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</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="spdy-implementing-push"></a>Implement a custom SPDY PushStrategy</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="spdy-implementing-push.html#d0e10368">
PushStrategy API
</a></span></dt><dt><span class="section"><a href="spdy-implementing-push.html#d0e10386">ReferrerPushStrategy</a></span></dt></dl></div><p>
The ReferrerPushStrategy that is distributed with Jetty (<a class="xref" href="spdy-configuring-push.html" title="Configuring SPDY push">Configuring SPDY push</a>) does a
great job to automatically detect subresources to push for a given main resource. However there might be
reasons to implement your own push strategy.
</p><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="d0e10368"></a>
PushStrategy API
</h3></div></div></div><p>The interface that needs to be implemented is<a class="link" href="http://download.eclipse.org/jetty/stable-9/apidocs/org/eclipse/jetty/spdy/server/http/PushStrategy.html" target="_top">PushStrategy</a>. For each
request Jetty will call the
<a class="link" href="http://download.eclipse.org/jetty/stable-9/apidocs/org/eclipse/jetty/spdy/server/http/PushStrategy.html#apply(org.eclipse.jetty.spdy.api.Stream, org.eclipse.jetty.util.Fields, org.eclipse.jetty.util.Fields)" target="_top">
apply
</a>
method, which will return a Set with the resources to push. This is the apply method's signature:
</p><div class="informalexample"><script type="syntaxhighlighter" class="brush: java;toolbar: false">
<![CDATA[
/**
* <p>Applies the SPDY push logic for the primary resource.</p>
*
* @param stream the primary resource stream
* @param requestHeaders the primary resource request headers
* @param responseHeaders the primary resource response headers
* @return a list of secondary resource URIs to push
*/
public Set<String> apply(Stream stream, Fields requestHeaders, Fields responseHeaders);
]]>
</script></div><p>
The parameters are the
<a class="link" href="http://download.eclipse.org/jetty/stable-9/apidocs/org/eclipse/jetty/spdy/api/Stream.html" target="_top">Stream
</a>
for the primary resource request, the request and the response header fields. Based on this information the
implementation has to decide which resources to push and return a Set&lt;String&gt; containing the URLs for
the resources to push.
Jetty will then open a push stream for each URL returned in that list and push the contents of that file.
This is the only method that you need to implement.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="d0e10386"></a>ReferrerPushStrategy</h3></div></div></div><p>For reference and as a working example use the
<a class="link" href="http://download.eclipse.org/jetty/stable-9/apidocs/org/eclipse/jetty/spdy/server/http/ReferrerPushStrategy.html" target="_top">ReferrerPushStrategy
</a>
source code:
</p><div class="informalexample"><script type="syntaxhighlighter" class="brush: java;toolbar: false">
<![CDATA[//
// ========================================================================
// Copyright (c) 1995-2013 Mort Bay Consulting Pty. Ltd.
// ------------------------------------------------------------------------
// All rights reserved. This program and the accompanying materials
// are made available under the terms of the Eclipse Public License v1.0
// and Apache License v2.0 which accompanies this distribution.
//
// The Eclipse Public License is available at
// http://www.eclipse.org/legal/epl-v10.html
//
// The Apache License v2.0 is available at
// http://www.opensource.org/licenses/apache2.0.php
//
// You may elect to redistribute this code under either of these licenses.
// ========================================================================
//
package org.eclipse.jetty.spdy.server.http;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Locale;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.CopyOnWriteArraySet;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;
import java.util.regex.Pattern;
import org.eclipse.jetty.spdy.api.Stream;
import org.eclipse.jetty.util.Fields;
import org.eclipse.jetty.util.log.Log;
import org.eclipse.jetty.util.log.Logger;
/**
* <p>A SPDY push strategy that auto-populates push metadata based on referrer URLs.<p>A typical request for a main
* resource such as {@code index.html} is immediately followed by a number of requests for associated resources.
* Associated resource requests will have a {@code Referer} HTTP header that points to {@code index.html}, which is
* used to link the associated resource to the main resource.<p>However, also following a hyperlink generates a
* HTTP request with a {@code Referer} HTTP header that points to {@code index.html}; therefore a proper value for
* {@link #setReferrerPushPeriod(int)} has to be set. If the referrerPushPeriod for a main resource has elapsed,
* no more associated resources will be added for that main resource.<p>This class distinguishes associated main
* resources by their URL path suffix and content type. CSS stylesheets, images and JavaScript files have
* recognizable URL path suffixes that are classified as associated resources. The suffix regexs can be configured by
* constructor argument</p>
* <p>When CSS stylesheets refer to images, the CSS image request will have the CSS stylesheet as referrer. This
* implementation will push also the CSS image.<p>The push metadata built by this implementation is limited by the
* number of pages of the application itself, and by the {@link #setMaxAssociatedResources(int)} max associated resources}
* parameter. This parameter limits the number of associated resources per each main resource, so that if a main
* resource has hundreds of associated resources, only up to the number specified by this parameter will be pushed.
*/
public class ReferrerPushStrategy implements PushStrategy
{
private static final Logger logger = Log.getLogger(ReferrerPushStrategy.class);
private final ConcurrentMap<String, MainResource> mainResources = new ConcurrentHashMap<>();
private final Set<Pattern> pushRegexps = new HashSet<>();
private final Set<String> pushContentTypes = new HashSet<>();
private final Set<Pattern> allowedPushOrigins = new HashSet<>();
private final Set<Pattern> userAgentBlacklist = new HashSet<>();
private volatile int maxAssociatedResources = 32;
private volatile int referrerPushPeriod = 5000;
public ReferrerPushStrategy()
{
List<String> defaultPushRegexps = Arrays.asList(".*\\.css", ".*\\.js", ".*\\.png", ".*\\.jpeg", ".*\\.jpg",
".*\\.gif", ".*\\.ico");
addPushRegexps(defaultPushRegexps);
List<String> defaultPushContentTypes = Arrays.asList(
"text/css",
"text/javascript", "application/javascript", "application/x-javascript",
"image/png", "image/x-png",
"image/jpeg",
"image/gif",
"image/x-icon", "image/vnd.microsoft.icon");
this.pushContentTypes.addAll(defaultPushContentTypes);
}
public void setPushRegexps(List<String> pushRegexps)
{
pushRegexps.clear();
addPushRegexps(pushRegexps);
}
private void addPushRegexps(List<String> pushRegexps)
{
for (String pushRegexp : pushRegexps)
this.pushRegexps.add(Pattern.compile(pushRegexp));
}
public void setPushContentTypes(List<String> pushContentTypes)
{
pushContentTypes.clear();
pushContentTypes.addAll(pushContentTypes);
}
public void setAllowedPushOrigins(List<String> allowedPushOrigins)
{
allowedPushOrigins.clear();
for (String allowedPushOrigin : allowedPushOrigins)
this.allowedPushOrigins.add(Pattern.compile(allowedPushOrigin.replace(".", "\\.").replace("*", ".*")));
}
public void setUserAgentBlacklist(List<String> userAgentPatterns)
{
userAgentBlacklist.clear();
for (String userAgentPattern : userAgentPatterns)
userAgentBlacklist.add(Pattern.compile(userAgentPattern));
}
public void setMaxAssociatedResources(int maxAssociatedResources)
{
this.maxAssociatedResources = maxAssociatedResources;
}
public void setReferrerPushPeriod(int referrerPushPeriod)
{
this.referrerPushPeriod = referrerPushPeriod;
}
public Set<Pattern> getPushRegexps()
{
return pushRegexps;
}
public Set<String> getPushContentTypes()
{
return pushContentTypes;
}
public Set<Pattern> getAllowedPushOrigins()
{
return allowedPushOrigins;
}
public Set<Pattern> getUserAgentBlacklist()
{
return userAgentBlacklist;
}
public int getMaxAssociatedResources()
{
return maxAssociatedResources;
}
public int getReferrerPushPeriod()
{
return referrerPushPeriod;
}
@Override
public Set<String> apply(Stream stream, Fields requestHeaders, Fields responseHeaders)
{
Set<String> result = Collections.<String>emptySet();
short version = stream.getSession().getVersion();
if (!isIfModifiedSinceHeaderPresent(requestHeaders) && isValidMethod(requestHeaders.get(HTTPSPDYHeader.METHOD
.name(version)).value()) && !isUserAgentBlacklisted(requestHeaders))
{
String scheme = requestHeaders.get(HTTPSPDYHeader.SCHEME.name(version)).value();
String host = requestHeaders.get(HTTPSPDYHeader.HOST.name(version)).value();
String origin = scheme + "://" + host;
String url = requestHeaders.get(HTTPSPDYHeader.URI.name(version)).value();
String absoluteURL = origin + url;
logger.debug("Applying push strategy for {}", absoluteURL);
if (isMainResource(url, responseHeaders))
{
MainResource mainResource = getOrCreateMainResource(absoluteURL);
result = mainResource.getResources();
}
else if (isPushResource(url, responseHeaders))
{
Fields.Field referrerHeader = requestHeaders.get("referer");
if (referrerHeader != null)
{
String referrer = referrerHeader.value();
MainResource mainResource = mainResources.get(referrer);
if (mainResource == null)
mainResource = getOrCreateMainResource(referrer);
Set<String> pushResources = mainResource.getResources();
if (!pushResources.contains(url))
mainResource.addResource(url, origin, referrer);
else
result = getPushResources(absoluteURL);
}
}
logger.debug("Pushing {} resources for {}: {}", result.size(), absoluteURL, result);
}
return result;
}
private Set<String> getPushResources(String absoluteURL)
{
Set<String> result = Collections.emptySet();
if (mainResources.get(absoluteURL) != null)
result = mainResources.get(absoluteURL).getResources();
return result;
}
private MainResource getOrCreateMainResource(String absoluteURL)
{
MainResource mainResource = mainResources.get(absoluteURL);
if (mainResource == null)
{
logger.debug("Creating new main resource for {}", absoluteURL);
MainResource value = new MainResource(absoluteURL);
mainResource = mainResources.putIfAbsent(absoluteURL, value);
if (mainResource == null)
mainResource = value;
}
return mainResource;
}
private boolean isIfModifiedSinceHeaderPresent(Fields headers)
{
return headers.get("if-modified-since") != null;
}
private boolean isValidMethod(String method)
{
return "GET".equalsIgnoreCase(method);
}
private boolean isMainResource(String url, Fields responseHeaders)
{
return !isPushResource(url, responseHeaders);
}
public boolean isUserAgentBlacklisted(Fields headers)
{
Fields.Field userAgentHeader = headers.get("user-agent");
if (userAgentHeader != null)
for (Pattern userAgentPattern : userAgentBlacklist)
if (userAgentPattern.matcher(userAgentHeader.value()).matches())
return true;
return false;
}
private boolean isPushResource(String url, Fields responseHeaders)
{
for (Pattern pushRegexp : pushRegexps)
{
if (pushRegexp.matcher(url).matches())
{
Fields.Field header = responseHeaders.get("content-type");
if (header == null)
return true;
String contentType = header.value().toLowerCase(Locale.ENGLISH);
for (String pushContentType : pushContentTypes)
if (contentType.startsWith(pushContentType))
return true;
}
}
return false;
}
private class MainResource
{
private final String name;
private final CopyOnWriteArraySet<String> resources = new CopyOnWriteArraySet<>();
private final AtomicLong firstResourceAdded = new AtomicLong(-1);
private MainResource(String name)
{
this.name = name;
}
public boolean addResource(String url, String origin, String referrer)
{
// We start the push period here and not when initializing the main resource, because a browser with a
// prefilled cache won't request the subresources. If the browser with warmed up cache now hits the main
// resource after a server restart, the push period shouldn't start until the first subresource is
// being requested.
firstResourceAdded.compareAndSet(-1, System.nanoTime());
long delay = TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - firstResourceAdded.get());
if (!referrer.startsWith(origin) && !isPushOriginAllowed(origin))
{
logger.debug("Skipped store of push metadata {} for {}: Origin: {} doesn't match or origin not allowed",
url, name, origin);
return false;
}
// This check is not strictly concurrent-safe, but limiting
// the number of associated resources is achieved anyway
// although in rare cases few more resources will be stored
if (resources.size() >= maxAssociatedResources)
{
logger.debug("Skipped store of push metadata {} for {}: max associated resources ({}) reached",
url, name, maxAssociatedResources);
return false;
}
if (delay > referrerPushPeriod)
{
logger.debug("Delay: {}ms longer than referrerPushPeriod: {}ms. Not adding resource: {} for: {}", delay, referrerPushPeriod, url, name);
return false;
}
logger.debug("Adding resource: {} for: {} with delay: {}ms.", url, name, delay);
resources.add(url);
return true;
}
public Set<String> getResources()
{
return Collections.unmodifiableSet(resources);
}
public String toString()
{
return "MainResource: " + name + " associated resources:" + resources.size();
}
private boolean isPushOriginAllowed(String origin)
{
for (Pattern allowedPushOrigin : allowedPushOrigins)
if (allowedPushOrigin.matcher(origin).matches())
return true;
return false;
}
}
}
]]>
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