nodes are starting because it will ping all nodes for topology discovery, AFAIK On Tue, Sep 23, 2014 at 7:31 PM, Donald Smith donald.sm...@audiencescience.com wrote: Is there any harm from having all the nodes listed in the seeds list in cassandra.yaml? *Donald A. Smith* | Senior Software Engineer P: 425.201.3900 x 3866 C: (206) 819-5965 F: (646) 443-2333 dona...@audiencescience.com [image: AudienceScience]
Re: CPU consumption of Cassandra
CPU consumption may be affected from the cassandra-stress tool in 2nd example as well. Running on a separate system eliminates it as a possible cause. There is a little extra work but not anything that I think would be that obvious. tracing (can enable with nodetool) or profiling (ie with yourkit) can give more exposure to the bottleneck. Id run test from separate system first. --- Chris Lohfink On Sep 23, 2014, at 12:48 PM, Leleu Eric eric.le...@worldline.com wrote: First of all, Thanks for your help ! :) Here is some details : With RF=N=2 your essentially testing a single machine locally which isnt the best indicator long term I will test with more nodes, (4 with RF = 2) but for now I'm limited to 2 nodes for non technical reason ... Well, first off you shouldn't run stress tool on the node your testing. Give it its own box. I performed the test in a new Keyspace in order to have a clear dataset. the 2nd query since its returning 10x the data and there will be more to go through within the partition I configured cassandra-stress in a way of each user has only one bucket so the amount of data is the same in the both case. (select * from buckets where name = ? and tenantid = ? limit 1 and select * from owner_to_buckets where owner = ? and tenantid = ? limit 10). Does cassandra perform extra read when the limit is bigger than the available data (even if the partition key contains only one single value in the clustering column) ? If the amount of data is the same, how can we explain the difference of CPU consumption? Regards, Eric De : Chris Lohfink [clohf...@blackbirdit.com] Date d'envoi : mardi 23 septembre 2014 19:23 À : user@cassandra.apache.org Objet : Re: CPU consumption of Cassandra Well, first off you shouldn't run stress tool on the node your testing. Give it its own box. With RF=N=2 your essentially testing a single machine locally which isnt the best indicator long term (optimizations available when reading data thats local to the node). 80k/sec on a system is pretty good though, your probably seeing slower on the 2nd query since its returning 10x the data and there will be more to go through within the partition. 42k/sec is still acceptable imho since these are smaller boxes. You are probably seeing high CPU because the system is doing a lot :) If you want to get more out of these systems can do some tuning probably, enable trace to see whats actually the bottleneck. Collections will very likely hurt more then help. --- Chris Lohfink On Sep 23, 2014, at 9:39 AM, Leleu Eric eric.le...@worldline.commailto:eric.le...@worldline.com wrote: I tried to run “cassandra-stress” on some of my table as proposed by Jake Luciani. For a simple table, this tool is able to perform 8 read op/s with a few CPU consumption if I request the table by the PK(name, tenanted) Ex : TABLE : CREATE TABLE IF NOT EXISTS buckets (tenantid varchar, name varchar, owner varchar, location varchar, description varchar, codeQuota varchar, creationDate timestamp, updateDate timestamp, PRIMARY KEY (name, tenantid)); QUERY : select * from buckets where name = ? and tenantid = ? limit 1; TOP output for 900 threads on cassandra-stress : top - 13:17:09 up 173 days, 21:54, 4 users, load average: 11.88, 4.30, 2.76 Tasks: 272 total, 1 running, 270 sleeping, 0 stopped, 1 zombie Cpu(s): 71.4%us, 14.0%sy, 0.0%ni, 13.1%id, 0.0%wa, 0.0%hi, 1.5%si, 0.0%st Mem: 98894704k total, 96367436k used, 2527268k free,15440k buffers Swap:0k total,0k used,0k free, 88194556k cached PID USER PR NI VIRT RES SHR S %CPU %MEMTIME+ COMMAND 25857 root 20 0 29.7g 1.5g 12m S 693.0 1.6 38:45.58 java == Cassandra-stress 29160 cassandr 20 0 16.3g 4.8g 10m S 1.3 5.0 44:46.89 java == Cassandra Now, If I run another query on a table that provides a list of buckets according to the owner, the number of op/s is divided by 2 (42000 op/s) and CPU consumption grow UP. Ex : TABLE : CREATE TABLE IF NOT EXISTS owner_to_buckets (tenantid varchar, name varchar, owner varchar, location varchar, description varchar, codeQuota varchar, creationDate timestamp, updateDate timestamp, PRIMARY KEY ((owner, tenantid), name)); QUERY : select * from owner_to_buckets where owner = ? and tenantid = ? limit 10; TOP output for 4 threads on cassandra-stress: top - 13:49:16 up 173 days, 22:26, 4 users, load average: 1.76, 1.48, 1.17 Tasks: 273 total, 1 running, 271 sleeping, 0 stopped, 1 zombie Cpu(s): 26.3%us, 8.0%sy, 0.0%ni, 64.7%id, 0.0%wa, 0.0%hi, 1.0%si, 0.0%st Mem: 98894704k total, 97512156k used, 1382548k free,14580k buffers Swap:0k total,0k used,0k free, 90413772k cached PID USER PR NI VIRT RES SHR S %CPU %MEMTIME+
Re: CPU consumption of Cassandra
I had done some benching in the past when we faced high CPU usage even though data set is very small, sitting entirely in memory, read the report there: https://github.com/doanduyhai/Cassandra_Data_Model_Bench Our *partial *conclusion were: 1) slice query fetching a page of 64kb of data and decoding columns is more CPU-expensive than a single read by column 2) the decoding of CompositeType costs more CPU for CQL3 data model than for old Thrift column family 3) since the Cell type for all CQL3 table is forced to BytesType to support any type of data, serialization/de-serialization may have a cost on CPU. The issue Eric Leleu is facing reminds me of point 1). When he puts limit to 1, it's a single read by column. The other query with limit 10 is translated internally to a slice query and may explain the CPU difference Now, do not take my words as granted. Those points are just *assumptions *and partial conclusions. I need extensive in depth debugging to confirm those. Did not have time lately. On Tue, Sep 23, 2014 at 10:46 PM, Chris Lohfink clohf...@blackbirdit.com wrote: CPU consumption may be affected from the cassandra-stress tool in 2nd example as well. Running on a separate system eliminates it as a possible cause. There is a little extra work but not anything that I think would be that obvious. tracing (can enable with nodetool) or profiling (ie with yourkit) can give more exposure to the bottleneck. Id run test from separate system first. --- Chris Lohfink On Sep 23, 2014, at 12:48 PM, Leleu Eric eric.le...@worldline.com wrote: First of all, Thanks for your help ! :) Here is some details : With RF=N=2 your essentially testing a single machine locally which isnt the best indicator long term I will test with more nodes, (4 with RF = 2) but for now I'm limited to 2 nodes for non technical reason ... Well, first off you shouldn't run stress tool on the node your testing. Give it its own box. I performed the test in a new Keyspace in order to have a clear dataset. the 2nd query since its returning 10x the data and there will be more to go through within the partition I configured cassandra-stress in a way of each user has only one bucket so the amount of data is the same in the both case. (select * from buckets where name = ? and tenantid = ? limit 1 and select * from owner_to_buckets where owner = ? and tenantid = ? limit 10). Does cassandra perform extra read when the limit is bigger than the available data (even if the partition key contains only one single value in the clustering column) ? If the amount of data is the same, how can we explain the difference of CPU consumption? Regards, Eric De : Chris Lohfink [clohf...@blackbirdit.com] Date d'envoi : mardi 23 septembre 2014 19:23 À : user@cassandra.apache.org Objet : Re: CPU consumption of Cassandra Well, first off you shouldn't run stress tool on the node your testing. Give it its own box. With RF=N=2 your essentially testing a single machine locally which isnt the best indicator long term (optimizations available when reading data thats local to the node). 80k/sec on a system is pretty good though, your probably seeing slower on the 2nd query since its returning 10x the data and there will be more to go through within the partition. 42k/sec is still acceptable imho since these are smaller boxes. You are probably seeing high CPU because the system is doing a lot :) If you want to get more out of these systems can do some tuning probably, enable trace to see whats actually the bottleneck. Collections will very likely hurt more then help. --- Chris Lohfink On Sep 23, 2014, at 9:39 AM, Leleu Eric eric.le...@worldline.com mailto:eric.le...@worldline.com eric.le...@worldline.com wrote: I tried to run “cassandra-stress” on some of my table as proposed by Jake Luciani. For a simple table, this tool is able to perform 8 read op/s with a few CPU consumption if I request the table by the PK(name, tenanted) Ex : TABLE : CREATE TABLE IF NOT EXISTS buckets (tenantid varchar, name varchar, owner varchar, location varchar, description varchar, codeQuota varchar, creationDate timestamp, updateDate timestamp, PRIMARY KEY (name, tenantid)); QUERY : select * from buckets where name = ? and tenantid = ? limit 1; TOP output for 900 threads on cassandra-stress : top - 13:17:09 up 173 days, 21:54, 4 users, load average: 11.88, 4.30, 2.76 Tasks: 272 total, 1 running, 270 sleeping, 0 stopped, 1 zombie Cpu(s): 71.4%us, 14.0%sy, 0.0%ni, 13.1%id, 0.0%wa, 0.0%hi, 1.5%si, 0.0%st Mem: 98894704k total, 96367436k used, 2527268k free,15440k buffers Swap:0k total,0k used,0k free, 88194556k cached PID USER PR NI VIRT RES SHR S %CPU %MEMTIME+ COMMAND 25857 root 20 0 29.7g 1.5g 12m S 693.0 1.6 38:45.58 java == Cassandra-stress 29160 cassandr 20 0
Re: CPU consumption of Cassandra
If I had to guess, it might be in part i could be due to inefficiencies in 2.0 with regards to CompositeType (which is used in CQL3 tables) - https://issues.apache.org/jira/browse/CASSANDRA-5417?focusedCommentId=13821243page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13821243 Ticket reports 45% performance increase in reading slices compared to trunk in 2.1 Thanks, Daniel On Tue, Sep 23, 2014 at 5:08 PM, DuyHai Doan doanduy...@gmail.com wrote: I had done some benching in the past when we faced high CPU usage even though data set is very small, sitting entirely in memory, read the report there: https://github.com/doanduyhai/Cassandra_Data_Model_Bench Our *partial *conclusion were: 1) slice query fetching a page of 64kb of data and decoding columns is more CPU-expensive than a single read by column 2) the decoding of CompositeType costs more CPU for CQL3 data model than for old Thrift column family 3) since the Cell type for all CQL3 table is forced to BytesType to support any type of data, serialization/de-serialization may have a cost on CPU. The issue Eric Leleu is facing reminds me of point 1). When he puts limit to 1, it's a single read by column. The other query with limit 10 is translated internally to a slice query and may explain the CPU difference Now, do not take my words as granted. Those points are just *assumptions *and partial conclusions. I need extensive in depth debugging to confirm those. Did not have time lately. On Tue, Sep 23, 2014 at 10:46 PM, Chris Lohfink clohf...@blackbirdit.com wrote: CPU consumption may be affected from the cassandra-stress tool in 2nd example as well. Running on a separate system eliminates it as a possible cause. There is a little extra work but not anything that I think would be that obvious. tracing (can enable with nodetool) or profiling (ie with yourkit) can give more exposure to the bottleneck. Id run test from separate system first. --- Chris Lohfink On Sep 23, 2014, at 12:48 PM, Leleu Eric eric.le...@worldline.com wrote: First of all, Thanks for your help ! :) Here is some details : With RF=N=2 your essentially testing a single machine locally which isnt the best indicator long term I will test with more nodes, (4 with RF = 2) but for now I'm limited to 2 nodes for non technical reason ... Well, first off you shouldn't run stress tool on the node your testing. Give it its own box. I performed the test in a new Keyspace in order to have a clear dataset. the 2nd query since its returning 10x the data and there will be more to go through within the partition I configured cassandra-stress in a way of each user has only one bucket so the amount of data is the same in the both case. (select * from buckets where name = ? and tenantid = ? limit 1 and select * from owner_to_buckets where owner = ? and tenantid = ? limit 10). Does cassandra perform extra read when the limit is bigger than the available data (even if the partition key contains only one single value in the clustering column) ? If the amount of data is the same, how can we explain the difference of CPU consumption? Regards, Eric De : Chris Lohfink [clohf...@blackbirdit.com] Date d'envoi : mardi 23 septembre 2014 19:23 À : user@cassandra.apache.org Objet : Re: CPU consumption of Cassandra Well, first off you shouldn't run stress tool on the node your testing. Give it its own box. With RF=N=2 your essentially testing a single machine locally which isnt the best indicator long term (optimizations available when reading data thats local to the node). 80k/sec on a system is pretty good though, your probably seeing slower on the 2nd query since its returning 10x the data and there will be more to go through within the partition. 42k/sec is still acceptable imho since these are smaller boxes. You are probably seeing high CPU because the system is doing a lot :) If you want to get more out of these systems can do some tuning probably, enable trace to see whats actually the bottleneck. Collections will very likely hurt more then help. --- Chris Lohfink On Sep 23, 2014, at 9:39 AM, Leleu Eric eric.le...@worldline.com mailto:eric.le...@worldline.com eric.le...@worldline.com wrote: I tried to run “cassandra-stress” on some of my table as proposed by Jake Luciani. For a simple table, this tool is able to perform 8 read op/s with a few CPU consumption if I request the table by the PK(name, tenanted) Ex : TABLE : CREATE TABLE IF NOT EXISTS buckets (tenantid varchar, name varchar, owner varchar, location varchar, description varchar, codeQuota varchar, creationDate timestamp, updateDate timestamp, PRIMARY KEY (name, tenantid)); QUERY : select * from buckets where name = ? and tenantid = ? limit 1; TOP output for 900 threads on cassandra-stress : top - 13:17:09 up 173 days, 21:54, 4 users, load average:
Re: CPU consumption of Cassandra
Nice catch Daniel. The comment from Sylvain explains a lot ! On Tue, Sep 23, 2014 at 11:33 PM, Daniel Chia danc...@coursera.org wrote: If I had to guess, it might be in part i could be due to inefficiencies in 2.0 with regards to CompositeType (which is used in CQL3 tables) - https://issues.apache.org/jira/browse/CASSANDRA-5417?focusedCommentId=13821243page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13821243 Ticket reports 45% performance increase in reading slices compared to trunk in 2.1 Thanks, Daniel On Tue, Sep 23, 2014 at 5:08 PM, DuyHai Doan doanduy...@gmail.com wrote: I had done some benching in the past when we faced high CPU usage even though data set is very small, sitting entirely in memory, read the report there: https://github.com/doanduyhai/Cassandra_Data_Model_Bench Our *partial *conclusion were: 1) slice query fetching a page of 64kb of data and decoding columns is more CPU-expensive than a single read by column 2) the decoding of CompositeType costs more CPU for CQL3 data model than for old Thrift column family 3) since the Cell type for all CQL3 table is forced to BytesType to support any type of data, serialization/de-serialization may have a cost on CPU. The issue Eric Leleu is facing reminds me of point 1). When he puts limit to 1, it's a single read by column. The other query with limit 10 is translated internally to a slice query and may explain the CPU difference Now, do not take my words as granted. Those points are just *assumptions *and partial conclusions. I need extensive in depth debugging to confirm those. Did not have time lately. On Tue, Sep 23, 2014 at 10:46 PM, Chris Lohfink clohf...@blackbirdit.com wrote: CPU consumption may be affected from the cassandra-stress tool in 2nd example as well. Running on a separate system eliminates it as a possible cause. There is a little extra work but not anything that I think would be that obvious. tracing (can enable with nodetool) or profiling (ie with yourkit) can give more exposure to the bottleneck. Id run test from separate system first. --- Chris Lohfink On Sep 23, 2014, at 12:48 PM, Leleu Eric eric.le...@worldline.com wrote: First of all, Thanks for your help ! :) Here is some details : With RF=N=2 your essentially testing a single machine locally which isnt the best indicator long term I will test with more nodes, (4 with RF = 2) but for now I'm limited to 2 nodes for non technical reason ... Well, first off you shouldn't run stress tool on the node your testing. Give it its own box. I performed the test in a new Keyspace in order to have a clear dataset. the 2nd query since its returning 10x the data and there will be more to go through within the partition I configured cassandra-stress in a way of each user has only one bucket so the amount of data is the same in the both case. (select * from buckets where name = ? and tenantid = ? limit 1 and select * from owner_to_buckets where owner = ? and tenantid = ? limit 10). Does cassandra perform extra read when the limit is bigger than the available data (even if the partition key contains only one single value in the clustering column) ? If the amount of data is the same, how can we explain the difference of CPU consumption? Regards, Eric De : Chris Lohfink [clohf...@blackbirdit.com] Date d'envoi : mardi 23 septembre 2014 19:23 À : user@cassandra.apache.org Objet : Re: CPU consumption of Cassandra Well, first off you shouldn't run stress tool on the node your testing. Give it its own box. With RF=N=2 your essentially testing a single machine locally which isnt the best indicator long term (optimizations available when reading data thats local to the node). 80k/sec on a system is pretty good though, your probably seeing slower on the 2nd query since its returning 10x the data and there will be more to go through within the partition. 42k/sec is still acceptable imho since these are smaller boxes. You are probably seeing high CPU because the system is doing a lot :) If you want to get more out of these systems can do some tuning probably, enable trace to see whats actually the bottleneck. Collections will very likely hurt more then help. --- Chris Lohfink On Sep 23, 2014, at 9:39 AM, Leleu Eric eric.le...@worldline.com mailto:eric.le...@worldline.com eric.le...@worldline.com wrote: I tried to run “cassandra-stress” on some of my table as proposed by Jake Luciani. For a simple table, this tool is able to perform 8 read op/s with a few CPU consumption if I request the table by the PK(name, tenanted) Ex : TABLE : CREATE TABLE IF NOT EXISTS buckets (tenantid varchar, name varchar, owner varchar, location varchar, description varchar, codeQuota varchar, creationDate timestamp, updateDate timestamp, PRIMARY KEY (name, tenantid)); QUERY : select * from buckets where
How to get data which has changed within x minutes using CQL?
I have a table structure like below - CREATE TABLE client_data ( client_id int, consumer_id text, last_modified_date timestamp, PRIMARY KEY (client_id, last_modified_date, consumer_id) ) I have a query pattern like this - Give me everything for what has changed withing last 15 minutes or 5 minutes? Is this possible to in CQL with the above tables?
Re: How to get data which has changed within x minutes using CQL?
It is possible to request a range of data according to the last_modified_date but you still need to provide the client_id , the partition key, in any case On Wed, Sep 24, 2014 at 12:23 AM, Check Peck comptechge...@gmail.com wrote: I have a table structure like below - CREATE TABLE client_data ( client_id int, consumer_id text, last_modified_date timestamp, PRIMARY KEY (client_id, last_modified_date, consumer_id) ) I have a query pattern like this - Give me everything for what has changed withing last 15 minutes or 5 minutes? Is this possible to in CQL with the above tables?
Re: How to get data which has changed within x minutes using CQL?
Yes I can provide client_id in my where clause. So now my query pattern will be - Give me everything for what has changed within last 15 minutes or 5 minutes whose client_id is equal to 1? How does my query will look like then? On Tue, Sep 23, 2014 at 3:26 PM, DuyHai Doan doanduy...@gmail.com wrote: It is possible to request a range of data according to the last_modified_date but you still need to provide the client_id , the partition key, in any case On Wed, Sep 24, 2014 at 12:23 AM, Check Peck comptechge...@gmail.com wrote: I have a table structure like below - CREATE TABLE client_data ( client_id int, consumer_id text, last_modified_date timestamp, PRIMARY KEY (client_id, last_modified_date, consumer_id) ) I have a query pattern like this - Give me everything for what has changed withing last 15 minutes or 5 minutes? Is this possible to in CQL with the above tables?
Re: How to get data which has changed within x minutes using CQL?
let previous15Min = now - 15 mins SELECT * FROM client_data WHERE client_id = 1 and last_modified_date = previous15Min Same thing for last 5 mins On Wed, Sep 24, 2014 at 12:32 AM, Check Peck comptechge...@gmail.com wrote: Yes I can provide client_id in my where clause. So now my query pattern will be - Give me everything for what has changed within last 15 minutes or 5 minutes whose client_id is equal to 1? How does my query will look like then? On Tue, Sep 23, 2014 at 3:26 PM, DuyHai Doan doanduy...@gmail.com wrote: It is possible to request a range of data according to the last_modified_date but you still need to provide the client_id , the partition key, in any case On Wed, Sep 24, 2014 at 12:23 AM, Check Peck comptechge...@gmail.com wrote: I have a table structure like below - CREATE TABLE client_data ( client_id int, consumer_id text, last_modified_date timestamp, PRIMARY KEY (client_id, last_modified_date, consumer_id) ) I have a query pattern like this - Give me everything for what has changed withing last 15 minutes or 5 minutes? Is this possible to in CQL with the above tables?
Re: How to get data which has changed within x minutes using CQL?
On Tue, Sep 23, 2014 at 3:41 PM, DuyHai Doan doanduy...@gmail.com wrote: now - 15 mins Can I run like this in CQL using cqlsh? SELECT * FROM client_data WHERE client_id = 1 and last_modified_date = now - 15 mins When I ran the above query I got an error on my cql client - Bad Request: line 1:81 no viable alternative at input '-'
Re: How to get data which has changed within x minutes using CQL?
No, you need to compute yourself now - 15mins. CQL3 does not offer built-in functions to deal with dates right now Le 24 sept. 2014 00:47, Check Peck comptechge...@gmail.com a écrit : On Tue, Sep 23, 2014 at 3:41 PM, DuyHai Doan doanduy...@gmail.com wrote: now - 15 mins Can I run like this in CQL using cqlsh? SELECT * FROM client_data WHERE client_id = 1 and last_modified_date = now - 15 mins When I ran the above query I got an error on my cql client - Bad Request: line 1:81 no viable alternative at input '-'
Reading SSTables Potential File Descriptor Leak 1.2.18
Hello, I ran in to a problem today where Cassandra 1.2.18 exhausted its number of permitted open file descriptors (65,535). This node has 256 tokens (vnodes) and runs in a test environment with relatively little traffic/data. As best I could tell, the majority of the file descriptors open were for a single SSTable '.db' file. Looking in the error logs I found quite a few exceptions that looked to have been identical: ERROR [ReadStage:3817] 2014-09-19 07:00:11,056 CassandraDaemon.java (line 191) Exception in thread Thread[ReadStage:3817,5,main] java.lang.RuntimeException: java.lang.IllegalArgumentException: unable to seek to position 29049 in /mnt/var/lib/cassandra/data/path/to/file.db (1855 bytes) in read-only mode Upon further investigation, it turns out this file became 'read-only' after the Cassandra node was gracefully restarted last week. I'd imagine this is a discussion for another email thread. I fixed the issue by running: nodetool scrub Keyspace nodetool repair Keyspace Attached to this email is one of the log entries/stacktrace for this exception. Before opening a JIRA ticket I thought I'd reach out to the list to see if anyone has seen any similar behavior as well as do a bit of source-diving to try and verify that the descriptor is actually leaking. Cheers! -Tim ERROR [ReadStage:3817] 2014-09-19 07:00:11,056 CassandraDaemon.java (line 191) Exception in thread Thread[ReadStage:3817,5,main] java.lang.RuntimeException: java.lang.IllegalArgumentException: unable to seek to position 29049 in /mnt/var/lib/cassandra/data/IzanagiQueue/WorkQueue/IzanagiQueue-WorkQueue-ic-1-Data.db (1855 bytes) in read-only mode at org.apache.cassandra.service.StorageProxy$DroppableRunnable.run(StorageProxy.java:1626) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:662) Caused by: java.lang.IllegalArgumentException: unable to seek to position 29049 in /mnt/var/lib/cassandra/data/IzanagiQueue/WorkQueue/IzanagiQueue-WorkQueue-ic-1-Data.db (1855 bytes) in read-only mode at org.apache.cassandra.io.util.RandomAccessReader.seek(RandomAccessReader.java:306) at org.apache.cassandra.io.util.PoolingSegmentedFile.getSegment(PoolingSegmentedFile.java:42) at org.apache.cassandra.io.sstable.SSTableReader.getFileDataInput(SSTableReader.java:1048) at org.apache.cassandra.db.columniterator.IndexedSliceReader.setToRowStart(IndexedSliceReader.java:130) at org.apache.cassandra.db.columniterator.IndexedSliceReader.init(IndexedSliceReader.java:91) at org.apache.cassandra.db.columniterator.SSTableSliceIterator.createReader(SSTableSliceIterator.java:68) at org.apache.cassandra.db.columniterator.SSTableSliceIterator.init(SSTableSliceIterator.java:44) at org.apache.cassandra.db.filter.SliceQueryFilter.getSSTableColumnIterator(SliceQueryFilter.java:104) at org.apache.cassandra.db.filter.QueryFilter.getSSTableColumnIterator(QueryFilter.java:68) at org.apache.cassandra.db.CollationController.collectAllData(CollationController.java:272) at org.apache.cassandra.db.CollationController.getTopLevelColumns(CollationController.java:65) at org.apache.cassandra.db.ColumnFamilyStore.getTopLevelColumns(ColumnFamilyStore.java:1398) at org.apache.cassandra.db.ColumnFamilyStore.getColumnFamily(ColumnFamilyStore.java:1214) at org.apache.cassandra.db.ColumnFamilyStore.getColumnFamily(ColumnFamilyStore.java:1130) at org.apache.cassandra.db.Table.getRow(Table.java:348) at org.apache.cassandra.db.SliceFromReadCommand.getRow(SliceFromReadCommand.java:70) at org.apache.cassandra.service.StorageProxy$LocalReadRunnable.runMayThrow(StorageProxy.java:1070) at org.apache.cassandra.service.StorageProxy$DroppableRunnable.run(StorageProxy.java:1622) ... 3 more
RE: Reading SSTables Potential File Descriptor Leak 1.2.18
Hi, It look like the offset in keycache is wrong !!. refresh the keycache may solve the issue. Thanks Regards Job M Thomas Platform Technology From: Tim Heckman [mailto:t...@pagerduty.com] Sent: Wed 9/24/2014 6:17 AM To: user@cassandra.apache.org Subject: Reading SSTables Potential File Descriptor Leak 1.2.18 Hello, I ran in to a problem today where Cassandra 1.2.18 exhausted its number of permitted open file descriptors (65,535). This node has 256 tokens (vnodes) and runs in a test environment with relatively little traffic/data. As best I could tell, the majority of the file descriptors open were for a single SSTable '.db' file. Looking in the error logs I found quite a few exceptions that looked to have been identical: ERROR [ReadStage:3817] 2014-09-19 07:00:11,056 CassandraDaemon.java (line 191) Exception in thread Thread[ReadStage:3817,5,main] java.lang.RuntimeException: java.lang.IllegalArgumentException: unable to seek to position 29049 in /mnt/var/lib/cassandra/data/path/to/file.db (1855 bytes) in read-only mode Upon further investigation, it turns out this file became 'read-only' after the Cassandra node was gracefully restarted last week. I'd imagine this is a discussion for another email thread. I fixed the issue by running: nodetool scrub Keyspace nodetool repair Keyspace Attached to this email is one of the log entries/stacktrace for this exception. Before opening a JIRA ticket I thought I'd reach out to the list to see if anyone has seen any similar behavior as well as do a bit of source-diving to try and verify that the descriptor is actually leaking. Cheers! -Tim
