Elasticsearch

Overview

The Elasticsearch Load Node allows for writing into an index of the Elasticsearch engine. This document describes how to setup the Elasticsearch Load Node to run SQL queries against Elasticsearch.

The Load Node can operate in upsert mode for exchanging UPDATE/DELETE messages with the external system using the primary key defined on the DDL.

If no primary key is defined on the DDL, the Load Node can only operate in append mode for exchanging INSERT only messages with external system.

Supported Version

Load Node	Version
elasticsearch	Elasticsearch: 5.x, 6.x, 7.x

Dependencies

In order to use the Elasticsearch Load Node the following dependencies are required for both projects using a build automation tool (such as Maven or SBT) and SQL Client with Sort Connectors JAR bundles.

• Elasticsearch 6

<dependency>
    <groupId>org.apache.inlong</groupId>
    <artifactId>sort-connector-elasticsearch6</artifactId>
    <version>1.5.0</version>
</dependency>

• Elasticsearch 7

<dependency>
    <groupId>org.apache.inlong</groupId>
    <artifactId>sort-connector-elasticsearch7</artifactId>
    <version>1.5.0</version>
</dependency>

How to create an Elasticsearch Load Node

Usage for SQL API

The example below shows how to create an Elasticsearch Load Node with Flink SQL :

CREATE TABLE myUserTable (
  user_id STRING,
  user_name STRING,
  uv BIGINT,
  pv BIGINT,
  PRIMARY KEY (user_id) NOT ENFORCED
) WITH (
  'connector' = 'elasticsearch-7-inlong',
  'hosts' = 'http://localhost:9200',
  'index' = 'users'
);

Usage for InLong Dashboard

TODO: It will be supported in the future.

Usage for InLong Manager Client

TODO: It will be supported in the future.

Elasticsearch Load Node Options

Option	Required	Default	Type	Description
connector	required	(none)	String	Specify what connector to use, valid values are: elasticsearch-6-inlong: connect to Elasticsearch 5.x and 6.x cluster. elasticsearch-7-inlong: connect to Elasticsearch 7.x and later versions cluster.
hosts	required	(none)	String	One or more Elasticsearch hosts to connect to, e.g. 'http://host_name:9092;http://host_name:9093'.
index	required	(none)	String	Elasticsearch index for every record. Can be a static index (e.g. 'myIndex') or a dynamic index (e.g. 'index-\{log_ts|yyyy-MM-dd}'). See the following Dynamic Index section for more details.
document-type	required in 5.x and 6.x	(none)	String	Elasticsearch document type. Not necessary anymore in elasticsearch-7.
document-id.key-delimiter	optional	_	String	Delimiter for composite keys ("_" by default), e.g., "$" would result in IDs "KEY1$KEY2$KEY3".
username	optional	(none)	String	Username used to connect to Elasticsearch instance. Please notice that Elasticsearch doesn't pre-bundled security feature, but you can enable it by following the guideline to secure an Elasticsearch cluster.
password	optional	(none)	String	Password used to connect to Elasticsearch instance. If username is configured, this option must be configured with non-empty string as well.
failure-handler	optional	fail	String	Failure handling strategy in case a request to Elasticsearch fails. Valid strategies are: fail: throws an exception if a request fails and thus causes a job failure. ignore: ignores failures and drops the request. retry-rejected: re-adds requests that have failed due to queue capacity saturation. custom class name: for failure handling with a ActionRequestFailureHandler subclass.
sink.flush-on-checkpoint	optional	true	Boolean	Flush on checkpoint or not. When disabled, a sink will not wait for all pending action requests to be acknowledged by Elasticsearch on checkpoints. Thus, a sink does NOT provide any strong guarantees for at-least-once delivery of action requests.
sink.bulk-flush.max-actions	optional	1000	Integer	Maximum number of buffered actions per bulk request. Can be set to '0' to disable it.
sink.bulk-flush.max-size	optional	2mb	MemorySize	Maximum size in memory of buffered actions per bulk request. Must be in MB granularity. Can be set to '0' to disable it.
sink.bulk-flush.interval	optional	1s	Duration	The interval to flush buffered actions. Can be set to '0' to disable it. Note, both 'sink.bulk-flush.max-size' and 'sink.bulk-flush.max-actions'can be set to '0' with the flush interval set allowing for complete async processing of buffered actions.
sink.bulk-flush.backoff.strategy	optional	DISABLED	String	Specify how to perform retries if any flush actions failed due to a temporary request error. Valid strategies are: DISABLED: no retry performed, i.e. fail after the first request error. CONSTANT: wait for backoff delay between retries. EXPONENTIAL: initially wait for backoff delay and increase exponentially between retries.
sink.bulk-flush.backoff.max-retries	optional	8	Integer	Maximum number of backoff retries.
sink.bulk-flush.backoff.delay	optional	50ms	Duration	Delay between each backoff attempt. For CONSTANT backoff, this is simply the delay between each retry. For EXPONENTIAL backoff, this is the initial base delay.
connection.max-retry-timeout	optional	(none)	Duration	Maximum timeout between retries.
connection.path-prefix	optional	(none)	String	Prefix string to be added to every REST communication, e.g., '/v1'.
routing.filed-name	optional	(none)	String	Using field value in the record to dynamically generate routing filed.
format	optional	json	String	Elasticsearch connector supports to specify a format. The format must produce a valid json document. By default uses built-in 'json' format. Please refer to JSON Format page for more details.
inlong.metric.labels	optional	(none)	String	Inlong metric label, format of value is groupId=[groupId]&streamId=[streamId]&nodeId=[nodeId].

Features

Key Handling

Elasticsearch sink can work in either upsert mode or append mode, it depends on whether primary key is defined. If primary key is defined, Elasticsearch sink works in upsert mode which can consume queries containing UPDATE/DELETE messages. If primary key is not defined, Elasticsearch sink works in append mode which can only consume queries containing INSERT only messages.

In Elasticsearch connector, the primary key is used to calculate the Elasticsearch document id, which is a string of up to 512 bytes. It cannot have whitespaces. The Elasticsearch connector generates a document ID string for every row by concatenating all primary key fields in the order defined in the DDL using a key delimiter specified by document-id.key-delimiter. Certain types are not allowed as primary key field as they do not have a good string representation, e.g. BYTES, ROW, ARRAY, MAP, etc. If no primary key is specified, Elasticsearch will generate a document id automatically.

See CREATE TABLE DDL for more details about PRIMARY KEY syntax.

Dynamic Index

Elasticsearch Load Node supports both static index and dynamic index.

If you want to have a static index, the index option value should be a plain string, e.g. 'myusers', all the records will be consistently written into "myusers" index.

If you want to have a dynamic index, you can use {field_name} to reference a field value in the record to dynamically generate a target index. You can also use '{field_name|date_format_string}' to convert a field value of TIMESTAMP/DATE/TIME type into the format specified by the date_format_string. The date_format_string is compatible with Java's DateTimeFormatter. For example, if the option value is 'myusers-{'{log_ts|yyyy-MM-dd}'}', then a record with log_ts field value 2020-03-27 12:25:55 will be written into "myusers-2020-03-27" index.

Data Type Mapping

JSON type	Flink SQL type
string	CHAR / VARCHAR / STRING
boolean	BOOLEAN
string with encoding: base64	BINARY / VARBINARY
number	DECIMAL
number	TINYINT
number	SMALLINT
number	INT
number	BIGINT
number	FLOAT
number	DOUBLE
string with format: date	DATE
string with format: time	TIME
string with format: date-time	TIMESTAMP
string with format: date-time (with UTC time zone)	TIMESTAMP_WITH_LOCAL_TIME_ZONE
number	INTERVAL
array	ARRAY
object	MAP / MULTISET
object	ROW