Demo Slack Attachments

In this lesson, you’ll learn how to send rich, interactive Slack notifications from Jenkins pipelines using attachments and Block Kit. We will:

• Explore Slack’s Block Kit Builder and message layouts
• Build JSON payloads with attachments and blocks
• Integrate payloads in Jenkins via a shared library
• Customize messages with emojis, images, and buttons

Quick Slack Notifications Example

Out of the box, Jenkins’ Slack plugin can send basic build statuses:

jenkins  APP  20:46
ABORTED: devsecops-numeric-application #72: http://…/job/devsecops-numeric-application/72/

jenkins  APP  21:00
SUCCESS: devsecops-numeric-application #73: http://…/job/devsecops-numeric-application/73/

These simple messages work, but to stand out you can leverage Slack’s rich layouts.

Slack API: Rich Message Layouts

Slack’s Messaging Layouts guide shows how to assemble messages with attachments and blocks:

Block Kit Builder

Prototype your message in Slack’s Block Kit Builder before coding.

Basic Section Block

{
  "blocks": [
    {
      "type": "section",
      "text": {
        "type": "mrkdwn",
        "text": "New Paid Time Off request from <https://example.com|Fred Enriquez>\n\n<https://example.com|View request>"
      }
    }
  ]
}

Interactive Message with Button and Image

{
  "blocks": [
    {
      "type": "section",
      "text": {
        "type": "mrkdwn",
        "text": "Hello, Assistant to the Regional Manager Dwight! *Michael Scott* wants to know where you'd like to take the investors to dinner.\n*Please select a restaurant:*"
      }
    },
    { "type": "divider" },
    {
      "type": "section",
      "text": {
        "type": "mrkdwn",
        "text": "*Farmhouse Thai Cuisine*\n⭐️⭐️⭐️⭐️ 1528 reviews\nThey do have some vegan options…"
      },
      "accessory": {
        "type": "image",
        "image_url": "https://s3-media3.fl.yelpcdn.com/bphoto/c7e05s9lC12mA3arueZ7A/o.jpg",
        "alt_text": "Thai restaurant"
      }
    }
  ]
}

Constructing an Attachment Payload

Wrap blocks in an attachments array to add colors, fallbacks, or pretext:

{
  "attachments": [
    {
      "color": "#2fc744",
      "blocks": [
        {
          "type": "section",
          "text": {
            "type": "mrkdwn",
            "text": "*Hi devsecops!*"
          }
        },
        { "type": "divider" },
        {
          "type": "section",
          "text": {
            "type": "mrkdwn",
            "text": "*Farmhouse Thai Cuisine*\n⭐️⭐️⭐️⭐️⭐️…"
          },
          "accessory": {
            "type": "image",
            "image_url": "https://s3-media1.fl.yelpcdn.com/photo/c7e0s5m9lC2mA3aruue7A/o.jpg",
            "alt_text": "Restaurant image"
          }
        }
      ]
    }
  ]
}

Jenkins Slack Notification Plugin

Jenkins uses the Slack Notification Plugin to send JSON payloads. You can pass your attachment payload directly:

slackSend(color: color, attachments: attachments)

Table: Build Status Mapping

Shared Library: sendNotifications.groovy

Use a shared library to assemble attachments dynamically:

def call(String buildStatus = 'STARTED') {
    buildStatus = buildStatus ?: 'SUCCESS'

    // Map status to color and emoji
    def (color, emoji) = buildStatus == 'SUCCESS' ? ['#47e05e', ':tada:']
                          : buildStatus == 'UNSTABLE'? ['#d9d26d', ':warning:']
                          : ['#ec2805', ':hulk:']

    def attachments = [
        [
            "color": color,
            "blocks": [
                [
                    "type": "header",
                    "text": [
                        "type": "plain_text",
                        "text": "K8S Deployment - ${env.JOB_NAME} ${emoji}",
                        "emoji": true
                    ]
                ],
                [
                    "type": "section",
                    "fields": [
                        ["type": "mrkdwn", "text": "*Job Name:*\n${env.JOB_NAME}"],
                        ["type": "mrkdwn", "text": "*Build Number:*\n${env.BUILD_NUMBER}"]
                    ],
                    "accessory": [
                        "type": "image",
                        "image_url": "https://raw.githubusercontent.com/sidd-harth/numeric/main/images/jenkins-slack.png",
                        "alt_text": "Slack Icon"
                    ]
                ],
                ["type": "divider"]
            ]
        ]
    ]

    slackSend(color: color, attachments: attachments)
}

Custom Emojis in Slack

Add custom emojis under Customize Slack → Add Emoji. For example, upload deadpool.png as :deadpool::

Ensure your team has emojis like :tada:, :warning:, and :hulk: available.

Integrating in Jenkinsfile

Call sendNotifications in your pipeline’s post section:

pipeline {
    agent any
    stages {
        stage('Integration Tests - PROD') {
            steps {
                withKubeConfig([credentialsId: 'kubeconfig']) {
                    sh 'bash integration-test-PROD.sh'
                }
            }
        }
        stage('Testing Slack') {
            steps {
                sh 'exit 0'
            }
        }
    }
    post {
        always { /* Optional reports */ }
        success {
            script {
                env.emoji = ':white_check_mark:'
                sendNotifications(currentBuild.result)
            }
        }
        failure {
            script {
                env.emoji = ':hulk:'
                sendNotifications(currentBuild.result)
            }
        }
    }
}

Resulting Slack Message

A successful pipeline produces a detailed Slack notification:

This message includes:

• A header with deployment name and emoji
• Job name and build number fields
• Custom icons and images
• Optional action buttons or links to Jenkins, Kubernetes, or GitHub

Use this approach to highlight failed stages or add actionable buttons directly in Slack.