added some information to the README and added Swarm placement constr…

…aints to the compose file

README.md

@@ -1 +1,18 @@
-# prometheus-swarm-discovery
+# Prometheus-Swarm service discovery
+
+This is POC that demonstrates Prometheus service discovery in Docker Swarm. It is implemented as a standalone tool
+that writes the scrape targets to a file, that is then read by Prometheus. This uses the `<file_sd_config>` config
+directive available in Prometheus.
+
+The discovery tool expects to have access to the Swarm API using `/var/run/docker.sock`. The provided `docker-compose.yaml`
+is configured to mount the `docker.sock` file inside the container, and this requires that the `swarm-discover` container
+is placed on the Swarm manager node.
+
+## Run Prometheus and the Swarm discovery tool
+
+The only thing required to run Prometheus and the discovery tool is to launch a Swarm stack using the provided docker-compose.yaml
+file.
+
+```
+$ docker stack deploy -c docker-compose.yaml prometheus
+```

docker-compose.yaml

@@ -9,14 +9,20 @@ services:
  - swarm-endpoints:/swarm-endpoints/
  labels:
  prometheus.ignore: "true"
+ placement:
+ constraints:
+ - node.role == manager
  prometheus:
  image: prom/prometheus:v1.5.2
  ports:
  - '9090:9090'
  volumes:
  - ./prometheus-configs/:/etc/prometheus
  - swarm-endpoints:/etc/swarm-endpoints/
- command: ["-storage.local.retention=48h", "-storage.local.memory-chunks=1048576", "-config.file=/etc/prometheus/prometheus.yaml"]
+ command: ["-storage.local.retention=2h", "-storage.local.memory-chunks=1048576", "-config.file=/etc/prometheus/prometheus.yaml"]
+ placement:
+ constraints:
+ - node.role == manager
 
 volumes:
- swarm-endpoints:
+ swarm-endpoints: