Remote_nodes.md

Adding a distributed table with remote agents

To understand how to add a distributed table with remote agents, it is important to first have a basic understanding of distributed tables In this article, we will focus on how to use a distributed table as the basis for creating a cluster of Manticore instances.

Here is an example of how to split data over 4 servers, each serving one of the shards:

ini:

table mydist {
          type  = distributed
          agent = box1:9312:shard1
          agent = box2:9312:shard2
          agent = box3:9312:shard3
          agent = box4:9312:shard4
}

In the event of a server failure, the distributed table will still work, but the results from the failed shard will be missing.

Now that we've added mirrors, each shard is found on 2 servers. By default, the master (the searchd instance with the distributed table) will randomly pick one of the mirrors.

The mode used for picking mirrors can be set using the ha_strategy setting. In addition to the default random mode there's also ha_strategy = roundrobin.

More advanced strategies based on latency-weighted probabilities include noerrors and nodeads. These not only take out mirrors with issues but also monitor response times and do balancing. If a mirror responds slower (for example, due to some operations running on it), it will receive fewer requests. When the mirror recovers and provides better times, it will receive more requests.

ini:

table mydist {
          type  = distributed
          agent = box1:9312|box5:9312:shard1
          agent = box2:9312:|box6:9312:shard2
          agent = box3:9312:|box7:9312:shard3
          agent = box4:9312:|box8:9312:shard4
}