Node Scheduler Properties#
The target value for the total number of splits that can be running for each worker node.
Using a higher value is recommended, if queries are submitted in large batches (e.g., running a large group of reports periodically), or for connectors that produce many splits that complete quickly. Increasing this value may improve query latency, by ensuring that the workers have enough splits to keep them fully utilized.
Setting this too high wastes memory and may result in lower performance due to splits not being balanced across workers. Ideally, it should be set such that there is always at least one split waiting to be processed, but not higher.
The number of outstanding splits that can be queued for each worker node for a single stage of a query, even when the node is already at the limit for total number of splits. Allowing a minimum number of splits per stage is required to prevent starvation and deadlocks.
This value must be smaller than
is usually increased for the same reasons, and has similar drawbacks
if set too high.
The minimum number of candidate nodes that are evaluated by the node scheduler when choosing the target node for a split. Setting this value too low may prevent splits from being properly balanced across all worker nodes. Setting it too high may increase query latency and increase CPU usage on the coordinator.
Sets the node scheduler policy to use when scheduling splits.
to schedule splits on the host where the data is located, while maintaining a uniform
distribution across all hosts.
topology tries to schedule splits according to
the topology distance between nodes and splits. It is recommended to use
for clusters where distributed storage runs on the same nodes as Presto workers.
A comma-separated string describing the meaning of each segment of a network location.
For example, setting
region,rack,machine means a network location contains three segments.
Sets the network topology type. To use this option,
node-scheduler.policy must be set to
flat has only one segment, with one value for each machine.
file loads the topology from a file as described below.
Load the network topology from a file. To use this option,
must be set to
file. Each line contains a mapping between a host name and a
network location, separated by whitespace. Network location must begin with a leading
/ and segments are separated by a
192.168.0.1 /region1/rack1/machine1 192.168.0.2 /region1/rack1/machine2 hdfs01.example.com /region2/rack2/machine3
Controls how often the network topology file is reloaded. To use this option,
node-scheduler.network-topology.type must be set to