Presto 320 Documentation

6.12. Kinesis Connector

6.12. Kinesis Connector

Kinesis is Amazon’s fully managed cloud-based service for real-time processing of large, distributed data streams.

This connector allows the use of Kinesis streams as tables in Presto, such that each data-blob (message) in a Kinesis stream is presented as a row in Presto. A flexible table mapping approach lets us treat fields of the messages as columns in the table.

Under the hood, a Kinesis shard iterator is used to retrieve the records, along with a series of GetRecords calls. The shard iterator starts by default 24 hours before the current time and works its way forward. To be able to query a stream, table mappings are needed. These table definitions can be stored on Amazon S3 (preferred) or stored in a local directory on each Presto node.

This connector is a read-only connector. It can only fetch data from Kinesis streams, but cannot create streams or push data into existing streams.

To configure the Kinesis connector, create a catalog properties file etc/catalog/kinesis.properties with the following contents, replacing the properties as appropriate:

connector.name=kinesis
kinesis.access-key=XXXXXX
kinesis.secret-key=XXXXXX

Configuration Properties

The following configuration properties are available:

Property Name Description
kinesis.access-key Access key to aws account or blank to use default provider chain
kinesis.secret-key Secret key to aws account or blank to use default provider chain
kinesis.aws-region AWS region to be used to read kinesis stream from
kinesis.default-schema Default schema name for tables
kinesis.table-description-dir Directory containing table description files
kinesis.table-descriptions-s3 Amazon S3 bucket URL with table description files
kinesis.hide-internal-columns Controls whether internal columns are part of the table schema or not
kinesis.batch-size Maximum number of records to return in one batch
kinesis.fetch-attempts Read attempts made when no records returned and not caught up
kinesis.max-batches Maximum batches to read from Kinesis in one single query
kinesis.sleep-time Time for thread to sleep waiting to make next attempt to fetch batch
kinesis.iter-from-timestamp Begin iterating from a given timestamp instead of the trim horizon
kinesis.iter-offset-seconds Number of seconds before current time to start iterating

kinesis.access-key

Defines the access key ID for AWS root account or IAM roles, which is used to sign programmatic requests to AWS Kinesis.

This property is optional; if not defined, connector will try to follow Default-Credential-Provider-Chain provided by AWS in the following order:

  • Environment Variable: Load credentials from environment variables AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY.
  • Java System Variable: Load from java system as aws.accessKeyId and aws.secretKey.
  • Profile Credentials File: Load from file typically located at ~/.aws/credentials.
  • Instance profile credentials: These credentials can be used on EC2 instances, and are delivered through the Amazon EC2 metadata service.

kinesis.secret-key

Defines the secret key for AWS root account or IAM roles, which together with Access Key ID, is used to sign programmatic requests to AWS Kinesis.

This property is optional; if not defined, connector will try to follow Default-Credential-Provider-Chain same as above.

kinesis.aws-region

Defines AWS Kinesis regional endpoint. Selecting appropriate region may reduce latency in fetching data.

This field is optional; The default region is us-east-1 referring to end point ‘kinesis.us-east-1.amazonaws.com’.

See Kinesis Data Streams regions for a current list of available regions.

kinesis.default-schema

Defines the schema which will contain all tables that were defined without a qualifying schema name.

This property is optional; the default is default.

kinesis.table-description-dir

References a folder within Presto deployment that holds one or more JSON files (must end with .json) which contain table description files.

This property is optional; the default is etc/kinesis.

kinesis.table-descriptions-s3

An S3 URL giving the location of the JSON table description files. When this is given, S3 will be used as the source of table description files and kinesis.table-description-dir is ignored. The S3 bucket and folder will be checked every 10 minutes for updates and changed files.

This property is optional; by default, kinesis.table-description-dir will be the source of the table definitions.

kinesis.batch-size

Defines maximum number of records to return in one request to Kinesis Streams. Maximum limit is 10000 records.

This field is optional; the default value is 10000.

kinesis.max-batches

The maximum number of batches to read in a single query. The default value is 1000.

kinesis.fetch-attempts

Defines number of attempts made to read a batch from Kinesis Streams when no records are returned and the millis behind latest parameter shows we are not yet caught up. When records are returned no additional attempts are necessary. GetRecords has been observed to return no records even though the shard is not empty. That is why multiple attempts need to be made.

This field is optional; the default value is 2.

kinesis.sleep-time

Defines the duration for which a thread needs to sleep between kinesis.fetch-attempts made to fetch data.

This field is optional; the default value is 1000ms.

kinesis.iterator-from-timestamp

Use an initial shard iterator type of AT_TIMESTAMP starting kinesis.iterator-offset-seconds before the current time. When this is false, an iterator type of TRIM_HORIZON will be used, meaning it will start from the oldest record in the stream.

The default is true.

kinesis.iterator-offset-seconds

When kinesis.iterator-from-timestamp is true, the shard iterator will start at kinesis.iter-offset-seconds before the current time.

The default is 86400 seconds (24 hours).

kinesis.hide-internal-columns

In addition to the data columns defined in a table description file, the connector maintains a number of additional columns for each table. If these columns are hidden, they can still be used in queries but do not show up in DESCRIBE <table-name> or SELECT *.

This property is optional; the default is true.

Internal Columns

For each defined table, the connector maintains the following columns:

Column name Type Description
_shard_id VARCHAR ID of the Kinesis stream shard which contains this row.
_shard_sequence_id VARCHAR Sequence id within the Kinesis shard for this row.
_segment_start BIGINT Lowest offset in the segment (inclusive) which contains this row. This offset is partition specific.
_segment_end BIGINT Highest offset in the segment (exclusive) which contains this row. The offset is partition specific. This is the same value as _segment_start of the next segment (if it exists).
_segment_count BIGINT Running count for the current row within the segment. For an uncompacted topic, _segment_start + _segment_count is equal to _partition_offset.
_message_valid BOOLEAN True if the decoder could decode the message successfully for this row. When false, data columns mapped from the message should be treated as invalid.
_message VARCHAR Message bytes as an UTF-8 encoded string. This is only useful for a text topic.
_message_length BIGINT Number of bytes in the message.
_message_timestamp TIMESTAMP Approximate arrival time of the message (milliseconds granularity).
_key VARCHAR Key bytes as an UTF-8 encoded string. This is only useful for textual keys.
_partition_key VARCHAR Partition Key bytes as a UTF-8 encoded string.

For tables without a table definition file, the _message_valid column will always be true.

Table Definition

A table definition file consists of a JSON definition for a table, which corresponds to one stream in Kinesis. The name of the file can be arbitrary but must end in .json. The structure of the table definition is as follows:

{
      "tableName": ...,
      "schemaName": ...,
      "key": {
          "dataFormat": ...,
          "fields": [
              ...
          ]
      },
      "value": {
          "dataFormat": ...,
          "fields": [
              ...
         ]
      }
  }
Field Required Type Description
tableName required string Presto table name defined by this file.
schemaName optional string Schema which will contain the table. If omitted, the default schema name is used.
streamName required string Name of the Kinesis Stream that is mapped
message optional JSON object Field definitions for data columns mapped to the message itself.

Every message in a Kinesis stream can be decoded using the definition provided in the message object. The JSON object message in the table definition contains two fields:

Field Required Type Description
dataFormat required string Selects the decoder for this group of fields.
fields required JSON array A list of field definitions. Each field definition creates a new column in the Presto table.

Each field definition is a JSON object. At a minimum, a name, type, and mapping must be provided. The overall structure looks like this:

{
    "name": ...,
    "type": ...,
    "dataFormat": ...,
    "mapping": ...,
    "formatHint": ...,
    "hidden": ...,
    "comment": ...
}
Field Required Type Description
name required string Name of the column in the Presto table.
type required string Presto type of the column.
dataFormat optional string Selects the column decoder for this field. Defaults to the default decoder for this row data format and column type.
mapping optional string Mapping information for the column. This is decoder specific – see below.
formatHint optional string Sets a column specific format hint to the column decoder.
hidden optional boolean Hides the column from DESCRIBE <table name> and SELECT *. Defaults to false.
comment optional string Adds a column comment which is shown with DESCRIBE <table name>.

The name field is exposed to Presto as the column name, while the mapping field is the portion of the message that gets mapped to that column. For JSON object messages, this refers to the field name of an object, and can be a path that drills into the object structure of the message. Additionally, you can map a field of the JSON object to a string column type, and if it is a more complex type (JSON array or JSON object) then the JSON itself will become the field value.

There is no limit on field descriptions for either key or message.