Weekly News 2002-11-17

Mnet Hack Day

There was no Mnet Hack Day on 2002-11-17, as almost everyone was away.

progress

Tschechow wrote a FileVerifier that determines how reliable a file is, by measuring how many of the shares that make up the file are available on block servers. Content Trackers use this information to hide "broken" files from search results.

issues

Mnet continues to use way too much memory, both during file downloading and during file verification (an operation which only Content Trackers perform). "Too much" here means "too many hundreds of megabytes". Tschechow has been investigating this behavior.

hacks needed

(This is a hold-over from last week's Mnet Weekly News. There are plenty of other jobs that need to be done, as can be seen in the bugs db and the tasks db, but this one seems like a particularly fun job because it doesn't require deep knowledge of Mnet components, and because it directly effects the most important performance measure: how quickly the Mnet node can download complete files from Block Servers.)

Mnet has a download system with two components. One component, named BlockWrangler, manages all of the logic which is required to have a correct download. The other component, named BlockWranglingStrategy, gets to make "strategic", or heuristic, decisions about which kind of peers you prefer to download from first, and how many simultaneous downloads you want to initiate. The current BlockWranglingStrategy is named "GSR" for Greedy, Simple, Random. It was intended mostly as a placeholder while developing the BlockWrangler, but it works well enough that people continue to use it. However, it has several serious shortcomings. I encourage people to write their own BlockWranglingStrategies and submit them for inclusion in the distribution. Details in a message to the mnet-devel list.

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