Switch deploy script from dry run to real deployment

.github/workflows/ci.yml

@@ -127,7 +127,7 @@ jobs:
 
       # The script is never copied to the server: bash reads it from stdin.
       # github.sha is exactly the commit the checks above have tested.
-      - name: Deploy to server (dry run)
+      - name: Deploy to server
         run: |
           ssh -i ~/.ssh/deploy_key \
             "${{ secrets.SSH_USER }}@${{ secrets.SSH_HOST }}" \

deploy/deploy.sh

@@ -2,14 +2,12 @@
 # Deploys one commit of the Coderr backend. Runs on the server and is fed
 # through ssh by the deploy job in .github/workflows/ci.yml:
 #   ssh <host> "bash -s -- <commit-sha>" < deploy/deploy.sh
-#
-# First version: dry run only. It reports what a deployment would change
-# and takes a database backup, but touches neither code nor database.
 set -euo pipefail
 
 APP_DIR=/var/www/coderr/backend
 BACKUP_DIR="$HOME/backups/coderr"
 KEEP_BACKUPS=10
+SERVICE=gunicorn-coderr
 
 sha="${1:-}"
 if [[ ! "$sha" =~ ^[0-9a-f]{40}$ ]]; then
@@ -50,6 +48,34 @@ backup_database() {
         | xargs -r rm --
 }
 
+# HUP makes the Gunicorn master start fresh workers with the new code while
+# the old ones finish their requests. Gunicorn runs as this user, so no
+# sudo is needed.
+reload_gunicorn() {
+    local pid old_workers new_workers common
+    pid="$(systemctl show -p MainPID --value "$SERVICE")"
+    if [ "$pid" = "0" ]; then
+        echo "$SERVICE is not running." >&2
+        exit 1
+    fi
+    old_workers="$(pgrep -P "$pid" | sort)" || true
+    kill -HUP "$pid"
+
+    # Gunicorn's graceful timeout is 30 seconds, so 40 seconds also covers
+    # an old worker that is still busy with a slow request.
+    for _ in $(seq 1 40); do
+        sleep 1
+        new_workers="$(pgrep -P "$pid" | sort)" || true
+        common="$(comm -12 <(echo "$old_workers") <(echo "$new_workers"))"
+        if [ -n "$new_workers" ] && [ -z "$common" ]; then
+            echo "Gunicorn reloaded, workers: $(echo $new_workers)"
+            return 0
+        fi
+    done
+    echo "Gunicorn workers were not replaced within 40 seconds." >&2
+    exit 1
+}
+
 cd "$APP_DIR"
 
 # Tracked files edited by hand on the server would get mixed with the new
@@ -76,8 +102,17 @@ echo "--- New migration files ---"
 git diff --name-only --diff-filter=A HEAD "$sha" -- '*/migrations/*.py'
 echo "--- Changes to requirements.txt ---"
 git diff HEAD "$sha" -- requirements.txt
-echo "--- Unapplied migrations of the running code ---"
-.venv/bin/python manage.py migrate --plan
 
 backup_database
-echo "Dry run finished, nothing was deployed."
+
+git merge --ff-only --quiet "$sha"
+echo "Code is now at $(git log --oneline -1 HEAD)"
+
+# These steps run on every deployment, changed or not. A deployment that
+# failed halfway is then completed by simply running the job again.
+.venv/bin/pip install --quiet --disable-pip-version-check -r requirements.txt
+.venv/bin/python manage.py check
+.venv/bin/python manage.py migrate --noinput
+.venv/bin/python manage.py collectstatic --noinput
+reload_gunicorn
+echo "Deployment finished."