feat: add GET /agents/{id}/metrics endpoint for JVM metrics

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

cameleer3-server-app/src/main/java/com/cameleer3/server/app/config/OpenApiConfig.java

@@ -34,7 +34,7 @@ public class OpenApiConfig {
             "ProcessorNode",
             "AppCatalogEntry", "RouteSummary", "AgentSummary",
             "RouteMetrics", "AgentEventResponse", "AgentInstanceResponse",
-            "ProcessorMetrics"
+            "ProcessorMetrics", "AgentMetricsResponse", "MetricBucket"
     );
 
     @Bean

cameleer3-server-app/src/main/java/com/cameleer3/server/app/controller/AgentMetricsController.java

@@ -0,0 +1,65 @@
+package com.cameleer3.server.app.controller;
+
+import com.cameleer3.server.app.dto.AgentMetricsResponse;
+import com.cameleer3.server.app.dto.MetricBucket;
+import org.springframework.jdbc.core.JdbcTemplate;
+import org.springframework.web.bind.annotation.*;
+
+import java.time.Instant;
+import java.time.temporal.ChronoUnit;
+import java.util.*;
+
+@RestController
+@RequestMapping("/api/v1/agents/{agentId}/metrics")
+public class AgentMetricsController {
+
+    private final JdbcTemplate jdbc;
+
+    public AgentMetricsController(JdbcTemplate jdbc) {
+        this.jdbc = jdbc;
+    }
+
+    @GetMapping
+    public AgentMetricsResponse getMetrics(
+            @PathVariable String agentId,
+            @RequestParam String names,
+            @RequestParam(required = false) Instant from,
+            @RequestParam(required = false) Instant to,
+            @RequestParam(defaultValue = "60") int buckets) {
+
+        if (from == null) from = Instant.now().minus(1, ChronoUnit.HOURS);
+        if (to == null) to = Instant.now();
+
+        List<String> metricNames = Arrays.asList(names.split(","));
+        long intervalMs = (to.toEpochMilli() - from.toEpochMilli()) / Math.max(buckets, 1);
+        String intervalStr = intervalMs + " milliseconds";
+
+        Map<String, List<MetricBucket>> result = new LinkedHashMap<>();
+        for (String name : metricNames) {
+            result.put(name.trim(), new ArrayList<>());
+        }
+
+        String sql = """
+            SELECT time_bucket(CAST(? AS interval), collected_at) AS bucket,
+                   metric_name,
+                   AVG(metric_value) AS avg_value
+            FROM agent_metrics
+            WHERE agent_id = ?
+              AND collected_at >= ? AND collected_at < ?
+              AND metric_name = ANY(?)
+            GROUP BY bucket, metric_name
+            ORDER BY bucket
+            """;
+
+        String[] namesArray = metricNames.stream().map(String::trim).toArray(String[]::new);
+        jdbc.query(sql, rs -> {
+            String metricName = rs.getString("metric_name");
+            Instant bucket = rs.getTimestamp("bucket").toInstant();
+            double value = rs.getDouble("avg_value");
+            result.computeIfAbsent(metricName, k -> new ArrayList<>())
+                  .add(new MetricBucket(bucket, value));
+        }, intervalStr, agentId, from, to, namesArray);
+
+        return new AgentMetricsResponse(result);
+    }
+}

cameleer3-server-app/src/main/java/com/cameleer3/server/app/dto/AgentMetricsResponse.java

@@ -0,0 +1,9 @@
+package com.cameleer3.server.app.dto;
+
+import java.util.List;
+import java.util.Map;
+import jakarta.validation.constraints.NotNull;
+
+public record AgentMetricsResponse(
+    @NotNull Map<String, List<MetricBucket>> metrics
+) {}

cameleer3-server-app/src/main/java/com/cameleer3/server/app/dto/MetricBucket.java

@@ -0,0 +1,9 @@
+package com.cameleer3.server.app.dto;
+
+import java.time.Instant;
+import jakarta.validation.constraints.NotNull;
+
+public record MetricBucket(
+    @NotNull Instant time,
+    double value
+) {}

cameleer3-server-app/src/main/java/com/cameleer3/server/app/security/SecurityConfig.java

@@ -80,6 +80,7 @@ public class SecurityConfig {
                         // Read-only data endpoints — viewer+
                         .requestMatchers(HttpMethod.GET, "/api/v1/executions/**").hasAnyRole("VIEWER", "OPERATOR", "ADMIN")
                         .requestMatchers(HttpMethod.GET, "/api/v1/diagrams/**").hasAnyRole("VIEWER", "OPERATOR", "ADMIN")
+                        .requestMatchers(HttpMethod.GET, "/api/v1/agents/*/metrics").hasAnyRole("VIEWER", "OPERATOR", "ADMIN")
                         .requestMatchers(HttpMethod.GET, "/api/v1/agents").hasAnyRole("VIEWER", "OPERATOR", "ADMIN")
                         .requestMatchers(HttpMethod.GET, "/api/v1/agents/events-log").hasAnyRole("VIEWER", "OPERATOR", "ADMIN")
                         .requestMatchers(HttpMethod.GET, "/api/v1/routes/**").hasAnyRole("VIEWER", "OPERATOR", "ADMIN")