PostgreSQL hot-standby replication support #103
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Add the is_replicating and lag_behind_master calls that DBIx::Class::Storage::DBI::Replicated::Pool::validate_replicants needs. This works with PostgreSQL's hot-standby functionality that was introduced in PostgreSQL 9.0. It may not work with other replication methods, like BDR or Slony. More info on hot-standby is available here: * https://wiki.postgresql.org/wiki/Hot_Standby Signed-off-by: Karl Kornel <akkornel@stanford.edu>
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Hello @akkornel Thanks for sending this upstream! I am going to poke a couple folks below, and also did shout out to the mailing list. Let's see what comes back... @ilmari That'd be something for you to look at, I am not sure of the specifics @wchristian IIRC you had a modified copy of the Replicated pipeline at |
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This looks good to me, but a slight nitpick would be that using |
| @@ -237,6 +237,23 @@ sub deployment_statements { | |||
| $self->next::method($schema, $type, $version, $dir, $sqltargs, @rest); | |||
| } | |||
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| sub is_replicating { | |||
| my $repl = 'select pg_last_xlog_receive_location() AS replicating'; | |||
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Even simpler:
return scalar shift->_get_dbh->selectrow_array('select pg_last_xlog_receive_location() is not null');`
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Hello!
We have been using some customizations to DBIx::Class::Storage::DBI::Pg for a while, which makes DBIx::Class replication-aware for Postgres. I'd like to push the changes upstream.
The changes work with PostgreSQL hot-standby replication, which was introduced in PostgreSQL 9.0. I don't know if it would work in other forms of PostgreSQL master-slave replication (such as Slony); I'm sure it won't work with PostgreSQL master-master replication (such as BDR), although I'm not sure you'd even want to use this in a multi-master environment.
The code was written by a co-worker, but I've gotten his OK to push this upstream.