Ready to use

Author: mcmarkj

Dockerfile

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+FROM python:3.7
+
+ADD send-slack.py .
+
+RUN pip install slack_sdk
+
+ENTRYPOINT ["python", "send-slack.py"]

action.yml

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+name: 'Simple Slack Notifier'
+description: 'Sends a slack notification on failure of a Github Pipeline'
+runs:
+  using: 'docker'
+  image: 'Dockerfile'

send-slack.py

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+from slack_sdk import WebClient
+from slack_sdk.errors import SlackApiError
+import os
+import sys
+
+channels_list = {}
+
+def fetch_channels(client: WebClient, next_cursor: str = ""):
+    try:
+        result = client.conversations_list(
+            exclude_archived=True,
+            limit=500,
+            types="public_channel,private_channel",
+            cursor=next_cursor,
+        )
+        for channel in result["channels"]:
+            channels_list[channel["name"]] = channel["id"]
+        return result
+    except SlackApiError as e:
+        print(f"Slack error: {e}")
+
+
+def validate_vars():
+    MANDATORY_ENV_VARS = ["SLACK_CHANNEL", "MESSAGE_CONTENT", "PIPELINE_NAME", "SLACK_BOT_TOKEN"]
+    for var in MANDATORY_ENV_VARS:
+        if var not in os.environ:
+            raise EnvironmentError("Error. Env var {} is not set and is required to run.".format(var))
+
+
+def main():
+    validate_vars()
+
+    slack_channel = os.environ["SLACK_CHANNEL"]
+    message_content = os.environ["MESSAGE_CONTENT"]
+    pipeline_name = os.environ["PIPELINE_NAME"]
+    slack_bot_token = os.environ["SLACK_BOT_TOKEN"]
+
+    try:
+        client = WebClient(token=slack_bot_token)
+
+        # Get the channel ID from the name
+        next_cursor = fetch_channels(client)["response_metadata"]["next_cursor"]
+        while next_cursor:
+            next_cursor = fetch_channels(client, next_cursor)["response_metadata"][
+                "next_cursor"
+            ]
+
+        channel_id = channels_list[slack_channel]
+
+        # Send the slack message, if it fails an exception will fire
+        client.chat_postMessage(
+            channel=channel_id, text=message_content, username=pipeline_name
+        )
+        print("Message sent.")
+    except SlackApiError as e:
+        print(f"Error posting message: {e}")
+        sys.exit(1)
+    except KeyError:
+        print(
+            f"Channel {slack_channel} not found. If it a private channel: Mention @Github_Actions & invite them to the channel first"
+        )
+        sys.exit(1)
+
+if __name__ == "__main__":
+    main()