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- The server prefs file contains an order (comma separated) list of node addresses
- The server reads that list of nodes on startup and caches the list somewhere on disk
- If the server starts up and notices the list of nodes in the prefs file is different from the one it cached, then it needs to do a rebalance!
Look on http://en.wikipedia.org/wiki/List_of_hash_functions for a 64 bit hash function OR use a stronger hash function but only take the first 8 bytes out the output.
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ByteBuffer buffer = ByteBuffer.wrap(hashArray);
long hash = buffer.getLong(); |
Locator Hashing
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// We need to get pp distinct nodes for the pool, so we continually hash the hash of the locator until we have everything we need. Integer[] partitionPool = new Integer[pp] IntegerLong hash = null; for(int i = 0; i < pp ; i++){ int slot = -1; while(slot == -1 || partitionPool[slot] != null){ slot = hash(hash == null ? locator : hash) % n; //n is number of nodes } partitionPool[i] = slot; } // We now have an array of node identifiers that form our partition pool. |
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// We need to get rp nodes from the partition pool, so we continually hash the hash of the locator and key until we have everything we need Integer[] redundancyPool = new Integer[rp] IntegerLong hash = null; for(int i = 0; i < rp; i++){ int slot = -1; while(slot == -1 || redundancyPool[slot] != null){ slot = hash(hash == null ? locator + key : hash) % partitionPool.length; } redundancyPool[i] = partitionPool[slot]; } //We now have an array of node identifiers that for our redundancy pool. |
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