nix/host-modules/swarm-otel.nix

@@ -1106,13 +1106,10 @@ in
                 # switch, and its `matches` field is an allowlist too, so
                 # "everything except user sessions" is not expressible.
                 #
-                # Attribution is journald's either way — these fields are
-                # written by it rather than by the logging process. ⚠️ Use
-                # `_MACHINE_ID` to tell machines apart, not `_HOSTNAME`: an
-                # agent container reports the NixOS default `nixos`. Whether
-                # every container does, and why the `networking.hostName`
-                # nixos-containers sets does not reach them, is unresolved —
-                # so rely on the field that is per-machine by construction.
+                # Attribution is journald's either way — `_HOSTNAME`,
+                # `_SYSTEMD_UNIT` and `_MACHINE_ID` are written by journald
+                # rather than by the logging process, so a reader can still
+                # tell the origins apart.
                 // lib.optionalAttrs collectLogs {
                   journald = {
                     directory = hostJournalDir;
@@ -1159,17 +1156,10 @@ in
                 # fields, so without `_msg_field` every record stores the
                 # literal `missing _msg field` as its message and text search
                 # finds nothing, while ingest keeps answering 200.
-                # `_stream_fields` is one stream per unit per machine.
-                # `_MACHINE_ID` is what makes that true — it is per-machine by
-                # construction, where `_HOSTNAME` is only as distinct as the
-                # hostnames happen to be, and an agent container's is the
-                # NixOS default `nixos`. Keying on the hostname alone merges
-                # the streams of any two machines sharing one, which is what
-                # the host and containerised `opentelemetry-collector.service`
-                # would do.
+                # `_stream_fields` is one stream per unit per machine instead
+                # of one for the whole host.
                 "otlphttp/victorialogs" = {
-                  logs_endpoint =
-                    logsPushUrl + "?_msg_field=MESSAGE&_stream_fields=_HOSTNAME,_MACHINE_ID,_SYSTEMD_UNIT";
+                  logs_endpoint = logsPushUrl + "?_msg_field=MESSAGE&_stream_fields=_HOSTNAME,_SYSTEMD_UNIT";
                 }
                 // lib.optionalAttrs haveCollectorSecret {
                   auth.authenticator = pushAuthenticator "victorialogs";

nix/module-eval.nix

@@ -1437,18 +1437,6 @@ let
         && lib.hasInfix "metrics.t.local" m
         && lib.hasInfix "logs.t.local" l;
     }
-    {
-      # `_HOSTNAME` cannot separate containers: none sets
-      # `networking.hostName`, so it is `nixos` for all of them and every
-      # container's stream for a unit name merges into one.
-      name = "the log stream is keyed by machine, not only by a hostname every container shares";
-      ok =
-        let
-          l = (otelSettings otelNoStores).exporters."otlphttp/victorialogs".logs_endpoint;
-          field = f: lib.hasInfix ("_stream_fields=" + f) l || lib.hasInfix ("," + f) l;
-        in
-        field "_MACHINE_ID" && field "_SYSTEMD_UNIT" && !(field "_NOSUCHFIELD");
-    }
     {
       # The collector reaches these routes through the gateway now, so each
       # store needs an ingest location of its own. Without one the write rides