infra/observability/tempo/tempo.yaml

@@ -25,3 +25,15 @@ storage:
       path: /var/tempo/blocks
     wal:
       path: /var/tempo/wal
+
+# #156: don't let the distributor evict its own ingester. Tempo runs single-binary here, so the
+# distributor and the ingester are the same process and the "pool" holds exactly one, in-process,
+# member. dskit still health-checks it over loopback gRPC with a 1s deadline (checkinterval 15s);
+# on the shared CI runner a transient stall blows that deadline, the only ingester is dropped from
+# the pool ("removing distributor_pool failing healthcheck"), and every push then fails ("pusher
+# failed to consume trace data", err="context canceled") until the next check — silently losing
+# spans, which is how verify-tracing flaked. With one in-process ingester the check can never route
+# around a failure, so it can only ever discard data. Turn it off.
+ingester_client:
+  pool_config:
+    healthcheckenabled: false

infra/tracing-check.py

@@ -59,6 +59,20 @@ def services_in_trace(trace_id):
     return names
 
 
+def tempo_ingest_state():
+    """#156: distinguish a broken trace chain from Tempo dropping spans. `ingester_clients` is 0
+    when the distributor has evicted its (single, in-process) ingester over a failed loopback
+    health check — pushes fail and spans are lost, which looks identical to missing instrumentation
+    from here. Diagnostics only; never fails the check."""
+    try:
+        for line in _get(f"{TEMPO}/metrics").decode().splitlines():
+            if line.startswith("tempo_distributor_ingester_clients "):
+                return f"tempo {line.strip()} (0 = no ingester in the pool — evicted, so pushes\n       are failing and spans are being dropped; see #156)"
+    except Exception as e:
+        return f"tempo /metrics unreadable: {e}"
+    return "tempo_distributor_ingester_clients not reported"
+
+
 def main():
     deadline = time.time() + TIMEOUT
     generate_traffic()
@@ -74,6 +88,7 @@ def main():
         generate_traffic()
     print(f"FAIL — no single trace spanned {sorted(WANT)}; services seen: {sorted(seen)}",
           file=sys.stderr)
+    print(f"       {tempo_ingest_state()}", file=sys.stderr)
     return 1