test: A2A health monitor tests

Part of #822

hermes_cli/a2a_health.py

@@ -0,0 +1,257 @@
+"""
+A2A Health Monitor — Fleet Agent Heartbeat (#822)
+
+Pings each fleet agent's A2A endpoint and tracks health status.
+Persists state to ~/.hermes/a2a_health.json.
+
+Usage:
+    from hermes_cli.a2a_health import check_fleet_health, check_agent_health
+    
+    report = check_fleet_health()
+    for agent in report["agents"]:
+        print(f"{agent['name']}: {agent['status']} ({agent['response_ms']}ms)")
+"""
+
+import json
+import time
+import urllib.request
+import urllib.error
+from pathlib import Path
+from typing import Any, Dict, List, Optional
+
+HERMES_HOME = Path.home() / ".hermes"
+FLEET_CONFIG = HERMES_HOME / "fleet_agents.json"
+HEALTH_STATE = HERMES_HOME / "a2a_health.json"
+
+CONSECUTIVE_FAILURE_THRESHOLD = 3
+SLOW_RESPONSE_MS = 10000
+
+
+def load_fleet_config() -> List[Dict[str, Any]]:
+    """Load fleet agent definitions."""
+    if not FLEET_CONFIG.exists():
+        return []
+    try:
+        with open(FLEET_CONFIG) as f:
+            data = json.load(f)
+        return data.get("agents", [])
+    except Exception:
+        return []
+
+
+def load_health_state() -> Dict[str, Any]:
+    """Load persisted health state."""
+    if not HEALTH_STATE.exists():
+        return {"agents": {}, "last_check": None}
+    try:
+        with open(HEALTH_STATE) as f:
+            return json.load(f)
+    except Exception:
+        return {"agents": {}, "last_check": None}
+
+
+def save_health_state(state: Dict[str, Any]):
+    """Persist health state."""
+    HEALTH_STATE.parent.mkdir(parents=True, exist_ok=True)
+    with open(HEALTH_STATE, "w") as f:
+        json.dump(state, f, indent=2)
+
+
+def ping_agent(base_url: str, timeout: int = 10) -> Dict[str, Any]:
+    """
+    Ping an agent's A2A endpoint.
+    
+    Tries /health first, falls back to /.well-known/agent-card.json.
+    """
+    start = time.monotonic()
+    endpoints = ["/health", "/.well-known/agent-card.json"]
+    
+    for endpoint in endpoints:
+        url = f"{base_url.rstrip('/')}{endpoint}"
+        try:
+            req = urllib.request.Request(url, method="GET")
+            req.add_header("User-Agent", "hermes-a2a-health/1.0")
+            with urllib.request.urlopen(req, timeout=timeout) as resp:
+                elapsed = (time.monotonic() - start) * 1000
+                body = resp.read(1024).decode("utf-8", errors="replace")
+                
+                result = {
+                    "alive": True,
+                    "status_code": resp.status,
+                    "endpoint": endpoint,
+                    "response_ms": round(elapsed, 1),
+                }
+                
+                # Parse agent card if available
+                if endpoint == "/.well-known/agent-card.json":
+                    try:
+                        card = json.loads(body)
+                        result["agent_card"] = {
+                            "name": card.get("name", "unknown"),
+                            "tools_count": len(card.get("skills", [])),
+                        }
+                    except Exception:
+                        pass
+                
+                return result
+        except urllib.error.URLError:
+            continue
+        except Exception:
+            continue
+    
+    elapsed = (time.monotonic() - start) * 1000
+    return {
+        "alive": False,
+        "error": "All endpoints unreachable",
+        "response_ms": round(elapsed, 1),
+    }
+
+
+def check_agent_health(agent: Dict[str, Any], prev_state: Dict[str, Any]) -> Dict[str, Any]:
+    """Check health of a single agent."""
+    name = agent.get("name", "unknown")
+    base_url = ""
+    
+    # Get URL from agent config
+    interfaces = agent.get("supportedInterfaces", [])
+    if interfaces:
+        base_url = interfaces[0].get("url", "")
+    if not base_url:
+        base_url = agent.get("url", "")
+    
+    if not base_url:
+        return {
+            "name": name,
+            "status": "error",
+            "error": "No URL configured",
+            "consecutive_failures": 0,
+        }
+    
+    # Ping
+    result = ping_agent(base_url)
+    
+    # Get previous state
+    prev = prev_state.get("agents", {}).get(name, {})
+    prev_failures = prev.get("consecutive_failures", 0)
+    
+    # Update failure count
+    if result["alive"]:
+        consecutive_failures = 0
+        status = "healthy"
+    else:
+        consecutive_failures = prev_failures + 1
+        if consecutive_failures >= CONSECUTIVE_FAILURE_THRESHOLD:
+            status = "down"
+        else:
+            status = "degraded"
+    
+    # Check for slow response
+    if result["alive"] and result.get("response_ms", 0) > SLOW_RESPONSE_MS:
+        status = "slow"
+    
+    return {
+        "name": name,
+        "url": base_url,
+        "status": status,
+        "alive": result["alive"],
+        "response_ms": result.get("response_ms"),
+        "endpoint": result.get("endpoint"),
+        "status_code": result.get("status_code"),
+        "agent_card": result.get("agent_card"),
+        "consecutive_failures": consecutive_failures,
+        "error": result.get("error"),
+        "checked_at": time.strftime("%Y-%m-%dT%H:%M:%S"),
+    }
+
+
+def check_fleet_health(
+    agent_name: Optional[str] = None,
+    timeout: int = 10,
+) -> Dict[str, Any]:
+    """
+    Check health of all (or one) fleet agent.
+    
+    Returns report dict with agents list and summary.
+    """
+    agents = load_fleet_config()
+    prev_state = load_health_state()
+    
+    if agent_name:
+        agents = [a for a in agents if a.get("name") == agent_name]
+    
+    results = []
+    for agent in agents:
+        result = check_agent_health(agent, prev_state)
+        results.append(result)
+    
+    # Update persisted state
+    new_state = {
+        "agents": {r["name"]: r for r in results},
+        "last_check": time.strftime("%Y-%m-%dT%H:%M:%S"),
+    }
+    save_health_state(new_state)
+    
+    # Summary
+    healthy = sum(1 for r in results if r["status"] == "healthy")
+    degraded = sum(1 for r in results if r["status"] == "degraded")
+    slow = sum(1 for r in results if r["status"] == "slow")
+    down = sum(1 for r in results if r["status"] in ("down", "error"))
+    
+    return {
+        "agents": results,
+        "summary": {
+            "total": len(results),
+            "healthy": healthy,
+            "degraded": degraded,
+            "slow": slow,
+            "down": down,
+            "all_healthy": down == 0 and degraded == 0,
+        },
+        "checked_at": time.strftime("%Y-%m-%dT%H:%M:%S"),
+    }
+
+
+def format_health_dashboard(report: Dict[str, Any]) -> str:
+    """Format health report as text dashboard."""
+    lines = []
+    summary = report["summary"]
+    
+    # Header
+    if summary["all_healthy"]:
+        lines.append("\u2705 All fleet agents healthy")
+    elif summary["down"] > 0:
+        lines.append(f"\u274c {summary['down']} agent(s) DOWN")
+    else:
+        lines.append(f"\u26a0\ufe0f Fleet degraded: {summary['degraded']} degraded, {summary['slow']} slow")
+    
+    lines.append(f"Checked: {report['checked_at']}")
+    lines.append("")
+    
+    # Agent details
+    for agent in report["agents"]:
+        status_icon = {
+            "healthy": "\u2705",
+            "degraded": "\u26a0\ufe0f",
+            "slow": "\u23f1\ufe0f",
+            "down": "\u274c",
+            "error": "\u274c",
+        }.get(agent["status"], "\u2753")
+        
+        name = agent["name"]
+        ms = agent.get("response_ms", "?")
+        failures = agent.get("consecutive_failures", 0)
+        
+        line = f"  {status_icon} {name}"
+        if agent.get("alive"):
+            line += f" — {ms}ms"
+            if agent.get("agent_card"):
+                tools = agent["agent_card"].get("tools_count", 0)
+                line += f" — {tools} tools"
+        else:
+            line += f" — {agent.get('error', 'unreachable')}"
+            if failures > 0:
+                line += f" ({failures} consecutive failures)"
+        
+        lines.append(line)
+    
+    return "\n".join(lines)

tests/test_a2a_health.py

@@ -0,0 +1,80 @@
+"""Tests for A2A health monitor (#822)."""
+
+import sys
+import json
+import tempfile
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).parent.parent))
+
+from hermes_cli.a2a_health import (
+    ping_agent,
+    check_agent_health,
+    check_fleet_health,
+    format_health_dashboard,
+    load_health_state,
+    save_health_state,
+)
+
+
+def test_ping_agent_unreachable():
+    """Ping returns alive=False for unreachable endpoint."""
+    result = ping_agent("http://192.0.2.1:9999", timeout=2)
+    assert not result["alive"]
+    assert "error" in result
+
+
+def test_check_agent_no_url():
+    """Agent without URL returns error status."""
+    result = check_agent_health({"name": "test"}, {})
+    assert result["status"] == "error"
+
+
+def test_format_dashboard():
+    """Dashboard formats correctly."""
+    report = {
+        "agents": [
+            {"name": "ezra", "status": "healthy", "alive": True, "response_ms": 50},
+            {"name": "allegro", "status": "down", "alive": False, "error": "timeout"},
+        ],
+        "summary": {"total": 2, "healthy": 1, "degraded": 0, "slow": 0, "down": 1, "all_healthy": False},
+        "checked_at": "2026-04-15T12:00:00",
+    }
+    dashboard = format_health_dashboard(report)
+    assert "ezra" in dashboard
+    assert "allegro" in dashboard
+    assert "DOWN" in dashboard
+
+
+def test_state_persistence():
+    """Health state persists correctly."""
+    with tempfile.TemporaryDirectory() as tmpdir:
+        state_file = Path(tmpdir) / "health.json"
+        state = {"agents": {"test": {"alive": True}}, "last_check": "now"}
+        
+        with open(state_file, "w") as f:
+            json.dump(state, f)
+        
+        with open(state_file) as f:
+            loaded = json.load(f)
+        
+        assert loaded["agents"]["test"]["alive"] is True
+
+
+def test_consecutive_failures():
+    """Failure count increments correctly."""
+    prev = {"agents": {"test": {"consecutive_failures": 2}}}
+    agent = {"name": "test", "url": "http://192.0.2.1:9999"}
+    result = check_agent_health(agent, prev)
+    assert result["consecutive_failures"] == 3
+    assert result["status"] == "down"
+
+
+if __name__ == "__main__":
+    tests = [test_ping_agent_unreachable, test_check_agent_no_url,
+             test_format_dashboard, test_state_persistence, test_consecutive_failures]
+    for t in tests:
+        print(f"Running {t.__name__}...")
+        t()
+        print("  PASS")
+    print("\nAll tests passed.")