what are cqlsh tracing entries meaning?

不打扰是莪最后的温柔 提交于 2021-02-07 19:14:16

问题


 activity                                                                                             | timestamp    | source        | source_elapsed
------------------------------------------------------------------------------------------------------+--------------+---------------+----------------
                                                                                   execute_cql3_query | 06:30:52,479 | 192.168.11.23 |              0
 Parsing select adid from userlastadevents where userid = '90000012' and type in (1,2,3) LIMIT 10000; | 06:30:52,479 | 192.168.11.23 |             44
                                                                                   Peparing statement | 06:30:52,479 | 192.168.11.23 |            146
                                                 Executing single-partition query on userlastadevents | 06:30:52,480 | 192.168.11.23 |            665
                                                                         Acquiring sstable references | 06:30:52,480 | 192.168.11.23 |            680
                                                 Executing single-partition query on userlastadevents | 06:30:52,480 | 192.168.11.23 |            696
                                                                         Acquiring sstable references | 06:30:52,480 | 192.168.11.23 |            704
                                                                          Merging memtable tombstones | 06:30:52,480 | 192.168.11.23 |            706
                                                                          Merging memtable tombstones | 06:30:52,480 | 192.168.11.23 |            721
                                                           Bloom filter allows skipping sstable 37398 | 06:30:52,480 | 192.168.11.23 |            758
                                                           Bloom filter allows skipping sstable 37426 | 06:30:52,480 | 192.168.11.23 |            762
                                                           Bloom filter allows skipping sstable 35504 | 06:30:52,480 | 192.168.11.23 |            768
                                                           Bloom filter allows skipping sstable 36671 | 06:30:52,480 | 192.168.11.23 |            771
                                                           Merging data from memtables and 0 sstables | 06:30:52,480 | 192.168.11.23 |            777
                                                           Merging data from memtables and 0 sstables | 06:30:52,480 | 192.168.11.23 |            780
                                                 Executing single-partition query on userlastadevents | 06:30:52,480 | 192.168.11.23 |            782
                                                                         Acquiring sstable references | 06:30:52,480 | 192.168.11.23 |            791
                                                                   Read 0 live and 0 tombstoned cells | 06:30:52,480 | 192.168.11.23 |            797
                                                                   Read 0 live and 0 tombstoned cells | 06:30:52,480 | 192.168.11.23 |            800
                                                                          Merging memtable tombstones | 06:30:52,480 | 192.168.11.23 |            815
                                                           Bloom filter allows skipping sstable 37432 | 06:30:52,480 | 192.168.11.23 |            857
                                                           Bloom filter allows skipping sstable 36918 | 06:30:52,480 | 192.168.11.23 |            866
                                                           Merging data from memtables and 0 sstables | 06:30:52,480 | 192.168.11.23 |            874
                                                                   Read 0 live and 0 tombstoned cells | 06:30:52,480 | 192.168.11.23 |            898
                                                                                     Request complete | 06:30:52,479 | 192.168.11.23 |            990

Above is the tracing output from cassandra cqlsh for a single query, but I couln't understand some the entries, at first the column "source_elapsed" what does it mean, does it mean time elapsed to execute particular task or cumulative time elapsed up to this task. second "timestamp" doesn't maintain chronology like "Request Complete" timestamp is 06:30:52,479 but "Merging data from memtables and 0 sstables" is 06:30:52,480 which is suppose to happen earlier but timestamp shows it happens later.

And couldn't understand some of the activities as well,

  1. Executing single-partition query -- doesn't it mean all the task as a whole or is it a starting point? what are the job it includes? And why is it repeating three times? is it link to replication factor.

  2. Acquiring sstable references -- What does it mean, does it checks all the sstable's bloom filters whether that contains a particular key we search for? An then find the reference in data file with the help of "Partition Index".

  3. Bloom filter allows skipping sstable -- when does it happen? How does it happen? it is taking same amount of time of finding sstable references.

  4. Request complete -- what does it mean? is it the finishing line or it is some job which takes most amount of time?


回答1:


Did you see the request tracing in Cassandra link that explains different tracing scenarios?

  1. source_elapsed: is the cumulative execution time on a specific node (if you check the above link it will be clearer)
  2. Executing single-partition query: (seems to represent) the start time
  3. Request complete: all work has been done for this request

For the rest you'd be better off reading the Reads in Cassandra docs as that would be much more detailed than I could summarize it here.



来源:https://stackoverflow.com/questions/18973827/what-are-cqlsh-tracing-entries-meaning

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