fix(self-host): keep seaweedfs inside its memory ceiling (#2579)

deploy/self-hosting/.env.example

@@ -188,7 +188,7 @@ FLUXER_CAPTCHA_TURNSTILE_SITE_KEY=
 FLUXER_CAPTCHA_TURNSTILE_SECRET_KEY=
 FLUXER_DISCOVERY_ENABLED=true
 
-# Container memory. The 25 limits sum to 16.75 GiB, which is a sum of ceilings and
+# Container memory. The 25 limits sum to 18.25 GiB, which is a sum of ceilings and
 # not an allocation, so the defaults fit a host with 8 GB and are sized for 16 GB.
 # The four reservations are cgroup memory.low, which biases the kernel away from
 # reclaiming from the services whose death takes the whole instance down. They do
@@ -199,7 +199,7 @@ FLUXER_DISCOVERY_ENABLED=true
 #FLUXER_VALKEY_MEMORY_LIMIT=256mb
 #FLUXER_NATS_MEMORY_LIMIT=256mb
 #FLUXER_MEILISEARCH_MEMORY_LIMIT=768mb
-#FLUXER_SEAWEEDFS_MEMORY_LIMIT=512mb
+#FLUXER_SEAWEEDFS_MEMORY_LIMIT=2gb
 #FLUXER_SEAWEEDFS_INIT_MEMORY_LIMIT=128mb
 #FLUXER_LIVEKIT_MEMORY_LIMIT=512mb
 #FLUXER_API_MEMORY_LIMIT=2560mb
@@ -227,6 +227,14 @@ FLUXER_DISCOVERY_ENABLED=true
 # which is the container ceiling the indexer shares with the search process.
 #FLUXER_MEILISEARCH_MAX_INDEXING_MEMORY=384mb
 
+# SeaweedFS heap ceiling. Go collects against this value instead of against the
+# container limit, which it cannot see, so without it an upload burst grows the
+# heap past FLUXER_SEAWEEDFS_MEMORY_LIMIT and the kernel OOM-kills the container
+# mid-upload (exit 137). Keep it near three quarters of that limit, and raise both
+# together: the peak is the parts of one upload in flight at once, which is 25 MB
+# times 20 for a 500 MB attachment.
+#FLUXER_SEAWEEDFS_GOMEMLIMIT=1536MiB
+
 # Node sizes its own heap from the container memory limit by default, at roughly
 # 55 percent of it, which always leaves room for the buffers and stacks that live
 # outside the heap. Leave these unset unless you have a reason to pin the value.