Added a metrics endpoint /api/v1/metrics/X which proxies to Prometheus (

#251)

trustgraph-flow/trustgraph/gateway/metrics.py

@@ -0,0 +1,73 @@
+
+#
+# This provides a Prometheus endpoint on the api-gateway.  It proxies
+# HTTP GET requests to Prometheus.
+# 
+
+import aiohttp
+from aiohttp import web
+import asyncio
+from pulsar.schema import JsonSchema
+import uuid
+import logging
+
+logger = logging.getLogger("endpoint")
+logger.setLevel(logging.INFO)
+
+class MetricsEndpoint:
+
+    def __init__(self, prometheus_url, endpoint_path, auth):
+
+        self.prometheus_url = prometheus_url
+        self.path = endpoint_path
+        self.auth = auth
+        self.operation = "service"
+
+    async def start(self):
+        pass
+
+    def add_routes(self, app):
+
+        app.add_routes([
+            web.get(self.path + "/{path:.*}", self.handle),
+        ])
+
+    async def handle(self, request):
+
+        print(request.path, "...")
+
+        try:
+            ht = request.headers["Authorization"]
+            tokens = ht.split(" ", 2)
+            if tokens[0] != "Bearer":
+                return web.HTTPUnauthorized()
+            token = tokens[1]
+        except:
+            token = ""
+
+        if not self.auth.permitted(token, self.operation):
+            return web.HTTPUnauthorized()
+
+        try:
+
+            path = request.match_info["path"]
+
+            async with aiohttp.ClientSession() as session:
+
+                url = (
+                    self.prometheus_url + "/api/v1/" + path + "?" +
+                    request.query_string
+                )
+
+                async with session.get(url) as resp:
+                    return web.Response(
+                        status=resp.status,
+                        text=await resp.text()
+                    )
+
+        except Exception as e:
+
+            logging.error(f"Exception: {e}")
+
+            raise web.HTTPInternalServerError()
+

trustgraph-flow/trustgraph/gateway/service.py

@@ -46,6 +46,7 @@
 from . mux import MuxEndpoint
 from . document_load import DocumentLoadSender
 from . text_load import TextLoadSender
+from . metrics import MetricsEndpoint
 
 from . endpoint import ServiceEndpoint
 from . auth import Authenticator
@@ -54,6 +55,7 @@
 logger.setLevel(logging.INFO)
 
 default_pulsar_host = os.getenv("PULSAR_HOST", "pulsar://pulsar:6650")
+default_prometheus_url = os.getenv("PROMETHEUS_URL", "http://prometheus:9090")
 default_timeout = 600
 default_port = 8088
 default_api_token = os.getenv("GATEWAY_SECRET", "")
@@ -71,6 +73,13 @@ def __init__(self, **config):
         self.timeout = int(config.get("timeout", default_timeout))
         self.pulsar_host = config.get("pulsar_host", default_pulsar_host)
 
+        self.prometheus_url = config.get(
+            "prometheus_url", default_prometheus_url,
+        )
+
+        if not self.prometheus_url.endswith("/"):
+            self.prometheus_url += "/"
+
         api_token = config.get("api_token", default_api_token)
 
         # Token not set, or token equal empty string means no auth
@@ -207,6 +216,11 @@ def __init__(self, **config):
                 auth = self.auth,
                 services = self.services,
             ),
+            MetricsEndpoint(
+                endpoint_path = "/api/v1/metrics",
+                prometheus_url = self.prometheus_url,
+                auth = self.auth,
+            ),
         ]
 
         for ep in self.endpoints:
@@ -235,6 +249,12 @@ def run():
         help=f'Pulsar host (default: {default_pulsar_host})',
     )
 
+    parser.add_argument(
+        '-m', '--prometheus-url',
+        default=default_prometheus_url,
+        help=f'Prometheus URL (default: {default_prometheus_url})',
+    )
+
     parser.add_argument(
         '--port',
         type=int,