Report query memory allocation in response body

deploy/adsabs/server/solr/collection1/conf/solrconfig.xml

@@ -298,6 +298,8 @@
 
   </requestDispatcher>
 
+  <searchComponent name="requestMemoryStart" class="org.adsabs.solr.metrics.memory.RequestMemoryStartComponent"/>
+  <searchComponent name="requestMemoryEnd" class="org.adsabs.solr.metrics.memory.RequestMemoryEndComponent"/>
   <requestHandler name="/select" class="solr.SearchHandler">
      <lst name="defaults">
        <str name="wt">json</str>
@@ -344,8 +346,12 @@
        <str name="aqp.allow.leading_wildcard">false</str>
        <str name="aqp.maxAbsolutePhraseLength">500</str>
      </lst>
+     <arr name="first-components">
+         <str>requestMemoryStart</str>
+     </arr>
      <arr name="last-components">
       <str>wordcloud</str>
+      <str>requestMemoryEnd</str>
      </arr>
     </requestHandler>
 

montysolr/src/main/java/org/adsabs/solr/metrics/memory/RequestMemoryEndComponent.java

@@ -0,0 +1,33 @@
+package org.adsabs.solr.metrics.memory;
+
+import com.sun.management.ThreadMXBean;
+import org.apache.solr.handler.component.ResponseBuilder;
+import org.apache.solr.handler.component.SearchComponent;
+
+import java.io.IOException;
+import java.lang.management.ManagementFactory;
+
+public class RequestMemoryEndComponent extends SearchComponent {
+    private static final ThreadMXBean THREAD_MX_BEAN =
+            (ThreadMXBean) ManagementFactory.getThreadMXBean();
+
+    @Override
+    public void prepare(ResponseBuilder rb) throws IOException {
+        // no-op
+    }
+
+    @Override
+    public void process(ResponseBuilder rb) throws IOException {
+        Long startAlloc = (Long) rb.req.getContext().get(RequestMemoryStartComponent.ALLOC_START_KEY);
+        if (startAlloc == null) return;
+
+        long allocated = THREAD_MX_BEAN.getCurrentThreadAllocatedBytes() - startAlloc;
+        rb.rsp.add("allocatedBytes", allocated);
+        rb.rsp.addHttpHeader("X-Allocated-Bytes", String.valueOf(allocated));
+    }
+
+    @Override
+    public String getDescription() {
+        return "Reports allocation delta at the end of a request.";
+    }
+}

montysolr/src/main/java/org/adsabs/solr/metrics/memory/RequestMemoryStartComponent.java

@@ -0,0 +1,34 @@
+package org.adsabs.solr.metrics.memory;
+
+import org.apache.solr.handler.component.ResponseBuilder;
+import org.apache.solr.handler.component.SearchComponent;
+
+import java.io.IOException;
+import java.lang.management.ManagementFactory;
+import com.sun.management.ThreadMXBean;
+
+public class RequestMemoryStartComponent extends SearchComponent {
+    static final String ALLOC_START_KEY = "allocation.tracking.start";
+    private static final ThreadMXBean THREAD_MX_BEAN =
+            (ThreadMXBean) ManagementFactory.getThreadMXBean();
+
+    static {
+        THREAD_MX_BEAN.setThreadAllocatedMemoryEnabled(true);
+    }
+
+    @Override
+    public void prepare(ResponseBuilder rb) throws IOException {
+        rb.req.getContext().put(ALLOC_START_KEY,
+                THREAD_MX_BEAN.getCurrentThreadAllocatedBytes());
+    }
+
+    @Override
+    public void process(ResponseBuilder rb) throws IOException {
+        // no-op
+    }
+
+    @Override
+    public String getDescription() {
+        return "Records allocated bytes at the start of a request.";
+    }
+}

montysolr/src/main/java/org/apache/lucene/search/AbstractSecondOrderCollector.java

@@ -52,7 +52,7 @@ public LeafCollector getLeafCollector(LeafReaderContext context) throws IOExcept
 
     public boolean searcherInitialization(IndexSearcher searcher, Weight firstOrderWeight) throws IOException {
         // this is pretty arbitrary, but 2nd order queries may return many hits...
-        ((ArrayList<CollectorDoc>) hits).ensureCapacity((int) (searcher.getIndexReader().maxDoc() * ensureCapacityRatio));
+        //((ArrayList<CollectorDoc>) hits).ensureCapacity((int) (searcher.getIndexReader().maxDoc() * ensureCapacityRatio));
         return true;
     }