feat(docker): overview findings say when the problem began

#5013 "Overview findings for containers and Swarm services carry since=null"

- Container problems are dated from their own evidence: a crash or restart
  loop from its first death in the hour, an OOM kill or error exit from the
  death that ended it, a failing healthcheck from its last turn to unhealthy.
  list_containers and get_container carry problem_since / problem_age_s.
- Swarm services carry trouble_since: a crash loop's first failure in the
  hour, a short service's oldest troubled task in each failing slot, a
  recovered service's first failure in 24h. list_swarm_services shows it.
- get_overview findings from the docker plugin now have since and age_s,
  so they rank by how long they have stood.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

plugins/docker/swarm_view.py

@@ -120,6 +120,46 @@ def task_summary(tasks: list[dict], now: datetime, crash_loop_deaths: int,
     }
 
 
+def _oldest_failure(tasks: list[dict], since: datetime) -> datetime | None:
+    times = [at for t in tasks if t.get("state") in FAILED_TASK_STATES
+             and (at := task_time(t)) is not None and at >= since]
+    return min(times, default=None)
+
+
+def trouble_since(tasks: list[dict], state: str, crash_looping: bool,
+                  now: datetime) -> datetime | None:
+    """When a service's current trouble began, as far as its retained tasks
+    tell; None when it has none, or the tasks cannot say.
+
+    A crash loop dates from its first failure in the last hour, and a healthy
+    service that lost tasks from its first failure in the last 24h. A service
+    short of replicas dates from its troubled slots (replicated: the slot;
+    global: the node): in each slot whose newest task is not running, the
+    oldest of its newest troubled tasks (failed, rejected, or carrying an
+    error), walking back until a running task interrupts them. Swarm keeps few
+    old tasks, so a long outage reads as the oldest one retained: a lower
+    bound.
+    """
+    if crash_looping:
+        return _oldest_failure(tasks, now - timedelta(hours=1))
+    if state == "healthy":
+        return _oldest_failure(tasks, now - timedelta(hours=24))
+    by_slot: dict = {}
+    for t in tasks:  # newest first, so each slot's list is too
+        by_slot.setdefault(t.get("slot") or t.get("node_id"), []).append(t)
+    began = []
+    for slot_tasks in by_slot.values():
+        oldest = None
+        for t in slot_tasks:
+            if t.get("state") == "running":
+                break
+            if t.get("state") in FAILED_TASK_STATES or t.get("error"):
+                oldest = task_time(t) or oldest
+        if oldest is not None:
+            began.append(oldest)
+    return min(began, default=None)
+
+
 def _slot_key(c) -> str:
     """A task container's slot within its service: "<service>.<slot>.<task>" for
     replicated services, "<service>.<node id>.<task>" for global ones."""
@@ -204,6 +244,7 @@ def build_swarm_services(containers, services, node_hostname: dict, host_name: d
                       without task data); crash_looping = failures_1h ≥ the
                       Settings → Thresholds crash-loop count
       last_error    = last_task_error(), plus `node` (the node's hostname)
+      trouble_since = trouble_since(): when the current trouble began, or None
     standalone[i] = {host_id, host, containers:[...]}  # non-swarm, by host
     superseded    = the task containers Swarm replaced, so callers can skip them
     """
@@ -282,15 +323,19 @@ def build_swarm_services(containers, services, node_hostname: dict, host_name: d
         if desired is None:
             desired = len(replicas)
 
+        tasks = tasks_by_svc.get(name, [])
+        state = _service_state(int(running or 0), int(desired or 0))
+        summary = task_summary(tasks, now, crash_loop_deaths, node_hostname)
         out_services.append({
             "name": name,
             "mode": getattr(svc, "mode", "replicated") if svc is not None else "replicated",
             "running": running,
             "desired": desired,
-            "state": _service_state(int(running or 0), int(desired or 0)),
+            "state": state,
             "replicas": replicas,
             "previous_tasks": previous.get(name, 0),
-            **task_summary(tasks_by_svc.get(name, []), now, crash_loop_deaths, node_hostname),
+            **summary,
+            "trouble_since": trouble_since(tasks, state, summary["crash_looping"], now),
         })
 
     # Non-swarm containers grouped by host, running-first order preserved.