fix(api): improve sqlite concurrency handling and return 503 when db is busy

quotes.py

@@ -14,13 +14,21 @@ random.seed()
 
 DB_FILE = "quotes.db"
 
+def get_db_connection():
+    """Create a SQLite connection tuned for concurrent reads/writes"""
+    conn = sqlite3.connect(DB_FILE, timeout=5)
+    conn.execute("PRAGMA journal_mode = WAL")
+    conn.execute("PRAGMA busy_timeout = 5000")
+    return conn
+
 def verify_db():
+    """Check to ensure the SQLite DB is available"""
     if not os.path.exists(DB_FILE):
         raise RuntimeError("quotes.db not found. Run add-quotes.py to initialize.")
 
 def get_random_quote():
     """Fetch a random quote from the database and increment delivered count"""
-    conn = sqlite3.connect(DB_FILE)
+    conn = get_db_connection()
     c = conn.cursor()
 
     # Pick a random quote ID
@@ -46,7 +54,11 @@ def main():
 @app.route("/quote")
 @limiter.limit("20/minute")
 def quote():
-    quote = get_random_quote()
+    try:
+        quote = get_random_quote()
+    except sqlite3.OperationalError:
+        return "Database is busy, please retry.", 503
+
     if not quote:
         return "No quotes found in database!", 500
     return f"{quote['quote']} - {quote['author']}"
@@ -54,7 +66,11 @@ def quote():
 @app.route("/api/quote")
 @limiter.limit("50/minute")
 def quote_api():
-    quote = get_random_quote()
+    try:
+        quote = get_random_quote()
+    except sqlite3.OperationalError:
+        return jsonify({"error": "Database is busy, please retry"}), 503
+
     if not quote:
         return jsonify({"error": "No quotes found"}), 500
     return jsonify(quote)
@@ -62,4 +78,4 @@ def quote_api():
 if __name__ == "__main__":
     verify_db()
     """Running on Oracle's private network, in my instance - here it is 0.0.0.0 so only one node is needed"""
-    app.run(host="0.0.0.0", port=5051, debug=True)
+    app.run(host="0.0.0.0", port=5051, debug=True)