我正在开发一个4节点cassandra 1.2.6群集，其中包含一个密钥空间，复制因子为2（最初为3，但已降为2）和10个左右的列族。它正在运行Oracle 1.7 jvm。它具有读写混合，可能是读取的两到三倍。
即使在少量负载下，我看到非常大的读取延迟，并且我获得了相当多的读取超时（使用datastax java驱动程序）。以下是其中一个列族的nodetool cfstats的示例输出：
Column Family: user_scores
SSTable count: 1
SSTables in each level: [1, 0, 0, 0, 0, 0, 0, 0, 0]
Space used (live): 7539098
Space used (total): 7549091
Number of Keys (estimate): 42112
Memtable Columns Count: 2267
Memtable Data Size: 1048576
Memtable Switch Count: 2
Read Count: 2101
**Read Latency: 272334.202 ms.**
Write Count: 24947
Write Latency: NaN ms.
Pending Tasks: 0
Bloom Filter False Positives: 0
Bloom Filter False Ratio: 0.00000
Bloom Filter Space Used: 55376
Compacted row minimum size: 447
Compacted row maximum size: 219342
Compacted row mean size: 1051
正如您所看到的，我尝试使用级别基础压缩策略来尝试改善读取延迟，但您也可以看到延迟很大。我有点难过。我有一个cassandra 1.1.6集群工作得很漂亮，但到目前为止1.2没有运气。
群集在VM上运行，具有4个CPU和7 Gb ram。数据驱动器设置为跨4个磁盘的条带raid。机器似乎没有IO限制。
我正在使用所有默认设置运行漂亮的vanilla配置。
我确实看到奇怪的CPU行为，即使在较小的负载下CPU也会出现尖峰。有时候我会看到压缩运行，但它们被剔除，所以我认为不是罪魁祸首。
我想弄清楚接下来要去哪里。任何帮助表示赞赏！
[使用rpc_timeout trace更新] 还在玩这个。这是一个示例跟踪。看起来合并步骤太长了。
activity | timestamp | source | source_elapsed
-------------------------------------------------------------------------+--------------+---------------+----------------
execute_cql3_query | 04:57:18,882 | 100.69.176.51 | 0
Parsing select * from user_scores where user_id='26257166' LIMIT 10000; | 04:57:18,884 | 100.69.176.51 | 1981
Peparing statement | 04:57:18,885 | 100.69.176.51 | 2997
Executing single-partition query on user_scores | 04:57:18,885 | 100.69.176.51 | 3657
Acquiring sstable references | 04:57:18,885 | 100.69.176.51 | 3724
Merging memtable tombstones | 04:57:18,885 | 100.69.176.51 | 3779
Key cache hit for sstable 32 | 04:57:18,886 | 100.69.176.51 | 3910
Seeking to partition beginning in data file | 04:57:18,886 | 100.69.176.51 | 3930
Merging data from memtables and 1 sstables | 04:57:18,886 | 100.69.176.51 | 4211
Request complete | 04:57:38,891 | 100.69.176.51 | 20009870
下面的旧痕迹：
[较新的跟踪] 通过完全重建集群数据存储库来解决日志中记录的问题之后，我仍然遇到了问题，尽管花了相当长的时间。这是我处于糟糕状态时抓住的痕迹：
追踪会议：a6dbefc0-ea49-11e2-84bb-ef447a7d9a48
activity | timestamp | source | source_elapsed
-------------------------------------------------------------------------------------------------+--------------+----------------+----------------
execute_cql3_query | 16:48:02,755 | 100.69.196.124 | 0
Parsing select * from user_scores limit 1; | 16:48:02,756 | 100.69.196.124 | 1774
Peparing statement | 16:48:02,759 | 100.69.196.124 | 4006
Determining replicas to query | 16:48:02,759 | 100.69.196.124 | 4286
Enqueuing request to /100.69.176.51 | 16:48:02,763 | 100.69.196.124 | 8849
Sending message to cdb002/100.69.176.51 | 16:48:02,764 | 100.69.196.124 | 9456
Message received from /100.69.196.124 | 16:48:03,449 | 100.69.176.51 | 160
Message received from /100.69.176.51 | 16:48:09,646 | 100.69.196.124 | 6891860
Processing response from /100.69.176.51 | 16:48:09,647 | 100.69.196.124 | 6892426
Executing seq scan across 1 sstables for [min(-9223372036854775808), min(-9223372036854775808)] | 16:48:10,288 | 100.69.176.51 | 6838754
Seeking to partition beginning in data file | 16:48:10,289 | 100.69.176.51 | 6839689
Read 1 live and 0 tombstoned cells | 16:48:10,289 | 100.69.176.51 | 6839927
Seeking to partition beginning in data file | 16:48:10,289 | 100.69.176.51 | 6839998
Read 1 live and 0 tombstoned cells | 16:48:10,289 | 100.69.176.51 | 6840082
Scanned 1 rows and matched 1 | 16:48:10,289 | 100.69.176.51 | 6840162
Enqueuing response to /100.69.196.124 | 16:48:10,289 | 100.69.176.51 | 6840229
Sending message to /100.69.196.124 | 16:48:10,299 | 100.69.176.51 | 6850072
Request complete | 16:48:09,648 | 100.69.196.124 | 6893029
[更新] 我应该补充说，在我的macbook pro上有一个独奏cassandra实例的东西很有用。 AKA在我的机器上工作...... :)
[使用跟踪数据更新]
这是一些跟踪数据。这是来自java驱动程序。缺点是我只能跟踪成功的查询。在每个查询开始超时之前，我总共进行了67次查询。奇怪的是，它看起来并不那么糟糕。在查询68，我不再得到响应，并且其中两个服务器正在运行。
2013-07-11 02:15:45 STDIO [INFO] ***************************************
66:Host (queried): cdb003/100.69.198.47
66:Host (tried): cdb003/100.69.198.47
66:Trace id: c95e51c0-e9cf-11e2-b9a9-5b3c0946787b
66:-----------------------------------------------------+--------------+-----------------+--------------
66: Enqueuing data request to /100.69.176.51 | 02:15:42.045 | /100.69.198.47 | 200
66: Enqueuing digest request to /100.69.176.51 | 02:15:42.045 | /100.69.198.47 | 265
66: Sending message to /100.69.196.124 | 02:15:42.045 | /100.69.198.47 | 570
66: Sending message to /100.69.176.51 | 02:15:42.045 | /100.69.198.47 | 574
66: Message received from /100.69.176.51 | 02:15:42.107 | /100.69.198.47 | 62492
66: Processing response from /100.69.176.51 | 02:15:42.107 | /100.69.198.47 | 62780
66: Message received from /100.69.198.47 | 02:15:42.508 | /100.69.196.124 | 31
66: Executing single-partition query on user_scores | 02:15:42.508 | /100.69.196.124 | 406
66: Acquiring sstable references | 02:15:42.508 | /100.69.196.124 | 473
66: Merging memtable tombstones | 02:15:42.508 | /100.69.196.124 | 577
66: Key cache hit for sstable 11 | 02:15:42.508 | /100.69.196.124 | 807
66: Seeking to partition beginning in data file | 02:15:42.508 | /100.69.196.124 | 849
66: Merging data from memtables and 1 sstables | 02:15:42.509 | /100.69.196.124 | 1500
66: Message received from /100.69.198.47 | 02:15:43.379 | /100.69.176.51 | 60
66: Executing single-partition query on user_scores | 02:15:43.379 | /100.69.176.51 | 399
66: Acquiring sstable references | 02:15:43.379 | /100.69.176.51 | 490
66: Merging memtable tombstones | 02:15:43.379 | /100.69.176.51 | 593
66: Key cache hit for sstable 7 | 02:15:43.380 | /100.69.176.51 | 1098
66: Seeking to partition beginning in data file | 02:15:43.380 | /100.69.176.51 | 1141
66: Merging data from memtables and 1 sstables | 02:15:43.380 | /100.69.176.51 | 1912
66: Read 1 live and 0 tombstoned cells | 02:15:43.438 | /100.69.176.51 | 59094
66: Enqueuing response to /100.69.198.47 | 02:15:43.438 | /100.69.176.51 | 59225
66: Sending message to /100.69.198.47 | 02:15:43.438 | /100.69.176.51 | 59373
66:Started at: 02:15:42.04466:Elapsed time in micros: 63105
2013-07-11 02:15:45 STDIO [INFO] ***************************************
67:Host (queried): cdb004/100.69.184.134
67:Host (tried): cdb004/100.69.184.134
67:Trace id: c9f365d0-e9cf-11e2-a4e5-7f3170333ff5
67:-----------------------------------------------------+--------------+-----------------+--------------
67: Message received from /100.69.184.134 | 02:15:42.536 | /100.69.198.47 | 36
67: Executing single-partition query on user_scores | 02:15:42.536 | /100.69.198.47 | 273
67: Acquiring sstable references | 02:15:42.536 | /100.69.198.47 | 311
67: Merging memtable tombstones | 02:15:42.536 | /100.69.198.47 | 353
67: Key cache hit for sstable 8 | 02:15:42.536 | /100.69.198.47 | 436
67: Seeking to partition beginning in data file | 02:15:42.536 | /100.69.198.47 | 455
67: Merging data from memtables and 1 sstables | 02:15:42.537 | /100.69.198.47 | 811
67: Read 1 live and 0 tombstoned cells | 02:15:42.550 | /100.69.198.47 | 14242
67: Enqueuing response to /100.69.184.134 | 02:15:42.550 | /100.69.198.47 | 14456
67: Sending message to /100.69.184.134 | 02:15:42.551 | /100.69.198.47 | 14694
67: Enqueuing data request to /100.69.198.47 | 02:15:43.021 | /100.69.184.134 | 323
67: Sending message to /100.69.198.47 | 02:15:43.021 | /100.69.184.134 | 565
67: Message received from /100.69.198.47 | 02:15:43.038 | /100.69.184.134 | 17029
67: Processing response from /100.69.198.47 | 02:15:43.038 | /100.69.184.134 | 17230
67:Started at: 02:15:43.021
67:Elapsed time in micros: 17622
这是使用cqlsh的跟踪：
Tracing session: d0f845d0-e9cf-11e2-8882-ef447a7d9a48
activity | timestamp | source | source_elapsed
-------------------------------------------------------------------------+--------------+----------------+----------------
execute_cql3_query | 19:15:54,833 | 100.69.196.124 | 0
Parsing select * from user_scores where user_id='39333433' LIMIT 10000; | 19:15:54,833 | 100.69.196.124 | 103
Peparing statement | 19:15:54,833 | 100.69.196.124 | 455
Executing single-partition query on user_scores | 19:15:54,834 | 100.69.196.124 | 1400
Acquiring sstable references | 19:15:54,834 | 100.69.196.124 | 1468
Merging memtable tombstones | 19:15:54,835 | 100.69.196.124 | 1575
Key cache hit for sstable 11 | 19:15:54,835 | 100.69.196.124 | 1780
Seeking to partition beginning in data file | 19:15:54,835 | 100.69.196.124 | 1822
Merging data from memtables and 1 sstables | 19:15:54,836 | 100.69.196.124 | 2562
Read 1 live and 0 tombstoned cells | 19:15:54,838 | 100.69.196.124 | 4808
Request complete | 19:15:54,838 | 100.69.196.124 | 5810
答案 0 :(得分：1)
跟踪似乎表明大部分时间都在做或正在等待网络操作。也许你的网络有问题？
如果只有一些操作失败，可能只有一个节点出现问题。当不需要那个节点时，事情就会起作用，但是当需要它时，事情会变得很糟糕。可能值得查看其他节点上的日志文件。
答案 1 :(得分：1)
看起来我遇到了1.2的性能问题。幸运的是，补丁刚刚应用于1.2分支，所以当我从源代码构建时，我的问题就消失了。
有关详细说明，请参阅https://issues.apache.org/jira/browse/CASSANDRA-5677。
全部谢谢！