Router Schedulers¶

Presto router provides multiple scheduling algorithms for load balancing across multiple clusters.

• RANDOM_CHOICE

Randomly selecting a cluster from a list of candidates.

• ROUND_ROBIN

Selecting clusters from a list of candidates in turn. Note that as the algorithm keeps the state of the selected index, it can only be used when the candidates are always consistent.

• USER_HASH

Selecting a clusters by hashing the username. This ensures queries from the same user will always be routed to the same cluster.

• WEIGHTED_RANDOM_CHOICE

Randomly selecting a cluster from a list of candidates with pre-defined weights. Clusters with higher weights have higher opportunity to be selected.

• WEIGHTED_ROUND_ROBIN

Selecting clusters from a list of candidates with pre-defined weights in turn. Note that similar to the ROUND_ROBIN approach, this algorithm keeps the state of the selected index so candidates and weights should be consistent.