Shards within the replicator enable data to be parallelized when they are
applied on the slave.
shardbyseqno filter updates the
shard ID, which is embedded into the event metadata, by a configurable
number of shards, set by the
shards parameter in the
The filter works by setting the shard ID in the event using the
setShardId() method on the event object:
event.setShardId(event.getSeqno() % shards);
Care should be taken with this filter, as it assumes that the events can
be applied in a completely random order by blindly updating the shard ID
to a computed valued. Sharding in this way is best used when
provisioning new slaves.