[JENKINS-75081] Avoid heap allocation when rendering large logs (#10515)

Author: jglick

bom/pom.xml

@@ -41,7 +41,7 @@ THE SOFTWARE.
     <commons-fileupload2.version>2.0.0-M2</commons-fileupload2.version>
     <groovy.version>2.4.21</groovy.version>
     <jelly.version>1.1-jenkins-20250108</jelly.version>
-    <stapler.version>1971.vf47a_d79853d7</stapler.version>
+    <stapler.version>1979.v5048d87384d7</stapler.version>
   </properties>
 
   <dependencyManagement>

core/src/main/java/hudson/console/AnnotatedLargeText.java

@@ -141,7 +141,10 @@ public void doProgressiveText(StaplerRequest req, StaplerResponse rsp) throws IO
      * and use this request attribute to differentiate.
      */
     private boolean isHtml() {
-        StaplerRequest2 req = Stapler.getCurrentRequest2();
+        return isHtml(Stapler.getCurrentRequest2());
+    }
+
+    private boolean isHtml(StaplerRequest2 req) {
         return req != null && req.getAttribute("html") != null;
     }
 
@@ -207,6 +210,11 @@ public long writeLogTo(long start, Writer w) throws IOException {
             return super.writeLogTo(start, w);
     }
 
+    @Override
+    protected boolean delegateToWriteLogTo(StaplerRequest2 req, StaplerResponse2 rsp) {
+        return isHtml(req);
+    }
+
     /**
      * Strips annotations using a {@link PlainTextConsoleOutputStream}.
      * {@inheritDoc}

core/src/main/java/hudson/console/ConsoleAnnotator.java

@@ -118,6 +118,11 @@ public ConsoleAnnotator annotate(T context, MarkupText text) {
                 default:    return this;
             }
         }
+
+        @Override
+        public String toString() {
+            return "ConsoleAnnotatorAggregator" + list;
+        }
     }
 
     /**

core/src/main/java/hudson/model/Run.java

@@ -72,7 +72,6 @@
 import io.jenkins.servlet.ServletExceptionWrapper;
 import jakarta.servlet.ServletException;
 import jakarta.servlet.http.HttpServletResponse;
-import java.io.BufferedInputStream;
 import java.io.ByteArrayInputStream;
 import java.io.File;
 import java.io.IOException;
@@ -1466,19 +1465,34 @@ public Collection<Fingerprint> getBuildFingerprints() {
      */
     @SuppressFBWarnings(value = "RV_RETURN_VALUE_IGNORED", justification = "method signature does not permit plumbing through the return value")
     public void writeLogTo(long offset, @NonNull XMLOutput out) throws IOException {
-        long start = offset;
+        AnnotatedLargeText<?> logText = getLogText();
         if (offset > 0) {
-            try (BufferedInputStream bufferedInputStream = new BufferedInputStream(getLogInputStream())) {
-                if (offset == bufferedInputStream.skip(offset)) {
-                    int r;
-                    do {
-                        r = bufferedInputStream.read();
-                        start = r == -1 ? 0 : start + 1;
-                    } while (r != -1 && r != '\n');
-                }
+            long _offset = offset;
+            try {
+                logText.writeRawLogTo(offset - 1, new OutputStream() {
+                    long pos = _offset;
+                    @Override
+                    public void write(int b) throws IOException {
+                        if (b == '\n') {
+                            throw new Halt(pos);
+                        } else {
+                            pos++;
+                        }
+                    }
+                });
+            } catch (Halt halt) {
+                offset = halt.offset;
             }
         }
-        getLogText().writeHtmlTo(start, out.asWriter());
+        logText.writeHtmlTo(offset, out.asWriter());
+    }
+
+    private static final class Halt extends IOException {
+        final long offset;
+
+        Halt(long offset) {
+            this.offset = offset;
+        }
     }
 
     /**

core/src/test/java/hudson/model/RunTest.java

@@ -280,6 +280,11 @@ public void wontPushOffsetOnRenderingFromBeginning() throws Exception {
         assertWriteLogToEquals(new String(new char[5]).replace("\0", SAMPLE_BUILD_OUTPUT) + "Finished: SUCCESS.\n", 0);
     }
 
+    @Test
+    public void wontPushOffsetOnRenderingFromBeginningOfLine() throws Exception {
+        assertWriteLogToEquals(new String(new char[3]).replace("\0", SAMPLE_BUILD_OUTPUT) + "Finished: SUCCESS.\n", 2 * SAMPLE_BUILD_OUTPUT.length());
+    }
+
     @Test
     public void willRenderNothingIfOffsetSetOnLastLine() throws Exception {
         assertWriteLogToEquals("", 5 * SAMPLE_BUILD_OUTPUT.length() + 6);

test/src/test/java/hudson/console/ConsoleAnnotatorTest.java

@@ -224,6 +224,11 @@ public ConsoleAnnotator annotate(Object build, MarkupText text) {
                 text.addMarkup(0, 5, "<b tag=" + n++ + ">", "</b>");
             return this;
         }
+
+        @Override
+        public String toString() {
+            return "StatefulAnnotator:" + n + " @" + System.identityHashCode(this);
+        }
     }