Author: christian.bauer(a)jboss.com Date: 2008-05-23 10:13:07 -0400 (Fri, 23 May 2008) New Revision: 8269 Modified: trunk/examples/wiki/src/main/org/jboss/seam/wiki/connectors/cache/ConnectorCache.java trunk/examples/wiki/src/main/org/jboss/seam/wiki/connectors/feed/FeedAggregatorDAO.java Log: Don't throw exception and kill thread on lock aquisition failure Modified: trunk/examples/wiki/src/main/org/jboss/seam/wiki/connectors/cache/ConnectorCache.java =================================================================== --- trunk/examples/wiki/src/main/org/jboss/seam/wiki/connectors/cache/ConnectorCache.java 2008-05-23 05:22:40 UTC (rev 8268) +++ trunk/examples/wiki/src/main/org/jboss/seam/wiki/connectors/cache/ConnectorCache.java 2008-05-23 14:13:07 UTC (rev 8269) @@ -18,6 +18,12 @@ /** * Caches lists of stuff and can asynchronously call a connector, upon configurable cache timeout, to * refresh these lists. + * <p> + * All method calls to this application-scoped component are synchronized by Seam. That means you might + * get an <tt>IllegalStateException</tt> when an exclusive lock couldn't be aquired by a thread (because + * some other thread was already accessing this instance). It's up to the caller to handle that exception, + * usually you'd log and swallow it and continue without the result of the cache. + * </p> * * @author Christian Bauer */ Modified: trunk/examples/wiki/src/main/org/jboss/seam/wiki/connectors/feed/FeedAggregatorDAO.java =================================================================== --- trunk/examples/wiki/src/main/org/jboss/seam/wiki/connectors/feed/FeedAggregatorDAO.java 2008-05-23 05:22:40 UTC (rev 8268) +++ trunk/examples/wiki/src/main/org/jboss/seam/wiki/connectors/feed/FeedAggregatorDAO.java 2008-05-23 14:13:07 UTC (rev 8269) @@ -65,13 +65,26 @@ List<FeedEntryDTO> feedEntries = new ArrayList<FeedEntryDTO>(); for (URL feedURL : feedURLs) { - // For each feed, get the feed entries and put them in a sorted collection, - // so we get overall sorting - log.debug("retrieving feed entries from connector for feed URL: " + feedURL); - List<FeedEntryDTO> result = feedConnector.getFeedEntries(feedURL.toString()); - log.debug("retrieved feed entries: " + result.size()); - feedEntries.addAll(result); - log.debug("number of aggregated feed entries so far: " + feedEntries.size()); + try { + // For each feed, get the feed entries and put them in a sorted collection, + // so we get overall sorting + log.debug("retrieving feed entries from connector for feed URL: " + feedURL); + + // TODO: This is a synchronized call. This probably means that this is a bottleneck for scalability because + // the Seam locking is very coarse-grained. It would be much better if we could aquire exclusive read/write + // locks, not just exclusive locks. + List<FeedEntryDTO> result = feedConnector.getFeedEntries(feedURL.toString()); + + log.debug("retrieved feed entries: " + result.size()); + feedEntries.addAll(result); + log.debug("number of aggregated feed entries so far: " + feedEntries.size()); + + } catch (IllegalStateException ex) { + // This is most likely (we hope) a message that says that an exlusive read lock couldn't be aquired. + // Too bad, we just continue without adding the result... the next user requesting it will probably + // get the lock and then we have the result. + log.warn("Illegal state exception thrown by feed connector: " + ex.getMessage()); + } } Collections.sort(