fix: replace eval with sed + exit if PROM_REMOTE_WRITE_TOKEN is empty (#301)

Author: apham0001

docker-compose.yml

@@ -153,7 +153,7 @@ services:
     user: ":"
     networks: [dvnode]
     environment:
-      PROM_REMOTE_WRITE_TOKEN: ${PROM_REMOTE_WRITE_TOKEN:-"obol-monitoring-token-needed"}
+      PROM_REMOTE_WRITE_TOKEN: ${PROM_REMOTE_WRITE_TOKEN}
       SERVICE_OWNER: ${SERVICE_OWNER:-"obol-cdvn"}
     volumes:
       - ./prometheus:/etc/prometheus

prometheus/run.sh

@@ -7,11 +7,13 @@ fi
 
 if [ -z "$PROM_REMOTE_WRITE_TOKEN" ]
 then
-  echo "\$PROM_REMOTE_WRITE_TOKEN variable is empty"
+  echo "\$PROM_REMOTE_WRITE_TOKEN variable is empty" >&2
+  exit 1
 fi
 
-# eval is used instead of envsubst, as prometheus user doesn't have permissions to install envsubst
-eval "echo \"$(cat /etc/prometheus/prometheus.yml.example)\"" > /etc/prometheus/prometheus.yml
+
+sed "s|\$PROM_REMOTE_WRITE_TOKEN|${PROM_REMOTE_WRITE_TOKEN}|g" \
+    /etc/prometheus/prometheus.yml.example > /etc/prometheus/prometheus.yml
 
 /bin/prometheus \
   --config.file=/etc/prometheus/prometheus.yml