add optional prometheus to dht_node script

scripts/dht_node.py

@@ -2,6 +2,8 @@ import asyncio
 import argparse
 import logging
 from typing import Optional
+from aiohttp import web
+from prometheus_client import generate_latest as prom_generate_latest, Gauge
 
 from lbry.dht.constants import generate_id
 from lbry.dht.node import Node
@@ -11,9 +13,43 @@ from lbry.conf import Config
 
 logging.basicConfig(level=logging.INFO, format="%(asctime)s %(levelname)-4s %(name)s:%(lineno)d: %(message)s")
 log = logging.getLogger(__name__)
+BLOBS_STORED = Gauge(
+    "blobs_stored", "Number of blob info received", namespace="dht_node",
+    labelnames=("method",)
+)
+PEERS = Gauge(
+    "known_peers", "Number of peers on routing table", namespace="dht_node",
+    labelnames=("method",)
+)
 
 
-async def main(host: str, port: int, db_file_path: str, bootstrap_node: Optional[str]):
+class SimpleMetrics:
+    def __init__(self, port):
+        self.prometheus_port = port
+
+    async def handle_metrics_get_request(self, request: web.Request):
+        try:
+            return web.Response(
+                text=prom_generate_latest().decode(),
+                content_type='text/plain; version=0.0.4'
+            )
+        except Exception:
+            log.exception('could not generate prometheus data')
+            raise
+
+    async def start(self):
+        prom_app = web.Application()
+        prom_app.router.add_get('/metrics', self.handle_metrics_get_request)
+        metrics_runner = web.AppRunner(prom_app)
+        await metrics_runner.setup()
+        prom_site = web.TCPSite(metrics_runner, "0.0.0.0", self.prometheus_port)
+        await prom_site.start()
+
+
+async def main(host: str, port: int, db_file_path: str, bootstrap_node: Optional[str], prometheus_port: int):
+    if prometheus_port > 0:
+        metrics = SimpleMetrics(prometheus_port)
+        await metrics.start()
     loop = asyncio.get_event_loop()
     conf = Config()
     storage = SQLiteStorage(conf, db_file_path, loop, loop.time)
@@ -30,6 +66,8 @@ async def main(host: str, port: int, db_file_path: str, bootstrap_node: Optional
     node.start(host, nodes)
     while True:
         await asyncio.sleep(10)
+        PEERS.labels('main').set(len(node.protocol.routing_table.get_peers()))
+        BLOBS_STORED.labels('main').set(len(node.protocol.data_store.get_storing_contacts()))
         log.info("Known peers: %d. Storing contact information for %d blobs from %d peers.",
                  len(node.protocol.routing_table.get_peers()), len(node.protocol.data_store),
                  len(node.protocol.data_store.get_storing_contacts()))
@@ -44,5 +82,6 @@ if __name__ == '__main__':
     parser.add_argument("--bootstrap_node", default=None, type=str,
                         help="Node to connect for bootstraping this node. Leave unset to use the default ones. "
                              "Format: host:port Example: lbrynet1.lbry.com:4444")
+    parser.add_argument("--prometheus_port", default=0, type=int, help="Port for Prometheus metrics. 0 to disable. Default: 0")
     args = parser.parse_args()
-    asyncio.run(main(args.host, args.port, args.db_file, args.bootstrap_node))
+    asyncio.run(main(args.host, args.port, args.db_file, args.bootstrap_node, args.prometheus_port))