Push errors back over sideband when possible

If an internal exception occurs while packing and the request
needs to abort, the HTTP response might already be committed due
to progress message having already been delivered to the client.
This prevents UploadPackServlet from resetting the response and
sending back an HTTP 500 response.

Try to catch all exceptions and report internal errors over the
sideband stream or as an ERR command during the initial ACK/NAK
negotiation phase. This allows JGit to transmit an error message
that the user will receive on their console without needing to
worry about resetting the (already gone) HTTP response.

Change-Id: Ie393fb8bb55d2b79ab1276adf71c781c1807f9fe
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

org.eclipse.jgit.http.server/src/org/eclipse/jgit/http/server/ReceivePackServlet.java

 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
+import org.eclipse.jgit.errors.UnpackException;
 import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.transport.ReceivePack;
 import org.eclipse.jgit.transport.RefAdvertiser.PacketLineOutRefAdvertiser;
 			};
 			rp.receive(getInputStream(req), out, null);
 			out.close();
+		} catch (UnpackException e) {
+			// This should be already reported to the client.
+			getServletContext().log(
+					HttpServerText.get().internalErrorDuringReceivePack,
+					e.getCause());
+
 		} catch (IOException e) {
 			getServletContext().log(HttpServerText.get().internalErrorDuringReceivePack, e);
-			rsp.sendError(SC_INTERNAL_SERVER_ERROR);
+			if (!rsp.isCommitted()) {
+				rsp.reset();
+				rsp.sendError(SC_INTERNAL_SERVER_ERROR);
+			}
 			return;
 		}
 	}

org.eclipse.jgit.http.server/src/org/eclipse/jgit/http/server/UploadPackServlet.java

 import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.transport.RefAdvertiser.PacketLineOutRefAdvertiser;
 import org.eclipse.jgit.transport.UploadPack;
+import org.eclipse.jgit.transport.UploadPackInternalServerErrorException;
 import org.eclipse.jgit.transport.UploadPackMayNotContinueException;
 import org.eclipse.jgit.transport.resolver.ServiceNotAuthorizedException;
 import org.eclipse.jgit.transport.resolver.ServiceNotEnabledException;
 			out.close();
 
 		} catch (UploadPackMayNotContinueException e) {
-			if (!e.isOutput())
+			if (!e.isOutput() && !rsp.isCommitted()) {
+				rsp.reset();
 				rsp.sendError(SC_SERVICE_UNAVAILABLE);
+			}
 			return;
 
+		} catch (UploadPackInternalServerErrorException e) {
+			getServletContext().log(
+					HttpServerText.get().internalErrorDuringUploadPack,
+					e.getCause());
+
 		} catch (IOException e) {
 			getServletContext().log(HttpServerText.get().internalErrorDuringUploadPack, e);
-			rsp.reset();
-			rsp.sendError(SC_INTERNAL_SERVER_ERROR);
+			if (!rsp.isCommitted()) {
+				rsp.reset();
+				rsp.sendError(SC_INTERNAL_SERVER_ERROR);
+			}
 			return;
 		}
 	}

org.eclipse.jgit/resources/org/eclipse/jgit/JGitText.properties

 indexWriteException=Modified index could not be written
 integerValueOutOfRange=Integer value {0}.{1} out of range
 internalRevisionError=internal revision error
+internalServerError=internal server error
 interruptedWriting=Interrupted writing {0}
 inTheFuture=in the future
 invalidAdvertisementOf=invalid advertisement of {0}

org.eclipse.jgit/src/org/eclipse/jgit/JGitText.java

 	/***/ public String indexWriteException;
 	/***/ public String integerValueOutOfRange;
 	/***/ public String internalRevisionError;
+	/***/ public String internalServerError;
 	/***/ public String interruptedWriting;
 	/***/ public String inTheFuture;
 	/***/ public String invalidAdvertisementOf;

org.eclipse.jgit/src/org/eclipse/jgit/transport/UploadPack.java

 			}
 		}
 
-		recvWants();
-		if (wantIds.isEmpty()) {
-			preUploadHook.onBeginNegotiateRound(this, wantIds, 0);
-			preUploadHook.onEndNegotiateRound(this, wantIds, 0, 0, false);
-			return;
-		}
+		boolean sendPack;
+		try {
+			recvWants();
+			if (wantIds.isEmpty()) {
+				preUploadHook.onBeginNegotiateRound(this, wantIds, 0);
+				preUploadHook.onEndNegotiateRound(this, wantIds, 0, 0, false);
+				return;
+			}
 
-		if (options.contains(OPTION_MULTI_ACK_DETAILED)) {
-			multiAck = MultiAck.DETAILED;
-			noDone = options.contains(OPTION_NO_DONE);
-		} else if (options.contains(OPTION_MULTI_ACK))
-			multiAck = MultiAck.CONTINUE;
-		else
-			multiAck = MultiAck.OFF;
+			if (options.contains(OPTION_MULTI_ACK_DETAILED)) {
+				multiAck = MultiAck.DETAILED;
+				noDone = options.contains(OPTION_NO_DONE);
+			} else if (options.contains(OPTION_MULTI_ACK))
+				multiAck = MultiAck.CONTINUE;
+			else
+				multiAck = MultiAck.OFF;
+
+			sendPack = negotiate();
+		} catch (PackProtocolException err) {
+			reportErrorDuringNegotiate(err.getMessage());
+			throw err;
+
+		} catch (UploadPackMayNotContinueException err) {
+			if (!err.isOutput() && err.getMessage() != null) {
+				try {
+					pckOut.writeString("ERR " + err.getMessage() + "\n");
+					err.setOutput();
+				} catch (Throwable err2) {
+					// Ignore this secondary failure (and not mark output).
+				}
+			}
+			throw err;
+
+		} catch (IOException err) {
+			reportErrorDuringNegotiate(JGitText.get().internalServerError);
+			throw err;
+		} catch (RuntimeException err) {
+			reportErrorDuringNegotiate(JGitText.get().internalServerError);
+			throw err;
+		} catch (Error err) {
+			reportErrorDuringNegotiate(JGitText.get().internalServerError);
+			throw err;
+		}
 
-		if (negotiate())
+		if (sendPack)
 			sendPack();
 	}
 
+	private void reportErrorDuringNegotiate(String msg) {
+		try {
+			pckOut.writeString("ERR " + msg + "\n");
+		} catch (Throwable err) {
+			// Ignore this secondary failure.
+		}
+	}
+
 	/**
 	 * Generate an advertisement of available refs and capabilities.
 	 *
 
 	private ObjectId processHaveLines(List<ObjectId> peerHas, ObjectId last)
 			throws IOException {
-		try {
-			preUploadHook.onBeginNegotiateRound(this, wantIds, peerHas.size());
-		} catch (UploadPackMayNotContinueException fail) {
-			if (fail.getMessage() != null) {
-				pckOut.writeString("ERR " + fail.getMessage() + "\n");
-				fail.setOutput();
-			}
-			throw fail;
-		}
-
+		preUploadHook.onBeginNegotiateRound(this, wantIds, peerHas.size());
 		if (peerHas.isEmpty())
 			return last;
 
 					if (wantIds.contains(id)) {
 						String msg = MessageFormat.format(
 								JGitText.get().wantNotValid, id.name());
-						pckOut.writeString("ERR " + msg);
 						throw new PackProtocolException(msg, notFound);
 					}
 					continue;
 					if (!advertised.contains(obj)) {
 						String msg = MessageFormat.format(
 								JGitText.get().wantNotValid, obj.name());
-						pckOut.writeString("ERR " + msg);
 						throw new PackProtocolException(msg);
 					}
 
 			sentReady = true;
 		}
 
-		try {
-			preUploadHook.onEndNegotiateRound(this, wantAll, //
-					haveCnt, missCnt, sentReady);
-		} catch (UploadPackMayNotContinueException fail) {
-			if (fail.getMessage() != null) {
-				pckOut.writeString("ERR " + fail.getMessage() + "\n");
-				fail.setOutput();
-			}
-			throw fail;
-		}
-
+		preUploadHook.onEndNegotiateRound(this, wantAll, haveCnt, missCnt, sentReady);
 		peerHas.clear();
 		return last;
 	}
 						"\\x" + Integer.toHexString(eof)));
 		}
 
+		if (sideband) {
+			try {
+				sendPack(true);
+			} catch (UploadPackMayNotContinueException noPack) {
+				// This was already reported on (below).
+				throw noPack;
+			} catch (IOException err) {
+				if (reportInternalServerErrorOverSideband())
+					throw new UploadPackInternalServerErrorException(err);
+				else
+					throw err;
+			} catch (RuntimeException err) {
+				if (reportInternalServerErrorOverSideband())
+					throw new UploadPackInternalServerErrorException(err);
+				else
+					throw err;
+			} catch (Error err) {
+				if (reportInternalServerErrorOverSideband())
+					throw new UploadPackInternalServerErrorException(err);
+				else
+					throw err;
+			}
+		} else {
+			sendPack(false);
+		}
+	}
+
+	private boolean reportInternalServerErrorOverSideband() {
+		try {
+			SideBandOutputStream err = new SideBandOutputStream(
+					SideBandOutputStream.CH_ERROR,
+					SideBandOutputStream.SMALL_BUF,
+					rawOut);
+			err.write(Constants.encode(JGitText.get().internalServerError));
+			err.flush();
+			return true;
+		} catch (Throwable cannotReport) {
+			// Ignore the reason. This is a secondary failure.
+			return false;
+		}
+	}
+
+	private void sendPack(final boolean sideband) throws IOException {
 		ProgressMonitor pm = NullProgressMonitor.INSTANCE;
 		OutputStream packOut = rawOut;
 		SideBandOutputStream msgOut = null;

org.eclipse.jgit/src/org/eclipse/jgit/transport/UploadPackInternalServerErrorException.java

+/*
+ * Copyright (C) 2011, 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 java.io.IOException;
+
+/** UploadPack has already reported an error to the client. */
+public class UploadPackInternalServerErrorException extends IOException {
+	private static final long serialVersionUID = 1L;
+
+	/**
+	 * Initialize a new exception.
+	 *
+	 * @param why
+	 *            root cause.
+	 */
+	public UploadPackInternalServerErrorException(Throwable why) {
+		super(why);
+	}
+}