// License: GPL. For details, see LICENSE file.
package org.openstreetmap.josm.data.cache;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.URL;
import java.security.SecureRandom;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.LinkedBlockingDeque;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.apache.commons.jcs.access.behavior.ICacheAccess;
import org.apache.commons.jcs.engine.behavior.ICacheElement;
import org.openstreetmap.gui.jmapviewer.FeatureAdapter;
import org.openstreetmap.josm.Main;
import org.openstreetmap.josm.data.cache.ICachedLoaderListener.LoadResult;
import org.openstreetmap.josm.data.preferences.IntegerProperty;
import org.openstreetmap.josm.tools.CheckParameterUtil;
import org.openstreetmap.josm.tools.HttpClient;
import org.openstreetmap.josm.tools.Utils;
/**
* Generic loader for HTTP based tiles. Uses custom attribute, to check, if entry has expired
* according to HTTP headers sent with tile. If so, it tries to verify using Etags
* or If-Modified-Since / Last-Modified.
*
* If the tile is not valid, it will try to download it from remote service and put it
* to cache. If remote server will fail it will try to use stale entry.
*
* This class will keep only one Job running for specified tile. All others will just finish, but
* listeners will be gathered and notified, once download job will be finished
*
* @author Wiktor Niesiobędzki
* @param <K> cache entry key type
* @param <V> cache value type
* @since 8168
*/
public abstract class JCSCachedTileLoaderJob<K, V extends CacheEntry> implements ICachedLoaderJob<K> {
private static final Logger LOG = FeatureAdapter.getLogger(JCSCachedTileLoaderJob.class.getCanonicalName());
protected static final long DEFAULT_EXPIRE_TIME = TimeUnit.DAYS.toMillis(7);
// Limit for the max-age value send by the server.
protected static final long EXPIRE_TIME_SERVER_LIMIT = TimeUnit.DAYS.toMillis(28);
// Absolute expire time limit. Cached tiles that are older will not be used,
// even if the refresh from the server fails.
protected static final long ABSOLUTE_EXPIRE_TIME_LIMIT = TimeUnit.DAYS.toMillis(365);
/**
* maximum download threads that will be started
*/
public static final IntegerProperty THREAD_LIMIT = new IntegerProperty("cache.jcs.max_threads", 10);
/*
* ThreadPoolExecutor starts new threads, until THREAD_LIMIT is reached. Then it puts tasks into LinkedBlockingDeque.
*
* The queue works FIFO, so one needs to take care about ordering of the entries submitted
*
* There is no point in canceling tasks, that are already taken by worker threads (if we made so much effort, we can at least cache
* the response, so later it could be used). We could actually cancel what is in LIFOQueue, but this is a tradeoff between simplicity
* and performance (we do want to have something to offer to worker threads before tasks will be resubmitted by class consumer)
*/
private static final ThreadPoolExecutor DEFAULT_DOWNLOAD_JOB_DISPATCHER = new ThreadPoolExecutor(
1, // we have a small queue, so threads will be quickly started (threads are started only, when queue is full)
THREAD_LIMIT.get(), // do not this number of threads
30, // keepalive for thread
TimeUnit.SECONDS,
// make queue of LIFO type - so recently requested tiles will be loaded first (assuming that these are which user is waiting to see)
new LinkedBlockingDeque<Runnable>(),
Utils.newThreadFactory("JCS-downloader-%d", Thread.NORM_PRIORITY)
);
private static final ConcurrentMap<String, Set<ICachedLoaderListener>> inProgress = new ConcurrentHashMap<>();
private static final ConcurrentMap<String, Boolean> useHead = new ConcurrentHashMap<>();
protected final long now; // when the job started
private final ICacheAccess<K, V> cache;
private ICacheElement<K, V> cacheElement;
protected V cacheData;
protected CacheEntryAttributes attributes;
// HTTP connection parameters
private final int connectTimeout;
private final int readTimeout;
private final Map<String, String> headers;
private final ThreadPoolExecutor downloadJobExecutor;
private Runnable finishTask;
private boolean force;
/**
* @param cache cache instance that we will work on
* @param headers HTTP headers to be sent together with request
* @param readTimeout when connecting to remote resource
* @param connectTimeout when connecting to remote resource
* @param downloadJobExecutor that will be executing the jobs
*/
public JCSCachedTileLoaderJob(ICacheAccess<K, V> cache,
int connectTimeout, int readTimeout,
Map<String, String> headers,
ThreadPoolExecutor downloadJobExecutor) {
CheckParameterUtil.ensureParameterNotNull(cache, "cache");
this.cache = cache;
this.now = System.currentTimeMillis();
this.connectTimeout = connectTimeout;
this.readTimeout = readTimeout;
this.headers = headers;
this.downloadJobExecutor = downloadJobExecutor;
}
/**
* @param cache cache instance that we will work on
* @param headers HTTP headers to be sent together with request
* @param readTimeout when connecting to remote resource
* @param connectTimeout when connecting to remote resource
*/
public JCSCachedTileLoaderJob(ICacheAccess<K, V> cache,
int connectTimeout, int readTimeout,
Map<String, String> headers) {
this(cache, connectTimeout, readTimeout,
headers, DEFAULT_DOWNLOAD_JOB_DISPATCHER);
}
private void ensureCacheElement() {
if (cacheElement == null && getCacheKey() != null) {
cacheElement = cache.getCacheElement(getCacheKey());
if (cacheElement != null) {
attributes = (CacheEntryAttributes) cacheElement.getElementAttributes();
cacheData = cacheElement.getVal();
}
}
}
@Override
public V get() {
ensureCacheElement();
return cacheData;
}
@Override
public void submit(ICachedLoaderListener listener, boolean force) throws IOException {
this.force = force;
boolean first = false;
URL url = getUrl();
String deduplicationKey = null;
if (url != null) {
// url might be null, for example when Bing Attribution is not loaded yet
deduplicationKey = url.toString();
}
if (deduplicationKey == null) {
LOG.log(Level.WARNING, "No url returned for: {0}, skipping", getCacheKey());
throw new IllegalArgumentException("No url returned");
}
synchronized (inProgress) {
Set<ICachedLoaderListener> newListeners = inProgress.get(deduplicationKey);
if (newListeners == null) {
newListeners = new HashSet<>();
inProgress.put(deduplicationKey, newListeners);
first = true;
}
newListeners.add(listener);
}
if (first || force) {
// submit all jobs to separate thread, so calling thread is not blocked with IO when loading from disk
LOG.log(Level.FINE, "JCS - Submitting job for execution for url: {0}", getUrlNoException());
downloadJobExecutor.execute(this);
}
}
/**
* This method is run when job has finished
*/
protected void executionFinished() {
if (finishTask != null) {
finishTask.run();
}
}
/**
*
* @return checks if object from cache has sufficient data to be returned
*/
protected boolean isObjectLoadable() {
if (cacheData == null) {
return false;
}
return cacheData.getContent().length > 0;
}
/**
* Simple implementation. All errors should be cached as empty. Though some JDK (JDK8 on Windows for example)
* doesn't return 4xx error codes, instead they do throw an FileNotFoundException or IOException
*
* @return true if we should put empty object into cache, regardless of what remote resource has returned
*/
protected boolean cacheAsEmpty() {
return attributes.getResponseCode() < 500;
}
/**
* @return key under which discovered server settings will be kept
*/
protected String getServerKey() {
try {
return getUrl().getHost();
} catch (IOException e) {
Main.trace(e);
return null;
}
}
@Override
public void run() {
final Thread currentThread = Thread.currentThread();
final String oldName = currentThread.getName();
currentThread.setName("JCS Downloading: " + getUrlNoException());
LOG.log(Level.FINE, "JCS - starting fetch of url: {0} ", getUrlNoException());
ensureCacheElement();
try {
// try to fetch from cache
if (!force && cacheElement != null && isCacheElementValid() && isObjectLoadable()) {
// we got something in cache, and it's valid, so lets return it
LOG.log(Level.FINE, "JCS - Returning object from cache: {0}", getCacheKey());
finishLoading(LoadResult.SUCCESS);
return;
}
// try to load object from remote resource
if (loadObject()) {
finishLoading(LoadResult.SUCCESS);
} else {
// if loading failed - check if we can return stale entry
if (isObjectLoadable()) {
// try to get stale entry in cache
finishLoading(LoadResult.SUCCESS);
LOG.log(Level.FINE, "JCS - found stale object in cache: {0}", getUrlNoException());
} else {
// failed completely
finishLoading(LoadResult.FAILURE);
}
}
} finally {
executionFinished();
currentThread.setName(oldName);
}
}
private void finishLoading(LoadResult result) {
Set<ICachedLoaderListener> listeners;
synchronized (inProgress) {
try {
listeners = inProgress.remove(getUrl().toString());
} catch (IOException e) {
listeners = null;
Main.trace(e);
}
}
if (listeners == null) {
LOG.log(Level.WARNING, "Listener not found for URL: {0}. Listener not notified!", getUrlNoException());
return;
}
for (ICachedLoaderListener l: listeners) {
l.loadingFinished(cacheData, attributes, result);
}
}
protected boolean isCacheElementValid() {
long expires = attributes.getExpirationTime();
// check by expire date set by server
if (expires != 0L) {
// put a limit to the expire time (some servers send a value
// that is too large)
expires = Math.min(expires, attributes.getCreateTime() + EXPIRE_TIME_SERVER_LIMIT);
if (now > expires) {
LOG.log(Level.FINE, "JCS - Object {0} has expired -> valid to {1}, now is: {2}",
new Object[]{getUrlNoException(), Long.toString(expires), Long.toString(now)});
return false;
}
} else if (attributes.getLastModification() > 0 &&
now - attributes.getLastModification() > DEFAULT_EXPIRE_TIME) {
// check by file modification date
LOG.log(Level.FINE, "JCS - Object has expired, maximum file age reached {0}", getUrlNoException());
return false;
} else if (now - attributes.getCreateTime() > DEFAULT_EXPIRE_TIME) {
LOG.log(Level.FINE, "JCS - Object has expired, maximum time since object creation reached {0}", getUrlNoException());
return false;
}
return true;
}
/**
* @return true if object was successfully downloaded, false, if there was a loading failure
*/
private boolean loadObject() {
if (attributes == null) {
attributes = new CacheEntryAttributes();
}
try {
// if we have object in cache, and host doesn't support If-Modified-Since nor If-None-Match
// then just use HEAD request and check returned values
if (isObjectLoadable() &&
Boolean.TRUE.equals(useHead.get(getServerKey())) &&
isCacheValidUsingHead()) {
LOG.log(Level.FINE, "JCS - cache entry verified using HEAD request: {0}", getUrl());
return true;
}
final HttpClient request = getRequest("GET", true);
if (isObjectLoadable() &&
(now - attributes.getLastModification()) <= ABSOLUTE_EXPIRE_TIME_LIMIT) {
request.setIfModifiedSince(attributes.getLastModification());
}
if (isObjectLoadable() && attributes.getEtag() != null) {
request.setHeader("If-None-Match", attributes.getEtag());
}
final HttpClient.Response urlConn = request.connect();
if (urlConn.getResponseCode() == 304) {
// If isModifiedSince or If-None-Match has been set
// and the server answers with a HTTP 304 = "Not Modified"
LOG.log(Level.FINE, "JCS - If-Modified-Since/ETag test: local version is up to date: {0}", getUrl());
return true;
} else if (isObjectLoadable() // we have an object in cache, but we haven't received 304 response code
&& (
(attributes.getEtag() != null && attributes.getEtag().equals(urlConn.getHeaderField("ETag"))) ||
attributes.getLastModification() == urlConn.getLastModified())
) {
// we sent ETag or If-Modified-Since, but didn't get 304 response code
// for further requests - use HEAD
String serverKey = getServerKey();
LOG.log(Level.INFO, "JCS - Host: {0} found not to return 304 codes for If-Modified-Since or If-None-Match headers",
serverKey);
useHead.put(serverKey, Boolean.TRUE);
}
attributes = parseHeaders(urlConn);
for (int i = 0; i < 5; ++i) {
if (urlConn.getResponseCode() == HttpURLConnection.HTTP_UNAVAILABLE) {
Thread.sleep(5000L+new SecureRandom().nextInt(5000));
continue;
}
attributes.setResponseCode(urlConn.getResponseCode());
byte[] raw;
if (urlConn.getResponseCode() == HttpURLConnection.HTTP_OK) {
raw = Utils.readBytesFromStream(urlConn.getContent());
} else {
raw = new byte[]{};
}
if (isResponseLoadable(urlConn.getHeaderFields(), urlConn.getResponseCode(), raw)) {
// we need to check cacheEmpty, so for cases, when data is returned, but we want to store
// as empty (eg. empty tile images) to save some space
cacheData = createCacheEntry(raw);
cache.put(getCacheKey(), cacheData, attributes);
LOG.log(Level.FINE, "JCS - downloaded key: {0}, length: {1}, url: {2}",
new Object[] {getCacheKey(), raw.length, getUrl()});
return true;
} else if (cacheAsEmpty()) {
cacheData = createCacheEntry(new byte[]{});
cache.put(getCacheKey(), cacheData, attributes);
LOG.log(Level.FINE, "JCS - Caching empty object {0}", getUrl());
return true;
} else {
LOG.log(Level.FINE, "JCS - failure during load - reponse is not loadable nor cached as empty");
return false;
}
}
} catch (FileNotFoundException e) {
LOG.log(Level.FINE, "JCS - Caching empty object as server returned 404 for: {0}", getUrlNoException());
attributes.setResponseCode(404);
attributes.setError(e);
boolean doCache = isResponseLoadable(null, 404, null) || cacheAsEmpty();
if (doCache) {
cacheData = createCacheEntry(new byte[]{});
cache.put(getCacheKey(), cacheData, attributes);
}
return doCache;
} catch (IOException e) {
LOG.log(Level.FINE, "JCS - IOExecption during communication with server for: {0}", getUrlNoException());
if (isObjectLoadable()) {
return true;
} else {
attributes.setError(e);
attributes.setResponseCode(599); // set dummy error code, greater than 500 so it will be not cached
return false;
}
} catch (InterruptedException e) {
attributes.setError(e);
LOG.log(Level.WARNING, "JCS - Exception during download {0}", getUrlNoException());
Main.warn(e);
Thread.currentThread().interrupt();
}
LOG.log(Level.WARNING, "JCS - Silent failure during download: {0}", getUrlNoException());
return false;
}
/**
* Check if the object is loadable. This means, if the data will be parsed, and if this response
* will finish as successful retrieve.
*
* This simple implementation doesn't load empty response, nor client (4xx) and server (5xx) errors
*
* @param headerFields headers sent by server
* @param responseCode http status code
* @param raw data read from server
* @return true if object should be cached and returned to listener
*/
protected boolean isResponseLoadable(Map<String, List<String>> headerFields, int responseCode, byte[] raw) {
if (raw == null || raw.length == 0 || responseCode >= 400) {
return false;
}
return true;
}
protected abstract V createCacheEntry(byte[] content);
protected CacheEntryAttributes parseHeaders(HttpClient.Response urlConn) {
CacheEntryAttributes ret = new CacheEntryAttributes();
Long lng = urlConn.getExpiration();
if (lng.equals(0L)) {
try {
String str = urlConn.getHeaderField("Cache-Control");
if (str != null) {
for (String token: str.split(",")) {
if (token.startsWith("max-age=")) {
lng = TimeUnit.SECONDS.toMillis(Long.parseLong(token.substring(8))) + System.currentTimeMillis();
}
}
}
} catch (NumberFormatException e) {
// ignore malformed Cache-Control headers
Main.trace(e);
}
}
ret.setExpirationTime(lng);
ret.setLastModification(now);
ret.setEtag(urlConn.getHeaderField("ETag"));
return ret;
}
private HttpClient getRequest(String requestMethod, boolean noCache) throws IOException {
final HttpClient urlConn = HttpClient.create(getUrl(), requestMethod);
urlConn.setAccept("text/html, image/png, image/jpeg, image/gif, */*");
urlConn.setReadTimeout(readTimeout); // 30 seconds read timeout
urlConn.setConnectTimeout(connectTimeout);
if (headers != null) {
urlConn.setHeaders(headers);
}
if (force || noCache) {
urlConn.useCache(false);
}
return urlConn;
}
private boolean isCacheValidUsingHead() throws IOException {
final HttpClient.Response urlConn = getRequest("HEAD", false).connect();
long lastModified = urlConn.getLastModified();
return (attributes.getEtag() != null && attributes.getEtag().equals(urlConn.getHeaderField("ETag"))) ||
(lastModified != 0 && lastModified <= attributes.getLastModification());
}
/**
* TODO: move to JobFactory
* cancels all outstanding tasks in the queue.
*/
public void cancelOutstandingTasks() {
for (Runnable r: downloadJobExecutor.getQueue()) {
if (downloadJobExecutor.remove(r) && r instanceof JCSCachedTileLoaderJob) {
((JCSCachedTileLoaderJob<?, ?>) r).handleJobCancellation();
}
}
}
/**
* Sets a job, that will be run, when job will finish execution
* @param runnable that will be executed
*/
public void setFinishedTask(Runnable runnable) {
this.finishTask = runnable;
}
/**
* Marks this job as canceled
*/
public void handleJobCancellation() {
finishLoading(LoadResult.CANCELED);
}
private URL getUrlNoException() {
try {
return getUrl();
} catch (IOException e) {
return null;
}
}
}