fix(self-host): size memory limits and make them overridable (#2234)

deploy/self-hosting/.env.example

@@ -65,3 +65,35 @@ FLUXER_EMAIL_SMTP_SECURE=true
 FLUXER_CAPTCHA_ENABLED=false
 FLUXER_CAPTCHA_PROVIDER=none
 FLUXER_DISCOVERY_ENABLED=true
+
+# Container memory. Every service limit and reservation below has a default that
+# assumes a host with at least 16 GB of RAM. Limits are per-container ceilings, so
+# their sum may exceed host RAM; the reservations are what protect the services
+# whose death takes the whole instance down. Lower these on a smaller host.
+#FLUXER_POSTGRES_MEMORY_LIMIT=5gb
+#FLUXER_POSTGRES_MEMORY_RESERVATION=3gb
+#FLUXER_API_MEMORY_LIMIT=2560mb
+#FLUXER_API_MEMORY_RESERVATION=1gb
+#FLUXER_WORKER_MEMORY_LIMIT=2560mb
+#FLUXER_WORKER_MEMORY_RESERVATION=1gb
+#FLUXER_GATEWAY_MEMORY_LIMIT=1gb
+#FLUXER_MEILISEARCH_MEMORY_LIMIT=768mb
+
+# The Node heap ceiling must stay below the container limit above, with room to
+# spare: V8 adds roughly 200 MB of semi-space on top of the value set here, and
+# buffers live outside the heap entirely. Around 70 percent of the container limit
+# is a safe ratio. If the heap ceiling exceeds the container limit, the kernel
+# OOM-kills the container (exit 137, no diagnostics) instead of Node reporting a
+# JavaScript heap out of memory error you can act on.
+#FLUXER_API_NODE_HEAP_MB=1792
+#FLUXER_WORKER_NODE_HEAP_MB=1792
+
+# Bundled Postgres tuning. Keep these consistent with FLUXER_POSTGRES_MEMORY_LIMIT:
+# budget roughly shared_buffers + (server max_connections x 12 MB) +
+# (3 x autovacuum_work_mem) + 300 MB for page cache and WAL. Note this is the
+# server setting, distinct from the per-service FLUXER_POSTGRES_MAX_CONNECTIONS
+# pool sizes used by the api, worker, app-proxy and shards.
+#FLUXER_POSTGRES_SERVER_MAX_CONNECTIONS=150
+#FLUXER_POSTGRES_SHARED_BUFFERS=512MB
+#FLUXER_POSTGRES_EFFECTIVE_CACHE_SIZE=2GB
+#FLUXER_POSTGRES_WORK_MEM=8MB