Change default to node.max_local_storage_nodes to 1 in "production mode"
#19679
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nik9000
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Aug 2, 2016
Defaulting `max_local_storage_nodes` to `50` is useful for testing so this patch moves that default from "all the time" to "if you don't bind a public ip". If you *do* bind a public IP and attempt to use more than a single node per data directory without *explicitly* setting `max_local_storage_nodes` then Elasticsearch will now fail to start. Since you can't change the default for a setting depending on the "prod-mode/non-prod-mode" flag we instead use a sentinel value (`0`) of `max_local_storage_nodes` to mean "user didn't specify, pick it from the "prod-mode/non-prod-mode" flag". Since we don't know if we're in prod mode when we pick the data directory we instead assume that we *aren't* and then check if the directory that we picked was OK when we run the `BootstrapCheck`s. The nice thing about doing it this way is that we warn the user if they have more than one Elasticsearch in their data directory even if they are running even in dev mode! While this is the easiest way to make this change the cost is that, even if Elasticsearch fails to start because it is in production mode and `max_local_storage_nodes` isn't configured it'll still create a directory. This also removes some of the documentation that suggests you override the setting on all production clusters. That is no longer important because Elasticsearch won't start in production mode if you try to start more than one node. Closes elastic#19679
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Currently Elasticsearch allows starting multiple nodes using the same data path by simply starting multiple processes. This is great for the OOB experience where people can simply build clusters without too much hassle. On the other side, this has caused much confusion in real clusters where people started a node before properly shutting down the first, which looks to the outside as data loss. There are valid production use cases where we want multiple nodes on the same servers but those are rare (and mostly involve running on servers with lots of memory).
I think it is a good idea to better protect people by using our new "production mode" definition to change the default of the
node.max_local_storage_nodesto 1, from the currently unbounded value.The text was updated successfully, but these errors were encountered: