question for rule based replica placement

[Wei <we...@gmail.com>]

Hi,

In rule based replica placement,  how to ensure there are no more than one
replica for any shard on the same host?   In the documentation there is an
example rule

        shard:*,replica:<2,node:*

Does 'node' refer to solr instance or actual physical host?  Is there an
example for defining the physical host?

Thanks,
Wei

Re: question for rule based replica placement

[Wei <we...@gmail.com>]

Thanks Erick. Suppose I have 5 hosts h1,h2,h3,h4,h5  and want to create a
5X2 solr cloud of 5 shards, 2 replicas per shard. On each host I will run
two solr JVMs, each hosts a single solr core. Solr's default 'snitch'
provide a 'host' tag, so I wonder if I can use it to prevent any host from
have two replicas from the same shard, when creating collection:

/solr/admin/collections?action=CREATE&name=mycollection&numShards=5&replicationFactor=2&maxShardsPerNode=1&rule=shard:*,
replica<2, host:*

Is this the correct way to use 'snitch'? I cannot find more relevant
documentation on how to configure and customize 'snitch'.

Thanks,
Wei

On Sun, Sep 2, 2018 at 9:30 PM Erick Erickson <er...@gmail.com>
wrote:

> You need to provide a "snitch" and define a rule appropriately. This
> is a variant of "rack awareness".
>
> Solr considers two JVMs running on the same physical host as
> completely separate Solr instances, so to get replicas on different
> hosts you need a snitch etc.
>
> Best,
> Erick
> On Sun, Sep 2, 2018 at 4:39 PM Wei <we...@gmail.com> wrote:
> >
> > Hi,
> >
> > In rule based replica placement,  how to ensure there are no more than
> one
> > replica for any shard on the same host?   In the documentation there is
> an
> > example rule
> >
> >         shard:*,replica:<2,node:*
> >
> > Does 'node' refer to solr instance or actual physical host?  Is there an
> > example for defining the physical host?
> >
> > Thanks,
> > Wei
>

Re: question for rule based replica placement

[Erick Erickson <er...@gmail.com>]

You need to provide a "snitch" and define a rule appropriately. This
is a variant of "rack awareness".

Solr considers two JVMs running on the same physical host as
completely separate Solr instances, so to get replicas on different
hosts you need a snitch etc.

Best,
Erick
On Sun, Sep 2, 2018 at 4:39 PM Wei <we...@gmail.com> wrote:
>
> Hi,
>
> In rule based replica placement,  how to ensure there are no more than one
> replica for any shard on the same host?   In the documentation there is an
> example rule
>
>         shard:*,replica:<2,node:*
>
> Does 'node' refer to solr instance or actual physical host?  Is there an
> example for defining the physical host?
>
> Thanks,
> Wei