Hello! Can't answer your question but there is another one: "why do we need to maintain counters with their known limitations (and I've heard of some issues with implementation of counters in Cassandra), when there exist really effective uuid generation algorithms which allow us to generate unique values?" https://begriffs.com/posts/2018-01-01-sql-keys-in-depth.html
<https://begriffs.com/posts/2018-01-01-sql-keys-in-depth.html>(the article is about keys in RDBMS's, but its statements are true for NoSQL as well) Regards, Kyrill ________________________________ From: jpar...@gmail.com <jpar...@gmail.com> on behalf of Javier Pareja <pareja.jav...@gmail.com> Sent: Monday, March 5, 2018 1:55:14 PM To: user@cassandra.apache.org Subject: How do counter updates work? Hello everyone, I am trying to understand how cassandra counter writes work in more detail but all that I could find is this: https://www.datastax.com/dev/blog/whats-new-in-cassandra-2-1-a-better-implementation-of-counters >From there I was able to extract the following process: (click here to edit<https://www.draw.io/?lightbox=1&highlight=0000ff&edit=_blank&layers=1&nav=1&title=Untitled%20Diagram.xml#R7VpRc6M2EP41nmkfcgPCYPKYOPHdTXudzCXtNY8yCKMGkCvk2LlfXwkkjATYjo0dp5O8BK2kZdldfftJ8sAZp6vPFM7jbyREyQBY4Wrg3AwAsIfA4%2F%2BE5KWU%2BP5lKZhRHMpBa8E9%2Fomk0JLSBQ5Rrg1khCQMz3VhQLIMBUyTQUrJUh8WkUR%2F6xzOUENwH8CkKf2BQxZLqW1Z644vCM9i%2BWrflR1TGDzNKFlk8n0D4ETFX9mdQqVLjs9jGJJlTeTcDpwxJYSVT%2BlqjBLhW%2BW2ct6ko7eym6KM7TRhhKDnjZDtBoCbGlwAXxrGXpQzUMh9I5uEspjMSAaT27X0uvhgJFTavBWzNJGPCZyi5LryyZgkhPKujGRiWs4gZVciXIZsghOhwVJtmSAub6MsVDOCBOY5Dh5inJUdcppdtmqT%2FkGMvcg2XDDCResP%2BZ2QuZyVM0qekLKSx84q%2FqoelQtibEQyNoEpTkSK%2F4VoCDMoxfJNvmy26ePhoS9%2Fi2%2F85Krmo%2FxktMKs1sVbj%2FKdzejKgOdkQQOVu45cMJDOkBwGSpGIZG2eTInPiKSIv58PoCiBDD%2FrqwDKxTSrxlVT7wjmlgBLLnwwlGktl%2F3Qt3QVpZ1yVj0tDUVDy1DkGorKj2so4qkBX2rD5mJA%2FgqDL62Ndjmbx%2FOH0gLVqjl3LSqWYPtydEvtzzBZIAUgB6xGS1%2BNuy6DTcnZmkjbc9KEGQXqtRy1vQNzshaFjU7uMqbm9dsVChYMceGYO5Mhyp%2F%2BnIdQiLyEG3w95SJvxiqP1CLEMX0uHmO0gty1fMgcUczNRHQtvVuLrpcxZuh%2BDgtvLXlF1cOmx7OqGNYO%2BPoKOOPYWRspi9YuMGeDDTgHEzzLBFajrPzWznR5RpSh1WATOqnekbEIZXNZq9RKFteLtHWE3AGN3PlBcZE5HDgI%2F%2FcNpQxOeW6YaaIXzS05cEjUvcBH02iXqIcQ%2BVFwnlH39aC7oCXqoCXqwx6ivjXIY5KmmCVk9nZRDkeX013XNvKC40W5EdKWwHdG%2BU3D7HxQ3zOnvq%2FmHS1cuB3Cz5gL24Yi7zy4sH1kLmxfnhcZtrVkrRK0z3QdtmSrc5TsHAI9eI6ZnR1JtUcchy1hlBxaUejvCIYDYVEp5xqrrmBBC5cpBcCKKEn5vxucPx1WbbvKYndp7aHAOZ7ueOCdsMB5jVBMyqOqSdOTMUmni3y7F%2Fso%2BsZuv43R%2B0ci9B%2FHXSep%2BT0D5aFHBR0V0DXIp7nmdi3ZZil1Lo%2BGrs0i%2BYjyRk7ztcmMQwWU45%2FFvrRMPMkO%2BGj3euDetNF7scZxAJMr2ZHiMCzWQ0fa148ROlFCnuBLSwbVwXg9AfyN6HFhffKA7%2BkOL1v75oMaQqIoR4dGSNG3D4g5CcTYNYAp4eacIcZx9oSYBo%2FYkcC9dldQGWi8p9OuzeMP3xU0D2v%2FIP8zvLOtwbsGPKcRoq9ZQFGq8%2Fip%2BCQWi8eFPFo3YTJJ8DxH2zkozOflLXCEVwI0j0FKHd89GSm1Rw0PHlRD9tz67gectszM%2Bi72ZFc7zR3OQ%2FGmxpaT7rHlXN8FjWEQH3ii33X03n1830NSm1cndtvus%2B3upJdTdKsRnO9X37jglwnM2a8b3GmdqTvNa2q%2FxZtHu5NoFsKbr%2Fe%2FCXfeJ2TZrztPczZiutNuu9k7mj%2FBdszlyPBcre8mb9ZdqBNcQURDmMfVdNG4g4zjSVZIgLVfGs8oDDHSOLE44EavuaxvRqTmcbfF4Up2IBu2DRJrbpN33m8bpLO6NeqZDJv2KrLbeURu3GYNnX7JMGgyrUahUwKxb9Ky2ft3QVTHRV6wgSuRhcP5at2ptNxdPXwpUnRdL0uF%2BkvqZXSHX0q8b5peAsQmmm6NvKFeIHpZNmJbW9d64QBdRS80vvXg%2Fq0BMYqCEPgbC1ELIEYRdK33AIgO6AkQvdMAommvve10wOCfYAuAuoZ%2B5eddxyv7Ov10aYzv%2BQ6z9Qd9xwRo8AHQNYAevhFAA03n6HBw5s31b8LL4esf3ju3%2FwE%3D>). [cid:ii_jee3zlby0_161f5cd7cfb1234b]</> PATH 1 will be much quicker than PATH 2 and its bottleneck (assuming HDD drives) will be the commitlog PATH 2 will need at least an access to disk to do a read (potentially even in a different machine) and an access to disk to do a write to the commitlog. This is at least twice as slow as PATH 1. This is all the info that I could get from the internet but a lot is missing. For example, there is no information about how the counter lock is acquired, is there a shared lock across all the nodes? Hope I am not oversimplifying things, but I think this will be useful to better understand how to tune up the system. Thanks in advance. F Javier Pareja
