khepri_cluster: Make join/3 idempotent
#219
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[Why]
If `khepri_cluster:join/3` is called twice in a row, the join succeeds
because the joining node is reset before it joins the cluster again.
This is not exactly idempotent, but the end result is the same.
However if the joining node was reset somehow (e.g. its data directory
was lost) and therefore thinks it is a standalone store, calling
`khepri_cluster:join/1` again would return `{error, already_member}`.
It is more comfortable if the function just does what it takes to
achieve the wanted result of expanding the cluster.
[How]
The `{error, already_member}` error is caught and the function returns
`ok` instead. Behind the scene, Ra did the correct thing and the joining
node is back in the cluster.
Codecov ReportPatch coverage:
Additional details and impacted files@@ Coverage Diff @@
## main #219 +/- ##
==========================================
- Coverage 89.36% 89.23% -0.14%
==========================================
Files 20 20
Lines 2822 2825 +3
==========================================
- Hits 2522 2521 -1
- Misses 300 304 +4
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Why
If
khepri_cluster:join/3is called twice in a row, the join succeeds because the joining node is reset before it joins the cluster again. This is not exactly idempotent, but the end result is the same.However if the joining node was reset somehow (e.g. its data directory was lost) and therefore thinks it is a standalone store, calling
khepri_cluster:join/1again would return{error, already_member}.It is more comfortable if the function just does what it takes to achieve the wanted result of expanding the cluster.
How
The
{error, already_member}error is caught and the function returnsokinstead. Behind the scene, Ra did the correct thing and the joining node is back in the cluster.