Tombstone control

Сергей Меженин

<msrgbin@gmail.com>

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May 5, 2022, 5:57:22 PM5/5/22

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Greetings!

Cassandra has tombstone control functionality and the ability to customize settings

tombstone_warn_threshold

tombstone_failure_threshold

Scylla does not have a convenient estimate of this indicator, there are no reports in the logs that reads take a long time due to the large number of tombstones.

The nodetool utility and its cfstats option has a field for displaying the number of tombstones, which works in Cassandra and only displays "0" in Scylla.

Average headstones per cut (last five minutes): 0.0

Maximum headstones per cut (last five minutes): 0

Thanks for your work!

Raphael S. Carvalho

<raphaelsc@scylladb.com>

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May 5, 2022, 6:28:16 PM5/5/22

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Hi,

We have an issue opened for implementing tombstone scanned histogram,
which can be very useful for increasing observability of tombstone
impact on reads. https://github.com/scylladb/scylla/issues/7636

As for tombstone_warn_threshold, we're still thinking about how we're
going to implement it. Bloating the log with warnings that are hard to
spot may be suboptimal. In ScyllaDB, we keep track of large
partitions, larger than a threshold, in a system table, and a similar
approach could be employed for tracking reads which # of tombstones
crossed a threshold.

Сергей Меженин

<msrgbin@gmail.com>

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May 6, 2022, 3:03:11 AM5/6/22

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Thank you!

пятница, 6 мая 2022 г. в 01:28:16 UTC+3, raph...@scylladb.com:

Andrey V. Bondarenko

<avbondarenko@gmail.com>

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May 6, 2022, 4:25:30 AM5/6/22

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Hello!

>Bloating the log with warnings that are hard to spot may be suboptimal

The number of warnings can be adjusted with the parameter tombstone_warn_threshold. With zero value for disable warning. The higher the value, the less frequent the warning will be. It would also be useful to add the number of tombstones read to the system_trace.node_ slow_log when the slow_query is enbled.

пятница, 6 мая 2022 г. в 10:03:11 UTC+3, msr...@gmail.com:

Taras Bor

<taras3bor@gmail.com>

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Aug 18, 2022, 2:36:48 PM8/18/22

to ScyllaDB users

Hello. I made a changes to version 4.6.6, that reproduce this cassandra functional on scylla:
https://github.com/soft-stech/scylladb/commit/8c40771c4b7b5643dafef982577c9a09323c6361
Please, could somebody from scylla developers team help me and check solution?

пятница, 6 мая 2022 г. в 11:25:30 UTC+3, Andrey V. Bondarenko:

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