Re: [Sqlgrey-users] multiple read/write database support patch

[Dan F. <da...@ha...>]

Hey Paul.

Thanks for the patch. Its pretty nice and clean :)

Paul B. Henson wrote:
> I'm setting up sqlgrey with a dual server multi-master mysql replication
> configuration. I wanted it to be able to failover between the two database
> servers, both of which are read/write. The write remotely, read locally
> clustering didn't really seem like it would do what I wanted.
>   
Well.. I must admit.. I actually patched the dbclustering DBIx 
component, so you never  write to a read-host. It was what i needed when 
i made the dbclustering support. I added a variable to the module called 
something like READ_HOSTS_NEVER_WRITE (from my memory).

2 questions:
1: Would allowing you to set the READ_HOSTS_NEVER_WRITE = 0 from config 
do the same for you? So ALL hosts defined are read & write hosts and 
switched between in a round robin manner.

2: How scalable is your setup? We currently run 1 write-host and 7 
read-hosts. Can multi-master be used in such a setup? (a little off 
topic i guess;)



> The attached patch adds a new configuration directive, db_hostlist, which
> takes a list of one or more database servers (presumably more than one, or
> one could just use db_host). 
If we need to specify more than 1 "write" hosts, would there be any 
logic in simply allowing multiple hosts to be defined on "db_host" 
instead (comma separated)? Just so we dont need an extra config 
directive to do the job that an existing directive could do.

> Also, the patch moves the logging of the database error to before the
> call to db_unavailable(). For some reason, DBI::errstr lost its value
> during the call to db_unavailable(), and with the logging message
> afterwards, no error was printed.
>   
Im hoping Lionel has the time to double-check this. I dont know much 
about that part of the code.:)




- Dan