Node scheduler properties#



The target value for the total number of splits that can be running for each worker node, assuming all splits have the standard split weight.

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 but do not support assigning split weight values to express that to the split scheduler. Increasing this value may improve query latency, by ensuring that the workers have enough splits to keep them fully utilized.

When connectors do support weight based split scheduling, the number of splits assigned will depend on the weight of the individual splits. If splits are small, more of them are allowed to be assigned to each worker to compensate.

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 with the standard split weight 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 node-scheduler.max-splits-per-node, is usually increased for the same reasons, and has similar drawbacks if set too high.


  • Type: integer

  • Minimum value: 1

  • Default value: 10

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.


  • Type: string

  • Allowed values: uniform, topology

  • Default value: uniform

Sets the node scheduler policy to use when scheduling splits. uniform attempts 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 uniform for clusters where distributed storage runs on the same nodes as Trino workers.

Network topology#

  • Type: string

  • Default value: machine

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.

  • Type: string

  • Allowed values: flat, file, subnet

  • Default value: flat

Sets the network topology type. To use this option, node-scheduler.policy must be set to topology.

  • flat: the topology has only one segment, with one value for each machine.

  • file: the topology is loaded from a file using the properties and described in the following sections.

  • subnet: the topology is derived based on subnet configuration provided through properties and described in the following sections.

File based network topology#

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 /. /region1/rack1/machine1 /region1/rack1/machine2 /region2/rack2/machine3

  • Type: duration

  • Minimum value: 1ms

  • Default value: 5m

Controls how often the network topology file is reloaded. To use this option, must be set to file.

Subnet based network topology#

  • Type: string

  • Allowed values: IPv4, IPv6

  • Default value: IPv4

Sets the IP address protocol to be used for computing subnet based topology. To use this option, must be set to subnet.

A comma-separated list of integer values defining CIDR prefix lengths for subnet masks. The prefix lengths must be in increasing order. The maximum prefix length values for IPv4 and IPv6 protocols are 32 and 128 respectively. To use this option, must be set to subnet.

For example, the value 24,25,27 for this property with IPv4 protocol means that masks applied on the IP address to compute location segments are, and So the segments created for an address are [,,,].