properties.rst

Presto C++ Configuration Properties

This section describes Presto C++ configuration properties.

The following is not a complete list of all configuration properties, and does not include any connector-specific catalog configuration properties or session properties.

For information on catalog configuration properties, see :doc:`Connectors </connector/>`.

For information on Presto C++ session properties, see :doc:`properties-session`.

• Coordinator Properties
• Worker Properties
• Memory Checker Properties
• Environment Variables As Values For Worker Properties

Coordinator Properties

Set the following configuration properties for the Presto coordinator exactly as they are shown in this code block to enable the Presto coordinator's use of Presto C++ workers.

native-execution-enabled=true
optimizer.optimize-hash-generation=false
regex-library=RE2J
use-alternative-function-signatures=true

These Presto coordinator configuration properties are described here, in alphabetical order.

driver.cancel-tasks-with-stuck-operators-threshold-ms

• Type: string

• Default value: 240000 (40 minutes)

  Cancels any task when at least one operator has been stuck for at least the time specified by this threshold.

  Set this property to 0 to disable canceling.

native-execution-enabled

• Type: boolean

• Default value: false

  This property is required when running Presto C++ workers because of underlying differences in behavior from Java workers.

optimizer.optimize-hash-generation

• Type: boolean

• Default value: true

  Set this property to false when running Presto C++ workers. Velox does not support optimized hash generation, instead using a HashTable with adaptive runtime optimizations that does not use extra hash fields.

regex-library

• Type: type

• Allowed values: RE2J

• Default value: JONI

  Only RE2J is currently supported by Velox.

use-alternative-function-signatures

• Type: boolean

• Default value: false

  Some aggregation functions use generic intermediate types which are not compatible with Velox aggregation function intermediate types. One example function is approx_distinct, whose intermediate type is VARBINARY. This property provides function signatures for built-in aggregation functions which are compatible with Velox.

presto.default-namespace

• Type: string

• Default value: presto.default

  Specifies the namespace prefix for native C++ functions.

Worker Properties

The configuration properties of Presto C++ workers are described here, in alphabetical order.

async-cache-persistence-interval

• Type: string

• Default value: 0s

  The interval for persisting in-memory cache to SSD. Setting this config to a non-zero value will activate periodic cache persistence.

async-data-cache-enabled

• Type: boolean

• Default value: true

  In-memory cache.

runtime-metrics-collection-enabled

• Type: boolean

• Default value: false

  Enables collection of worker level metrics.

task.max-drivers-per-task

• Type: integer

• Default value: number of hardware CPUs

  Number of drivers to use per task. Defaults to hardware CPUs.

query.max-memory-per-node

• Type: string

• Default value: 4GB

  Max memory usage for each query.

system-memory-gb

• Type: integer

• Default value: 40

  Memory allocation limit enforced by an internal memory allocator. It consists of two parts: 1) Memory used by the queries as specified in query-memory-gb; 2) Memory used by the system, such as disk spilling and cache prefetch.

  Set system-memory-gb to the available machine memory of the deployment.

query-memory-gb

• Type: integer

• Default value: 38

  Specifies the total amount of memory in GB that can be used for all queries on a worker node. Memory for system usage such as disk spilling and cache prefetch are not counted in it.

max_spill_bytes

• Type: integer

• Default value: 100UL << 30

  Specifies the max spill bytes limit set for each query. This is used to cap the storage used for spilling. If it is zero, then there is no limit and spilling might exhaust the storage or takes too long to run.

shared-arbitrator.reserved-capacity

• Type: string

• Default value: 4GB

  Specifies the total amount of memory in GB reserved for the queries on a worker node. A query can only allocate from this reserved space if 1) the non-reserved space in query-memory-gb is used up; and 2) the amount it tries to get is less than shared-arbitrator.memory-pool-reserved-capacity.

shared-arbitrator.memory-pool-initial-capacity

• Type: string

• Default value: 128MB

  The initial memory pool capacity in bytes allocated on creation.

shared-arbitrator.global-arbitration-enabled

• Type: string

• Default value: false

  If true, it allows shared arbitrator to reclaim used memory across query memory pools.

shared-arbitrator.memory-pool-reserved-capacity

• Type: string

• Default value: 64MB

  The amount of memory in bytes reserved for each query memory pool. When a query tries to allocate memory from the reserved space whose size is specified by shared-arbitrator.reserved-capacity, it cannot allocate more than the value specified in shared-arbitrator.memory-pool-reserved-capacity.

shared-arbitrator.memory-pool-transfer-capacity

• Type: string

• Default value: 32MB

  The minimal memory capacity in bytes transferred between memory pools during memory arbitration.

shared-arbitrator.max-memory-arbitration-time

• Type: string

• Default value: 5m

  Specifies the max time to wait for memory reclaim by arbitration. The memory reclaim might fail if the max wait time has exceeded. If it is zero, then there is no timeout.

shared-arbitrator.fast-exponential-growth-capacity-limit

• Type: string

• Default value: 512MB

  When shared arbitrator grows memory pool's capacity, the growth bytes will be adjusted in the following way:

  • If 2 * current capacity is less than or equal to shared-arbitrator.fast-exponential-growth-capacity-limit, grow through fast path by at least doubling the current capacity, when conditions allow (see below NOTE section).
  • If 2 * current capacity is greater than shared-arbitrator.fast-exponential-growth-capacity-limit, grow through slow path by growing capacity by at least shared-arbitrator.slow-capacity-grow-pct * current capacity if allowed (see below NOTE section).

  NOTE: If original requested growth bytes is larger than the adjusted growth bytes or adjusted growth bytes reaches max capacity limit, the adjusted growth bytes will not be respected.

  NOTE: Capacity growth adjust is only enabled if both shared-arbitrator.fast-exponential-growth-capacity-limit and shared-arbitrator.slow-capacity-grow-pct are set, otherwise it is disabled.

shared-arbitrator.slow-capacity-grow-pct

• Type: string

• Default value: 0.25

  See description for shared-arbitrator.fast-exponential-growth-capacity-limit

shared-arbitrator.memory-pool-min-free-capacity

• Type: string

• Default value: 128MB

  When shared arbitrator shrinks memory pool's capacity, the shrink bytes will be adjusted in a way such that AFTER shrink, the stricter (whichever is smaller) of the following conditions is met, in order to better fit the pool's current memory usage:

  • Free capacity is greater or equal to capacity * shared-arbitrator.memory-pool-min-free-capacity-pct
  • Free capacity is greater or equal to shared-arbitrator.memory-pool-min-free-capacity

  NOTE: In the conditions when original requested shrink bytes ends up with more free capacity than above two conditions, the adjusted shrink bytes is not respected.

  NOTE: Capacity shrink adjustment is enabled when both shared-arbitrator.memory-pool-min-free-capacity-pct and shared-arbitrator.memory-pool-min-free-capacity are set.

shared-arbitrator.memory-pool-min-free-capacity-pct

• Type: string

• Default value: 0.25

  See description for shared-arbitrator.memory-pool-min-free-capacity

Memory Checker Properties

The LinuxMemoryChecker extends from PeriodicMemoryChecker and is used for Linux systems only. The LinuxMemoryChecker can be enabled by setting the CMake flag PRESTO_MEMORY_CHECKER_TYPE=LINUX_MEMORY_CHECKER. The following properties for PeriodicMemoryChecker are as follows:

system-mem-pushback-enabled

• Type: boolean
• Default value: false

If set to true, starts memory limit checker to trigger memory pushback when server is under low memory pressure.

system-mem-limit-gb

• Type: integer
• Default value: 55

Specifies the system memory limit that triggers the memory pushback or heap dump if the server memory usage is beyond this limit. A value of zero means no limit is set. This only applies if system-mem-pushback-enabled is true.

system-mem-shrink-gb

• Type: integer
• Default value: 8

Specifies the amount of memory to shrink when the memory pushback is triggered. This only applies if system-mem-pushback-enabled is true.

Environment Variables As Values For Worker Properties

This section applies to worker configurations in the config.properties file and catalog property files only.

The value in a key-value pair can reference an environment variable by using a leading $ followed by enclosing the environment variable name in brackets ({}).

key=${ENV_VAR_NAME}

The environment variable name must match exactly with the defined variable.

This allows a worker to read sensitive data such as access keys from an environment variable rather than having the actual value hard coded in a configuration file on disk, improving the security of deployments.

For example, consider the hive connector's hive.s3.aws-access-key property. This is sensitive data and can be stored in an environment variable such as AWS_S3_ACCESS_KEY which is set to the actual access key value.

One mechanism is to create a preload library that is injected at the time presto_server is started that decrypts encrypted secrets and sets environment variables specific to the presto_server process. These can then be referenced in the properties.

Once decrypted the preloaded library sets the AWS_S3_ACCESS_KEY environment variable which then can be accessed by providing it in the catalog properties:

hive.s3.aws-access-key=${AWS_S3_ACCESS_KEY}