001// License: GPL. For details, see LICENSE file.
002package org.openstreetmap.josm.data.cache;
003
004import java.io.FileNotFoundException;
005import java.io.IOException;
006import java.net.HttpURLConnection;
007import java.net.URL;
008import java.security.SecureRandom;
009import java.util.HashSet;
010import java.util.List;
011import java.util.Map;
012import java.util.Set;
013import java.util.concurrent.ConcurrentHashMap;
014import java.util.concurrent.ConcurrentMap;
015import java.util.concurrent.LinkedBlockingDeque;
016import java.util.concurrent.ThreadPoolExecutor;
017import java.util.concurrent.TimeUnit;
018import java.util.logging.Level;
019import java.util.logging.Logger;
020
021import org.apache.commons.jcs.access.behavior.ICacheAccess;
022import org.apache.commons.jcs.engine.behavior.ICacheElement;
023import org.openstreetmap.gui.jmapviewer.FeatureAdapter;
024import org.openstreetmap.josm.Main;
025import org.openstreetmap.josm.data.cache.ICachedLoaderListener.LoadResult;
026import org.openstreetmap.josm.data.preferences.IntegerProperty;
027import org.openstreetmap.josm.tools.CheckParameterUtil;
028import org.openstreetmap.josm.tools.HttpClient;
029import org.openstreetmap.josm.tools.Utils;
030
031/**
032 * Generic loader for HTTP based tiles. Uses custom attribute, to check, if entry has expired
033 * according to HTTP headers sent with tile. If so, it tries to verify using Etags
034 * or If-Modified-Since / Last-Modified.
035 *
036 * If the tile is not valid, it will try to download it from remote service and put it
037 * to cache. If remote server will fail it will try to use stale entry.
038 *
039 * This class will keep only one Job running for specified tile. All others will just finish, but
040 * listeners will be gathered and notified, once download job will be finished
041 *
042 * @author Wiktor Niesiobędzki
043 * @param <K> cache entry key type
044 * @param <V> cache value type
045 * @since 8168
046 */
047public abstract class JCSCachedTileLoaderJob<K, V extends CacheEntry> implements ICachedLoaderJob<K> {
048    private static final Logger LOG = FeatureAdapter.getLogger(JCSCachedTileLoaderJob.class.getCanonicalName());
049    protected static final long DEFAULT_EXPIRE_TIME = 1000L * 60 * 60 * 24 * 7; // 7 days
050    // Limit for the max-age value send by the server.
051    protected static final long EXPIRE_TIME_SERVER_LIMIT = 1000L * 60 * 60 * 24 * 28; // 4 weeks
052    // Absolute expire time limit. Cached tiles that are older will not be used,
053    // even if the refresh from the server fails.
054    protected static final long ABSOLUTE_EXPIRE_TIME_LIMIT = 1000L * 60 * 60 * 24 * 365; // 1 year
055
056    /**
057     * maximum download threads that will be started
058     */
059    public static final IntegerProperty THREAD_LIMIT = new IntegerProperty("cache.jcs.max_threads", 10);
060
061    /*
062     * ThreadPoolExecutor starts new threads, until THREAD_LIMIT is reached. Then it puts tasks into LinkedBlockingDeque.
063     *
064     * The queue works FIFO, so one needs to take care about ordering of the entries submitted
065     *
066     * 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
067     * the response, so later it could be used). We could actually cancel what is in LIFOQueue, but this is a tradeoff between simplicity
068     * and performance (we do want to have something to offer to worker threads before tasks will be resubmitted by class consumer)
069     */
070
071    private static final ThreadPoolExecutor DEFAULT_DOWNLOAD_JOB_DISPATCHER = new ThreadPoolExecutor(
072            1, // we have a small queue, so threads will be quickly started (threads are started only, when queue is full)
073            THREAD_LIMIT.get(), // do not this number of threads
074            30, // keepalive for thread
075            TimeUnit.SECONDS,
076            // make queue of LIFO type - so recently requested tiles will be loaded first (assuming that these are which user is waiting to see)
077            new LinkedBlockingDeque<Runnable>(),
078            Utils.newThreadFactory("JCS-downloader-%d", Thread.NORM_PRIORITY)
079            );
080
081
082
083    private static final ConcurrentMap<String, Set<ICachedLoaderListener>> inProgress = new ConcurrentHashMap<>();
084    private static final ConcurrentMap<String, Boolean> useHead = new ConcurrentHashMap<>();
085
086    protected final long now; // when the job started
087
088    private final ICacheAccess<K, V> cache;
089    private ICacheElement<K, V> cacheElement;
090    protected V cacheData;
091    protected CacheEntryAttributes attributes;
092
093    // HTTP connection parameters
094    private final int connectTimeout;
095    private final int readTimeout;
096    private final Map<String, String> headers;
097    private final ThreadPoolExecutor downloadJobExecutor;
098    private Runnable finishTask;
099    private boolean force;
100
101    /**
102     * @param cache cache instance that we will work on
103     * @param headers HTTP headers to be sent together with request
104     * @param readTimeout when connecting to remote resource
105     * @param connectTimeout when connecting to remote resource
106     * @param downloadJobExecutor that will be executing the jobs
107     */
108    public JCSCachedTileLoaderJob(ICacheAccess<K, V> cache,
109            int connectTimeout, int readTimeout,
110            Map<String, String> headers,
111            ThreadPoolExecutor downloadJobExecutor) {
112        CheckParameterUtil.ensureParameterNotNull(cache, "cache");
113        this.cache = cache;
114        this.now = System.currentTimeMillis();
115        this.connectTimeout = connectTimeout;
116        this.readTimeout = readTimeout;
117        this.headers = headers;
118        this.downloadJobExecutor = downloadJobExecutor;
119    }
120
121    /**
122     * @param cache cache instance that we will work on
123     * @param headers HTTP headers to be sent together with request
124     * @param readTimeout when connecting to remote resource
125     * @param connectTimeout when connecting to remote resource
126     */
127    public JCSCachedTileLoaderJob(ICacheAccess<K, V> cache,
128            int connectTimeout, int readTimeout,
129            Map<String, String> headers) {
130        this(cache, connectTimeout, readTimeout,
131                headers, DEFAULT_DOWNLOAD_JOB_DISPATCHER);
132    }
133
134    private void ensureCacheElement() {
135        if (cacheElement == null && getCacheKey() != null) {
136            cacheElement = cache.getCacheElement(getCacheKey());
137            if (cacheElement != null) {
138                attributes = (CacheEntryAttributes) cacheElement.getElementAttributes();
139                cacheData = cacheElement.getVal();
140            }
141        }
142    }
143
144    @Override
145    public V get() {
146        ensureCacheElement();
147        return cacheData;
148    }
149
150    @Override
151    public void submit(ICachedLoaderListener listener, boolean force) throws IOException {
152        this.force = force;
153        boolean first = false;
154        URL url = getUrl();
155        String deduplicationKey = null;
156        if (url != null) {
157            // url might be null, for example when Bing Attribution is not loaded yet
158            deduplicationKey = url.toString();
159        }
160        if (deduplicationKey == null) {
161            LOG.log(Level.WARNING, "No url returned for: {0}, skipping", getCacheKey());
162            throw new IllegalArgumentException("No url returned");
163        }
164        synchronized (inProgress) {
165            Set<ICachedLoaderListener> newListeners = inProgress.get(deduplicationKey);
166            if (newListeners == null) {
167                newListeners = new HashSet<>();
168                inProgress.put(deduplicationKey, newListeners);
169                first = true;
170            }
171            newListeners.add(listener);
172        }
173
174        if (first || force) {
175            // submit all jobs to separate thread, so calling thread is not blocked with IO when loading from disk
176            LOG.log(Level.FINE, "JCS - Submitting job for execution for url: {0}", getUrlNoException());
177            downloadJobExecutor.execute(this);
178        }
179    }
180
181    /**
182     * This method is run when job has finished
183     */
184    protected void executionFinished() {
185        if (finishTask != null) {
186            finishTask.run();
187        }
188    }
189
190    /**
191     *
192     * @return checks if object from cache has sufficient data to be returned
193     */
194    protected boolean isObjectLoadable() {
195        if (cacheData == null) {
196            return false;
197        }
198        byte[] content = cacheData.getContent();
199        return content != null && content.length > 0;
200    }
201
202    /**
203     * Simple implementation. All errors should be cached as empty. Though some JDK (JDK8 on Windows for example)
204     * doesn't return 4xx error codes, instead they do throw an FileNotFoundException or IOException
205     *
206     * @return true if we should put empty object into cache, regardless of what remote resource has returned
207     */
208    protected boolean cacheAsEmpty() {
209        return attributes.getResponseCode() < 500;
210    }
211
212    /**
213     * @return key under which discovered server settings will be kept
214     */
215    protected String getServerKey() {
216        return getUrlNoException().getHost();
217    }
218
219    @Override
220    public void run() {
221        final Thread currentThread = Thread.currentThread();
222        final String oldName = currentThread.getName();
223        currentThread.setName("JCS Downloading: " + getUrlNoException());
224        LOG.log(Level.FINE, "JCS - starting fetch of url: {0} ", getUrlNoException());
225        ensureCacheElement();
226        try {
227            // try to fetch from cache
228            if (!force && cacheElement != null && isCacheElementValid() && isObjectLoadable()) {
229                // we got something in cache, and it's valid, so lets return it
230                LOG.log(Level.FINE, "JCS - Returning object from cache: {0}", getCacheKey());
231                finishLoading(LoadResult.SUCCESS);
232                return;
233            }
234
235            // try to load object from remote resource
236            if (loadObject()) {
237                finishLoading(LoadResult.SUCCESS);
238            } else {
239                // if loading failed - check if we can return stale entry
240                if (isObjectLoadable()) {
241                    // try to get stale entry in cache
242                    finishLoading(LoadResult.SUCCESS);
243                    LOG.log(Level.FINE, "JCS - found stale object in cache: {0}", getUrlNoException());
244                } else {
245                    // failed completely
246                    finishLoading(LoadResult.FAILURE);
247                }
248            }
249        } finally {
250            executionFinished();
251            currentThread.setName(oldName);
252        }
253    }
254
255    private void finishLoading(LoadResult result) {
256        Set<ICachedLoaderListener> listeners;
257        synchronized (inProgress) {
258            listeners = inProgress.remove(getUrlNoException().toString());
259        }
260        if (listeners == null) {
261            LOG.log(Level.WARNING, "Listener not found for URL: {0}. Listener not notified!", getUrlNoException());
262            return;
263        }
264        for (ICachedLoaderListener l: listeners) {
265            l.loadingFinished(cacheData, attributes, result);
266        }
267    }
268
269    protected boolean isCacheElementValid() {
270        long expires = attributes.getExpirationTime();
271
272        // check by expire date set by server
273        if (expires != 0L) {
274            // put a limit to the expire time (some servers send a value
275            // that is too large)
276            expires = Math.min(expires, attributes.getCreateTime() + EXPIRE_TIME_SERVER_LIMIT);
277            if (now > expires) {
278                LOG.log(Level.FINE, "JCS - Object {0} has expired -> valid to {1}, now is: {2}",
279                        new Object[]{getUrlNoException(), Long.toString(expires), Long.toString(now)});
280                return false;
281            }
282        } else if (attributes.getLastModification() > 0 &&
283                now - attributes.getLastModification() > DEFAULT_EXPIRE_TIME) {
284            // check by file modification date
285            LOG.log(Level.FINE, "JCS - Object has expired, maximum file age reached {0}", getUrlNoException());
286            return false;
287        } else if (now - attributes.getCreateTime() > DEFAULT_EXPIRE_TIME) {
288            LOG.log(Level.FINE, "JCS - Object has expired, maximum time since object creation reached {0}", getUrlNoException());
289            return false;
290        }
291        return true;
292    }
293
294    /**
295     * @return true if object was successfully downloaded, false, if there was a loading failure
296     */
297    private boolean loadObject() {
298        if (attributes == null) {
299            attributes = new CacheEntryAttributes();
300        }
301        try {
302            // if we have object in cache, and host doesn't support If-Modified-Since nor If-None-Match
303            // then just use HEAD request and check returned values
304            if (isObjectLoadable() &&
305                    Boolean.TRUE.equals(useHead.get(getServerKey())) &&
306                    isCacheValidUsingHead()) {
307                LOG.log(Level.FINE, "JCS - cache entry verified using HEAD request: {0}", getUrl());
308                return true;
309            }
310
311            final HttpClient request = getRequest("GET", true);
312
313            if (isObjectLoadable() &&
314                    (now - attributes.getLastModification()) <= ABSOLUTE_EXPIRE_TIME_LIMIT) {
315                request.setIfModifiedSince(attributes.getLastModification());
316            }
317            if (isObjectLoadable() && attributes.getEtag() != null) {
318                request.setHeader("If-None-Match", attributes.getEtag());
319            }
320
321            final HttpClient.Response urlConn = request.connect();
322
323            if (urlConn.getResponseCode() == 304) {
324                // If isModifiedSince or If-None-Match has been set
325                // and the server answers with a HTTP 304 = "Not Modified"
326                LOG.log(Level.FINE, "JCS - If-Modified-Since/ETag test: local version is up to date: {0}", getUrl());
327                return true;
328            } else if (isObjectLoadable() // we have an object in cache, but we haven't received 304 response code
329                    && (
330                            (attributes.getEtag() != null && attributes.getEtag().equals(urlConn.getHeaderField("ETag"))) ||
331                            attributes.getLastModification() == urlConn.getLastModified())
332                    ) {
333                // we sent ETag or If-Modified-Since, but didn't get 304 response code
334                // for further requests - use HEAD
335                String serverKey = getServerKey();
336                LOG.log(Level.INFO, "JCS - Host: {0} found not to return 304 codes for If-Modified-Since or If-None-Match headers",
337                        serverKey);
338                useHead.put(serverKey, Boolean.TRUE);
339            }
340
341            attributes = parseHeaders(urlConn);
342
343            for (int i = 0; i < 5; ++i) {
344                if (urlConn.getResponseCode() == HttpURLConnection.HTTP_UNAVAILABLE) {
345                    Thread.sleep(5000L+new SecureRandom().nextInt(5000));
346                    continue;
347                }
348
349                attributes.setResponseCode(urlConn.getResponseCode());
350                byte[] raw;
351                if (urlConn.getResponseCode() == HttpURLConnection.HTTP_OK) {
352                    raw = Utils.readBytesFromStream(urlConn.getContent());
353                } else {
354                    raw = new byte[]{};
355                }
356
357                if (isResponseLoadable(urlConn.getHeaderFields(), urlConn.getResponseCode(), raw)) {
358                    // we need to check cacheEmpty, so for cases, when data is returned, but we want to store
359                    // as empty (eg. empty tile images) to save some space
360                    cacheData = createCacheEntry(raw);
361                    cache.put(getCacheKey(), cacheData, attributes);
362                    LOG.log(Level.FINE, "JCS - downloaded key: {0}, length: {1}, url: {2}",
363                            new Object[] {getCacheKey(), raw.length, getUrl()});
364                    return true;
365                } else if (cacheAsEmpty()) {
366                    cacheData = createCacheEntry(new byte[]{});
367                    cache.put(getCacheKey(), cacheData, attributes);
368                    LOG.log(Level.FINE, "JCS - Caching empty object {0}", getUrl());
369                    return true;
370                } else {
371                    LOG.log(Level.FINE, "JCS - failure during load - reponse is not loadable nor cached as empty");
372                    return false;
373                }
374            }
375        } catch (FileNotFoundException e) {
376            LOG.log(Level.FINE, "JCS - Caching empty object as server returned 404 for: {0}", getUrlNoException());
377            attributes.setResponseCode(404);
378            attributes.setError(e);
379            boolean doCache = isResponseLoadable(null, 404, null) || cacheAsEmpty();
380            if (doCache) {
381                cacheData = createCacheEntry(new byte[]{});
382                cache.put(getCacheKey(), cacheData, attributes);
383            }
384            return doCache;
385        } catch (IOException e) {
386            LOG.log(Level.FINE, "JCS - IOExecption during communication with server for: {0}", getUrlNoException());
387            if (isObjectLoadable()) {
388                return true;
389            } else {
390                attributes.setError(e);
391                attributes.setResponseCode(599); // set dummy error code, greater than 500 so it will be not cached
392                return false;
393            }
394
395        } catch (InterruptedException e) {
396            attributes.setError(e);
397            LOG.log(Level.WARNING, "JCS - Exception during download {0}", getUrlNoException());
398            Main.warn(e);
399        }
400        LOG.log(Level.WARNING, "JCS - Silent failure during download: {0}", getUrlNoException());
401        return false;
402    }
403
404    /**
405     * Check if the object is loadable. This means, if the data will be parsed, and if this response
406     * will finish as successful retrieve.
407     *
408     * This simple implementation doesn't load empty response, nor client (4xx) and server (5xx) errors
409     *
410     * @param headerFields headers sent by server
411     * @param responseCode http status code
412     * @param raw data read from server
413     * @return true if object should be cached and returned to listener
414     */
415    protected boolean isResponseLoadable(Map<String, List<String>> headerFields, int responseCode, byte[] raw) {
416        if (raw == null || raw.length == 0 || responseCode >= 400) {
417            return false;
418        }
419        return true;
420    }
421
422    protected abstract V createCacheEntry(byte[] content);
423
424    protected CacheEntryAttributes parseHeaders(HttpClient.Response urlConn) {
425        CacheEntryAttributes ret = new CacheEntryAttributes();
426
427        Long lng = urlConn.getExpiration();
428        if (lng.equals(0L)) {
429            try {
430                String str = urlConn.getHeaderField("Cache-Control");
431                if (str != null) {
432                    for (String token: str.split(",")) {
433                        if (token.startsWith("max-age=")) {
434                            lng = Long.parseLong(token.substring(8)) * 1000 +
435                                    System.currentTimeMillis();
436                        }
437                    }
438                }
439            } catch (NumberFormatException e) {
440                // ignore malformed Cache-Control headers
441                Main.trace(e);
442            }
443        }
444
445        ret.setExpirationTime(lng);
446        ret.setLastModification(now);
447        ret.setEtag(urlConn.getHeaderField("ETag"));
448
449        return ret;
450    }
451
452    private HttpClient getRequest(String requestMethod, boolean noCache) throws IOException {
453        final HttpClient urlConn = HttpClient.create(getUrl(), requestMethod);
454        urlConn.setAccept("text/html, image/png, image/jpeg, image/gif, */*");
455        urlConn.setReadTimeout(readTimeout); // 30 seconds read timeout
456        urlConn.setConnectTimeout(connectTimeout);
457        if (headers != null) {
458            urlConn.setHeaders(headers);
459        }
460
461        if (force || noCache) {
462            urlConn.useCache(false);
463        }
464        return urlConn;
465    }
466
467    private boolean isCacheValidUsingHead() throws IOException {
468        final HttpClient.Response urlConn = getRequest("HEAD", false).connect();
469        long lastModified = urlConn.getLastModified();
470        return (attributes.getEtag() != null && attributes.getEtag().equals(urlConn.getHeaderField("ETag"))) ||
471                (lastModified != 0 && lastModified <= attributes.getLastModification());
472    }
473
474    /**
475     * TODO: move to JobFactory
476     * cancels all outstanding tasks in the queue.
477     */
478    public void cancelOutstandingTasks() {
479        for (Runnable r: downloadJobExecutor.getQueue()) {
480            if (downloadJobExecutor.remove(r) && r instanceof JCSCachedTileLoaderJob) {
481                ((JCSCachedTileLoaderJob<?, ?>) r).handleJobCancellation();
482            }
483        }
484    }
485
486    /**
487     * Sets a job, that will be run, when job will finish execution
488     * @param runnable that will be executed
489     */
490    public void setFinishedTask(Runnable runnable) {
491        this.finishTask = runnable;
492
493    }
494
495    /**
496     * Marks this job as canceled
497     */
498    public void handleJobCancellation() {
499        finishLoading(LoadResult.CANCELED);
500    }
501
502    private URL getUrlNoException() {
503        try {
504            return getUrl();
505        } catch (IOException e) {
506            return null;
507        }
508    }
509}