/**
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.solr.servlet.cache;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.Collections;
import java.util.Map;
import java.util.WeakHashMap;
import java.util.List;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.lucene.index.IndexReader;
import org.apache.solr.core.SolrCore;
import org.apache.solr.core.SolrConfig;
import org.apache.solr.core.SolrConfig.HttpCachingConfig.LastModFrom;
import org.apache.solr.common.SolrException;
import org.apache.solr.common.SolrException.ErrorCode;
import org.apache.solr.search.SolrIndexSearcher;
import org.apache.solr.request.SolrQueryRequest;
import org.apache.solr.response.SolrQueryResponse;
import org.apache.commons.codec.binary.Base64;
public final class HttpCacheHeaderUtil {
public static void sendNotModified(HttpServletResponse res)
throws IOException {
res.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
}
public static void sendPreconditionFailed(HttpServletResponse res)
throws IOException {
res.setStatus(HttpServletResponse.SC_PRECONDITION_FAILED);
}
/**
* Weak Ref based cache for keeping track of core specific etagSeed
* and the last computed etag.
*
* @see #calcEtag
*/
private static Map<SolrCore, EtagCacheVal> etagCoreCache
= new WeakHashMap<SolrCore, EtagCacheVal>();
/** @see #etagCoreCache */
private static class EtagCacheVal {
private final String etagSeed;
private String etagCache = null;
private long indexVersionCache=-1;
public EtagCacheVal(final String etagSeed) {
this.etagSeed = etagSeed;
}
public String calcEtag(final long currentIndexVersion) {
if (currentIndexVersion != indexVersionCache) {
indexVersionCache=currentIndexVersion;
try {
etagCache = "\""
+ new String(Base64.encodeBase64((Long.toHexString
(Long.reverse(indexVersionCache))
+ etagSeed).getBytes()), "US-ASCII")
+ "\"";
} catch (UnsupportedEncodingException e) {
throw new RuntimeException(e); // may not happen
}
}
return etagCache;
}
}
/**
* Calculates a tag for the ETag header.
*
* @param solrReq
* @return a tag
*/
public static String calcEtag(final SolrQueryRequest solrReq) {
final SolrCore core = solrReq.getCore();
final long currentIndexVersion
= solrReq.getSearcher().getReader().getVersion();
EtagCacheVal etagCache = etagCoreCache.get(core);
if (null == etagCache) {
final String etagSeed
= core.getSolrConfig().getHttpCachingConfig().getEtagSeed();
etagCache = new EtagCacheVal(etagSeed);
etagCoreCache.put(core, etagCache);
}
return etagCache.calcEtag(currentIndexVersion);
}
/**
* Checks if one of the tags in the list equals the given etag.
*
* @param headerList
* the ETag header related header elements
* @param etag
* the ETag to compare with
* @return true if the etag is found in one of the header elements - false
* otherwise
*/
public static boolean isMatchingEtag(final List<String> headerList,
final String etag) {
for (String header : headerList) {
final String[] headerEtags = header.split(",");
for (String s : headerEtags) {
s = s.trim();
if (s.equals(etag) || "*".equals(s)) {
return true;
}
}
}
return false;
}
/**
* Calculate the appropriate last-modified time for Solr relative the current request.
*
* @param solrReq
* @return the timestamp to use as a last modified time.
*/
public static long calcLastModified(final SolrQueryRequest solrReq) {
final SolrCore core = solrReq.getCore();
final SolrIndexSearcher searcher = solrReq.getSearcher();
final LastModFrom lastModFrom
= core.getSolrConfig().getHttpCachingConfig().getLastModFrom();
long lastMod;
try {
// assume default, change if needed (getOpenTime() should be fast)
lastMod =
LastModFrom.DIRLASTMOD == lastModFrom
? IndexReader.lastModified(searcher.getReader().directory())
: searcher.getOpenTime();
} catch (IOException e) {
// we're pretty freaking screwed if this happens
throw new SolrException(ErrorCode.SERVER_ERROR, e);
}
// Get the time where the searcher has been opened
// We get rid of the milliseconds because the HTTP header has only
// second granularity
return lastMod - (lastMod % 1000L);
}
/**
* Set the Cache-Control HTTP header (and Expires if needed)
* based on the SolrConfig.
* @param conf The config of the SolrCore handling this request
* @param resp The servlet response object to modify
* @param method The request method (GET, POST, ...) used by this request
*/
public static void setCacheControlHeader(final SolrConfig conf,
final HttpServletResponse resp, final Method method) {
// We do not emit HTTP header for POST and OTHER request types
if (Method.POST==method || Method.OTHER==method) {
return;
}
final String cc = conf.getHttpCachingConfig().getCacheControlHeader();
if (null != cc) {
resp.setHeader("Cache-Control", cc);
}
Long maxAge = conf.getHttpCachingConfig().getMaxAge();
if (null != maxAge) {
resp.setDateHeader("Expires", System.currentTimeMillis()
+ (maxAge * 1000L));
}
return;
}
/**
* Sets HTTP Response cache validator headers appropriately and
* validates the HTTP Request against these using any conditional
* request headers.
*
* If the request contains conditional headers, and those headers
* indicate a match with the current known state of the system, this
* method will return "true" indicating that a 304 Status code can be
* returned, and no further processing is needed.
*
*
* @return true if the request contains conditional headers, and those
* headers indicate a match with the current known state of the
* system -- indicating that a 304 Status code can be returned to
* the client, and no further request processing is needed.
*/
public static boolean doCacheHeaderValidation(final SolrQueryRequest solrReq,
final HttpServletRequest req,
final Method reqMethod,
final HttpServletResponse resp)
throws IOException {
if (Method.POST==reqMethod || Method.OTHER==reqMethod) {
return false;
}
final long lastMod = HttpCacheHeaderUtil.calcLastModified(solrReq);
final String etag = HttpCacheHeaderUtil.calcEtag(solrReq);
resp.setDateHeader("Last-Modified", lastMod);
resp.setHeader("ETag", etag);
if (checkETagValidators(req, resp, reqMethod, etag)) {
return true;
}
if (checkLastModValidators(req, resp, lastMod)) {
return true;
}
return false;
}
/**
* Check for etag related conditional headers and set status
*
* @return true if no request processing is necessary and HTTP response status has been set, false otherwise.
* @throws IOException
*/
@SuppressWarnings("unchecked")
public static boolean checkETagValidators(final HttpServletRequest req,
final HttpServletResponse resp,
final Method reqMethod,
final String etag)
throws IOException {
// First check If-None-Match because this is the common used header
// element by HTTP clients
final List<String> ifNoneMatchList = Collections.list(req
.getHeaders("If-None-Match"));
if (ifNoneMatchList.size() > 0 && isMatchingEtag(ifNoneMatchList, etag)) {
if (reqMethod == Method.GET || reqMethod == Method.HEAD) {
sendNotModified(resp);
} else {
sendPreconditionFailed(resp);
}
return true;
}
// Check for If-Match headers
final List<String> ifMatchList = Collections.list(req
.getHeaders("If-Match"));
if (ifMatchList.size() > 0 && !isMatchingEtag(ifMatchList, etag)) {
sendPreconditionFailed(resp);
return true;
}
return false;
}
/**
* Check for modify time related conditional headers and set status
*
* @return true if no request processing is necessary and HTTP response status has been set, false otherwise.
* @throws IOException
*/
public static boolean checkLastModValidators(final HttpServletRequest req,
final HttpServletResponse resp,
final long lastMod)
throws IOException {
try {
// First check for If-Modified-Since because this is the common
// used header by HTTP clients
final long modifiedSince = req.getDateHeader("If-Modified-Since");
if (modifiedSince != -1L && lastMod <= modifiedSince) {
// Send a "not-modified"
sendNotModified(resp);
return true;
}
final long unmodifiedSince = req.getDateHeader("If-Unmodified-Since");
if (unmodifiedSince != -1L && lastMod > unmodifiedSince) {
// Send a "precondition failed"
sendPreconditionFailed(resp);
return true;
}
} catch (IllegalArgumentException iae) {
// one of our date headers was not formated properly, ignore it
/* NOOP */
}
return false;
}
/**
* Checks if the downstream request handler wants to avoid HTTP caching of
* the response.
*
* @param solrRsp The Solr response object
* @param resp The HTTP servlet response object
* @param reqMethod The HTTP request type
*/
public static void checkHttpCachingVeto(final SolrQueryResponse solrRsp,
HttpServletResponse resp, final Method reqMethod) {
// For POST we do nothing. They never get cached
if (Method.POST == reqMethod || Method.OTHER == reqMethod) {
return;
}
// If the request handler has not vetoed and there is no
// exception silently return
if (solrRsp.isHttpCaching() && solrRsp.getException() == null) {
return;
}
// Otherwise we tell the caches that we don't want to cache the response
resp.setHeader("Cache-Control", "no-cache, no-store");
// For HTTP/1.0 proxy caches
resp.setHeader("Pragma", "no-cache");
// This sets the expiry date to a date in the past
// As long as no time machines get invented this is safe
resp.setHeader("Expires", "Sat, 01 Jan 2000 01:00:00 GMT");
// We signal "just modified" just in case some broken
// proxy cache does not follow the above headers
resp.setDateHeader("Last-Modified", System.currentTimeMillis());
// We override the ETag with something different
resp.setHeader("ETag", '"'+Long.toHexString(System.currentTimeMillis())+'"');
}
}