What does Solr index do and how to handle its high avaliablity?

[luckydog xf]

Thanks a lot.

On Sat, Jun 15, 2019 at 11:33 AM Shawn Heisey via dovecot <
dovecot at dovecot.org> wrote:

> On 6/14/2019 2:11 AM, luckydog xf via dovecot wrote:
> >    And based on
> https://dovecot.org/pipermail/dovecot/2019-April/115575.html
> > I'm going to use an VIP to host 2 mail servers. Currently, it works in
> > fail over and fail back test except solr index, so how to resolve this?
>
> Solr has high availability options.  Probably the easiest is SolrCloud,
> because the legacy master-slave replication option basically has the
> master as a single point of failure.  Switching a slave to master is a
> very manual job.  SolrCloud is a true cluster -- no masters and no slaves.
>
> Normally I would suggest a load balancer in front of Solr, but with
> SolrCloud and this usage, you could have a VIP switch between two hosts.
>   You will need at least three servers for a redundant SolrCloud
> install, because ZooKeeper absolutely requires three servers for
> redundancy.  SolrCloud is Solr+ZooKeeper.  Only two of the servers would
> need to run Solr, though.  The third server would only need to run
> ZooKeeper, and normally the system requirements for that are very low.
>
> > Is it possible to put dovecot index on shared storage like NFS?
>
> Solr does not do well on network file systems.  They usually don't offer
> the file locking capability that Lucene wants.  Solr is written using
> the Lucene API.
>
> And you can't have two running Solr servers using the same index
> directory even if you disable file locking so that NFS works.  Each
> server needs its own copy of the index.
>
> > How to rebuild if I don't put index data on shared storage in case of
> > fail over?
>
> Building and rebuilding is accomplished by dovecot.  Here's a wiki page
> for rebuilding Solr indexes.  Admittedly it falls into the "not all that
> helpful" category:
>
> https://wiki.apache.org/solr/HowToReindex
>
> Thanks,
> Shawn
>
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