Slack Chat Resources

This repository provides Concourse resource types to read, act on, and reply to messages on Slack.

There are two resource types:

• slack-read-resource: For reading messages.
• slack-post-resource: For posting messages.

There are two resource types because a system does not want to respond to messages that it posts itself. Concourse assumes that an output of a resource is also a valid input. Therefore, separate resources are used for reading and posting. Since using a single resource has no benefits over separate resources, reading and posting are split into two resource types..

The posting resource offers similar functionality to the older slack-notification-resource, with the following benefits:

• Support for replying to threads.
• More powerful interpolation of contents of arbitrary files into message text and other parameters.
• Written in Go as opposed to Bash, in case you care about this :).

Docker Store:

• varmakarthik12/slack-read-resource
• varmakarthik12/slack-post-resource

Version Format

Timestamps of Slack messages are used as resource versions. For example, a message may be represented by a version like this:

timestamp: 1234567890.123

A timestamp uniquely identifies a message within a channel. See Slack API for details.

Reading Messages

Usage in a pipeline:

resource_types:
    - name: slack-read-resource
      type: docker-image
      source:
        repository: varmakarthik12/slack-read-resource

resources:
    - name: slack-in
      type: slack-read-resource
      source: ...

Source Configuration

The source field configures the resource for reading messages from a specific channel. It allows filtering messages by their author and text pattern:

• token: Required. A Slack API token that allows reading all messages on a selected channel.
• channel_id: Required. The selected channel ID. The resource only reads messages on this channel.
• matching: Optional. Only report messages matching this filter. See below for details.
• not_replied_by: Optional. Ignore messages that have a reply matching this filter. See below for details.

The values of matching and not_replied_by represent message filters. They are maps with the following elements:

• author: Optional. User ID that must match the author of the message - either the user or the bot_id field. See Slack API regarding authorship.
• text_pattern: Optional. Regular expression that must match the message text. Wrap in single quotes instead of double, to avoid having to escape \. See Slack API for details on text formatting.

The resource only reports messages that begin new threads and not replies to other messages.

When given a message timestamp as the current version, it only reads messages with that timestamp and later. In any case though, it reads at most 100 of the latest messages. Therefore, the resource must be checked often enough to avoid missing messages.

If source has a not_replied_by filter, and it matches a message that also matches the matching filter, then all messages older than the latest such message are also considered obsolete and are not read.

Example

resources:
  - name: slack-in
    type: slack-read-resource
    source:
      token: "xxxx-xxxxxxxxxx-xxxx"
      channel_id: "C11111111"
      matching:
        text_pattern: '<@U22222222>\s+(.+)'
      not_replied_by:
        author: U22222222

This configures a resource reading messages from channel with ID C11111111. It reads only messages that begin by mentioning the user with ID U22222222. It ignores messages already replied to by that same user.

get: Read a Message

Reads the message with the requested timestamp and produces the following files:

• timestamp: The message timestamp.
• text: The message text.
• text_part1, text_part2, etc.: Parts of text parsed using the text_pattern parameter described below.

Parameters:

• text_pattern: Optional. A regular expression to match against the message text. The text matched by each capturing group is stored into a file text_part<num> where <num> is the group index starting with 1. Wrap in single quotes instead of double, to avoid having to escape \. See Slack API for details on text formatting.

Example

- get: slack-in
  params:
      text_pattern: '([A-Z]+) ([0-9]+)'

When this configuration sees a message with the text abc 123 and timestamp 111.222, it will produce the following files and contents:

• timestamp: 111.222
• text: abc 123
• text_part1: abc
• text_part2: 123

Posting Messages

Usage in a pipeline:

resource_types:
    - name: slack-post-resource
      type: docker-image
      source:
        repository: varmakarthik12/slack-post-resource

resources:
    - name: slack-out
      type: slack-post-resource
      source: ...

Source Configuration

The source field configures the resource for posting on a specific channel:

• token: Required. A Slack API token that allows posting on a selected channel.
• channel_id: Required. The selected channel ID. The resource only posts messages on this channel.

Example

resources:
  - name: slack-out
    type: slack-post-resource
    source:
      token: "xxxx-xxxxxxxxxx-xxxx"
      channel_id: "C11111111"

This configures the resource to post on the channel with ID C11111111.

put: Post a Message

Posts a message to the selected channel.

Parameters:

• message: Optional. The message to send described in YAML.
• message_file: Optional. The file containing the message to send described in JSON.

Either message or message_file must be present. If both are present, message_file takes precedence and message is ignored.

The message is described just as the argument to the chat.postMessage method of the Slack API. All fields are supported, except that token and channel are ignored and instead the resource configuration in source is used.

When using message, some message parameters support string interpolation to insert contents of arbitrary files or values of environment variables. The following table gives rules for substitution:

Pattern	Substituted By
{{filename}}	Contents of file filename
{{$variable}}	Value of environment variable variable

The following message fields support string interpolation:

• text
• thread_ts

The following fields of an attachment support string interpolation:

• fallback
• title
• title_link
• pretext
• text
• footer

Example

Consider a job with the get: slack-in step from the example above followed by this step:

- put: slack-out
  params:
    message:
        thread_ts: "{{slack-in/timestamp}}"
        text: "Hi {{slack-in/text_part1}}! I will do {{slack-in/text_part2}} right away!!"

This will reply to the message read by the get step (since thread is the timestamp of the original message), and the reply will read:

Hi abc! I will do 123 right away!