On Tue, Oct 20, 2009 at 2:03 PM, Jonathan Ellis <[email protected]> wrote: > Okay, so we have 2 problems: > > - the read is simply too slow > - we're doing unnecessary(?) read repairs > > For the first I think it's going to be easiest if you can export the > row in question so we can do some profiling. (Eric will have a tool > to do this soon.)
Ok - I've created a cassandra setup with just the row in question and tarred up the data + storage-conf.xml for the three nodes: http://demo.ooyala.com/cassandra/cassandra-1.tgz http://demo.ooyala.com/cassandra/cassandra-2.tgz http://demo.ooyala.com/cassandra/cassandra-3.tgz > > For the second, how sure are you that the repair is unnecessary? Does > it repeat the repair when you do the query again after letting the > callbacks complete? I didn't do any writes as I was debugging the issue whereas I was reading the same data a whole bunch of times, so the repair should've been unnecessary. Thanks for your help, Edmond > > -Jonathan > > On Mon, Oct 19, 2009 at 11:38 PM, Edmond Lau <[email protected]> wrote: >> A single local read with debug logging takes 3-4 secs on the node with >> 3 data files. It actually takes roughly as long on the other nodes as >> well (I was incorrect in saying that they were fast). >> >> DEBUG [pool-1-thread-22] 2009-10-20 04:26:06,953 CassandraServer.java >> (line 219) get_slice >> DEBUG [pool-1-thread-22] 2009-10-20 04:26:06,955 StorageProxy.java >> (line 468) weakreadlocal reading >> SliceFromReadCommand(table='Analytics', key='o:movie', >> column_parent='QueryPath(columnFamilyName='movie', >> superColumnName='[...@26e00675', columnName='null')', start='', >> finish='', reversed=false, count=1) >> DEBUG [pool-1-thread-22] 2009-10-20 04:26:10,382 SliceQueryFilter.java >> (line 115) collecting 1000036:false:5...@1255978226411394 >> DEBUG [CONSISTENCY-MANAGER:2] 2009-10-20 04:26:10,383 >> ConsistencyManager.java (line 168) Reading consistency digest for >> o:movie from 2...@[172.16.129.71:7000, 172.16.129.72:7000] >> DEBUG [RESPONSE-STAGE:1] 2009-10-20 04:26:13,332 >> ResponseVerbHandler.java (line 34) Processing response on a callback >> from [email protected]:7000 >> DEBUG [RESPONSE-STAGE:3] 2009-10-20 04:26:13,675 >> ResponseVerbHandler.java (line 34) Processing response on a callback >> from [email protected]:7000 >> DEBUG [RESPONSE-STAGE:3] 2009-10-20 04:26:13,677 >> ConsistencyManager.java (line 96) Performing read repair for o:movie >> to 2...@[172.16.129.71:7000, 172.16.129.72:7000, 172.16.129.75:7000] >> >> Also, it's unclear why there's a read repair going on above, since I >> haven't made any updates. >> >> Doing a quorum read on the node with 3 data files takes 7 seconds w/ >> debug logging and leads to a DigestMismatchException, again even >> though I haven't made any updates. >> >> DEBUG [pool-1-thread-25] 2009-10-20 04:30:00,892 CassandraServer.java >> (line 219) get_slice >> DEBUG [pool-1-thread-25] 2009-10-20 04:30:00,894 StorageProxy.java >> (line 374) strongread reading data for >> SliceFromReadCommand(table='Analytics', key='o:movie', >> column_parent='QueryPath(columnFamilyName='movie', >> superColumnName='[...@2cf50c5f', columnName='null')', start='', >> finish='', reversed=false, count=1) from [email protected]:7000 >> DEBUG [pool-1-thread-25] 2009-10-20 04:30:00,894 StorageProxy.java >> (line 381) strongread reading digest for >> SliceFromReadCommand(table='Analytics', key='o:movie', >> column_parent='QueryPath(columnFamilyName='movie', >> superColumnName='[...@2cf50c5f', columnName='null')', start='', >> finish='', reversed=false, count=1) from [email protected]:7000 >> DEBUG [pool-1-thread-25] 2009-10-20 04:30:00,895 StorageProxy.java >> (line 381) strongread reading digest for >> SliceFromReadCommand(table='Analytics', key='o:movie', >> column_parent='QueryPath(columnFamilyName='movie', >> superColumnName='[...@2cf50c5f', columnName='null')', start='', >> finish='', reversed=false, count=1) from [email protected]:7000 >> DEBUG [RESPONSE-STAGE:3] 2009-10-20 04:30:03,994 >> ResponseVerbHandler.java (line 34) Processing response on a callback >> from [email protected]:7000 >> DEBUG [RESPONSE-STAGE:2] 2009-10-20 04:30:04,107 >> ResponseVerbHandler.java (line 34) Processing response on a callback >> from [email protected]:7000 >> DEBUG [ROW-READ-STAGE:9] 2009-10-20 04:30:04,787 SliceQueryFilter.java >> (line 115) collecting 1000036:false:5...@1255978226411394 >> DEBUG [ROW-READ-STAGE:9] 2009-10-20 04:30:04,788 ReadVerbHandler.java >> (line 100) Read key o:movie; sending response to >> [email protected]:7000 >> DEBUG [RESPONSE-STAGE:4] 2009-10-20 04:30:04,788 >> ResponseVerbHandler.java (line 34) Processing response on a callback >> from [email protected]:7000 >> DEBUG [pool-1-thread-25] 2009-10-20 04:30:04,789 >> ReadResponseResolver.java (line 84) Response deserialization time : 0 >> ms. >> DEBUG [pool-1-thread-25] 2009-10-20 04:30:04,790 >> ReadResponseResolver.java (line 84) Response deserialization time : 0 >> ms. >> DEBUG [pool-1-thread-25] 2009-10-20 04:30:04,791 >> ReadResponseResolver.java (line 84) Response deserialization time : 1 >> ms. >> INFO [pool-1-thread-25] 2009-10-20 04:30:04,792 StorageProxy.java >> (line 410) DigestMismatchException: o:movie >> DEBUG [RESPONSE-STAGE:1] 2009-10-20 04:30:07,953 >> ResponseVerbHandler.java (line 34) Processing response on a callback >> from [email protected]:7000 >> DEBUG [RESPONSE-STAGE:3] 2009-10-20 04:30:08,130 >> ResponseVerbHandler.java (line 34) Processing response on a callback >> from [email protected]:7000 >> DEBUG [pool-1-thread-25] 2009-10-20 04:30:08,132 >> ReadResponseResolver.java (line 84) Response deserialization time : 1 >> ms. >> DEBUG [pool-1-thread-25] 2009-10-20 04:30:08,132 >> ReadResponseResolver.java (line 84) Response deserialization time : 0 >> ms. >> DEBUG [pool-1-thread-25] 2009-10-20 04:30:08,132 >> ReadResponseResolver.java (line 149) resolve: 1 ms. >> DEBUG [ROW-READ-STAGE:10] 2009-10-20 04:30:08,235 >> SliceQueryFilter.java (line 115) collecting >> 1000036:false:5...@1255978226411394 >> DEBUG [ROW-READ-STAGE:10] 2009-10-20 04:30:08,235 ReadVerbHandler.java >> (line 100) Read key o:movie; sending response to >> [email protected]:7000 >> >> Edmond >> >> On Mon, Oct 19, 2009 at 8:04 PM, Jonathan Ellis <[email protected]> wrote: >>> On Mon, Oct 19, 2009 at 9:48 PM, Edmond Lau <[email protected]> wrote: >>>> 8 data files total. 3 nodes have 1, 1 has 2, the 3rd has 3. >>>> >>>>> Does it still take ~8s if you direct a CL.ONE query at one of the >>>>> nodes you know has the data (i.e., a local read)? >>>> >>>> Local reads return quickly, but if you look at the logs below, there's >>>> 6 secs from when cassandra prints that it's reading a consistency >>>> digest to when it processes a callback. >>> >>> That's from when it sends the digest command, to when it gets a callback. >>> >>> Something doesn't add up. If computing &sending a digest response >>> takes 6s, either reading the row or computing the digest must be >>> taking substantial time. But if local reads are fast, it's not >>> reading the row that is slow, and if resolve is fast (from your logs, >>> it is 2ms) then it's not computing the digest that is slow. >>> >>> Try doing a local read from the node with 3 data files, see if that is >>> slower. >>> >>> If you still see a fast read there, add some more debug logging in >>> ReadVerbHandler.java, where it says something like (I'm going from >>> trunk here but 0.4.1 is similar) >>> >>> Row row = readCommand.getRow(table); >>> ReadResponse readResponse; >>> if (readCommand.isDigestQuery()) >>> { >>> readResponse = new ReadResponse(row.digest()); >>> >>> time the getRow and the row.digest() calls and log how long those take >>> in the quorum scenario. >>> >>> -Jonathan >>> >> >
