这是来自运行 1.2.6 的 4 节点 cassandra 集群的跟踪。当集群处于空载状态时，我看到一个简单的选择超时，我需要一些帮助才能深入了解它。
activity | timestamp | source | source_elapsed
-------------------------------------------------------------------------+--------------+---------------+----------------
execute_cql3_query | 05:21:00,848 | 100.69.176.51 | 0
Parsing select * from user_scores where user_id='26257166' LIMIT 10000; | 05:21:00,848 | 100.69.176.51 | 77
Peparing statement | 05:21:00,848 | 100.69.176.51 | 225
Executing single-partition query on user_scores | 05:21:00,849 | 100.69.176.51 | 589
Acquiring sstable references | 05:21:00,849 | 100.69.176.51 | 626
Merging memtable tombstones | 05:21:00,849 | 100.69.176.51 | 676
Key cache hit for sstable 34 | 05:21:00,849 | 100.69.176.51 | 817
Seeking to partition beginning in data file | 05:21:00,849 | 100.69.176.51 | 836
Key cache hit for sstable 32 | 05:21:00,849 | 100.69.176.51 | 1135
Seeking to partition beginning in data file | 05:21:00,849 | 100.69.176.51 | 1153
Merging data from memtables and 2 sstables | 05:21:00,850 | 100.69.176.51 | 1394
Request complete | 05:21:20,881 | 100.69.176.51 | 20033807
这是架构。您可以看到它包含一些集合。
create table user_scores
(
user_id varchar,
post_type varchar,
score double,
team_to_score_map map<varchar, double>,
affiliation_to_score_map map<varchar, double>,
campaign_to_score_map map<varchar, double>,
person_to_score_map map<varchar, double>,
primary key(user_id, post_type)
)
with compaction =
{
'class' : 'LeveledCompactionStrategy',
'sstable_size_in_mb' : 10
};
我添加了分级压缩策略，因为它应该有助于降低读取延迟。
我想了解在合并阶段可能导致集群超时的原因。并非所有查询都超时。对于具有大量条目的映射的行，它似乎更频繁地发生。
这是另一个很好的措施失败的痕迹。这是非常可重复的：
activity | timestamp | source | source_elapsed
-------------------------------------------------------------------------+--------------+----------------+----------------
execute_cql3_query | 05:51:34,557 | 100.69.176.51 | 0
Message received from /100.69.176.51 | 05:51:34,195 | 100.69.184.134 | 102
Executing single-partition query on user_scores | 05:51:34,199 | 100.69.184.134 | 3512
Acquiring sstable references | 05:51:34,199 | 100.69.184.134 | 3741
Merging memtable tombstones | 05:51:34,199 | 100.69.184.134 | 3890
Key cache hit for sstable 5 | 05:51:34,199 | 100.69.184.134 | 4040
Seeking to partition beginning in data file | 05:51:34,199 | 100.69.184.134 | 4059
Merging data from memtables and 1 sstables | 05:51:34,200 | 100.69.184.134 | 4412
Parsing select * from user_scores where user_id='26257166' LIMIT 10000; | 05:51:34,558 | 100.69.176.51 | 91
Peparing statement | 05:51:34,558 | 100.69.176.51 | 238
Enqueuing data request to /100.69.184.134 | 05:51:34,558 | 100.69.176.51 | 567
Sending message to /100.69.184.134 | 05:51:34,558 | 100.69.176.51 | 979
Request complete | 05:51:54,562 | 100.69.176.51 | 20005209
以及它何时工作的痕迹：
activity | timestamp | source | source_elapsed
--------------------------------------------------------------------------+--------------+----------------+----------------
execute_cql3_query | 05:55:07,772 | 100.69.176.51 | 0
Message received from /100.69.176.51 | 05:55:07,408 | 100.69.184.134 | 53
Executing single-partition query on user_scores | 05:55:07,409 | 100.69.184.134 | 1014
Acquiring sstable references | 05:55:07,409 | 100.69.184.134 | 1087
Merging memtable tombstones | 05:55:07,410 | 100.69.184.134 | 1209
Partition index with 0 entries found for sstable 5 | 05:55:07,410 | 100.69.184.134 | 1681
Seeking to partition beginning in data file | 05:55:07,410 | 100.69.184.134 | 1732
Merging data from memtables and 1 sstables | 05:55:07,411 | 100.69.184.134 | 2415
Read 1 live and 0 tombstoned cells | 05:55:07,412 | 100.69.184.134 | 3274
Enqueuing response to /100.69.176.51 | 05:55:07,412 | 100.69.184.134 | 3534
Sending message to /100.69.176.51 | 05:55:07,412 | 100.69.184.134 | 3936
Parsing select * from user_scores where user_id='305722020' LIMIT 10000; | 05:55:07,772 | 100.69.176.51 | 96
Peparing statement | 05:55:07,772 | 100.69.176.51 | 262
Enqueuing data request to /100.69.184.134 | 05:55:07,773 | 100.69.176.51 | 600
Sending message to /100.69.184.134 | 05:55:07,773 | 100.69.176.51 | 847
Message received from /100.69.184.134 | 05:55:07,778 | 100.69.176.51 | 6103
Processing response from /100.69.184.134 | 05:55:07,778 | 100.69.176.51 | 6341
Request complete | 05:55:07,778 | 100.69.176.51 | 6780