protected CrawlURI peekItem(final WorkQueueFrontier frontier) throws IOException {
final BdbMultipleWorkQueues queues = ((BdbFrontier) frontier).getWorkQueues();
DatabaseEntry key = new DatabaseEntry(origin);
CrawlURI curi = null;
int tries = 1;
while (true) {
try {
curi = queues.get(key);
} catch (DatabaseException e) {
LOGGER.log(Level.SEVERE, "peekItem failure; retrying", e);
}
// ensure CrawlURI, if any, came from acceptable range:
if (!ArchiveUtils.startsWith(key.getData(), origin)) {
LOGGER.severe(
"inconsistency: "
+ classKey
+ "("
+ getPrefixClassKey(origin)
+ ") with "
+ getCount()
+ " items gave "
+ curi
+ "("
+ getPrefixClassKey(key.getData()));
// clear curi to allow retry
curi = null;
// reset key to original origin for retry
key.setData(origin);
}
if (curi != null) {
// success
break;
}
if (tries > 3) {
LOGGER.severe("no item where expected in queue " + classKey);
break;
}
tries++;
LOGGER.severe(
"Trying get #"
+ Integer.toString(tries)
+ " in queue "
+ classKey
+ " with "
+ getCount()
+ " items using key "
+ getPrefixClassKey(key.getData()));
}
return curi;
}
