Prevent downgrades from 8.x to 7.x #78638
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Users sometimes attempt to downgrade a node in place, but downgrades are totally untested and unsupported and generally don't work. We protect against this by recording the node version in the metadata and refusing to start if we encounter metadata written by a future version. However in 8.0 (elastic#42489) we changed the directory layout so that a 7.x node won't find the upgraded metadata, or indeed any other data, and will proceed as if it's a fresh node. That's almost certainly not what the user wants, so with this commit we create a file at `${path.data}/nodes` at each startup, preventing an older node from starting. Closes elastic#52414
DaveCTurner
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Pinging @elastic/es-distributed (Team:Distributed) |
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In elastic#78638 we introduced a simple mechanism for blocking downgrades from 8.x to 7.x, but the exception message it generates is not very helpful: org.elasticsearch.bootstrap.StartupException: ElasticsearchException[failed to bind service]; nested: FileSystemException[{path.data}/nodes/0: Not a directory]; We can't fix earlier 7.x versions to do something better, but this commit at least means that sufficiently recent 7.x versions will yield a slightly more helpful message.
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In #78638 we introduced a simple mechanism for blocking downgrades from 8.x to 7.x, but the exception message it generates is not very helpful: org.elasticsearch.bootstrap.StartupException: ElasticsearchException[failed to bind service]; nested: FileSystemException[{path.data}/nodes/0: Not a directory]; We can't fix earlier 7.x versions to do something better, but this commit at least means that sufficiently recent 7.x versions will yield a slightly more helpful message.
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I think this will no longer conflict with #78525 so I'll merge it after a green CI run. |
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Users sometimes attempt to downgrade a node in place, but downgrades are
totally untested and unsupported and generally don't work. We protect
against this by recording the node version in the metadata and refusing
to start if we encounter metadata written by a future version.
However in 8.0 (#42489) we changed the directory layout so that a 7.x
node won't find the upgraded metadata, or indeed any other data, and
will proceed as if it's a fresh node. That's almost certainly not what
the user wants, so with this commit we create a file at
${path.data}/nodesat each startup, preventing an older node fromstarting.
Closes #52414