XDCR advanced settings

XDCR advanced settings

XDCR advanced settings are internal settings that are available for configuration.

Advanced settings that can be updated include:

XDCR Max Replications per Bucket
Maximum concurrent replications per bucket, 8 to 256. This controls the number of parallel replication streams per node. If you are running your cluster on hardware with high-performance CPUs, you can increase this value to improve replication speed.
XDCR Checkpoint Interval
Interval between checkpoints, 60 to 14400 (seconds). Default 1800. At this time interval, batches of data via XDCR replication will be placed in the front of the disk persistence queue. This time interval determines the volume of data that will be replicated via XDCR should replication need to restart. The greater this value, the longer amount of time transpires for XDCR queues to grow. For example, if you set this to 10 minutes and a network error occurs, when XDCR restarts replication, 10 minutes of items will have accrued for replication.

Changing this to a smaller value could impact cluster operations when you have significant amount of write operations on a destination cluster and you are performing bidirectional replication with XDCR. For instance, if you set this to 5 minutes, the incoming batches of data via XDCR replication will take priority in the disk write queue over incoming write workload for a destination cluster. This may result in the problem of having an ever growing disk-write queue on a destination cluster; also items in the disk-write queue that are higher priority than the XDCR items will grow staler/older before they are persisted.

XDCR Batch Count
Document batching count, 500 to 10000. Default 500. In general, increasing this value by 2 or 3 times will improve XDCR transmissions rates, since larger batches of data will be sent in the same timed interval. For unidirectional replication from a source to a destination cluster, adjusting this setting by 2 or 3 times will improve overall replication performance as long as persistence to disk is fast enough on the destination cluster. Note however that this can have a negative impact on the destination cluster if you are performing bidirectional replication between two clusters and the destination already handles a significant volume of reads/writes.
XDCR Batch Size (kilobytes)
Document batching size, 10 to 100000 (kilobytes). Default 2048. In general, increasing this value by 2 or 3 times will improve XDCR transmissions rates, since larger batches of data will be sent in the same timed interval. For unidirectional replication from a source to a destination cluster, adjusting this setting by 2 or 3 times will improve overall replication performance as long as persistence to disk is fast enough on the destination cluster. Note however that this can have a negative impact on the destination cluster if you are performing bidirectional replication between two clusters and the destination already handles a significant volume of reads/writes.
XDCR Failure Retry Interval
Interval for restarting failed XDCR, 1 to 300 (seconds). Default 30. If you expect more frequent network or server failures, you may want to set this to a lower value. This is the time that XDCR waits before it attempts to restart replication after a server or network failure.
XDCR Optimistic Replication Threshold
This is compressed document size in bytes. 0 to 20971520 Bytes (20MB). Default is 256 Bytes. XDCR will get metadata for documents larger than this size on a single time before replicating the uncompressed document to a destination cluster. This option improves XDCR latency.