No, the disks on all nodes have about 750GB free space. Also as mentioned in my follow-up email, writing with ConsistencyLevel.ALL makes the slowdowns / crashes go away.
-- Ilya On Mon, Apr 5, 2010 at 11:46 PM, Ran Tavory <[email protected]> wrote: > Do you see one of the disks used by cassandra filled up when a node crashes? > > On Tue, Apr 6, 2010 at 9:39 AM, Ilya Maykov <[email protected]> wrote: >> >> I'm running the nodes with a JVM heap size of 6GB, and here are the >> related options from my storage-conf.xml. As mentioned in the first >> email, I left everything at the default value. I briefly googled >> around for "Cassandra performance tuning" etc but haven't found a >> definitive guide ... any help with tuning these parameters is greatly >> appreciated! >> >> <DiskAccessMode>auto</DiskAccessMode> >> <RowWarningThresholdInMB>512</RowWarningThresholdInMB> >> <SlicedBufferSizeInKB>64</SlicedBufferSizeInKB> >> <FlushDataBufferSizeInMB>32</FlushDataBufferSizeInMB> >> <FlushIndexBufferSizeInMB>8</FlushIndexBufferSizeInMB> >> <ColumnIndexSizeInKB>64</ColumnIndexSizeInKB> >> <MemtableThroughputInMB>64</MemtableThroughputInMB> >> <BinaryMemtableThroughputInMB>256</BinaryMemtableThroughputInMB> >> <MemtableOperationsInMillions>0.3</MemtableOperationsInMillions> >> <MemtableFlushAfterMinutes>60</MemtableFlushAfterMinutes> >> <ConcurrentReads>8</ConcurrentReads> >> <ConcurrentWrites>64</ConcurrentWrites> >> <CommitLogSync>periodic</CommitLogSync> >> <CommitLogSyncPeriodInMS>10000</CommitLogSyncPeriodInMS> >> <GCGraceSeconds>864000</GCGraceSeconds> >> >> -- Ilya >> >> On Mon, Apr 5, 2010 at 11:26 PM, Boris Shulman <[email protected]> wrote: >> > You are running out of memory on your nodes. Before the final crash >> > your nodes are probably slow due to GC. What is your memtable size? >> > What cache options did you configure? >> > >> > On Tue, Apr 6, 2010 at 7:31 AM, Ilya Maykov <[email protected]> wrote: >> >> Hi all, >> >> >> >> I've just started experimenting with Cassandra to get a feel for the >> >> system. I've set up a test cluster and to get a ballpark idea of its >> >> performance I wrote a simple tool to load some toy data into the >> >> system. Surprisingly, I am able to "overwhelm" my 4-node cluster with >> >> writes from a single client. I'm trying to figure out if this is a >> >> problem with my setup, if I'm hitting bugs in the Cassandra codebase, >> >> or if this is intended behavior. Sorry this email is kind of long, >> >> here is the TLDR version: >> >> >> >> While writing to Cassandra from a single node, I am able to get the >> >> cluster into a bad state, where nodes are randomly disconnecting from >> >> each other, write performance plummets, and sometimes nodes even >> >> crash. Further, the nodes do not recover as long as the writes >> >> continue (even at a much lower rate), and sometimes do not recover at >> >> all unless I restart them. I can get this to happen simply by throwing >> >> data at the cluster fast enough, and I'm wondering if this is a known >> >> issue or if I need to tweak my setup. >> >> >> >> Now, the details. >> >> >> >> First, a little bit about the setup: >> >> >> >> 4-node cluster of identical machines, running cassandra-0.6.0-rc1 with >> >> the fixes for CASSANDRA-933, CASSANDRA-934, and CASSANDRA-936 patched >> >> in. Node specs: >> >> 8-core Intel Xeon [email protected] >> >> 8GB RAM >> >> 1Gbit ethernet >> >> Red Hat Linux 2.6.18 >> >> JVM 1.6.0_19 64-bit >> >> 1TB spinning disk houses both commitlog and data directories (which I >> >> know is not ideal). >> >> The client machine is on the same local network and has very similar >> >> specs. >> >> >> >> The cassandra nodes are started with the following JVM options: >> >> >> >> ./cassandra JVM_OPTS="-Xms6144m -Xmx6144m -XX:+UseConcMarkSweepGC -d64 >> >> -XX:NewSize=1024m -XX:MaxNewSize=1024m -XX:+DisableExplicitGC" >> >> >> >> I'm using default settings for all of the tunable stuff at the bottom >> >> of storage-conf.xml. I also selected my initial tokens to evenly >> >> partition the key space when the cluster was bootstrapped. I am using >> >> the RandomPartitioner. >> >> >> >> Now, about the test. Basically I am trying to get an idea of just how >> >> fast I can make this thing go. I am writing ~250M data records into >> >> the cluster, replicated at 3x, using Ran Tavory's Hector client >> >> (Java), writing with ConsistencyLevel.ZERO and >> >> FailoverPolicy.FAIL_FAST. The client is using 32 threads with 8 >> >> threads talking to each of the 4 nodes in the cluster. Records are >> >> identified by a numeric id, and I'm writing them in batches of up to >> >> 10k records per row, with each record in its own column. The row key >> >> identifies the bucket into which records fall. So, records with ids 0 >> >> - 9999 are written to row "0", 10000 - 19999 are written to row >> >> "10000", etc. Each record is a JSON object with ~10-20 fields. >> >> >> >> Records: { // Column Family >> >> 0 : { // row key for the start of the bucket. Buckets span a range >> >> of up to 10000 records >> >> 1 : "{ /* some JSON */ }", // Column for record with id=1 >> >> 3 : "{ /* some more JSON */ }", // Column for record with id=3 >> >> ... >> >> 9999 : "{ /* ... */ }" >> >> }, >> >> 10000 : { // row key for the start of the next bucket >> >> 10001 : ... >> >> 10004 : >> >> } >> >> >> >> I am reading the data out of a local, sorted file on the client, so I >> >> only write a row to Cassandra once all records for that row have been >> >> read, and each row is written to exactly once. I'm using a >> >> producer-consumer queue to pump data from the input reader thread to >> >> the output writer threads. I found that I have to throttle the reader >> >> thread heavily in order to get good behavior. So, if I make the reader >> >> sleep for 7 seconds every 1M records, everything is fine - the data >> >> loads in about an hour, half of which is spent by the reader thread >> >> sleeping. In between the sleeps, I see ~40-50 MB/s throughput on the >> >> client's network interface while the reader is not sleeping, and it >> >> takes ~7-8 seconds to write each batch of 1M records. >> >> >> >> Now, if I remove the 7 second sleeps on the client side, things get >> >> bad after the first ~8M records are written to the client. Write >> >> throughput drops to <5 MB/s. I start seeing messages about nodes >> >> disconnecting and reconnecting in Cassandra's system.log, as well as >> >> lots of GC messages: >> >> >> >> ... >> >> INFO [Timer-1] 2010-04-06 04:03:27,178 Gossiper.java (line 179) >> >> InetAddress /10.15.38.88 is now dead. >> >> INFO [GC inspection] 2010-04-06 04:03:30,259 GCInspector.java (line >> >> 110) GC for ConcurrentMarkSweep: 2989 ms, 55326320 reclaimed leaving >> >> 1035998648 used; max is 1211170816 >> >> INFO [GC inspection] 2010-04-06 04:03:41,838 GCInspector.java (line >> >> 110) GC for ConcurrentMarkSweep: 3004 ms, 24377240 reclaimed leaving >> >> 1066120952 used; max is 1211170816 >> >> INFO [Timer-1] 2010-04-06 04:03:44,136 Gossiper.java (line 179) >> >> InetAddress /10.15.38.55 is now dead. >> >> INFO [GMFD:1] 2010-04-06 04:03:44,138 Gossiper.java (line 568) >> >> InetAddress /10.15.38.55 is now UP >> >> INFO [GC inspection] 2010-04-06 04:03:52,957 GCInspector.java (line >> >> 110) GC for ConcurrentMarkSweep: 2319 ms, 4504888 reclaimed leaving >> >> 1086023832 used; max is 1211170816 >> >> INFO [Timer-1] 2010-04-06 04:04:19,508 Gossiper.java (line 179) >> >> InetAddress /10.15.38.242 is now dead. >> >> INFO [Timer-1] 2010-04-06 04:05:03,039 Gossiper.java (line 179) >> >> InetAddress /10.15.38.55 is now dead. >> >> INFO [GMFD:1] 2010-04-06 04:05:03,041 Gossiper.java (line 568) >> >> InetAddress /10.15.38.55 is now UP >> >> INFO [GC inspection] 2010-04-06 04:05:08,539 GCInspector.java (line >> >> 110) GC for ConcurrentMarkSweep: 2375 ms, 39534920 reclaimed leaving >> >> 1051620856 used; max is 1211170816 >> >> ... >> >> >> >> Finally followed by this and some/all nodes going down: >> >> >> >> ERROR [COMPACTION-POOL:1] 2010-04-06 04:05:05,475 >> >> DebuggableThreadPoolExecutor.java (line 94) Error in executor >> >> futuretask >> >> java.util.concurrent.ExecutionException: java.lang.OutOfMemoryError: >> >> Java heap space >> >> at java.util.concurrent.FutureTask$Sync.innerGet(Unknown Source) >> >> at java.util.concurrent.FutureTask.get(Unknown Source) >> >> at >> >> org.apache.cassandra.concurrent.DebuggableThreadPoolExecutor.afterExecute(DebuggableThreadPoolExecutor.java:86) >> >> at >> >> org.apache.cassandra.db.CompactionManager$CompactionExecutor.afterExecute(CompactionManager.java:582) >> >> at >> >> java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source) >> >> at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown >> >> Source) >> >> at java.lang.Thread.run(Unknown Source) >> >> Caused by: java.lang.OutOfMemoryError: Java heap space >> >> at java.util.Arrays.copyOf(Unknown Source) >> >> at java.io.ByteArrayOutputStream.write(Unknown Source) >> >> at java.io.DataOutputStream.write(Unknown Source) >> >> at >> >> org.apache.cassandra.io.IteratingRow.echoData(IteratingRow.java:69) >> >> at >> >> org.apache.cassandra.io.CompactionIterator.getReduced(CompactionIterator.java:138) >> >> at >> >> org.apache.cassandra.io.CompactionIterator.getReduced(CompactionIterator.java:1) >> >> at >> >> org.apache.cassandra.utils.ReducingIterator.computeNext(ReducingIterator.java:73) >> >> at >> >> com.google.common.collect.AbstractIterator.tryToComputeNext(AbstractIterator.java:135) >> >> at >> >> com.google.common.collect.AbstractIterator.hasNext(AbstractIterator.java:130) >> >> at >> >> org.apache.commons.collections.iterators.FilterIterator.setNextObject(FilterIterator.java:183) >> >> at >> >> org.apache.commons.collections.iterators.FilterIterator.hasNext(FilterIterator.java:94) >> >> at >> >> org.apache.cassandra.db.CompactionManager.doCompaction(CompactionManager.java:299) >> >> at >> >> org.apache.cassandra.db.CompactionManager$1.call(CompactionManager.java:102) >> >> at >> >> org.apache.cassandra.db.CompactionManager$1.call(CompactionManager.java:1) >> >> at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source) >> >> at java.util.concurrent.FutureTask.run(Unknown Source) >> >> ... 3 more >> >> >> >> At first I thought that with ConsistencyLevel.ZERO I must be doing >> >> async writes so Cassandra can't push back on the client threads (by >> >> blocking them), thus the server is getting overwhelmed. But, I would >> >> expect it to start dropping data and not crash in that case (after >> >> all, I did say ZERO so I can't expect any reliability, right?). >> >> However, I see similar slowdown / node dropout behavior when I set the >> >> consistency level to ONE. Does Cassandra push back on writers under >> >> heavy load? Is there some magic setting I need to tune to have it not >> >> fall over? Do I just need a bigger cluster? Thanks in advance, >> >> >> >> -- Ilya >> >> >> >> P.S. I realize that it's still handling a LOT of data with just 4 >> >> nodes, and in practice nobody would run a system that gets 125k writes >> >> per second on top of a 4 node cluster. I was just surprised that I >> >> could make Cassandra fall over at all using a single client that's >> >> pumping data at 40-50 MB/s. >> >> >> > > >
