Configure collector.textfile for node exporter

Future metrics can write text files for metrics,
this will be useful for tracking archive upload lag & LSNs

Author: serprex

common/assets/node_exporter.service

@@ -17,6 +17,8 @@ ExecStart=/usr/bin/node_exporter \
     --collector.meminfo \
     --collector.netdev \
     --collector.uname \
+    --collector.textfile \
+    --collector.textfile.directory=/var/lib/node_exporter \
     --web.disable-exporter-metrics \
     --collector.diskstats.device-exclude="^(z?ram|loop|fd|(h|s|v|xv)d[a-z]|nvme\\d+n\\d+p)\\d+$|vda|vdc" \
     --collector.filesystem.mount-points-exclude="^/(dev|proc|run|sys|var|boot|)($|/)"

common/setup_monitoring.sh

@@ -45,6 +45,7 @@ echo "=== [setup_monitoring.sh] Installing systemd service files ==="
 echo "[setup_monitoring.sh] Copying systemd unit files..."
 cp /tmp/common/assets/prometheus.service /etc/systemd/system/prometheus.service
 cp /tmp/common/assets/node_exporter.service /etc/systemd/system/node_exporter.service
+mkdir -p /var/lib/node_exporter
 cp /tmp/common/assets/postgres_exporter.service /etc/systemd/system/postgres_exporter.service
 cp /tmp/common/assets/wal-g.service /etc/systemd/system/wal-g.service