Add disk-space and DB-size monitoring to Telegraf

Telegraf now collects host filesystem usage ([[inputs.disk]], via a
read-only /hostfs mount) and PostgreSQL database + per-table sizes
([[inputs.postgresql_extensible]]) into InfluxDB. Surfaces RIB growth
and disk pressure — relevant now that the full-table GoBGP feed has
pushed the openbmp DB to ~30 GB.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docker-compose.yml

@@ -339,10 +339,20 @@ services:
     entrypoint: ["telegraf"]
     volumes:
       - /var/run/docker.sock:/var/run/docker.sock
+      # Host root, read-only — lets [[inputs.disk]] report the real host
+      # filesystems (Postgres/Kafka/InfluxDB data) instead of the container's.
+      - /:/hostfs:ro
     depends_on:
       - influxdb
     environment:
       - INFLUXDB_TOKEN=openbmp-telemetry-token
+      # Point gopsutil-based inputs (disk) at the host filesystem mount above.
+      - HOST_MOUNT_PREFIX=/hostfs
+      - HOST_PROC=/hostfs/proc
+      - HOST_SYS=/hostfs/sys
+      - HOST_ETC=/hostfs/etc
+      # PostgreSQL credentials for [[inputs.postgresql_extensible]] (DB size).
+      - POSTGRES_PASSWORD=${POSTGRES_PASSWORD:-openbmp}
       # gNMI fleet — quoted, comma-separated host:port list. Default = the two
       # ESXi CORE routers; extend via GNMI_ADDRESSES in .env for more routers.
       - 'GNMI_ADDRESSES=${GNMI_ADDRESSES:-"10.100.0.100:57400", "10.100.0.200:57400"}'

telegraf/telegraf.conf

@@ -64,6 +64,28 @@
   total = true
   timeout = "10s"
 
+## Host filesystem usage — free/used space on the volumes holding the
+## Postgres data, Kafka, InfluxDB and the OpenBMP data root. The host root is
+## bind-mounted read-only at /hostfs and HOST_MOUNT_PREFIX / HOST_PROC (set in
+## docker-compose.yml) point the plugin at the host, not the container.
+[[inputs.disk]]
+  interval = "60s"
+  ignore_fs = ["tmpfs", "devtmpfs", "devfs", "overlay", "aufs", "squashfs", "ramfs", "nsfs", "iso9660"]
+
+## PostgreSQL database + table sizes — tracks RIB growth, which expands
+## sharply once the full-table GoBGP feed is ingesting (~1M routes).
+[[inputs.postgresql_extensible]]
+  interval = "60s"
+  address = "host=localhost port=5432 user=openbmp password=${POSTGRES_PASSWORD} dbname=openbmp sslmode=disable"
+  [[inputs.postgresql_extensible.query]]
+    sqlquery = "SELECT datname, pg_database_size(datname) AS bytes FROM pg_database WHERE datname = 'openbmp'"
+    measurement = "postgresql_db_size"
+    tagvalue = "datname"
+  [[inputs.postgresql_extensible.query]]
+    sqlquery = "SELECT c.relname AS tablename, pg_total_relation_size(c.oid) AS bytes FROM pg_class c JOIN pg_namespace n ON n.oid = c.relnamespace WHERE n.nspname = 'public' AND c.relkind = 'r' ORDER BY 2 DESC LIMIT 20"
+    measurement = "postgresql_table_size"
+    tagvalue = "tablename"
+
 ###############################################################################
 #                            OUTPUT PLUGINS                                   #
 ###############################################################################