public PageCache getPageCache(final long pageId) {
try {
boolean needToRead = false;
PageCache cache = null;
synchronized (softCache) {
if (pageId > pagingStore.getCurrentWritingPage()) {
return null;
}
cache = softCache.get(pageId);
if (cache == null) {
if (!pagingStore.checkPageFileExists((int) pageId)) {
return null;
}
cache = createPageCache(pageId);
needToRead = true;
// anyone reading from this cache will have to wait reading to finish first
// we also want only one thread reading this cache
cache.lock();
if (isTrace) {
HornetQServerLogger.LOGGER.trace(
"adding " + pageId + " into cursor = " + this.pagingStore.getAddress());
}
softCache.put(pageId, cache);
}
}
// Reading is done outside of the synchronized block, however
// the page stays locked until the entire reading is finished
if (needToRead) {
Page page = null;
try {
page = pagingStore.createPage((int) pageId);
storageManager.beforePageRead();
page.open();
List<PagedMessage> pgdMessages = page.read(storageManager);
cache.setMessages(pgdMessages.toArray(new PagedMessage[pgdMessages.size()]));
} finally {
try {
if (page != null) {
page.close();
}
} catch (Throwable ignored) {
}
storageManager.afterPageRead();
cache.unlock();
}
}
return cache;
} catch (Exception e) {
throw new RuntimeException(
"Couldn't complete paging due to an IO Exception on Paging - " + e.getMessage(), e);
}
}
/* Protected as we may let test cases to instrument the test */
protected PageCacheImpl createPageCache(final long pageId) throws Exception {
return new PageCacheImpl(pagingStore.createPage((int) pageId));
}