Optimize RefAdvertiser for wire protocol

The native wire protocol sends ref advertisements in the pkt-line
format, which requires encoding the ObjectId and ref name onto a byte
sequence.  Busy servers show this is a very high source of garbage,
which pushes the garbage collector harder when there are many refs in
the repository (e.g.  70k, in a Gerrit managed repository).

Optimize the side band advertiser by retaining the CharsetEncoder,
minimizing the amount of temporary garbage built during encoding.

Change-Id: I406c654bf82c1eb94b38862da2425e98396134cb

1 files changed, 116 insertions, 0 deletions

diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/transport/RefAdvertiserTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/transport/RefAdvertiserTest.java
new file mode 100644
index 0000000000..ce69adf9c1
--- /dev/null
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/transport/RefAdvertiserTest.java
@@ -0,0 +1,116 @@
+/*
+ * Copyright (C) 2016, Google Inc.
+ * and other copyright owners as documented in the project's IP log.
+ *
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Distribution License v1.0 which
+ * accompanies this distribution, is reproduced below, and is
+ * available at http://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package org.eclipse.jgit.transport;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertSame;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+
+import org.eclipse.jgit.lib.Constants;
+import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.lib.ObjectInserter;
+import org.eclipse.jgit.transport.RefAdvertiser.PacketLineOutRefAdvertiser;
+import org.eclipse.jgit.util.NB;
+import org.junit.Test;
+
+public class RefAdvertiserTest {
+	@Test
+	public void advertiser() throws IOException {
+		ByteArrayOutputStream buf = new ByteArrayOutputStream();
+		PacketLineOut pckOut = new PacketLineOut(buf);
+		PacketLineOutRefAdvertiser adv = new PacketLineOutRefAdvertiser(pckOut);
+
+		// Advertisement of capability and id both happen in order of call,
+		// which may not match Git standards. Callers are responsible for
+		// making calls in the correct ordering. Here in this test we do them
+		// in a "wrong" order to assert the method just writes to the network.
+
+		adv.advertiseCapability("test-1");
+		adv.advertiseCapability("sideband");
+		adv.advertiseId(id(1), "refs/heads/master");
+		adv.advertiseId(id(4), "refs/" + padStart("F", 987));
+		adv.advertiseId(id(2), "refs/heads/next");
+		adv.advertiseId(id(3), "refs/Iñtërnâtiônàlizætiøn☃💩");
+		adv.end();
+		assertFalse(adv.isEmpty());
+
+		PacketLineIn pckIn = new PacketLineIn(
+				new ByteArrayInputStream(buf.toByteArray()));
+		String s = pckIn.readStringRaw();
+		assertEquals(id(1).name() + " refs/heads/master\0 test-1 sideband\n",
+				s);
+
+		s = pckIn.readStringRaw();
+		assertEquals(id(4).name() + " refs/" + padStart("F", 987) + '\n', s);
+
+		s = pckIn.readStringRaw();
+		assertEquals(id(2).name() + " refs/heads/next\n", s);
+
+		s = pckIn.readStringRaw();
+		assertEquals(id(3).name() + " refs/Iñtërnâtiônàlizætiøn☃💩\n", s);
+
+		s = pckIn.readStringRaw();
+		assertSame(PacketLineIn.END, s);
+	}
+
+	private static ObjectId id(int i) {
+		try (ObjectInserter.Formatter f = new ObjectInserter.Formatter()) {
+			byte[] tmp = new byte[4];
+			NB.encodeInt32(tmp, 0, i);
+			return f.idFor(Constants.OBJ_BLOB, tmp);
+		}
+	}
+
+	private static String padStart(String s, int len) {
+		StringBuilder b = new StringBuilder(len);
+		for (int i = s.length(); i < len; i++) {
+			b.append((char) ('a' + (i % 26)));
+		}
+		return b.append(s).toString();
+	}
+}