add metrics ingestion diagnostics and upgrade cameleer3-common to 0.0.3

- Add logging to MetricsController: warn on parse failures, debug on
  received metrics, buffer depth on 503
- Add GET /api/v1/admin/database/metrics-pipeline diagnostic endpoint
  (buffer depth, row count, distinct agents/metrics, latest timestamp)
- Fix BackpressureIT test JSON to match actual MetricsSnapshot schema
  (collectedAt/metricName/metricValue instead of timestamp/metrics)
- Upgrade cameleer3-common from 1.0-SNAPSHOT to 0.0.3 (adds engineLevel)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

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

@@ -7,6 +7,7 @@ import com.cameleer3.server.app.dto.TableSizeResponse;
 import com.cameleer3.server.core.admin.AuditCategory;
 import com.cameleer3.server.core.admin.AuditResult;
 import com.cameleer3.server.core.admin.AuditService;
+import com.cameleer3.server.core.ingestion.IngestionService;
 import com.zaxxer.hikari.HikariDataSource;
 import com.zaxxer.hikari.HikariPoolMXBean;
 import io.swagger.v3.oas.annotations.Operation;
@@ -24,7 +25,9 @@ import org.springframework.web.bind.annotation.RestController;
 import org.springframework.web.server.ResponseStatusException;
 
 import javax.sql.DataSource;
+import java.time.Instant;
 import java.util.List;
+import java.util.Map;
 
 @RestController
 @RequestMapping("/api/v1/admin/database")
@@ -35,11 +38,14 @@ public class DatabaseAdminController {
     private final JdbcTemplate jdbc;
     private final DataSource dataSource;
     private final AuditService auditService;
+    private final IngestionService ingestionService;
 
-    public DatabaseAdminController(JdbcTemplate jdbc, DataSource dataSource, AuditService auditService) {
+    public DatabaseAdminController(JdbcTemplate jdbc, DataSource dataSource,
+                                   AuditService auditService, IngestionService ingestionService) {
         this.jdbc = jdbc;
         this.dataSource = dataSource;
         this.auditService = auditService;
+        this.ingestionService = ingestionService;
     }
 
     @GetMapping("/status")
@@ -117,6 +123,29 @@ public class DatabaseAdminController {
         return ResponseEntity.ok().build();
     }
 
+    @GetMapping("/metrics-pipeline")
+    @Operation(summary = "Get metrics ingestion pipeline diagnostics")
+    public ResponseEntity<Map<String, Object>> getMetricsPipeline() {
+        int bufferDepth = ingestionService.getMetricsBufferDepth();
+
+        Long totalRows = jdbc.queryForObject(
+                "SELECT count(*) FROM agent_metrics", Long.class);
+        List<String> agentIds = jdbc.queryForList(
+                "SELECT DISTINCT agent_id FROM agent_metrics ORDER BY agent_id", String.class);
+        Instant latestCollected = jdbc.queryForObject(
+                "SELECT max(collected_at) FROM agent_metrics", Instant.class);
+        List<String> metricNames = jdbc.queryForList(
+                "SELECT DISTINCT metric_name FROM agent_metrics ORDER BY metric_name", String.class);
+
+        return ResponseEntity.ok(Map.of(
+                "bufferDepth", bufferDepth,
+                "totalRows", totalRows != null ? totalRows : 0,
+                "distinctAgents", agentIds,
+                "distinctMetrics", metricNames,
+                "latestCollectedAt", latestCollected != null ? latestCollected.toString() : "none"
+        ));
+    }
+
     private String extractHost(DataSource ds) {
         try {
             if (ds instanceof HikariDataSource hds) {

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

@@ -44,13 +44,23 @@ public class MetricsController {
     @Operation(summary = "Ingest agent metrics",
             description = "Accepts an array of MetricsSnapshot objects")
     @ApiResponse(responseCode = "202", description = "Data accepted for processing")
+    @ApiResponse(responseCode = "400", description = "Invalid payload")
     @ApiResponse(responseCode = "503", description = "Buffer full, retry later")
-    public ResponseEntity<Void> ingestMetrics(@RequestBody String body) throws JsonProcessingException {
-        List<MetricsSnapshot> metrics = parsePayload(body);
-        boolean accepted = ingestionService.acceptMetrics(metrics);
+    public ResponseEntity<Void> ingestMetrics(@RequestBody String body) {
+        List<MetricsSnapshot> metrics;
+        try {
+            metrics = parsePayload(body);
+        } catch (JsonProcessingException e) {
+            log.warn("Failed to parse metrics payload: {}", e.getMessage());
+            return ResponseEntity.badRequest().build();
+        }
 
+        log.debug("Received {} metric(s) from agent(s)", metrics.size());
+
+        boolean accepted = ingestionService.acceptMetrics(metrics);
         if (!accepted) {
-            log.warn("Metrics buffer full, returning 503");
+            log.warn("Metrics buffer full ({} items), returning 503",
+                    ingestionService.getMetricsBufferDepth());
             return ResponseEntity.status(HttpStatus.SERVICE_UNAVAILABLE)
                     .header("Retry-After", "5")
                     .build();

cameleer3-server-app/src/test/java/com/cameleer3/server/app/controller/BackpressureIT.java

@@ -50,11 +50,11 @@ class BackpressureIT extends AbstractPostgresIT {
         // Fill the metrics buffer completely with a batch of 5
         String batchJson = """
                 [
-                  {"agentId":"bp-agent","timestamp":"2026-03-11T10:00:00Z","metrics":{}},
-                  {"agentId":"bp-agent","timestamp":"2026-03-11T10:00:01Z","metrics":{}},
-                  {"agentId":"bp-agent","timestamp":"2026-03-11T10:00:02Z","metrics":{}},
-                  {"agentId":"bp-agent","timestamp":"2026-03-11T10:00:03Z","metrics":{}},
-                  {"agentId":"bp-agent","timestamp":"2026-03-11T10:00:04Z","metrics":{}}
+                  {"agentId":"bp-agent","collectedAt":"2026-03-11T10:00:00Z","metricName":"test.metric","metricValue":1.0,"tags":{}},
+                  {"agentId":"bp-agent","collectedAt":"2026-03-11T10:00:01Z","metricName":"test.metric","metricValue":2.0,"tags":{}},
+                  {"agentId":"bp-agent","collectedAt":"2026-03-11T10:00:02Z","metricName":"test.metric","metricValue":3.0,"tags":{}},
+                  {"agentId":"bp-agent","collectedAt":"2026-03-11T10:00:03Z","metricName":"test.metric","metricValue":4.0,"tags":{}},
+                  {"agentId":"bp-agent","collectedAt":"2026-03-11T10:00:04Z","metricName":"test.metric","metricValue":5.0,"tags":{}}
                 ]
                 """;
 
@@ -66,7 +66,7 @@ class BackpressureIT extends AbstractPostgresIT {
 
         // Now buffer should be full -- next POST should get 503
         String overflowJson = """
-                [{"agentId":"bp-agent","timestamp":"2026-03-11T10:00:05Z","metrics":{}}]
+                [{"agentId":"bp-agent","collectedAt":"2026-03-11T10:00:05Z","metricName":"test.metric","metricValue":6.0,"tags":{}}]
                 """;
 
         ResponseEntity<String> response = restTemplate.postForEntity(

pom.xml

@@ -28,7 +28,7 @@
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <java.version>17</java.version>
         <jackson.version>2.17.3</jackson.version>
-        <cameleer3-common.version>1.0-SNAPSHOT</cameleer3-common.version>
+        <cameleer3-common.version>0.0.3</cameleer3-common.version>
         <testcontainers.version>2.0.3</testcontainers.version>
     </properties>