Include new task to train models with task cluster (#3748)

.taskcluster.yml

@@ -27,6 +27,10 @@ tasks:
       then: ${event.pull_request.head.repo.html_url}
       else: ${event.repository.html_url}
 
+    pr_description:
+      $if: 'tasks_for == "github-pull-request"'
+      then: ${event.pull_request.body}
+
     taskboot_image: "mozilla/taskboot:0.4.2"
   in:
     $if: 'tasks_for == "github-push" || (tasks_for == "github-pull-request" && event["action"] in ["opened", "reopened", "synchronize"])'
@@ -206,6 +210,33 @@ tasks:
           owner: [email protected]
           source: ${repository}/raw/${head_rev}/.taskcluster.yml
 
+      - $if: 'tasks_for == "github-pull-request" && "Train on Taskcluster: " in pr_description'
+        then:
+          dependencies:
+            - { $eval: as_slugid("docker_build") }
+          taskId: { $eval: as_slugid("train_on_taskcluster") }
+          created: { $fromNow: "" }
+          deadline: { $fromNow: "1 day" }
+          provisionerId: proj-bugbug
+          workerType: compute-large
+          payload:
+            maxRunTime: 10800
+            image:
+              type: task-image
+              path: public/bugbug/bugbug-base.tar.zst
+              taskId: { $eval: as_slugid("docker_build") }
+            env:
+              PR_DESCRIPTION: "${pr_description}"
+            command:
+              - "/bin/sh"
+              - "-lcx"
+              - "python -m scripts.trainer $(python -m scripts.trainer_extract_args)"
+          metadata:
+            name: bugbug train on TC
+            description: Train a BugBug model on Taskcluster
+            owner: [email protected]
+            source: ${repository}/raw/${head_rev}/.taskcluster.yml
+
       - taskId: { $eval: as_slugid("frontend_build") }
         created: { $fromNow: "" }
         deadline: { $fromNow: "1 hour" }

scripts/trainer_extract_args.py

@@ -0,0 +1,39 @@
+# -*- coding: utf-8 -*-
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this file,
+# You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import logging
+import os
+import re
+
+logging.basicConfig(level=logging.INFO)
+logger = logging.getLogger(__name__)
+
+
+def get_model_name() -> str | None:
+    pr_description = os.environ.get("PR_DESCRIPTION")
+    if not pr_description:
+        logger.error("The PR_DESCRIPTION environment variable does not exist")
+        return None
+
+    match = re.search(r"Train on Taskcluster:\s+([a-z_1-9]+)", pr_description)
+    if not match:
+        logger.error(
+            "Could not identify the model name using the 'Train on Taskcluster' keyword from the Pull Request description"
+        )
+        return None
+
+    model_name = match.group(1)
+
+    return model_name
+
+
+def main():
+    model = get_model_name()
+    if model:
+        print(model)
+
+
+if __name__ == "__main__":
+    main()