fix(mnesia): load ram_copies table from 'better' copy when start#11020
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fix(mnesia): load ram_copies table from 'better' copy when start#11020qzhuyan wants to merge 1 commit into
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Without this fix, ram_copies is 'safe loaded' locally when remote nodes
have not been connected (yet). This makes the table accessible by application
becasue 'where_to_read' is set to local node().
```
mnesia:dirty_read(emqx_route_filters,1).
[]
```
Also when remote node is connected afterwards, ram_copies table will not load the 'better'
copy, this makes the data inconsistent within the cluster.
This commit fix that during mnesia start, ram_copy table should NOT
do local safe load when there is a better copy from the remote. the
where_to_read will stay in 'nowhere' and table access won't be served.
```
mnesia:dirty_read(emqx_route_filters,1).
** exception exit: {aborted,{no_exists,[emqx_route_filters,1]}}
```
After remote node is connected, local node will do `net_load_table` from
the remote.
Resue `adopt_orphans` function to resolve the conflicts when there is a
deadlock of deciding the better copy, that is the same behaviour for
disc_copies tables.
note1: BetterCopies0 = mnesia_lib:remote_copy_holders(Cs) -- Downs
note2: disc copy table has no such issue.
note3: if there is no better copy (when other nodes are down before
current one), it is correct to load from local.
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fix #11021
Without this fix, ram_copies is 'safe loaded' locally when remote nodes have not been connected (yet). This makes the table accessible by application becasue 'where_to_read' is set to local node().
Also when remote node is connected afterwards, ram_copies table will not load the 'better' copy, this makes the data inconsistent within the cluster.
This commit fix that during mnesia start, ram_copy table should NOT do local safe load when there is a better copy from the remote. the where_to_read will stay in 'nowhere' and table access won't be served.
After remote node is connected, local node will do
net_load_tablefrom the remote.Resue
adopt_orphansfunction to resolve the conflicts when there is a deadlock of deciding the better copy, that is the same behaviour for disc_copies tables.note1: BetterCopies0 = mnesia_lib:remote_copy_holders(Cs) -- Downs
note2: disc copy table has no such issue.
note3: if there is no better copy (when other nodes are down before current one), it is correct to load from local.