Hi Zlatin, I agree that this access is unsynchronized and thus can be stale. Looking at the implementation of HashMap.size, it doesn't need to do anything except copy a single int, so it shouldn't be a cause for any errors beyond stale data (ie it can't throw a ConcurrentModificationException).
In general, the contract for metrics throughout Hadoop doesn't imply anything about consistency or exact up-to-date values. They're generally meant for operational monitoring where exact values are less important. Thanks -Todd On Wed, Jan 13, 2010 at 9:24 AM, <zlatin.balev...@barclayscapital.com>wrote: > Hello all, > > Unless I'm missing something, the synchronization in FSNameSystemMetrics > on the 0.20 does not appear correct. It locks on itself while pulling > various metrics from the FSNameSystem object. For example, > FSNameSystem.getBlocksTotal() delegates to BlocksMap.size() which > delegates to the contained HashMap object. None of those methods are > synchronized on FSNameSystem, so one cannot get accurate data for that > metric. Is this intentional? > > Zlatin > _______________________________________________ > > This e-mail may contain information that is confidential, privileged or > otherwise protected from disclosure. If you are not an intended recipient of > this e-mail, do not duplicate or redistribute it by any means. Please delete > it and any attachments and notify the sender that you have received it in > error. Unless specifically indicated, this e-mail is not an offer to buy or > sell or a solicitation to buy or sell any securities, investment products or > other financial product or service, an official confirmation of any > transaction, or an official statement of Barclays. Any views or opinions > presented are solely those of the author and do not necessarily represent > those of Barclays. This e-mail is subject to terms available at the > following link: www.barcap.com/emaildisclaimer. By messaging with Barclays > you consent to the foregoing. Barclays Capital is the investment banking > division of Barclays Bank PLC, a company registered in England (number > 1026167) with its registered office at 1 Churchill Place, London, E14 5HP. > This email may relate to or be sent from other members of the Barclays > Group. > _______________________________________________ >
