Raft (algorithm): Difference between revisions

Revision as of 04:02, 2 May 2019

Revision as of 23:23, 6 August 2019

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Timing is critical in Raft to elect and maintain a steady leader over time, in order to have a perfect availability of your cluster. Stability is ensured by respecting the ''timing requirement'' of the algorithm :<blockquote>''broadcastTime << electionTimeout << MTBF''</blockquote>

* ''broadcastTime'' is the average time it takes a server to send request to every server in the cluster and receive responses. It is relative to the infrastructure you are using.

* ''MTBF' (Mean Time Between Failures)' is the average time between failures for a server. It is also relative to your infrastructure.

* ''electionTimeout'' is the same as described in the Leader Election section. It is something you must choose.

Typical number for these values can be 0.5ms to 20ms for ''broadcastTime'', which implies that you set the ''electionTimeout'' somewhere between 10ms and 500ms. It can take several weeks or months between single server failures, which means the values are all right for a stable cluster to work.