I need some clarification regarding the behavior of CrateDB when it comes to relocation of shards during an upgrade (particularly during the graceful shutdown of a node): Recently, we’ve upgraded our 3-node CrateDB cluster from 4.6.5 to 4.6.6.
During the graceful shutdown of the first node, I’ve realized that most of the CrateDB data were moved to the remaining two nodes.
Before and during that process, I didn’t change the default value of
cluster.graceful_stop.min_availability. In other words, it had the default of
On top of that, our largest data, that is time series table had
'0-1' as the number of replicas:
number_of_replicas = '0-1'
It looks like that shards have been relocated to the two remaining nodes. This would be the case if the number of replicas would be set to
0-1) or if the min availability is set to full.
But as I wrote above, even though the
number_of_replicas for that large table had the default value of
cluster.graceful_stop.min_availability had the default value of
primaries, I still observed that most of the data on the node being gracefully shut down moved to the remaining two nodes.
Can one of the CrateDB experts clarify this situation, so that for the next upgrade I’ll have a better understanding?