feat: optional export task and expandable config parsing with named tuples

main.py

@@ -5,16 +5,19 @@ import asyncio
 import threading
 import logging
 import signal
+from collections import namedtuple
 import aioprocessing
 from dotenv import load_dotenv
 
-from src.const import DEFAULT_EXPORT_INTERVAL, DEFAULT_MODE
+from src.const import DEFAULT_MODE, DEFAULT_EXPORT_INTERVAL, DEFAULT_IS_EXPORT
 from src.mempool import WebSocketThread, QueueProcessor
 from src.db import Handler, periodic_export
 
+Config = namedtuple("Config", ["mode", "export_interval", "is_export"])
+
 
 async def shutdown(loop, signal=None):
-    """Cleanup tasks tied to the service's shutdown."""
+    """Run cleanup tasks tied to the service's shutdown."""
     if signal:
         logging.info("Received exit signal %s", signal.name)
 
@@ -34,40 +37,34 @@ async def shutdown(loop, signal=None):
 
 
 def load_cfg(dotenv_path=".env"):
+    """Parse configuration from environment variables located in `dotenv_path` or from defaults."""
     load_dotenv(dotenv_path)
-    cfg = {}
-
     print(f"[+] Environment variables loaded from '{dotenv_path}'\n---")
 
-    cfg["MODE"] = os.getenv("MODE")
-    cfg["EXPORT_INTERVAL"] = os.getenv("EXPORT_INTERVAL")
+    mode = os.getenv("MODE", DEFAULT_MODE).lower()
+    export_interval = int(os.getenv("EXPORT_INTERVAL", DEFAULT_EXPORT_INTERVAL))
+    is_export = os.getenv("IS_EXPORT", DEFAULT_IS_EXPORT).lower() in ("true", "1", "t")
 
-    if cfg["MODE"] is None:
-        cfg["MODE"] = DEFAULT_MODE
-
-    if cfg["EXPORT_INTERVAL"] is None:
-        cfg["EXPORT_INTERVAL"] = DEFAULT_EXPORT_INTERVAL
-    else:
-        cfg["EXPORT_INTERVAL"] = int(cfg["EXPORT_INTERVAL"])
+    cfg = Config(mode, export_interval, is_export)
 
     return cfg
 
 
 def main():
     cfg = load_cfg()
-    mode = cfg["MODE"]
 
-    if mode.lower() == "production":
+    if cfg.mode == "production":
         log_level = logging.INFO
     else:
         log_level = logging.DEBUG
 
     logging.basicConfig(format="%(asctime)s %(levelname)s: %(message)s", level=log_level)
     logging.info("Logger initialized")
-    logging.info("MODE: %s", cfg["MODE"])
-    logging.info("EXPORT_INTERVAL: %d (seconds)", cfg["EXPORT_INTERVAL"])
+    logging.info("MODE: %s", cfg.mode)
+    logging.info("EXPORT_INTERVAL: %d (seconds)", cfg.export_interval)
+    logging.info("IS_EXPORT: %r", cfg.is_export)
 
-    # FIFO queue for crosst-thread communications
+    # FIFO queue for cross-thread communications
     q = aioprocessing.AioQueue()
     handler = Handler()
     shutdown_event = threading.Event()
@@ -77,12 +74,14 @@ def main():
 
     ws_thread = WebSocketThread(q, shutdown_event)
     qp_thread = QueueProcessor(q, shutdown_event, handler)
+
     export_thread = threading.Thread(
         target=periodic_export,
         args=(
             export_loop,
             handler,
-            cfg["EXPORT_INTERVAL"],
+            cfg.export_interval,
+            cfg.is_export,
             shutdown_event,
         ),
     )
@@ -116,8 +115,12 @@ def main():
     finally:
         export_loop.stop()
         export_loop.close()
+        logging.info("Export loop shut down")
+
         shutdown_loop.stop()
         shutdown_loop.close()
+        logging.info("Shutdown loop shut down")
+
         logging.info("Shutdown sequence completed successfully!")
 
 

src/const.py

@@ -1,12 +1,24 @@
 import json
 
-DEFAULT_MODE = "production"
-
+# Blockchain.com endpoint and the subscription message which initializes the "transaction stream"
 WS_ADDR = "wss://ws.blockchain.info/coins"
 # Optionally `confirmed_transaction` can be used (bursts of data instead of a steady stream, which is worse for the overall performance)
 SUB_MSG = json.dumps({"coin": "eth", "command": "subscribe", "entity": "pending_transaction"})
-WS_RECONNECT_PAUSE = 2  # Seconds
-WS_INTERMSG_TIMEOUT = 1  # Seconds
 
+# Pause before reconnecting after the WebSocket connection is accidentally dropped by either party
+WS_RECONNECT_PAUSE = 2
+
+# Timeout for asynchronous WebSocket reading (seconds)
+WS_INTERMSG_TIMEOUT = 1
+
+# Timeout for asynchronous queue operations (`coro_get` and `coro_put`, seconds)
+QUEUE_OP_TIMEOUT = 1
+
+# Paths inside the Docker container where data is stored/exported (should match with the mounted volume in `deploy.sh`)
+DEFAULT_DB_PATH = "./data/chainmapper.sqlite3"
 DEFAULT_EXPORT_PATH = "./data/export.json"
-DEFAULT_EXPORT_INTERVAL = 10800  # 3 hours
+
+# Defaults to environment variables (must be strings for this reason, interval in seconds)
+DEFAULT_MODE = "production"
+DEFAULT_EXPORT_INTERVAL = "10800"
+DEFAULT_IS_EXPORT = "False"

src/db.py

@@ -4,13 +4,13 @@ import logging
 import threading
 import asyncio
 
-from src.const import DEFAULT_EXPORT_PATH
+from src.const import DEFAULT_DB_PATH, DEFAULT_EXPORT_PATH
 
 
 class Handler:
     """Handle all SQLite connections required to create, update, and export the stored addresses."""
 
-    def __init__(self, database="chainmapper.sqlite3"):
+    def __init__(self, database=DEFAULT_DB_PATH):
         self.database = database
         # Notably `connect` automatically creates the database if it doesn't already exist
         self.con = sqlite3.connect(self.database, check_same_thread=False)
@@ -78,7 +78,9 @@ class Handler:
         logging.info("Data exported to '%s'", filepath)
 
 
-def periodic_export(loop, handler, interval, shutdown_event):
+def periodic_export(loop, handler, interval, is_export, shutdown_event):
+    """Create a task that exports the internal database based on `interval` (seconds) until `shutdown_event` is set"""
+
     async def task(handler, interval, shutdown_event):
         logging.info("Scheduled export task initialized")
 
@@ -96,5 +98,6 @@ def periodic_export(loop, handler, interval, shutdown_event):
 
         logging.info("Periodic export thread quitting")
 
+    if is_export:
         asyncio.set_event_loop(loop)
         loop.run_until_complete(task(handler, interval, shutdown_event))