Added logic to track response size

Author: subkanthi

ice-rest-catalog/src/main/java/com/altinity/ice/rest/catalog/internal/metrics/HttpMetrics.java

@@ -25,6 +25,7 @@ public class HttpMetrics {
   private final Counter responsesTotal;
   private final Histogram requestDuration;
   private final Gauge requestsInFlight;
+  private final Counter responseSizeBytes;
 
   public static HttpMetrics getInstance() {
     if (instance == null) {
@@ -65,20 +66,31 @@ private HttpMetrics() {
             .name(HTTP_REQUESTS_IN_FLIGHT_NAME)
             .help(HTTP_REQUESTS_IN_FLIGHT_HELP)
             .register();
+
+    this.responseSizeBytes =
+        Counter.builder()
+            .name(HTTP_RESPONSE_SIZE_BYTES_NAME)
+            .help(HTTP_RESPONSE_SIZE_BYTES_HELP)
+            .labelNames(HTTP_REQUEST_LABELS)
+            .register();
   }
 
   public void recordRequestStart(String method, String route) {
     requestsTotal.labelValues(method, route).inc();
     requestsInFlight.inc();
   }
 
-  public void recordRequestEnd(String method, String route, int statusCode, long startTimeNanos) {
+  public void recordRequestEnd(
+      String method, String route, int statusCode, long startTimeNanos, long responseSize) {
     requestsInFlight.dec();
 
     double durationSeconds =
         (System.nanoTime() - startTimeNanos) / (double) TimeUnit.SECONDS.toNanos(1);
     requestDuration.labelValues(method, route).observe(durationSeconds);
     responsesTotal.labelValues(method, route, Integer.toString(statusCode)).inc();
+    if (responseSize > 0) {
+      responseSizeBytes.labelValues(method, route).inc(responseSize);
+    }
   }
 
   public RequestTimer startRequest(String method, String route) {
@@ -91,6 +103,7 @@ public static class RequestTimer implements AutoCloseable {
     private final String route;
     private final long startTimeNanos;
     private int statusCode = 200;
+    private long responseSize = 0;
 
     RequestTimer(HttpMetrics metrics, String method, String route) {
       this.metrics = metrics;
@@ -105,9 +118,14 @@ public void setStatusCode(int statusCode) {
       this.statusCode = statusCode;
     }
 
+    /** Set the response size in bytes before closing. */
+    public void setResponseSize(long responseSize) {
+      this.responseSize = responseSize;
+    }
+
     @Override
     public void close() {
-      metrics.recordRequestEnd(method, route, statusCode, startTimeNanos);
+      metrics.recordRequestEnd(method, route, statusCode, startTimeNanos, responseSize);
     }
   }
 }

ice-rest-catalog/src/main/java/com/altinity/ice/rest/catalog/internal/metrics/IcebergMetricNames.java

@@ -188,6 +188,9 @@ private IcebergMetricNames() {}
   public static final String HTTP_REQUESTS_IN_FLIGHT_HELP =
       "Number of HTTP requests currently being processed";
 
+  public static final String HTTP_RESPONSE_SIZE_BYTES_NAME = "iceberg_http_response_size_bytes";
+  public static final String HTTP_RESPONSE_SIZE_BYTES_HELP = "HTTP response size in bytes";
+
   /** HTTP request duration buckets (in seconds) - suitable for REST API calls. */
   public static final double[] HTTP_DURATION_BUCKETS = {
     0.001, 0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 2.5, 5, 10

ice-rest-catalog/src/main/java/com/altinity/ice/rest/catalog/internal/rest/RESTCatalogServlet.java

@@ -97,7 +97,9 @@ protected void handle(HttpServletRequest request, HttpServletResponse response)
                 .withType("BadRequestException")
                 .withMessage(String.format("No route for %s %s", method, path))
                 .build();
-        RESTObjectMapper.mapper().writeValue(response.getWriter(), res);
+        byte[] responseBytes = RESTObjectMapper.mapper().writeValueAsBytes(res);
+        timer.setResponseSize(responseBytes.length);
+        response.getOutputStream().write(responseBytes);
       }
       return;
     }
@@ -152,15 +154,19 @@ protected void handle(HttpServletRequest request, HttpServletResponse response)
         timer.setStatusCode(error.code());
         response.setStatus(error.code());
         response.setHeader(HttpHeaders.CONTENT_TYPE, ContentType.APPLICATION_JSON.getMimeType());
-        RESTObjectMapper.mapper().writeValue(response.getWriter(), error);
+        byte[] errorBytes = RESTObjectMapper.mapper().writeValueAsBytes(error);
+        timer.setResponseSize(errorBytes.length);
+        response.getOutputStream().write(errorBytes);
         return;
       }
 
       timer.setStatusCode(HttpServletResponse.SC_OK);
       response.setStatus(HttpServletResponse.SC_OK);
       response.setHeader(HttpHeaders.CONTENT_TYPE, ContentType.APPLICATION_JSON.getMimeType());
       if (responseBody != null) {
-        RESTObjectMapper.mapper().writeValue(response.getWriter(), responseBody);
+        byte[] responseBytes = RESTObjectMapper.mapper().writeValueAsBytes(responseBody);
+        timer.setResponseSize(responseBytes.length);
+        response.getOutputStream().write(responseBytes);
       }
     }
   }

ice/src/main/resources/logback.xml

@@ -14,6 +14,8 @@
   <logger name="org.eclipse.jetty" level="WARN"/>
   <!-- hide "Unable to load metrics class: 'org.apache.iceberg.hadoop.HadoopMetricsContext', falling back to null metrics" -->
   <logger name="org.apache.iceberg.aws.s3.S3FileIO" level="ERROR"/>
+  <!-- hide "Unclosed input stream" warnings from Iceberg's S3InputStream finalizer -->
+  <logger name="org.apache.iceberg.aws.s3.S3InputStream" level="ERROR"/>
   <logger name="org.apache.iceberg.BaseMetastoreTableOperations" level="WARN"/>
   <logger name="io.grpc.internal" level="ERROR"/>