Updates docs

Author: grussorusso

docs/metrics.md

@@ -1,90 +1,26 @@
 # Metrics
 
+A simple metrics system is available to export/retrieve metrics to/from Prometheus.
+
 The metrics system must be enabled via `metrics.enabled`.
-If enabled, metrics are exposed at `http://localhost:2112/metrics`.
+If enabled, metrics can be scraped by any Prometheus server through the `/metrics` 
+API of every Serverledge node.
 
-You can check that the metrics system is working without starting a Prometheus
-server:
+If you have a local Serverledge node, you can check that the metrics system is
+working without starting a Prometheus server:
 
-	$ curl 127.0.0.1:2112/metrics 
+	$ curl 127.0.0.1:1323/metrics 
 
+If you start a local Prometheus server, you can browse `http://127.0.0.1:9090`.
 
 ## Available metrics
 
-A few metrics are currently exposed (just for demonstration purposes):
-
-- `sedge_completed_total`: number of completed invocations (Counter, per function)
-- `sedge_exectime`: execution time for each function (Histogram, per function)
-
-
-## Prometheus Integration
-
-Various Prometheus configurations can be considered to scrape Serverledge
-metrics:
-
-- A centralized Prometheus server in the Cloud (likely not scalable...)
-- A Prometheus server in each Edge zone
-- A Prometheus server in the Cloud with a Prometheus Agent on each Serverledge
-  node (details below)
-
-### Example: Prometheus Agent + Cloud
-
-As regards the last option, it requires Prometheus instances to use the
-following (minimal) configuration.
-
-In the Serverledge node,
-Prometheus must be started with `--enable-feature=agent` and the following
-lines in the configuration:
-
-	remote_write:
-	  - url: "http://<prometheus_cloud_host>:9091/api/v1/write"
-
-Example configuration:
-
-	global:
-	  scrape_interval: 15s # Set the scrape interval to every 15 seconds. Default is every 1 minute.
-	  evaluation_interval: 15s # Evaluate rules every 15 seconds. The default is every 1 minute.
-	  # scrape_timeout is set to the global default (10s).
-
-	# A scrape configuration containing exactly one endpoint to scrape:
-	scrape_configs:
-	  - job_name: "serverledge"
-	    # metrics_path defaults to '/metrics'
-	    # scheme defaults to 'http'.
-	    static_configs:
-	      - targets: ["<serverledge_host>:2112"]
-
-	remote_write:
-	  - url: "http://<prometheus_cloud_host>:9091/api/v1/write"
-
-In the Cloud, Prometheus must be started with `--web.enable-remote-write-receiver`.
-Example configuration:
-
-	global:
-	  scrape_interval: 15s # Set the scrape interval to every 15 seconds. Default is every 1 minute.
-	  evaluation_interval: 15s # Evaluate rules every 15 seconds. The default is every 1 minute.
-
-Example script to launch both Prometheus instances on the same host (for
-testing):
-
-	docker run \
-	    --name prom \
-	    -d \
-	    -p 9090:9090 \
-	    -v $(pwd)/prometheus.yml:/etc/prometheus/prometheus.yml \
-	    prom/prometheus --enable-feature=agent \
-		--config.file=/etc/prometheus/prometheus.yml
+A few metrics are currently updated (see `internal/metrics/metrics.go`).
 
-	docker run \
-	    --name promRemote \
-	    -d\
-	    \
-	    -p 9091:9090 \
-	    -v $(pwd)/prometheus_remote.yml:/etc/prometheus/prometheus.yml \
-	    prom/prometheus --web.enable-remote-write-receiver \
-		--config.file=/etc/prometheus/prometheus.yml
+## Configuration
 
-### References
+Relevant configuration options:
 
-- [Prometheus Agent Mode](https://prometheus.io/blog/2021/11/16/agent/)
-- [Prometheus + Go](https://prometheus.io/docs/guides/go-application/)
+- `metrics.prometheus.host`: Prometheus server IP/hostname (for queries)
+- `metrics.prometheus.port`: Prometheus server port (for queries)
+- `metrics.retriever.interval`: Interval (in seconds) for metrics retrieval from Prometheus