I've got one question regarding elastic search cluster settings. I managed to setup elastic cluster on Rancher platform but I came across one weird (at least to me) issue. When one node goes down, cluster seems to be unavailable for over 1.5 minute. To be honest, I was hoping to get faster node failure detection. As far as I understand, this can be speed up by changing:
Is there any reason I should leave such high values or is it safe to set ping_timeout to, let's say, 5s? My healthchecks in Rancher are set to default (interval: 2s, timeout: 2s, retries: 3) and they work just fine.
Thanks in advance for help!
When you say "down" do you mean that Elasticsearch is shutting down cleanly or just that its container is being terminated? On a clean shutdown the settings you quote should have little effect.
The risk with reducing the fault detection values is they will pick up more false positives. On a node failure Elasticsearch must rebalance itself, perhaps electing a new master, promoting some new shards to primaries, and recovering any missing shard copies, all of which can be quite a lot of work, so it's worth trying to avoid false positives.
By “down” I meant host/network failure, not a clean shutdown.
I understand that rebalancing can be time-consuming so how about increasing recovery delay so it won’t kick in right after node failure (I think there were some settings for that as well)? I assume that failed node will be replaced (most probably without data loss) within short period of time so there’s no point in starting the rebalancing procedure.
Ok, this makes it indistinguishable from packet loss, and a temporary network failure is the most likely cause of that. This shouldn't make the cluster unavailable, but indexing that's trying to hit the lost node will wait for the shards on the lost node to either respond or time out and be failed, which might be what you're seeing.
Yes, I think you mean
index.unassigned.node_left.delayed_timeout. That stops shards from being reallocated elsewhere when the master decides that a node has failed, but doesn't stop another master election, nor any replicas being promoted to primaries.
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