Slack Connector for Apache Flink®

Compatibility matrix

Apache Flink	Slack Connector for Apache Flink	Release date
1.14.x - 1.15.x	v1.0	17.10.2022
1.15.x	v1.0.1-1.15	16.11.2022
1.16.x	v1.0.1-1.16	16.11.2022

Since 1.0.1 versioning looks like <major>.<minor>.<patch>-<flink-major>.<flink-minor> according to Externalized Connector development

To start using Slack connector for Flink put flink-slack-connector-<version>.jar to lib/ folder of Flink and restart Flink.

Build locally

./mvnw clean verify -DskipTests

or in case of Windows

mvnw clean verify -DskipTests

To build with tests it is required to define SLACK_FOR_FLINK_BOT_TOKEN and SLACK_FOR_FLINK_CHANNEL_ID env variables. SLACK_FOR_FLINK_BOT_TOKEN contains Bot User OAuth Token (see below) SLACK_FOR_FLINK_CHANNEL_ID contains a channel id used during unit tests

Set-up Slack Application

Create your Slack app at Slack API
In Oauth & Permissions in Scopes add chat:write
In Oauth & Permissions copy Bot User OAuth Token and use for placeholder BOT_USER_OAUTH_ACCESS_TOKEN
Reinstall the app
Add app to the channel where it should post by mentioning the app name in a message (e.g. @APP_NAME) and confirming the invitation
Collect the Channel Id by right clicking on the channel name -> View Channel details and scrolling at the bottom of the window. The channel id should start with C and have a format similar to CXXXXXXXXX

Channel ID shown at the bottom of the window

Send message

Messages could be sent in plain text or formatted way. Also, messages could be sent as normal messages or as replies. To send messages it is required that app has chat:write permission and bot is added to channel where a message should be post.

First create table

CREATE TEMPORARY TABLE slack_example (
    `channel_id` STRING,
    `message` STRING 
) WITH (
    'connector' = 'slack',
    'token' = BOT_USER_OAUTH_ACCESS_TOKEN
);

To be able to send messages in a table there should be column with name channel_id and message (or text). Now to send a simple plain text message to channel_id CHANNEL_ID

INSERT INTO slack_example VALUES('CHANNEL_ID', 'Hello world!');

Send message as reply

To send message as reply it is required to specify thread to reply.

CREATE TEMPORARY TABLE slack_example_with_reply (
    `channel_id` STRING,
    `thread` STRING,
    `message` STRING 
) WITH (
    'connector' = 'slack',
    'token' = BOT_USER_OAUTH_ACCESS_TOKEN
);

Now to reply a simple plain text message to thread THREAD_ID in channel_id CHANNEL_ID

INSERT INTO slack_example_with_reply VALUES('CHANNEL_ID', 'THREAD_ID', 'Hello world!');

In case THREAD_ID is null it will be a normal message e.g.

INSERT INTO slack_example_with_reply VALUES('CHANNEL_ID', CAST(NULL AS STRING), 'Hello world!');

Send formatted message

To send formatted message there should be blocks_as_str or formatted column

CREATE TEMPORARY TABLE slack_example_formatted (
    `channel_id` STRING,
    `thread` STRING,
    `formatted` STRING 
) WITH (
    'connector' = 'slack',
    'token' = BOT_USER_OAUTH_ACCESS_TOKEN
);

Now to send a formatted message to channel_id CHANNEL_ID

INSERT INTO slack_example_formatted VALUES('CHANNEL_ID', CAST(NULL AS STRING), '[{"type": "divider"}]');

And similar message replying to THREAD_ID

INSERT INTO slack_example_formatted VALUES('CHANNEL_ID', 'THREAD_ID', '[{"type": "divider"}]');

More examples of formatted messages could be found at block-kit-builder

Note: in formatted there should be passed only value for blocks.

Source

For querying there are available type, ts, user, text, team, thread_ts columns. While querying it is also required to specify channel_id like

CREATE TEMPORARY TABLE table_for_quering (
    `ts` DECIMAL(16, 6),
    `channel` STRING,
    `type` STRING,
    `username` STRING,
    `user` STRING,
    `text` STRING 
) WITH (
    'connector' = 'slack',
    'token' = :BOT_TOKEN,
    'channel_id' = :CHANNEL_ID
);

Common errors

When creating a Flink job, the following are common error messages and related solutions:

not_in_channel: The app has the right permissions, but is not invited in the channel where it should post. Mention the app name in a message (e.g. @APP_NAME) and confirm the invitation.

Trademarks

Apache Flink is either registered trademarks or trademarks of the Apache Software Foundation in the United States and/or other countries.

Slack is a trademark and service mark of Slack Technologies, Inc., registered in the U.S. and in other countries.

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