private static Map<Integer, Long> findLocalSources(
Collection<IndexSnapshotRequestConfig.PartitionRanges> partitionRanges, SiteTracker tracker) {
Set<Integer> partitions = Sets.newHashSet();
for (IndexSnapshotRequestConfig.PartitionRanges partitionRange : partitionRanges) {
partitions.add(partitionRange.partitionId);
}
Map<Integer, Long> pidToLocalHSId = Maps.newHashMap();
List<Long> localSites = Longs.asList(tracker.getLocalSites());
for (long hsId : localSites) {
int pid = tracker.getPartitionForSite(hsId);
if (partitions.contains(pid)) {
pidToLocalHSId.put(pid, hsId);
}
}
return pidToLocalHSId;
}
private static List<Long> computeDedupedLocalSites(long txnId, SiteTracker tracker) {
MessageDigest digest;
try {
digest = MessageDigest.getInstance("SHA-1");
} catch (NoSuchAlgorithmException e) {
throw new AssertionError(e);
}
/*
* List of partitions to include if this snapshot is
* going to be deduped. Attempts to break up the work
* by seeding and RNG selecting
* a random replica to do the work. Will not work in failure
* cases, but we don't use dedupe when we want durability.
*
* Originally used the partition id as the seed, but it turns out
* that nextInt(2) returns a 1 for seeds 0-4095. Now use SHA-1
* on the txnid + partition id.
*/
List<Long> sitesToInclude = new ArrayList<Long>();
for (long localSite : tracker.getLocalSites()) {
final int partitionId = tracker.getPartitionForSite(localSite);
List<Long> sites =
new ArrayList<Long>(tracker.getSitesForPartition(tracker.getPartitionForSite(localSite)));
Collections.sort(sites);
digest.update(Longs.toByteArray(txnId));
final long seed =
Longs.fromByteArray(Arrays.copyOf(digest.digest(Ints.toByteArray(partitionId)), 8));
int siteIndex = new java.util.Random(seed).nextInt(sites.size());
if (localSite == sites.get(siteIndex)) {
sitesToInclude.add(localSite);
}
}
return sitesToInclude;
}