ping database with python instead of mysql client (CTFd#1862)

* Replaces `mysqladmin ping` with a custom script
* Closes CTFd#725

Dockerfile

@@ -6,7 +6,6 @@ RUN mkdir -p /opt/CTFd /var/log/CTFd /var/uploads
 RUN apt-get update \
     && apt-get install -y --no-install-recommends \
         build-essential \
-        default-mysql-client \
         python3-dev \
         libffi-dev \
         libssl-dev \

docker-entrypoint.sh

@@ -7,7 +7,6 @@ ACCESS_LOG=${ACCESS_LOG:--}
 ERROR_LOG=${ERROR_LOG:--}
 WORKER_TEMP_DIR=${WORKER_TEMP_DIR:-/dev/shm}
 SECRET_KEY=${SECRET_KEY:-}
-DATABASE_URL=${DATABASE_URL:-}
 
 # Check that a .ctfd_secret_key file or SECRET_KEY envvar is set
 if [ ! -f .ctfd_secret_key ] && [ -z "$SECRET_KEY" ]; then
@@ -19,22 +18,8 @@ if [ ! -f .ctfd_secret_key ] && [ -z "$SECRET_KEY" ]; then
     fi
 fi
 
-# Check that the database is available
-if [ -n "$DATABASE_URL" ]
-    then
-    url=`echo $DATABASE_URL | awk -F[@//] '{print $4}'`
-    database=`echo $url | awk -F[:] '{print $1}'`
-    port=`echo $url | awk -F[:] '{print $2}'`
-    echo "Waiting for $database:$port to be ready"
-    while ! mysqladmin ping -h "$database" -P "$port" --silent; do
-        # Show some progress
-        echo -n '.';
-        sleep 1;
-    done
-    echo "$database is ready"
-    # Give it another second.
-    sleep 1;
-fi
+# Ensures that the database is available
+python ping.py
 
 # Initialize database
 python manage.py db upgrade

ping.py

@@ -0,0 +1,34 @@
+"""
+Script for checking that a database server is available.
+Essentially a cross-platform, database agnostic mysqladmin.
+"""
+import time
+
+from sqlalchemy import create_engine
+from sqlalchemy.engine.url import make_url
+
+from CTFd.config import Config
+
+url = make_url(Config.DATABASE_URL)
+
+# Ignore sqlite databases
+if url.drivername.startswith("sqlite"):
+    exit(0)
+
+# Null out the database so raw_connection doesnt error if it doesnt exist
+# CTFd will create the database if it doesnt exist
+url.database = None
+
+# Wait for the database server to be available
+engine = create_engine(url)
+print(f"Waiting for {url} to be ready")
+while True:
+    try:
+        engine.raw_connection()
+        break
+    except Exception:
+        print(".", end="", flush=True)
+        time.sleep(1)
+
+print(f"{url} is ready")
+time.sleep(1)