Adds isolated instance mode description #5136
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The ```isolated:true``` option moves the instance to RO mode In this mode, various debugging & maintanance operations can be performed Fixes #4632
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Fixes language and syntax
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| The isolated mode moves the instance to the read-only state, in which: | ||
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| * iproto stops listening for new connections | ||
| * iproto drops all the current connections | ||
| * The instance is disconnected from all the replication upstreams | ||
| * Other replicaset members exclude the isolated instance from the replication upstreams |
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This wording seems a bit misleading: 'read-only state, which stops iproto and disconnects replication'. In fact, the isolated state/mode sets the read-only state, stops iproto and so on.
| * The instance is disconnected from all the replication upstreams | ||
| * Other replicaset members exclude the isolated instance from the replication upstreams | ||
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| Once the mode is enabled, any request trying to change persistent data will fail with the ``ER_READONLY`` error. |
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A remote request likely just fails, because we drop iproto connections. Not sure that we should add a note regarding ER_READONLY.
| i-002: {} | ||
| i-003: {} | ||
| i-004: | ||
| isolated: true |
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Nit: GitHub shows a red circle, when there is no newline symbol at the end of the file.
doc/admin/troubleshoot.rst
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| .. NOTE:: | ||
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| To avoid brain split between two masters, one of the instances may be put in the :ref:`isolated mode <_configuration_reference_isolated_mode>`. |
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It gives a false impression that the isolated mode somehow helps to avoid split-brain, but it means that we should detect is somehow faster than tarantool itself. It seems strange.
Here we can fight with consequences of split-brain to some extent. At least, isolate the broken instance from client requests using the config option.
Let's discuss how to better express it.
isolated:trueoption moves the instance to RO modeFixes config: isolated mode for an instance #4632