Reduce overhead count by 2 rather than 1 for non-overhead frames

This means that the overhead count for a well-behaved conenction should trend downwards over time.
apache · Jun 15, 2021 · 9448048 · 9448048
1 parent f0a3e1f
commit 9448048
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Showing 3 changed files with 9 additions and 2 deletions.
diff --git a/java/org/apache/coyote/http2/Http2Protocol.java b/java/org/apache/coyote/http2/Http2Protocol.java
@@ -68,7 +68,7 @@ public class Http2Protocol implements UpgradeProtocol {
     static final int DEFAULT_OVERHEAD_COUNT_FACTOR = 1;
     // Not currently configurable. This makes the practical limit for
     // overheadCountFactor to be 2.
-    static final int DEFAULT_OVERHEAD_REDUCTION_FACTOR = -1;
+    static final int DEFAULT_OVERHEAD_REDUCTION_FACTOR = -2;
     static final int DEFAULT_OVERHEAD_CONTINUATION_THRESHOLD = 1024;
     static final int DEFAULT_OVERHEAD_DATA_THRESHOLD = 1024;
     static final int DEFAULT_OVERHEAD_WINDOW_UPDATE_THRESHOLD = 1024;

diff --git a/webapps/docs/changelog.xml b/webapps/docs/changelog.xml
@@ -127,6 +127,13 @@
         overhead count that Tomcat uses to detect and close potentially
         malicious connections. (markt)
       </add>
+      <update>
+        Many HTTP/2 requests from browsers will trigger one overhead frame and
+        one non-overhead frame. Change the overhead calculation so that a
+        non-overhead frame reduces the current overhead count by 2 rather than
+        1. This means that, over time, the overhead count for a well-behaved
+        connection will trend downwards. (markt)
+      </update>
     </changelog>
   </subsection>
   <subsection name="Other">

diff --git a/webapps/docs/config/http2.xml b/webapps/docs/config/http2.xml
@@ -219,7 +219,7 @@
     <attribute name="overheadCountFactor" required="false">
       <p>The factor to apply when counting overhead frames to determine if a
       connection has too high an overhead and should be closed. The overhead
-      count starts at <code>-10</code>. The count is decreased for each
+      count starts at <code>-10</code>. The count is decreased by 2 for each
       data frame sent or received and each headers frame received. The count is
       increased by the <code>overheadCountFactor</code>for each setting
       received, priority frame received and ping received. If the overhead count