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yacy_search_server/source/de/anomic/plasma/plasmaHTCache.java

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// plasmaHTCache.java
// -----------------------
// part of YaCy
// (C) by Michael Peter Christen; mc@anomic.de
// first published on http://www.anomic.de
// Frankfurt, Germany, 2004
// last major change: 12.02.2004
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
//
// Using this software in any meaning (reading, learning, copying, compiling,
// running) means that you agree that the Author(s) is (are) not responsible
// for cost, loss of data or any harm that may be caused directly or indirectly
// by usage of this softare or this documentation. The usage of this software
// is on your own risk. The installation and usage (starting/running) of this
// software may allow other people or application to access your computer and
// any attached devices and is highly dependent on the configuration of the
// software which must be done by the user of the software; the author(s) is
// (are) also not responsible for proper configuration and usage of the
// software, even if provoked by documentation provided together with
// the software.
//
// Any changes to this file according to the GPL as documented in the file
// gpl.txt aside this file in the shipment you received can be done to the
// lines that follows this copyright notice here, but changes must not be
// done inside the copyright notive above. A re-distribution must contain
// the intact and unchanged copyright notice.
// Contributions and changes to the program code must be marked as such.
/*
Class documentation:
This class has two purposes:
1. provide a object that carries path and header information
that shall be used as objects within a scheduler's stack
2. static methods for a cache control and cache aging
the class shall also be used to do a cache-cleaning and index creation
*/
package de.anomic.plasma;
import java.io.*;
import java.net.*;
import java.util.*;
import de.anomic.kelondro.*;
import de.anomic.tools.*;
import de.anomic.htmlFilter.*;
import de.anomic.http.*;
import de.anomic.server.*;
public final class plasmaHTCache {
private static final int stackLimit = 150; // if we exceed that limit, we do not check idle
private static final long idleDelay = 2000; // 2 seconds no hits until we think that we idle
private static final long oneday = 1000 * 60 * 60 * 24; // milliseconds of a day
private final plasmaSwitchboard switchboard;
private kelondroMap responseHeaderDB = null;
private final LinkedList cacheStack;
private final TreeMap cacheAge; // a <date+hash, cache-path> - relation
public long currCacheSize;
public long maxCacheSize;
private long lastAcc;
private final File cachePath;
public static serverLog log;
public static final int CACHE_UNFILLED = 0; // default case without assignment
public static final int CACHE_FILL = 1; // this means: update == true
public static final int CACHE_HIT = 2; // the best case: reading from Cache
public static final int CACHE_STALE_NO_RELOAD = 3; // this shall be treated as a rare case that should not appear
public static final int CACHE_STALE_RELOAD_GOOD = 4; // this means: update == true
public static final int CACHE_STALE_RELOAD_BAD = 5; // this updates only the responseHeader, not the content
public static final int CACHE_PASSING = 6; // does not touch cache, just passing
public plasmaHTCache(plasmaSwitchboard switchboard, int bufferkb) {
this.switchboard = switchboard;
int loglevel = Integer.parseInt(switchboard.getConfig("plasmaLoglevel", "2"));
this.log = new serverLog("HTCACHE", loglevel);
// set cache path
cachePath = new File(switchboard.getRootPath(),switchboard.getConfig("proxyCache","HTCACHE"));
if (!(cachePath.exists())) {
// make the cache path
cachePath.mkdir();
}
if (!(cachePath.isDirectory())) {
// if the cache does not exists or is a file and not a directory, panic
System.out.println("the cache path " + cachePath.toString() + " is not a directory or does not exists and cannot be created");
System.exit(0);
}
// open the response header database
File dbfile = new File(cachePath, "responseHeader.db");
try {
if (dbfile.exists())
responseHeaderDB = new kelondroMap(new kelondroDyn(dbfile, bufferkb * 0x400));
else
responseHeaderDB = new kelondroMap(new kelondroDyn(dbfile, bufferkb * 0x400, plasmaCrawlLURL.urlHashLength, 150));
} catch (IOException e) {
System.out.println("the request header database could not be opened: " + e.getMessage());
System.exit(0);
}
// init stack
cacheStack = new LinkedList();
// init idle check
lastAcc = System.currentTimeMillis();
// init cache age and size management
cacheAge = new TreeMap();
currCacheSize = 0;
maxCacheSize = Long.parseLong(switchboard.getConfig("proxyCacheSize", "2")); // this is megabyte
maxCacheSize = maxCacheSize * 1024 * 1024; // now it's the number of bytes
// start the cache startup thread
// this will collect information about the current cache size and elements
serverInstantThread.oneTimeJob(this, "cacheScan", log, 5000);
}
public void close() throws IOException {
responseHeaderDB.close();
}
private String ageString(long date, File f) {
String s = Integer.toHexString(f.hashCode());
while (s.length() < 8) s = "0" + s;
s = Long.toHexString(date) + s;
while (s.length() < 24) s = "0" + s;
return s;
}
public void cacheScan() {
//log.logSystem("STARTING CACHE SCANNING");
kelondroMScoreCluster doms = new kelondroMScoreCluster();
int c = 0;
enumerateFiles ef = new enumerateFiles(cachePath, true, false, true);
File f;
while (ef.hasMoreElements()) {
c++;
f = (File) ef.nextElement();
long d = f.lastModified();
//System.out.println("Cache: " + dom(f));
doms.incScore(dom(f));
currCacheSize += f.length();
cacheAge.put(ageString(d, f), f);
}
//System.out.println("%" + (String) cacheAge.firstKey() + "=" + cacheAge.get(cacheAge.firstKey()));
long ageHours = (System.currentTimeMillis() -
Long.parseLong(((String) cacheAge.firstKey()).substring(0, 16), 16)) / 3600000;
log.logSystem("CACHE SCANNED, CONTAINS " + c +
" FILES = " + currCacheSize/1048576 + "MB, OLDEST IS " +
((ageHours < 24) ? (ageHours + " HOURS") : ((ageHours / 24) + " DAYS")) +
" OLD");
// start to prefetch ip's from dns
String dom;
long start = System.currentTimeMillis();
String ip, result = "";
c = 0;
while ((doms.size() > 0) && (c < 50) && ((System.currentTimeMillis() - start) < 60000)) {
dom = (String) doms.getMaxObject();
ip = httpc.dnsResolve(dom);
if (ip == null) break;
result += ", " + dom + "=" + ip;
log.logSystem("PRE-FILLED " + dom + "=" + ip);
c++;
doms.deleteScore(dom);
// wait a short while to prevent that this looks like a DoS
try {Thread.currentThread().sleep(100);} catch (InterruptedException e) {}
}
if (result.length() > 2) log.logSystem("PRE-FILLED DNS CACHE, FETCHED " + c +
" ADDRESSES: " + result.substring(2));
}
private String dom(File f) {
String s = f.toString().substring(cachePath.toString().length() + 1);
int p = s.indexOf("/");
if (p < 0) p = s.indexOf("\\");
if (p < 0) return null;
return s.substring(0, p);
}
public httpHeader getCachedResponse(String urlHash) throws IOException {
httpHeader header = new httpHeader(null, responseHeaderDB.get(urlHash));
//System.out.println("DEBUG: getCachedResponse hash=" + urlHash + ", header=" + header.toString());
return header;
}
public boolean idle() {
return (System.currentTimeMillis() > (idleDelay + lastAcc));
}
public boolean full() {
return (cacheStack.size() > stackLimit);
}
public boolean empty() {
return (cacheStack.size() == 0);
}
synchronized public void stackProcess(Entry entry) throws IOException {
lastAcc = System.currentTimeMillis();
if (full())
process(entry);
else
cacheStack.add(entry);
}
synchronized public void stackProcess(Entry entry, byte[] cacheArray) throws IOException {
lastAcc = System.currentTimeMillis();
entry.cacheArray = cacheArray;
if (full())
process(entry);
else
cacheStack.add(entry);
}
public int size() {
return cacheStack.size();
}
synchronized public void process(Entry entry) throws IOException {
if (entry == null) return;
// store response header
if ((entry.status == CACHE_FILL) ||
(entry.status == CACHE_STALE_RELOAD_GOOD) ||
(entry.status == CACHE_STALE_RELOAD_BAD)) {
responseHeaderDB.set(entry.nomalizedURLHash, entry.responseHeader);
}
// work off unwritten files and undone parsing
String storeError = null;
if (((entry.status == CACHE_FILL) || (entry.status == CACHE_STALE_RELOAD_GOOD)) &&
((storeError = entry.shallStoreCache()) == null)) {
// write file if not written yet
if (entry.cacheArray != null) try {
if (entry.cacheFile.exists()) {
currCacheSize -= entry.cacheFile.length();
entry.cacheFile.delete();
}
entry.cacheFile.getParentFile().mkdirs();
log.logInfo("WRITE FILE (" + entry.cacheArray.length + " bytes) " + entry.cacheFile);
serverFileUtils.write(entry.cacheArray, entry.cacheFile);
log.logDebug("AFTER WRITE cacheArray = " + entry.cacheFile + ": " + ((entry.cacheArray == null) ? "empty" : "full"));
//entry.cacheArray = null;
} catch (FileNotFoundException e) {
// this is the case of a "(Not a directory)" error, which should be prohibited
// by the shallStoreCache() property. However, sometimes the error still occurs
// In this case do nothing.
log.logError("File storage failed: " + e.getMessage());
}
// update statistics
currCacheSize += entry.cacheFile.length();
cacheAge.put(ageString(entry.cacheFile.lastModified(), entry.cacheFile), entry.cacheFile);
// enqueue in switchboard
switchboard.enQueue(entry);
} else if (entry.status == CACHE_PASSING) {
// even if the file should not be stored in the cache, it can be used to be indexed
if (storeError != null) log.logDebug("NOT STORED " + entry.cacheFile + ":" + storeError);
// enqueue in switchboard
switchboard.enQueue(entry);
}
// write log
switch (entry.status) {
case CACHE_UNFILLED:
log.logInfo("CACHE UNFILLED: " + entry.cacheFile); break;
case CACHE_FILL:
log.logInfo("CACHE FILL: " + entry.cacheFile +
((entry.cacheArray == null) ? "" : " (cacheArray is filled)") +
((entry.scraper == null) ? "" : " (scraper is filled)"));
break;
case CACHE_HIT:
log.logInfo("CACHE HIT: " + entry.cacheFile); break;
case CACHE_STALE_NO_RELOAD:
log.logInfo("CACHE STALE, NO RELOAD: " + entry.cacheFile); break;
case CACHE_STALE_RELOAD_GOOD:
log.logInfo("CACHE STALE, NECESSARY RELOAD: " + entry.cacheFile); break;
case CACHE_STALE_RELOAD_BAD:
log.logInfo("CACHE STALE, SUPERFLUOUS RELOAD: " + entry.cacheFile); break;
case CACHE_PASSING:
log.logInfo("PASSING: " + entry.cacheFile); break;
default:
log.logInfo("CACHE STATE UNKNOWN: " + entry.cacheFile); break;
}
}
public boolean job() {
if (empty()) return false;
try {
File f;
int workoff;
workoff = 1 + cacheStack.size() / 10;
// we want to work off always 10 % to prevent that we collaps
while ((workoff-- > 0) && (!(empty()))) {
process((Entry) cacheStack.removeFirst());
}
// loop until we are not idle or nothing more to do
while ((!empty()) && (idle())) {
// work off stack and store entries to file system
process((Entry) cacheStack.removeFirst());
// clean up cache to have enough space for next entries
while (currCacheSize > maxCacheSize) {
f = (File) cacheAge.remove(cacheAge.firstKey());
if (f.exists()) {
currCacheSize -= f.length();
f.delete();
log.logInfo("DELETED OLD CACHE : " + f.toString());
}
}
}
} catch (IOException e) {
System.out.println("The proxy cache manager has died because of an IO-problem: " + e.getMessage());
e.printStackTrace(System.out);
System.exit(-1);
}
return true;
}
public static boolean isPicture(httpHeader response) {
Object ct = response.get("Content-Type");
if (ct == null) return false;
return ((String)ct).toUpperCase().startsWith("IMAGE");
}
public static boolean isText(httpHeader response) {
Object ct = response.get("Content-Type");
if (ct == null) return false;
return ((String)ct).toUpperCase().startsWith("TEXT");
}
public static boolean noIndexingURL(String urlString) {
if (urlString == null) return false;
urlString = urlString.toLowerCase();
return (
(urlString.endsWith(".gz")) ||
(urlString.endsWith(".msi")) ||
(urlString.endsWith(".doc")) ||
(urlString.endsWith(".zip")) ||
(urlString.endsWith(".tgz")) ||
(urlString.endsWith(".rar")) ||
(urlString.endsWith(".pdf")) ||
(urlString.endsWith(".ppt")) ||
(urlString.endsWith(".xls")) ||
(urlString.endsWith(".log")) ||
(urlString.endsWith(".java")) ||
(urlString.endsWith(".c")) ||
(urlString.endsWith(".p"))
);
}
// this method creates from a given host and path a cache path
public File getCachePath(URL url) {
// from a given host (which may also be an IPv4 - number, but not IPv6 or
// a domain; all without leading 'http://') and a path (which must start
// with a leading '/', and may also end in an '/') a path to a file
// in the file system with root as given in cachePath is constructed
// it will also be ensured, that the complete path exists; if necessary
// that path will be generated
//System.out.println("DEBUG: getCachedPath=" + url.toString());
String remotePath = url.getPath();
if (!(remotePath.startsWith("/"))) remotePath = "/" + remotePath;
if (remotePath.endsWith("/")) remotePath = remotePath + "ndx";
if (remotePath.indexOf('#') > 0) remotePath.substring(0, remotePath.indexOf('#'));
remotePath.replace('?', '_'); remotePath.replace('&', '_'); // yes this is not reversible, but that is not needed
int port = url.getPort();
if (port < 0) port = 80;
return new File(this.cachePath, url.getHost() + ((port == 80) ? "" : ("+" + port)) + remotePath);
}
public static URL getURL(File cachePath, File f) {
// this is the reverse function to getCachePath: it constructs the url as string
// from a given storage path
String s = f.toString().replace('\\', '/');
String c = cachePath.toString().replace('\\', '/');
//System.out.println("DEBUG: getURL for c=" + c + ", s=" + s);
int p = s.lastIndexOf(c);
if (p >= 0) {
s = s.substring(p + c.length());
while (s.startsWith("/")) s = s.substring(1);
if ((p = s.indexOf("+")) >= 0) {
s = s.substring(0, p) + ":" + s.substring(p + 1);
} else {
p = s.indexOf("/");
if (p < 0)
s = s + ":80/";
else
s = s.substring(0, p) + ":80" + s.substring(p);
}
if (s.endsWith("ndx")) s = s.substring(0, s.length() - 3);
//System.out.println("DEBUG: getURL url=" + s);
try {
return new URL("http://" + s);
} catch (Exception e) {
return null;
}
}
return null;
}
public static boolean isPOST(String urlString) {
return ((urlString.indexOf("?") >= 0) ||
(urlString.indexOf("&") >= 0));
}
public static boolean isCGI(String urlString) {
return ((urlString.toLowerCase().indexOf(".cgi") >= 0) ||
(urlString.toLowerCase().indexOf(".exe") >= 0));
}
public Entry newEntry(Date initDate, int depth, URL url,
httpHeader requestHeader,
String responseStatus, httpHeader responseHeader,
String initiator,
plasmaCrawlProfile.entry profile) {
//System.out.println("NEW ENTRY: " + url.toString()); // DEBUG
return new Entry(initDate, depth, url, requestHeader, responseStatus, responseHeader, initiator, profile);
}
public final class Entry {
// the class objects
public Date initDate; // the date when the request happened; will be used as a key
public int depth; // the depth of prefetching
public httpHeader requestHeader; // we carry also the header to prevent too many file system access
public String responseStatus;
public httpHeader responseHeader; // we carry also the header to prevent too many file system access
public File cacheFile; // the cache file
public byte[] cacheArray; // or the cache as byte-array
public URL url;
public String nomalizedURLHash;
public String nomalizedURLString;
public int status; // cache load/hit/stale etc status
public Date lastModified;
public char doctype;
public String language;
public plasmaCrawlProfile.entry profile;
private String initiator;
public htmlFilterContentScraper scraper;
public Entry(Date initDate, int depth, URL url,
httpHeader requestHeader,
String responseStatus, httpHeader responseHeader,
String initiator,
plasmaCrawlProfile.entry profile) {
// normalize url
this.nomalizedURLString = htmlFilterContentScraper.urlNormalform(url);
try {
this.url = new URL(nomalizedURLString);
} catch (MalformedURLException e) {
System.out.println("internal error at httpdProxyCache.Entry: " + e);
System.exit(-1);
}
this.cacheFile = getCachePath(this.url);
this.nomalizedURLHash = plasmaCrawlLURL.urlHash(nomalizedURLString);
// assigned:
this.initDate = initDate;
this.depth = depth;
this.requestHeader = requestHeader;
this.responseStatus = responseStatus;
this.responseHeader = responseHeader;
this.profile = profile;
this.initiator = (initiator == null) ? null : ((initiator.length() == 0) ? null: initiator);
// calculated:
if (responseHeader == null) {
try {
throw new RuntimeException("RESPONSE HEADER = NULL");
} catch (Exception e) {
System.out.println("RESPONSE HEADER = NULL in " + url);
e.printStackTrace();
System.exit(0);
}
lastModified = new Date();
} else {
lastModified = responseHeader.lastModified();
if (lastModified == null) lastModified = new Date(); // does not exist in header
}
this.doctype = plasmaWordIndexEntry.docType(nomalizedURLString);
this.language = plasmaWordIndexEntry.language(url);
// to be defined later:
this.cacheArray = null;
this.status = CACHE_UNFILLED;
this.scraper = null;
}
public String initiator() {
return initiator;
}
public boolean proxy() {
return initiator() == null;
}
public long size() {
if (cacheArray == null) return 0; else return cacheArray.length;
}
public URL referrerURL() {
if (requestHeader == null) return null;
try {
return new URL((String) requestHeader.get("Referer", ""));
} catch (Exception e) {
return null;
}
}
public boolean update() {
return ((status == CACHE_FILL) || (status == CACHE_STALE_RELOAD_GOOD));
}
// the following three methods for cache read/write granting shall be as loose as possible
// but also as strict as necessary to enable caching of most items
public String shallStoreCache() {
// returns NULL if the answer is TRUE
// in case of FALSE, the reason as String is returned
// check profile
if (!(profile.storeHTCache())) return "storage_not_wanted";
// decide upon header information if a specific file should be stored to the cache or not
// if the storage was requested by prefetching, the request map is null
// check status code
if (!((responseStatus.startsWith("200")) || (responseStatus.startsWith("203")))) return "bad_status_" + responseStatus.substring(0,3);
// check storage location
// sometimes a file name is equal to a path name in the same directory;
// or sometimes a file name is equal a directory name created earlier;
// we cannot match that here in the cache file path and therefore omit writing into the cache
if ((cacheFile.getParentFile().isFile()) || (cacheFile.isDirectory())) return "path_ambiguous";
if (cacheFile.toString().indexOf("..") >= 0) return "path_dangerous";
// -CGI access in request
// CGI access makes the page very individual, and therefore not usable in caches
if ((isPOST(nomalizedURLString)) && (!(profile.crawlingQ()))) return "dynamic_post";
if (isCGI(nomalizedURLString)) return "dynamic_cgi";
// -authorization cases in request
// authorization makes pages very individual, and therefore we cannot use the
// content in the cache
if ((requestHeader != null) && (requestHeader.containsKey("AUTHORIZATION"))) return "personalized";
// -ranges in request and response
// we do not cache partial content
if ((requestHeader != null) && (requestHeader.containsKey("RANGE"))) return "partial";
if ((responseHeader != null) && (responseHeader.containsKey("CONTENT-RANGE"))) return "partial";
// -if-modified-since in request
// we do not care about if-modified-since, because this case only occurres if the
// cache file does not exist, and we need as much info as possible for the indexing
// -cookies in request
// we do not care about cookies, because that would prevent loading more pages
// from one domain once a request resulted in a client-side stored cookie
// -set-cookie in response
// we do not care about cookies in responses, because that info comes along
// any/many pages from a server and does not express the validity of the page
// in modes of life-time/expiration or individuality
// -pragma in response
// if we have a pragma non-cache, we don't cache. usually if this is wanted from
// the server, it makes sense
if ((responseHeader.containsKey("PRAGMA")) &&
(((String) responseHeader.get("Pragma")).toUpperCase().equals("NO-CACHE"))) return "controlled_no_cache";
// -expires in response
// we do not care about expires, because at the time this is called the data is
// obvious valid and that header info is used in the indexing later on
// -cache-control in response
// the cache-control has many value options.
String cacheControl = (String) responseHeader.get("Cache-Control");
if (cacheControl != null) {
cacheControl = cacheControl.trim().toUpperCase();
if (cacheControl.startsWith("MAX-AGE=")) {
// we need also the load date
Date date = responseHeader.date();
if (date == null) return "stale_no_date_given_in_response";
try {
long ttl = 1000 * Long.parseLong(cacheControl.substring(8)); // milliseconds to live
if ((new Date()).getTime() - date.getTime() > ttl) {
//System.out.println("***not indexed because cache-control");
return "stale_expired";
}
} catch (Exception e) {
return "stale_error_" + e.getMessage() + ")";
}
}
}
return null;
}
public boolean shallUseCache() {
// decide upon header information if a specific file should be taken from the cache or not
//System.out.println("SHALL READ CACHE: requestHeader = " + requestHeader.toString() + ", responseHeader = " + responseHeader.toString());
// -CGI access in request
// CGI access makes the page very individual, and therefore not usable in caches
if (isPOST(nomalizedURLString)) return false;
if (isCGI(nomalizedURLString)) return false;
// -authorization cases in request
if (requestHeader.containsKey("AUTHORIZATION")) return false;
// -ranges in request
// we do not cache partial content
if ((requestHeader != null) && (requestHeader.containsKey("RANGE"))) return false;
//Date d1, d2;
// -if-modified-since in request
// The entity has to be transferred only if it has
// been modified since the date given by the If-Modified-Since header.
if (requestHeader.containsKey("IF-MODIFIED-SINCE")) {
// checking this makes only sense if the cached response contains
// a Last-Modified field. If the field does not exist, we go the safe way
if (!(responseHeader.containsKey("Last-Modified"))) return false;
// parse date
Date d1, d2;
d2 = responseHeader.lastModified(); if (d2 == null) d2 = new Date();
d1 = requestHeader.ifModifiedSince(); if (d1 == null) d1 = new Date();
// finally, we shall treat the cache as stale if the modification time is after the if-.. time
if (d2.after(d1)) return false;
}
boolean isNotPicture = !isPicture(responseHeader);
// -cookies in request
// unfortunately, we should reload in case of a cookie
// but we think that pictures can still be considered as fresh
if ((requestHeader.containsKey("COOKIE")) && (isNotPicture)) return false;
// -set-cookie in cached response
// this is a similar case as for COOKIE.
if ((responseHeader.containsKey("SET-COOKIE")) && (isNotPicture)) return false; // too strong
if ((responseHeader.containsKey("SET-COOKIE2")) && (isNotPicture)) return false; // too strong
// -pragma in cached response
// logically, we would not need to care about no-cache pragmas in cached response headers,
// because they cannot exist since they are not written to the cache.
// So this IF should always fail..
if ((responseHeader.containsKey("PRAGMA")) &&
(((String) responseHeader.get("Pragma")).toUpperCase().equals("NO-CACHE"))) return false;
// calculate often needed values for freshness attributes
Date date = responseHeader.date();
Date expires = responseHeader.expires();
Date lastModified = responseHeader.lastModified();
String cacheControl = (String) responseHeader.get("Cache-Control");
// see for documentation also:
// http://www.web-caching.com/cacheability.html
// http://vancouver-webpages.com/CacheNow/
// look for freshnes information
// if we don't have any freshnes indication, we treat the file as stale.
// no handle for freshness control:
if ((expires == null) && (cacheControl == null) && (lastModified == null)) return false;
// -expires in cached response
// the expires value gives us a very easy hint when the cache is stale
if (expires != null) {
Date yesterday = new Date((new Date()).getTime() - oneday);
if (expires.before(yesterday)) return false;
}
// -lastModified in cached response
// we can apply a TTL (Time To Live) heuristic here. We call the time delta between the last read
// of the file and the last modified date as the age of the file. If we consider the file as
// middel-aged then, the maximum TTL would be cache-creation plus age.
// This would be a TTL factor of 100% we want no more than 10% TTL, so that a 10 month old cache
// file may only be treated as fresh for one more month, not more.
if (lastModified != null) {
if (date == null) date = new Date();
long age = date.getTime() - lastModified.getTime();
if (age < 0) return false;
// TTL (Time-To-Live) is age/10 = (d2.getTime() - d1.getTime()) / 10
// the actual living-time is new Date().getTime() - d2.getTime()
// therefore the cache is stale, if Date().getTime() - d2.getTime() > age/10
if ((new Date()).getTime() - date.getTime() > age / 10) return false;
}
// -cache-control in cached response
// the cache-control has many value options.
if (cacheControl != null) {
cacheControl = cacheControl.trim().toUpperCase();
if (cacheControl.startsWith("PUBLIC")) {
// ok, do nothing
} else if ((cacheControl.startsWith("PRIVATE")) ||
(cacheControl.startsWith("NO-CACHE")) ||
(cacheControl.startsWith("NO-STORE"))) {
// easy case
return false;
} else if (cacheControl.startsWith("MAX-AGE=")) {
// we need also the load date
if (date == null) return false;
try {
long ttl = 1000 * Long.parseLong(cacheControl.substring(8)); // milliseconds to live
if ((new Date()).getTime() - date.getTime() > ttl) {
return false;
}
} catch (Exception e) {
return false;
}
}
}
return true;
}
public String shallIndexCacheForProxy() {
// decide upon header information if a specific file should be indexed
// this method returns null if the answer is 'YES'!
// if the answer is 'NO' (do not index), it returns a string with the reason
// to reject the crawling demand in clear text
// check profile
if (!(profile.localIndexing())) return "Indexing_Not_Allowed";
// -CGI access in request
// CGI access makes the page very individual, and therefore not usable in caches
if ((isPOST(nomalizedURLString)) && (!(profile.crawlingQ()))) return "Dynamic_(POST)";
if ((isCGI(nomalizedURLString)) && (!(profile.crawlingQ()))) return "Dynamic_(CGI)";
// -authorization cases in request
// we checked that in shallStoreCache
// -ranges in request
// we checked that in shallStoreCache
// a picture cannot be indexed
if (isPicture(responseHeader)) return "Media_Content_(Picture)";
if (!(isText(responseHeader))) return "Media_Content_(not_text)";
if (noIndexingURL(nomalizedURLString)) return "Media_Content_(forbidden)";
// -if-modified-since in request
// if the page is fresh at the very moment we can index it
if ((requestHeader != null) &&
(requestHeader.containsKey("IF-MODIFIED-SINCE")) &&
(responseHeader.containsKey("Last-Modified"))) {
// parse date
Date d1, d2;
d2 = responseHeader.lastModified(); if (d2 == null) d2 = new Date();
d1 = requestHeader.ifModifiedSince(); if (d1 == null) d1 = new Date();
// finally, we shall treat the cache as stale if the modification time is after the if-.. time
if (d2.after(d1)) {
//System.out.println("***not indexed because if-modified-since");
return "Stale_(Last-Modified>Modified-Since)";
}
}
// -cookies in request
// unfortunately, we cannot index pages which have been requested with a cookie
// because the returned content may be special for the client
if ((requestHeader != null) && (requestHeader.containsKey("COOKIE"))) {
//System.out.println("***not indexed because cookie");
return "Dynamic_(Requested_With_Cookie)";
}
// -set-cookie in response
// the set-cookie from the server does not indicate that the content is special
// thus we do not care about it here for indexing
// -pragma in cached response
if ((responseHeader.containsKey("PRAGMA")) &&
(((String) responseHeader.get("Pragma")).toUpperCase().equals("NO-CACHE"))) return "Denied_(pragma_no_cache)";
// see for documentation also:
// http://www.web-caching.com/cacheability.html
// calculate often needed values for freshness attributes
Date date = responseHeader.date();
Date expires = responseHeader.expires();
Date lastModified = responseHeader.lastModified();
String cacheControl = (String) responseHeader.get("Cache-Control");
// look for freshnes information
// -expires in cached response
// the expires value gives us a very easy hint when the cache is stale
// sometimes, the expires date is set to the past to prevent that a page is cached
// we use that information to see if we should index it
if (expires != null) {
Date yesterday = new Date((new Date()).getTime() - oneday);
if (expires.before(yesterday)) return "Stale_(Expired)";
}
// -lastModified in cached response
// this information is too weak to use it to prevent indexing
// even if we can apply a TTL heuristic for cache usage
// -cache-control in cached response
// the cache-control has many value options.
if (cacheControl != null) {
cacheControl = cacheControl.trim().toUpperCase();
/* we have the following cases for cache-control:
"public" -- can be indexed
"private", "no-cache", "no-store" -- cannot be indexed
"max-age=<delta-seconds>" -- stale/fresh dependent on date
*/
if (cacheControl.startsWith("PUBLIC")) {
// ok, do nothing
} else if ((cacheControl.startsWith("PRIVATE")) ||
(cacheControl.startsWith("NO-CACHE")) ||
(cacheControl.startsWith("NO-STORE"))) {
// easy case
return "Stale_(denied_by_cache-control=" + cacheControl+ ")";
} else if (cacheControl.startsWith("MAX-AGE=")) {
// we need also the load date
if (date == null) return "Stale_(no_date_given_in_response)";
try {
long ttl = 1000 * Long.parseLong(cacheControl.substring(8)); // milliseconds to live
if ((new Date()).getTime() - date.getTime() > ttl) {
//System.out.println("***not indexed because cache-control");
return "Stale_(expired_by_cache-control)";
}
} catch (Exception e) {
return "Error_(" + e.getMessage() + ")";
}
}
}
return null;
}
public String shallIndexCacheForCrawler() {
// decide upon header information if a specific file should be indexed
// this method returns null if the answer is 'YES'!
// if the answer is 'NO' (do not index), it returns a string with the reason
// to reject the crawling demand in clear text
// check profile
if (!(profile.localIndexing())) return "Indexing_Not_Allowed";
// -CGI access in request
// CGI access makes the page very individual, and therefore not usable in caches
if ((isPOST(nomalizedURLString)) && (!(profile.crawlingQ()))) return "Dynamic_(POST)";
if ((isCGI(nomalizedURLString)) && (!(profile.crawlingQ()))) return "Dynamic_(CGI)";
// -authorization cases in request
// we checked that in shallStoreCache
// -ranges in request
// we checked that in shallStoreCache
// a picture cannot be indexed
if (isPicture(responseHeader)) return "Media_Content_(Picture)";
if (!(isText(responseHeader))) return "Media_Content_(not_text)";
if (noIndexingURL(nomalizedURLString)) return "Media_Content_(forbidden)";
// -if-modified-since in request
// if the page is fresh at the very moment we can index it
// -> this does not apply for the crawler
// -cookies in request
// unfortunately, we cannot index pages which have been requested with a cookie
// because the returned content may be special for the client
// -> this does not apply for a crawler
// -set-cookie in response
// the set-cookie from the server does not indicate that the content is special
// thus we do not care about it here for indexing
// -> this does not apply for a crawler
// -pragma in cached response
// -> in the crawler we ignore this
// look for freshnes information
// -expires in cached response
// the expires value gives us a very easy hint when the cache is stale
// sometimes, the expires date is set to the past to prevent that a page is cached
// we use that information to see if we should index it
// -> this does not apply for a crawler
// -lastModified in cached response
// this information is too weak to use it to prevent indexing
// even if we can apply a TTL heuristic for cache usage
// -cache-control in cached response
// the cache-control has many value options.
// -> in the crawler we ignore this
return null;
}
}
}