Presto C++ Features

Presto C++ Features

Endpoints

HTTP endpoints related to tasks are registered to Proxygen in TaskResource.cpp. Important endpoints implemented include:

POST: v1/task: This processes a TaskUpdateRequest
GET: v1/task: This returns a serialized TaskInfo (used for comprehensive metrics, may be reported less frequently)
GET: v1/task/status: This returns a serialized TaskStatus (used for query progress tracking, must be reported frequently)

Other HTTP endpoints include:

POST: v1/memory: Reports memory, but no assignments are adjusted unlike in Java workers

GET: v1/info/metrics: Returns worker level metrics in Prometheus Data format. Refer section Worker Metrics Collection for more info. Here is a sample Metrics data returned by this API.

# TYPE presto_cpp_num_http_request counter
presto_cpp_num_http_request{cluster="testing",worker=""} 0
# TYPE presto_cpp_num_http_request_error counter
presto_cpp_num_http_request_error{cluster="testing",worker=""} 0
# TYPE presto_cpp_memory_pushback_count counter
presto_cpp_memory_pushback_count{cluster="testing",worker=""} 0
# TYPE velox_driver_yield_count counter
velox_driver_yield_count{cluster="testing",worker=""} 0
# TYPE velox_cache_shrink_count counter
velox_cache_shrink_count{cluster="testing",worker=""} 0
# TYPE velox_memory_cache_num_stale_entries counter
velox_memory_cache_num_stale_entries{cluster="testing",worker=""} 0
# TYPE velox_arbitrator_requests_count counter
velox_arbitrator_requests_count{cluster="testing",worker=""} 0

GET: v1/info: Returns basic information about the worker. Here is an example:

{"coordinator":false,"environment":"testing","nodeVersion":{"version":"testversion"},"starting":false,"uptime":"49.00s"}

GET: v1/status: Returns memory pool information.

The request/response flow of Presto C++ is identical to Java workers. The tasks or new splits are registered via TaskUpdateRequest. Resource utilization and query progress are sent to the coordinator via task endpoints.

Remote Function Execution

Presto C++ supports remote execution of scalar functions. This feature is useful for cases when the function code is not written in C++, or if for security or flexibility reasons, the function code cannot be linked to the same executable as the main engine.

Remote function signatures need to be provided using a JSON file, following the format implemented by JsonFileBasedFunctionNamespaceManager. The following properties allow the configuration of remote function execution:

`remote-function-server.signature.files.directory.path`

Type: string
Default value: ""

The local filesystem path where JSON files containing remote function signatures are located. If not empty, the Presto native worker will recursively search, open, parse, and register function definitions from these JSON files.

`remote-function-server.catalog-name`

Type: string
Default value: ""

The catalog name to be added as a prefix to the function names registered in Velox. The function name pattern registered is catalog.schema.function_name, where catalog is defined by this parameter, and schema and function_name are read from the input JSON file.

If empty, the function is registered as schema.function_name.

`remote-function-server.serde`

Type: string
Default value: "presto_page"

The serialization/deserialization method to use when communicating with the remote function server. Supported values are presto_page or spark_unsafe_row.

`remote-function-server.thrift.address`

Type: string
Default value: ""

The location (ip address or hostname) that hosts the remote function server, if any remote functions were registered using remote-function-server.signature.files.directory.path. If not specified, falls back to the loopback interface (::1)

`remote-function-server.thrift.port`

Type: integer
Default value: 0

The port that hosts the remote function server. If not specified and remote functions are trying to be registered, an exception is thrown.

`remote-function-server.thrift.uds-path`

Type: string
Default value: ""

The UDS (unix domain socket) path to communicate with a local remote function server. If specified, takes precedence over remote-function-server.thrift.address and remote-function-server.thrift.port.

JWT authentication support

C++ based Presto supports JWT authentication for internal communication. For details on the generally supported parameters visit JWT.

There is also an additional parameter:

`internal-communication.jwt.expiration-seconds`

Type integer
Default value: 300

There is a time period between creating the JWT on the client and verification by the server. If the time period is less than or equal to the parameter value, the request is valid. If the time period exceeds the parameter value, the request is rejected as authentication failure (HTTP 401).

Async Data Cache and Prefetching

`connector.num-io-threads-hw-multiplier`

Type double
Default value: 1.0
Presto on Spark default value: 0.0

Size of IO executor for connectors to do preload/prefetch. Prefetch is disabled if connector.num-io-threads-hw-multiplier is set to zero.

`async-data-cache-enabled`

Type bool
Default value: true
Presto on Spark default value: false

Whether async data cache is enabled.

`async-cache-ssd-gb`

Type integer
Default value: 0

Size of the SSD cache when async data cache is enabled.

`enable-old-task-cleanup`

Type bool
Default value: true
Presto on Spark default value: false

Enable periodic clean up of old tasks. The default value is true for Presto C++. For Presto on Spark this property defaults to false, as zombie or stuck tasks are handled by Spark by speculative execution.

`old-task-cleanup-ms`

Type integer
Default value: 60000

Duration after which a task should be considered as old and will be eligible for cleanup. Only applicable when enable-old-task-cleanup is true. Old task is defined as a PrestoTask which has not received heartbeat for at least old-task-cleanup-ms, or is not running and has an end time more than old-task-cleanup-ms ago.

Worker metrics collection

Users can enable collection of worker level metrics by setting the property:

`runtime-metrics-collection-enabled`

Type: boolean
Default value: false

When true, the default behavior is a no-op. There is a prior setup that must be done before enabling this flag. To enable metrics collection in Prometheus Data Format refer here.

Session Properties

The following are the native session properties for C++ based Presto.

`driver_cpu_time_slice_limit_ms`

Type: integer
Default value: 1000

Native Execution only. Defines the maximum CPU time in milliseconds that a driver thread is permitted to run before it must yield to other threads,facilitating fair CPU usage across multiple threads.

A positive value enforces this limit, ensuring threads do not monopolize CPU resources.

Negative values are considered invalid and are treated as a request to use the system default setting, which is 1000 ms in this case.

Note: Setting the property to 0 allows a thread to run indefinitely without yielding, which is not recommended in a shared environment as it can lead to resource contention.

`legacy_timestamp`

Type: boolean
Default value: true

Native Execution only. Use legacy TIME and TIMESTAMP semantics.

`native_aggregation_spill_memory_threshold`

Type: integer
Default value: 0

Native Execution only. Specifies the maximum memory in bytes that a final aggregation operation can utilize before it starts spilling to disk. If set to 0, there is no limit, allowing the aggregation to consume unlimited memory resources, which may impact system performance.

`native_debug_validate_output_from_operators`

Type: boolean
Default value: false

If set to true, then during the execution of tasks, the output vectors of every operator are validated for consistency. It can help identify issues where a malformed vector causes failures or crashes, facilitating the debugging of operator output issues.

Note: This is an expensive check and should only be used for debugging purposes.

`native_join_spill_enabled`

Type: boolean
Default value: true

Native Execution only. Enable join spilling on native engine.

`native_join_spill_memory_threshold`

Type: integer
Default value: 0

Native Execution only. Specifies the maximum memory, in bytes, that a hash join operation can use before starting to spill to disk. A value of 0 indicates no limit, permitting the join operation to use unlimited memory resources, which might affect overall system performance.

`native_join_spiller_partition_bits`

Type: integer
Default value: 2

Native Execution only. Specifies the number of bits (N) used to calculate the spilling partition number for hash join and RowNumber operations. The partition number is determined as 2 raised to the power of N, defining how data is partitioned during the spill process.

`native_max_spill_file_size`

Type: integer
Default value: 0

Specifies the maximum allowed spill file size in bytes. If set to 0, there is no limit on the spill file size, allowing spill files to grow as large as necessary based on available disk space. Use native_max_spill_file_size to manage disk space usage during operations that require spilling to disk.

`native_max_spill_level`

Type: integer
Default value: 4

Native Execution only. The maximum allowed spilling level for hash join build. 0 is the initial spilling level, -1 means unlimited.

`native_order_by_spill_memory_threshold`

Type: integer
Default value: 0

Native Execution only. Specifies the maximum memory, in bytes, that the ORDER BY operation can utilize before starting to spill data to disk. If set to 0, there is no limit on memory usage, potentially leading to large memory allocations for sorting operations. Use this threshold to manage memory usage more efficiently during ORDER BY operations.

`native_row_number_spill_enabled`

Type: boolean
Default value: true

Native Execution only. Enable row number spilling on native engine.

`native_simplified_expression_evaluation_enabled`

Type: boolean
Default value: false

Native Execution only. Enable simplified path in expression evaluation.

`native_spill_compression_codec`

Type: varchar
Default value: none

Native Execution only. Specifies the compression CODEC used to compress spilled data. Supported compression CODECs are: ZLIB, SNAPPY, LZO, ZSTD, LZ4, and GZIP. Setting this property to none disables compression.

`native_spill_file_create_config`

Type: varchar
Default value: ""

Native Execution only. Specifies the configuration parameters used to create spill files. These parameters are provided to the underlying file system, allowing for customizable spill file creation based on the requirements of the environment. The format and options of these parameters are determined by the capabilities of the underlying file system and may include settings such as file location, size limits, and file system-specific optimizations.

`native_spill_write_buffer_size`

Type: bigint
Default value: 1048576

Native Execution only. The maximum size in bytes to buffer the serialized spill data before writing to disk for IO efficiency. If set to 0, buffering is disabled.

`native_topn_row_number_spill_enabled`

Type: boolean
Default value: true

Native Execution only. Enable topN row number spilling on native engine.

`native_window_spill_enabled`

Type: boolean
Default value: true

Native Execution only. Enable window spilling on native engine.

`native_writer_spill_enabled`

Type: boolean
Default value: true

Native Execution only. Enable writer spilling on native engine.