Request limits policy

A workload group's request limits policy allows limiting the resources used by the request during its execution.

The policy object

Each limit consists of:

• A typed Value - the value of the limit.
• IsRelaxable - a boolean value that defines if the limit can be relaxed by the caller, as part of the request's Client request properties.

The following limits are configurable:

Name	Type	Description	Supported values	Matching client request property
DataScope	QueryDataScope	The query's data scope - whether the query applies to all data or just the 'hot' portion of it.	All, HotCache, or null	query_datascope
MaxMemoryPerQueryPerNode	long	The maximum amount of memory (in bytes) a query can allocate.	[1, 50% of a single node's total RAM]	max_memory_consumption_per_query_per_node
MaxMemoryPerIterator	long	The maximum amount of memory (in bytes) a query operator can allocate.	[1, 50% of a single node's total RAM]	maxmemoryconsumptionperiterator
MaxFanoutThreadsPercentage	int	The percentage of threads on each node to fan out query execution to. When set to 100%, the cluster will assign all CPUs on each node. For example, 16 CPUs on a cluster deployed on Azure D14_v2 nodes.	[1, 100]	query_fanout_threads_percent
MaxFanoutNodesPercentage	int	The percentage of nodes on the cluster to fan out query execution to. Functions in a similar manner to MaxFanoutThreadsPercentage.	[1, 100]	query_fanout_nodes_percent
MaxResultRecords	long	maximum number of records a request is allowed to return to the caller, above which the results are truncated.	[1, 9223372036854775807]	truncationmaxrecords
MaxResultBytes	long	The maximum data size (in bytes) a request is allowed to return to the caller, above which the results are truncated.	[1, 9223372036854775807]	truncationmaxsize
MaxExecutionTime	timespan	The maximum duration the request may run for. Notes: 1) This can be used to place an additional limit on top of the default limits on execution time, but not extend them. 2) Timeout processing isn't at the resolution of seconds, rather it's designed to prevent a query from running for minutes. 3) The time it takes to read the payload back at the client isn't treated as part of the timeout. It depends on how quickly the caller pulls the data from the stream. 4) Total execution time may exceed the configured value if aborting execution takes longer to complete.	(00:00:00, 01:00:00]	servertimeout

Notes

• A limit that isn't defined, or is defined as null, is taken from the default workload group's request limits policy.
• When altering the policy for the default workload group, a limit must be defined and have a non-null value.
• The truncation limits MaxResultRecords and MaxResultBytes affect the final result of the query, as delivered back to the client. They do not apply to intermediates results of sub-queries, such as those that result from having cross-cluster references.
• In the default policy for the default workload group, all limits have IsRelaxable set to true.
• Backwards compatibility:
  • Requests limits are disabled, and limits set in the policy don't apply for the following types of commands, when they are classified to the default workload group:
    • .export commands.
    • Commands that ingest from a query (such as .set-or-append or .set-or-replace).
  • If these commands are classified to a non-default workload group, the request limits in the policy apply.

Example

{
  "DataScope": {
    "IsRelaxable": true,
    "Value": "HotCache"
  },
  "MaxMemoryPerQueryPerNode": {
    "IsRelaxable": true,
    "Value": 2684354560
  },
  "MaxMemoryPerIterator": {
    "IsRelaxable": true,
    "Value": 2684354560
  },
  "MaxFanoutThreadsPercentage": {
    "IsRelaxable": true,
    "Value": 50
  },
  "MaxFanoutNodesPercentage": {
    "IsRelaxable": true,
    "Value": 50
  },
  "MaxResultRecords": {
    "IsRelaxable": true,
    "Value": 1000
  },
  "MaxResultBytes": {
    "IsRelaxable": true,
    "Value": 33554432
  },
  "MaxExecutiontime": {
    "IsRelaxable": true,
    "Value": "00:01:00"
  }
}

The default workload group

The default workload group has the following policy defined by default. This policy can be altered.

{
  "DataScope": {
    "IsRelaxable": true,
    "Value": "All"
  },
  "MaxMemoryPerQueryPerNode": {
    "IsRelaxable": true,
    "Value": < 50% of a single node's total RAM >
  },
  "MaxMemoryPerIterator": {
    "IsRelaxable": true,
    "Value": 5368709120
  },
  "MaxFanoutThreadsPercentage": {
    "IsRelaxable": true,
    "Value": 100
  },
  "MaxFanoutNodesPercentage": {
    "IsRelaxable": true,
    "Value": 100
  },
  "MaxResultRecords": {
    "IsRelaxable": true,
    "Value": 500000
  },
  "MaxResultBytes": {
    "IsRelaxable": true,
    "Value": 67108864
  },
  "MaxExecutiontime": {
    "IsRelaxable": true,
    "Value": "00:04:00"
  }
}

Control commands

Manage the workload group's request limits policy with Workload groups control commands.