bundles/org.eclipse.equinox.p2.artifact.repository/src/org/eclipse/equinox/internal/p2/artifact/repository/MirrorRequest.java - equinox/rt.equinox.p2 - Git at Google

 /*******************************************************************************
  * Copyright (c) 2007, 2017 IBM Corporation and others.
  *
  * This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License 2.0
  * which accompanies this distribution, and is available at
  * https://www.eclipse.org/legal/epl-2.0/
  *
  * SPDX-License-Identifier: EPL-2.0
  *
  * Contributors:
  *     IBM Corporation - initial API and implementation
  *  	Compeople AG (Stefan Liebig) - various ongoing maintenance
  *   	Genuitec LLC - various bug fixes
  *      Sonatype, Inc. - transport split
  *      Yatta Solutions GmbH - bug 457619
  *******************************************************************************/
 package org.eclipse.equinox.internal.p2.artifact.repository;

 import java.io.*;
 import java.net.URI;
 import java.net.URISyntaxException;
 import java.util.HashMap;
 import java.util.Map;
 import org.eclipse.core.runtime.*;
 import org.eclipse.equinox.internal.p2.artifact.processors.pgp.PGPSignatureVerifier;
 import org.eclipse.equinox.internal.p2.artifact.repository.simple.SimpleArtifactDescriptor;
 import org.eclipse.equinox.internal.p2.core.helpers.LogHelper;
 import org.eclipse.equinox.internal.p2.repository.Transport;
 import org.eclipse.equinox.internal.provisional.p2.artifact.repository.processing.ProcessingStepHandler;
 import org.eclipse.equinox.internal.provisional.p2.core.eventbus.IProvisioningEventBus;
 import org.eclipse.equinox.internal.provisional.p2.repository.IStateful;
 import org.eclipse.equinox.p2.core.ProvisionException;
 import org.eclipse.equinox.p2.metadata.IArtifactKey;
 import org.eclipse.equinox.p2.repository.artifact.IArtifactDescriptor;
 import org.eclipse.equinox.p2.repository.artifact.IArtifactRepository;
 import org.eclipse.equinox.p2.repository.artifact.spi.ArtifactDescriptor;
 import org.eclipse.osgi.util.NLS;

 /**
  * A request to mirror (copy) an artifact into a given destination artifact repository.
  */
 public class MirrorRequest extends ArtifactRequest {

 	/**
 	 * A Status code that represents an error while processing the artifact. This error is not
 	 * related to transport, but rather a problem with the processing step.
 	 */
 	public static final int ARTIFACT_PROCESSING_ERROR = 2;

 	/**
 	 * Maximum number of times a request for a single artifact should be tried
 	 */
 	private static final int MAX_RETRY_REQUEST = 200;

 	/**
 	 * The name of a repository property on an artifact repository, indicating the base URI
 	 * to be used for reporting download statistics.
 	 */
 	private static final String PROP_STATS_URI = "p2.statsURI"; //$NON-NLS-1$

 	/**
 	 * The name of a property on an artifact descriptor, indicating the relative download URI
 	 * to be used to report download statistics for that artifact. The value of this property,
 	 * if present, is appended to the {@link #PROP_STATS_URI} to create the full URI
 	 * for reporting download statistics for that artifact.
 	 */
 	private static final String PROP_DOWNLOAD_STATS = "download.stats"; //$NON-NLS-1$
 	/**
 	 * The additional parameters for downloading statistics
 	 */
 	private String downloadStatsParamters;

 	protected final IArtifactRepository target;

 	private final Map<String, String> targetDescriptorProperties;
 	private final Map<String, String> targetRepositoryProperties;
 	protected IArtifactDescriptor descriptor;

 	public MirrorRequest(IArtifactKey key, IArtifactRepository targetRepository, Map<String, String> targetDescriptorProperties, Map<String, String> targetRepositoryProperties, Transport transport) {
 		this(key, targetRepository, targetDescriptorProperties, targetRepositoryProperties, transport, null);
 	}

 	public MirrorRequest(IArtifactKey key, IArtifactRepository targetRepository, Map<String, String> targetDescriptorProperties, Map<String, String> targetRepositoryProperties, Transport transport, String statsParameters) {
 		super(key, transport);
 		target = targetRepository;
 		if (targetDescriptorProperties == null || targetDescriptorProperties.isEmpty()) {
 			this.targetDescriptorProperties = null;
 		} else {
 			this.targetDescriptorProperties = new HashMap<>();
 			this.targetDescriptorProperties.putAll(targetDescriptorProperties);
 		}

 		if (targetRepositoryProperties == null || targetRepositoryProperties.isEmpty()) {
 			this.targetRepositoryProperties = null;
 		} else {
 			this.targetRepositoryProperties = new HashMap<>();
 			this.targetRepositoryProperties.putAll(targetRepositoryProperties);
 		}
 		this.downloadStatsParamters = statsParameters;
 	}

 	@Override
 	protected void setSourceRepository(IArtifactRepository value) {
 		if (value != getSourceRepository()) {
 			// This refreshes the descriptor from the new repository as it might be different.
 			// If a MirrorRequest fails for a local repository the descriptor might indicate a "folder based" artifact
 			// which causes the MirrorRequest to fail again with a remote repository if the descriptor is not fetched again.
 			// see https://bugs.eclipse.org/bugs/show_bug.cgi?id=457619
 			descriptor = null;
 		}
 		super.setSourceRepository(value);
 	}

 	@Override
 	public void perform(IArtifactRepository sourceRepository, IProgressMonitor monitor) {
 		monitor.subTask(NLS.bind(Messages.downloading, getArtifactKey().getId()));
 		setSourceRepository(sourceRepository);
 		// Do we already have the artifact in the target?
 		if (target.contains(getArtifactKey())) {
 			setResult(new Status(IStatus.OK, Activator.ID, NLS.bind(Messages.available_already_in, getArtifactKey())));
 			return;
 		}

 		// if the request does not have a descriptor then try to fill one in by getting
 		// the list of all and randomly picking one that appears to be optimized.
 		IArtifactDescriptor optimized = null;
 		IArtifactDescriptor canonical = null;
 		if (descriptor == null) {
 			IArtifactDescriptor[] descriptors = source.getArtifactDescriptors(getArtifactKey());
 			if (descriptors.length > 0) {
 				for (IArtifactDescriptor descriptor2 : descriptors) {
 					if (descriptor2.getProperty(IArtifactDescriptor.FORMAT) == null)
 						canonical = descriptor2;
 					else if (ProcessingStepHandler.canProcess(descriptor2))
 						optimized = descriptor2;
 				}
 				boolean chooseCanonical = source.getLocation().getScheme().equals("file"); //$NON-NLS-1$
 				// If the source repo is local then look for a canonical descriptor so we don't waste processing time.
 				descriptor = chooseCanonical ? canonical : optimized;
 				// if the descriptor is still null then we could not find our first choice of format so switch the logic.
 				if (descriptor == null)
 					descriptor = !chooseCanonical ? canonical : optimized;
 			}
 		}

 		// if the descriptor is not set now then the repo does not have the requested artifact
 		// TODO improve the reporting here.  It may be the case that the repo has the artifact
 		// but the client does not have a processor
 		if (descriptor == null) {
 			setResult(new Status(IStatus.ERROR, Activator.ID, NLS.bind(Messages.artifact_not_found, getArtifactKey())));
 			return;
 		}

 		IArtifactDescriptor destinationDescriptor = getDestinationDescriptor(descriptor, descriptor == canonical);
 		IStatus status = transfer(destinationDescriptor, descriptor, monitor);
 		// if ok, cancelled or transfer has already been done with the canonical form return with status set
 		if (status.getSeverity() == IStatus.CANCEL) {
 			setResult(status);
 			return;
 		}
 		if (monitor.isCanceled()) {
 			setResult(Status.CANCEL_STATUS);
 			return;
 		}
 		if (status.isOK()) {
 			setResult(status);
 			return;
 		}

 		// failed, first remove possibly erroneously added descriptor
 		if (target.contains(destinationDescriptor))
 			target.removeDescriptor(destinationDescriptor);

 		if (descriptor == canonical || canonical == null) {
 			setResult(status);
 			return;
 		}

 		IStatus canonicalStatus = transfer(getDestinationDescriptor(canonical, true), canonical, monitor);
 		// To prevent the optimized transfer status severity from dominating the canonical, only merge
 		// if the canonical severity is equal to or higher than the optimized transfer severity.
 		if (canonicalStatus.getSeverity() < status.getSeverity())
 			setResult(canonicalStatus);
 		else
 			setResult(new MultiStatus(Activator.ID, canonicalStatus.getCode() != 0 ? canonicalStatus.getCode() : status.getCode(), new IStatus[] {status, canonicalStatus}, Messages.MirrorRequest_multipleDownloadProblems, null));
 	}

 	private IArtifactDescriptor getDestinationDescriptor(IArtifactDescriptor sourceDescriptor, boolean isCanonical) {
 		// Get the descriptor to use to store the artifact
 		// Since we are mirroring, ensure we clear out data from the original descriptor that may
 		// not apply in the new repo location.
 		// TODO this is brittle.  perhaps the repo itself should do this?  there are cases where
 		// we really do need to give the repo the actual descriptor to use however...
 		IArtifactDescriptor destinationDescriptor = target.createArtifactDescriptor(sourceDescriptor.getArtifactKey());
 		//		destinationDescriptor.setProcessingSteps(EMPTY_STEPS);
 		//		destinationDescriptor.setProperty(IArtifactDescriptor.DOWNLOAD_MD5, null);
 		//		destinationDescriptor.setProperty(IArtifactDescriptor.DOWNLOAD_CONTENTTYPE, null);
 		//		destinationDescriptor.setProperty(IArtifactDescriptor.FORMAT, null);
 		if (targetDescriptorProperties != null && destinationDescriptor instanceof ArtifactDescriptor)
 			((ArtifactDescriptor) destinationDescriptor).addProperties(targetDescriptorProperties);
 		if (targetRepositoryProperties != null && destinationDescriptor instanceof SimpleArtifactDescriptor)
 			((SimpleArtifactDescriptor) destinationDescriptor).addRepositoryProperties(targetRepositoryProperties);
 		if (isCanonical && destinationDescriptor instanceof ArtifactDescriptor) {
 			// keep some safety properties
 			if (sourceDescriptor.getProperty(PGPSignatureVerifier.PGP_SIGNATURES_PROPERTY_NAME) != null) {
 				((ArtifactDescriptor) destinationDescriptor)
 						.addProperties(Map.of(PGPSignatureVerifier.PGP_SIGNATURES_PROPERTY_NAME,
 								sourceDescriptor.getProperty(PGPSignatureVerifier.PGP_SIGNATURES_PROPERTY_NAME)));
 			}
 		}
 		return destinationDescriptor;
 	}

 	/**
 	 * Keep retrying the source repository until it reports back that it will be impossible
 	 * to get the artifact from it.
 	 * @param destinationDescriptor
 	 * @param sourceDescriptor
 	 * @param monitor
 	 * @return the status of the transfer operation
 	 */
 	protected IStatus transfer(IArtifactDescriptor destinationDescriptor, IArtifactDescriptor sourceDescriptor, IProgressMonitor monitor) {
 		MultiStatus allResults = new MultiStatus(Activator.ID, 0, NLS.bind(Messages.MirrorRequest_transferFailed, sourceDescriptor), null);
 		IStatus lastResult = Status.OK_STATUS;
 		// go until we get one (OK), there are no more mirrors to consider or the operation is cancelled.
 		// Put a hard limit of MAX_RETRY_REQUEST so we don't end up in an infinite loop.
 		// Really, if you've tried MAX_RETRY_REQUEST times without success, it's time to give up
 		// TODO Should we log that we gave up because of the retry count?
 		// TODO this needs to be redone with a much better mirror management scheme.

 		int counter = 0;
 		do {
 			lastResult = transferSingle(destinationDescriptor, sourceDescriptor, monitor);
 			allResults.add(lastResult);
 			if (lastResult.getException() instanceof Error) {
 				// Error is more severe than Exception - e.g. an OutOfMemoryError should not be ignored and might hinder further processing
 				throw (Error) lastResult.getException();
 			}
 		} while (lastResult.getSeverity() == IStatus.ERROR && lastResult.getCode() == IArtifactRepository.CODE_RETRY && counter++ < MAX_RETRY_REQUEST);
 		IProvisioningEventBus bus = source.getProvisioningAgent().getService(IProvisioningEventBus.class);
 		if (bus != null)
 			bus.publishEvent(new MirrorEvent(source, sourceDescriptor, lastResult.isOK() ? lastResult : (allResults.getChildren().length <= 1 ? lastResult : allResults)));
 		if (lastResult.isOK()) {
 			collectStats(sourceDescriptor, monitor);
 			return lastResult;
 		} else if (allResults.getChildren().length <= 1) {
 			return lastResult;
 		}
 		return allResults;
 	}

 	/**
 	 * Collect download statistics, if specified by the descriptor and the source repository
 	 */
 	private void collectStats(IArtifactDescriptor sourceDescriptor, IProgressMonitor monitor) {
 		final String statsProperty = sourceDescriptor.getProperty(PROP_DOWNLOAD_STATS);
 		if (statsProperty == null)
 			return;
 		String statsRoot = sourceDescriptor.getRepository().getProperties().get(PROP_STATS_URI);
 		if (statsRoot == null)
 			return;
 		URI statsURI;
 		try {
 			statsURI = URIUtil.append(new URI(statsRoot), statsProperty);
 			if (downloadStatsParamters != null) {
 				try {
 					statsURI = new URI(statsURI.getScheme(), statsURI.getUserInfo(), statsURI.getHost(), statsURI.getPort(), statsURI.getPath(), statsURI.getQuery() == null ? downloadStatsParamters : downloadStatsParamters + "&" + statsURI.getQuery(), statsURI.getFragment()); //$NON-NLS-1$
 				} catch (URISyntaxException e) {
 					LogHelper.log(new Status(IStatus.WARNING, Activator.ID, "Unable to create download statistics due to invalid URL query: " + statsRoot + " suffix: " + statsProperty + " query: " + downloadStatsParamters)); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
 				}
 			}
 		} catch (URISyntaxException e) {
 			LogHelper.log(new Status(IStatus.WARNING, Activator.ID, "Unable to report download statistics due to invalid URL: " + statsRoot + " suffix: " + statsProperty)); //$NON-NLS-1$ //$NON-NLS-2$
 			return;
 		}
 		try {
 			transport.getLastModified(statsURI, monitor);
 		} catch (FileNotFoundException e) {
 			//ignore because it is expected that the statistics URI doesn't represent an existing file
 		} catch (Exception e) {
 			LogHelper.log(new Status(IStatus.WARNING, Activator.ID, "Failure reporting download statistics to URL: " + statsURI, e)); //$NON-NLS-1$
 		}
 	}

 	private IStatus transferSingle(IArtifactDescriptor destinationDescriptor, IArtifactDescriptor sourceDescriptor, IProgressMonitor monitor) {
 		OutputStream destination;
 		try {
 			destination = target.getOutputStream(destinationDescriptor);
 		} catch (ProvisionException e) {
 			return e.getStatus();
 		}

 		IStatus status = null;
 		Throwable priorException = null;
 		// Do the actual transfer
 		try {
 			status = getArtifact(sourceDescriptor, destination, monitor);
 			if (destination instanceof IStateful && status != null && !status.isOK()) {
 				IStatus destStatus = ((IStateful) destination).getStatus();
 				IStatus root = extractRootCause(status);
 				Throwable e = root != null ? root.getException() : null;
 				((IStateful) destination).setStatus(new MultiStatus(Activator.ID, status.getCode(), new IStatus[] {status, destStatus}, status.getMessage(), e));
 			}
 		} catch (RuntimeException e) {
 			priorException = e;
 			throw e;
 		} catch (Error e) {
 			priorException = e;
 			throw e;
 		} finally {
 			try {
 				destination.close();
 			} catch (IOException e) {
 				if (priorException == null) // don't mask a formerly thrown Exception/Error
 				{
 					if (status != null && status.getSeverity() == IStatus.ERROR && status.getCode() == IArtifactRepository.CODE_RETRY)
 						return new MultiStatus(Activator.ID, status.getCode(), new IStatus[] {status}, NLS.bind(Messages.error_closing_stream, getArtifactKey(), target.getLocation()), e);
 					return new Status(IStatus.ERROR, Activator.ID, NLS.bind(Messages.error_closing_stream, getArtifactKey(), target.getLocation()), e);
 				}
 				// otherwise it is already thrown
 			}
 		}
 		return status;
 	}

 	protected IStatus getArtifact(IArtifactDescriptor sourceDescriptor, OutputStream destination, IProgressMonitor monitor) {
 		return getSourceRepository().getArtifact(sourceDescriptor, destination, monitor);
 	}

 	/**
 	 * Extract the root cause. The root cause is the first severe non-MultiStatus status
 	 * containing an exception when searching depth first otherwise null.
 	 * @param status
 	 * @return root cause
 	 */
 	private static IStatus extractRootCause(IStatus status) {
 		if (status == null)
 			return null;
 		if (!status.isMultiStatus())
 			return constraintStatus(status);

 		IStatus[] children = ((MultiStatus) status).getChildren();
 		if (children == null)
 			return constraintStatus(status);

 		for (IStatus element : children) {
 			IStatus deeper = extractRootCause(element);
 			if (deeper != null)
 				return deeper;
 		}

 		return constraintStatus(status);
 	}

 	private static IStatus constraintStatus(IStatus status) {
 		return status.getSeverity() == IStatus.ERROR && status.getException() != null ? status : null;
 	}

 	@Override
 	public String toString() {
 		return Messages.mirroring + getArtifactKey() + " into " + target; //$NON-NLS-1$
 	}
 }
	/*******************************************************************************
	* Copyright (c) 2007, 2017 IBM Corporation and others.
	*
	* This program and the accompanying materials
	* are made available under the terms of the Eclipse Public License 2.0
	* which accompanies this distribution, and is available at
	* https://www.eclipse.org/legal/epl-2.0/
	*
	* SPDX-License-Identifier: EPL-2.0
	*
	* Contributors:
	* IBM Corporation - initial API and implementation
	* Compeople AG (Stefan Liebig) - various ongoing maintenance
	* Genuitec LLC - various bug fixes
	* Sonatype, Inc. - transport split
	* Yatta Solutions GmbH - bug 457619
	*******************************************************************************/
	package org.eclipse.equinox.internal.p2.artifact.repository;

	import java.io.*;
	import java.net.URI;
	import java.net.URISyntaxException;
	import java.util.HashMap;
	import java.util.Map;
	import org.eclipse.core.runtime.*;
	import org.eclipse.equinox.internal.p2.artifact.processors.pgp.PGPSignatureVerifier;
	import org.eclipse.equinox.internal.p2.artifact.repository.simple.SimpleArtifactDescriptor;
	import org.eclipse.equinox.internal.p2.core.helpers.LogHelper;
	import org.eclipse.equinox.internal.p2.repository.Transport;
	import org.eclipse.equinox.internal.provisional.p2.artifact.repository.processing.ProcessingStepHandler;
	import org.eclipse.equinox.internal.provisional.p2.core.eventbus.IProvisioningEventBus;
	import org.eclipse.equinox.internal.provisional.p2.repository.IStateful;
	import org.eclipse.equinox.p2.core.ProvisionException;
	import org.eclipse.equinox.p2.metadata.IArtifactKey;
	import org.eclipse.equinox.p2.repository.artifact.IArtifactDescriptor;
	import org.eclipse.equinox.p2.repository.artifact.IArtifactRepository;
	import org.eclipse.equinox.p2.repository.artifact.spi.ArtifactDescriptor;
	import org.eclipse.osgi.util.NLS;

	/**
	* A request to mirror (copy) an artifact into a given destination artifact repository.
	*/
	public class MirrorRequest extends ArtifactRequest {

	/**
	* A Status code that represents an error while processing the artifact. This error is not
	* related to transport, but rather a problem with the processing step.
	*/
	public static final int ARTIFACT_PROCESSING_ERROR = 2;

	/**
	* Maximum number of times a request for a single artifact should be tried
	*/
	private static final int MAX_RETRY_REQUEST = 200;

	/**
	* The name of a repository property on an artifact repository, indicating the base URI
	* to be used for reporting download statistics.
	*/
	private static final String PROP_STATS_URI = "p2.statsURI"; //$NON-NLS-1$

	/**
	* The name of a property on an artifact descriptor, indicating the relative download URI
	* to be used to report download statistics for that artifact. The value of this property,
	* if present, is appended to the {@link #PROP_STATS_URI} to create the full URI
	* for reporting download statistics for that artifact.
	*/
	private static final String PROP_DOWNLOAD_STATS = "download.stats"; //$NON-NLS-1$
	/**
	* The additional parameters for downloading statistics
	*/
	private String downloadStatsParamters;

	protected final IArtifactRepository target;

	private final Map<String, String> targetDescriptorProperties;
	private final Map<String, String> targetRepositoryProperties;
	protected IArtifactDescriptor descriptor;

	public MirrorRequest(IArtifactKey key, IArtifactRepository targetRepository, Map<String, String> targetDescriptorProperties, Map<String, String> targetRepositoryProperties, Transport transport) {
	this(key, targetRepository, targetDescriptorProperties, targetRepositoryProperties, transport, null);
	}

	public MirrorRequest(IArtifactKey key, IArtifactRepository targetRepository, Map<String, String> targetDescriptorProperties, Map<String, String> targetRepositoryProperties, Transport transport, String statsParameters) {
	super(key, transport);
	target = targetRepository;
	if (targetDescriptorProperties == null \|\| targetDescriptorProperties.isEmpty()) {
	this.targetDescriptorProperties = null;
	} else {
	this.targetDescriptorProperties = new HashMap<>();
	this.targetDescriptorProperties.putAll(targetDescriptorProperties);
	}

	if (targetRepositoryProperties == null \|\| targetRepositoryProperties.isEmpty()) {
	this.targetRepositoryProperties = null;
	} else {
	this.targetRepositoryProperties = new HashMap<>();
	this.targetRepositoryProperties.putAll(targetRepositoryProperties);
	}
	this.downloadStatsParamters = statsParameters;
	}

	@Override
	protected void setSourceRepository(IArtifactRepository value) {
	if (value != getSourceRepository()) {
	// This refreshes the descriptor from the new repository as it might be different.
	// If a MirrorRequest fails for a local repository the descriptor might indicate a "folder based" artifact
	// which causes the MirrorRequest to fail again with a remote repository if the descriptor is not fetched again.
	// see https://bugs.eclipse.org/bugs/show_bug.cgi?id=457619
	descriptor = null;
	}
	super.setSourceRepository(value);
	}

	@Override
	public void perform(IArtifactRepository sourceRepository, IProgressMonitor monitor) {
	monitor.subTask(NLS.bind(Messages.downloading, getArtifactKey().getId()));
	setSourceRepository(sourceRepository);
	// Do we already have the artifact in the target?
	if (target.contains(getArtifactKey())) {
	setResult(new Status(IStatus.OK, Activator.ID, NLS.bind(Messages.available_already_in, getArtifactKey())));
	return;
	}

	// if the request does not have a descriptor then try to fill one in by getting
	// the list of all and randomly picking one that appears to be optimized.
	IArtifactDescriptor optimized = null;
	IArtifactDescriptor canonical = null;
	if (descriptor == null) {
	IArtifactDescriptor[] descriptors = source.getArtifactDescriptors(getArtifactKey());
	if (descriptors.length > 0) {
	for (IArtifactDescriptor descriptor2 : descriptors) {
	if (descriptor2.getProperty(IArtifactDescriptor.FORMAT) == null)
	canonical = descriptor2;
	else if (ProcessingStepHandler.canProcess(descriptor2))
	optimized = descriptor2;
	}
	boolean chooseCanonical = source.getLocation().getScheme().equals("file"); //$NON-NLS-1$
	// If the source repo is local then look for a canonical descriptor so we don't waste processing time.
	descriptor = chooseCanonical ? canonical : optimized;
	// if the descriptor is still null then we could not find our first choice of format so switch the logic.
	if (descriptor == null)
	descriptor = !chooseCanonical ? canonical : optimized;
	}
	}

	// if the descriptor is not set now then the repo does not have the requested artifact
	// TODO improve the reporting here. It may be the case that the repo has the artifact
	// but the client does not have a processor
	if (descriptor == null) {
	setResult(new Status(IStatus.ERROR, Activator.ID, NLS.bind(Messages.artifact_not_found, getArtifactKey())));
	return;
	}

	IArtifactDescriptor destinationDescriptor = getDestinationDescriptor(descriptor, descriptor == canonical);
	IStatus status = transfer(destinationDescriptor, descriptor, monitor);
	// if ok, cancelled or transfer has already been done with the canonical form return with status set
	if (status.getSeverity() == IStatus.CANCEL) {
	setResult(status);
	return;
	}
	if (monitor.isCanceled()) {
	setResult(Status.CANCEL_STATUS);
	return;
	}
	if (status.isOK()) {
	setResult(status);
	return;
	}

	// failed, first remove possibly erroneously added descriptor
	if (target.contains(destinationDescriptor))
	target.removeDescriptor(destinationDescriptor);

	if (descriptor == canonical \|\| canonical == null) {
	setResult(status);
	return;
	}

	IStatus canonicalStatus = transfer(getDestinationDescriptor(canonical, true), canonical, monitor);
	// To prevent the optimized transfer status severity from dominating the canonical, only merge
	// if the canonical severity is equal to or higher than the optimized transfer severity.
	if (canonicalStatus.getSeverity() < status.getSeverity())
	setResult(canonicalStatus);
	else
	setResult(new MultiStatus(Activator.ID, canonicalStatus.getCode() != 0 ? canonicalStatus.getCode() : status.getCode(), new IStatus[] {status, canonicalStatus}, Messages.MirrorRequest_multipleDownloadProblems, null));
	}

	private IArtifactDescriptor getDestinationDescriptor(IArtifactDescriptor sourceDescriptor, boolean isCanonical) {
	// Get the descriptor to use to store the artifact
	// Since we are mirroring, ensure we clear out data from the original descriptor that may
	// not apply in the new repo location.
	// TODO this is brittle. perhaps the repo itself should do this? there are cases where
	// we really do need to give the repo the actual descriptor to use however...
	IArtifactDescriptor destinationDescriptor = target.createArtifactDescriptor(sourceDescriptor.getArtifactKey());
	// destinationDescriptor.setProcessingSteps(EMPTY_STEPS);
	// destinationDescriptor.setProperty(IArtifactDescriptor.DOWNLOAD_MD5, null);
	// destinationDescriptor.setProperty(IArtifactDescriptor.DOWNLOAD_CONTENTTYPE, null);
	// destinationDescriptor.setProperty(IArtifactDescriptor.FORMAT, null);
	if (targetDescriptorProperties != null && destinationDescriptor instanceof ArtifactDescriptor)
	((ArtifactDescriptor) destinationDescriptor).addProperties(targetDescriptorProperties);
	if (targetRepositoryProperties != null && destinationDescriptor instanceof SimpleArtifactDescriptor)
	((SimpleArtifactDescriptor) destinationDescriptor).addRepositoryProperties(targetRepositoryProperties);
	if (isCanonical && destinationDescriptor instanceof ArtifactDescriptor) {
	// keep some safety properties
	if (sourceDescriptor.getProperty(PGPSignatureVerifier.PGP_SIGNATURES_PROPERTY_NAME) != null) {
	((ArtifactDescriptor) destinationDescriptor)
	.addProperties(Map.of(PGPSignatureVerifier.PGP_SIGNATURES_PROPERTY_NAME,
	sourceDescriptor.getProperty(PGPSignatureVerifier.PGP_SIGNATURES_PROPERTY_NAME)));
	}
	}
	return destinationDescriptor;
	}

	/**
	* Keep retrying the source repository until it reports back that it will be impossible
	* to get the artifact from it.
	* @param destinationDescriptor
	* @param sourceDescriptor
	* @param monitor
	* @return the status of the transfer operation
	*/
	protected IStatus transfer(IArtifactDescriptor destinationDescriptor, IArtifactDescriptor sourceDescriptor, IProgressMonitor monitor) {
	MultiStatus allResults = new MultiStatus(Activator.ID, 0, NLS.bind(Messages.MirrorRequest_transferFailed, sourceDescriptor), null);
	IStatus lastResult = Status.OK_STATUS;
	// go until we get one (OK), there are no more mirrors to consider or the operation is cancelled.
	// Put a hard limit of MAX_RETRY_REQUEST so we don't end up in an infinite loop.
	// Really, if you've tried MAX_RETRY_REQUEST times without success, it's time to give up
	// TODO Should we log that we gave up because of the retry count?
	// TODO this needs to be redone with a much better mirror management scheme.

	int counter = 0;
	do {
	lastResult = transferSingle(destinationDescriptor, sourceDescriptor, monitor);
	allResults.add(lastResult);
	if (lastResult.getException() instanceof Error) {
	// Error is more severe than Exception - e.g. an OutOfMemoryError should not be ignored and might hinder further processing
	throw (Error) lastResult.getException();
	}
	} while (lastResult.getSeverity() == IStatus.ERROR && lastResult.getCode() == IArtifactRepository.CODE_RETRY && counter++ < MAX_RETRY_REQUEST);
	IProvisioningEventBus bus = source.getProvisioningAgent().getService(IProvisioningEventBus.class);
	if (bus != null)
	bus.publishEvent(new MirrorEvent(source, sourceDescriptor, lastResult.isOK() ? lastResult : (allResults.getChildren().length <= 1 ? lastResult : allResults)));
	if (lastResult.isOK()) {
	collectStats(sourceDescriptor, monitor);
	return lastResult;
	} else if (allResults.getChildren().length <= 1) {
	return lastResult;
	}
	return allResults;
	}

	/**
	* Collect download statistics, if specified by the descriptor and the source repository
	*/
	private void collectStats(IArtifactDescriptor sourceDescriptor, IProgressMonitor monitor) {
	final String statsProperty = sourceDescriptor.getProperty(PROP_DOWNLOAD_STATS);
	if (statsProperty == null)
	return;
	String statsRoot = sourceDescriptor.getRepository().getProperties().get(PROP_STATS_URI);
	if (statsRoot == null)
	return;
	URI statsURI;
	try {
	statsURI = URIUtil.append(new URI(statsRoot), statsProperty);
	if (downloadStatsParamters != null) {
	try {
	statsURI = new URI(statsURI.getScheme(), statsURI.getUserInfo(), statsURI.getHost(), statsURI.getPort(), statsURI.getPath(), statsURI.getQuery() == null ? downloadStatsParamters : downloadStatsParamters + "&" + statsURI.getQuery(), statsURI.getFragment()); //$NON-NLS-1$
	} catch (URISyntaxException e) {
	LogHelper.log(new Status(IStatus.WARNING, Activator.ID, "Unable to create download statistics due to invalid URL query: " + statsRoot + " suffix: " + statsProperty + " query: " + downloadStatsParamters)); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
	}
	}
	} catch (URISyntaxException e) {
	LogHelper.log(new Status(IStatus.WARNING, Activator.ID, "Unable to report download statistics due to invalid URL: " + statsRoot + " suffix: " + statsProperty)); //$NON-NLS-1$ //$NON-NLS-2$
	return;
	}
	try {
	transport.getLastModified(statsURI, monitor);
	} catch (FileNotFoundException e) {
	//ignore because it is expected that the statistics URI doesn't represent an existing file
	} catch (Exception e) {
	LogHelper.log(new Status(IStatus.WARNING, Activator.ID, "Failure reporting download statistics to URL: " + statsURI, e)); //$NON-NLS-1$
	}
	}

	private IStatus transferSingle(IArtifactDescriptor destinationDescriptor, IArtifactDescriptor sourceDescriptor, IProgressMonitor monitor) {
	OutputStream destination;
	try {
	destination = target.getOutputStream(destinationDescriptor);
	} catch (ProvisionException e) {
	return e.getStatus();
	}

	IStatus status = null;
	Throwable priorException = null;
	// Do the actual transfer
	try {
	status = getArtifact(sourceDescriptor, destination, monitor);
	if (destination instanceof IStateful && status != null && !status.isOK()) {
	IStatus destStatus = ((IStateful) destination).getStatus();
	IStatus root = extractRootCause(status);
	Throwable e = root != null ? root.getException() : null;
	((IStateful) destination).setStatus(new MultiStatus(Activator.ID, status.getCode(), new IStatus[] {status, destStatus}, status.getMessage(), e));
	}
	} catch (RuntimeException e) {
	priorException = e;
	throw e;
	} catch (Error e) {
	priorException = e;
	throw e;
	} finally {
	try {
	destination.close();
	} catch (IOException e) {
	if (priorException == null) // don't mask a formerly thrown Exception/Error
	{
	if (status != null && status.getSeverity() == IStatus.ERROR && status.getCode() == IArtifactRepository.CODE_RETRY)
	return new MultiStatus(Activator.ID, status.getCode(), new IStatus[] {status}, NLS.bind(Messages.error_closing_stream, getArtifactKey(), target.getLocation()), e);
	return new Status(IStatus.ERROR, Activator.ID, NLS.bind(Messages.error_closing_stream, getArtifactKey(), target.getLocation()), e);
	}
	// otherwise it is already thrown
	}
	}
	return status;
	}

	protected IStatus getArtifact(IArtifactDescriptor sourceDescriptor, OutputStream destination, IProgressMonitor monitor) {
	return getSourceRepository().getArtifact(sourceDescriptor, destination, monitor);
	}

	/**
	* Extract the root cause. The root cause is the first severe non-MultiStatus status
	* containing an exception when searching depth first otherwise null.
	* @param status
	* @return root cause
	*/
	private static IStatus extractRootCause(IStatus status) {
	if (status == null)
	return null;
	if (!status.isMultiStatus())
	return constraintStatus(status);

	IStatus[] children = ((MultiStatus) status).getChildren();
	if (children == null)
	return constraintStatus(status);

	for (IStatus element : children) {
	IStatus deeper = extractRootCause(element);
	if (deeper != null)
	return deeper;
	}

	return constraintStatus(status);
	}

	private static IStatus constraintStatus(IStatus status) {
	return status.getSeverity() == IStatus.ERROR && status.getException() != null ? status : null;
	}

	@Override
	public String toString() {
	return Messages.mirroring + getArtifactKey() + " into " + target; //$NON-NLS-1$
	}
	}