bbeaudreault commented on code in PR #5037:
URL: https://github.com/apache/hbase/pull/5037#discussion_r1111033584
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hbase-client/src/main/java/org/apache/hadoop/hbase/client/AsyncNonMetaRegionLocator.java:
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@@ -217,6 +217,223 @@ private boolean tryComplete(LocateRequest req,
CompletableFuture<RegionLocations
}
}
+ /**
+ * Wrapper around ConcurrentSkipListMap ensuring proper access to cached
items. Updates are
+ * synchronized, but reads are not.
+ */
+ private static final class RegionLocationCache {
+
+ private final ConcurrentNavigableMap<byte[], RegionLocations> cache =
+ new ConcurrentSkipListMap<>(BYTES_COMPARATOR);
+
+ /**
+ * Add the given locations to the cache, merging with existing if
necessary. Also cleans out any
+ * previously cached locations which may have been superseded by this one
(i.e. in case of
+ * merged regions). See {@link #cleanOverlappingRegions(RegionLocations)}
+ * @param locs the locations to cache
+ * @return the final location (possibly merged) that was added to the cache
+ */
+ public synchronized RegionLocations add(RegionLocations locs) {
+ byte[] startKey = locs.getRegionLocation().getRegion().getStartKey();
+ RegionLocations oldLocs = cache.putIfAbsent(startKey, locs);
+ if (oldLocs == null) {
+ cleanOverlappingRegions(locs);
+ return locs;
+ }
+
+ // check whether the regions are the same, this usually happens when
table is split/merged,
+ // or deleted and recreated again.
+ RegionInfo region = locs.getRegionLocation().getRegion();
+ RegionInfo oldRegion = oldLocs.getRegionLocation().getRegion();
+ if (region.getEncodedName().equals(oldRegion.getEncodedName())) {
+ RegionLocations mergedLocs = oldLocs.mergeLocations(locs);
+ if (isEqual(mergedLocs, oldLocs)) {
+ // the merged one is the same with the old one, give up
+ LOG.trace("Will not add {} to cache because the old value {} "
+ + " is newer than us or has the same server name."
+ + " Maybe it is updated before we replace it", locs, oldLocs);
+ return oldLocs;
+ }
+ locs = mergedLocs;
+ } else {
+ // the region is different, here we trust the one we fetched. This
maybe wrong but finally
+ // the upper layer can detect this and trigger removal of the wrong
locations
+ if (LOG.isDebugEnabled()) {
+ LOG.debug("The newly fetch region {} is different from the old one
{} for row '{}',"
+ + " try replaying the old one...", region, oldRegion,
Bytes.toStringBinary(startKey));
+ }
+ }
+
+ cache.put(startKey, locs);
+ cleanOverlappingRegions(locs);
+ return locs;
+ }
+
+ /**
+ * When caching a location, the region may have been the result of a
merge. Check to see if the
+ * region's boundaries overlap any other cached locations. Those would
have been merge parents
+ * which no longer exist. We need to proactively clear them out to avoid a
case where a merged
+ * region which receives no requests never gets cleared. This causes
requests to other merged
+ * regions after it to see the wrong cached location. See HBASE-27650
+ * @param locations the new location that was just cached
+ */
+ private void cleanOverlappingRegions(RegionLocations locations) {
+ RegionInfo region = locations.getRegionLocation().getRegion();
+
+ boolean isLast = isEmptyStopRow(region.getEndKey());
+
+ while (true) {
+ Map.Entry<byte[], RegionLocations> overlap =
+ isLast ? cache.lastEntry() : cache.lowerEntry(region.getEndKey());
+ if (
+ overlap == null || overlap.getValue() == locations
+ || Bytes.equals(overlap.getKey(), region.getStartKey())
+ ) {
+ break;
+ }
+
+ if (LOG.isInfoEnabled()) {
+ LOG.info(
+ "Removing cached location {} (endKey={}) because it overlaps with "
+ + "new location {} (endKey={})",
+ overlap.getValue(),
+
Bytes.toStringBinary(overlap.getValue().getRegionLocation().getRegion().getEndKey()),
+ locations,
Bytes.toStringBinary(locations.getRegionLocation().getRegion().getEndKey()));
+ }
+
+ cache.remove(overlap.getKey());
+ }
+ }
+
+ private boolean isEqual(RegionLocations locs1, RegionLocations locs2) {
+ HRegionLocation[] locArr1 = locs1.getRegionLocations();
+ HRegionLocation[] locArr2 = locs2.getRegionLocations();
+ if (locArr1.length != locArr2.length) {
+ return false;
+ }
+ for (int i = 0; i < locArr1.length; i++) {
+ // do not need to compare region info
+ HRegionLocation loc1 = locArr1[i];
+ HRegionLocation loc2 = locArr2[i];
+ if (loc1 == null) {
+ if (loc2 != null) {
+ return false;
+ }
+ } else {
+ if (loc2 == null) {
+ return false;
+ }
+ if (loc1.getSeqNum() != loc2.getSeqNum()) {
+ return false;
+ }
+ if (!Objects.equal(loc1.getServerName(), loc2.getServerName())) {
+ return false;
+ }
+ }
+ }
+ return true;
+ }
+
+ /** Returns all cached RegionLocations */
+ public Collection<RegionLocations> getAll() {
+ return cache.values();
+ }
+
+ /**
+ * Gets the RegionLocations for a given region's startKey. This is a
direct lookup, if the key
+ * does not exist in the cache it will return null.
+ * @param startKey region start key to directly look up
+ */
+ public RegionLocations get(byte[] startKey) {
+ return cache.get(startKey);
+ }
+
+ /**
+ * Finds the RegionLocations for the region with the greatest startKey
less than or equal to the
+ * given row
+ * @param row row to find locations
+ */
+ public RegionLocations findForRow(byte[] row) {
+ Map.Entry<byte[], RegionLocations> entry = cache.floorEntry(row);
+ if (entry == null) {
+ return null;
+ }
+ return entry.getValue();
+ }
+
+ /**
+ * Finds the RegionLocations for the region with the greatest startKey
strictly less than the
+ * given row
+ * @param row row to find locations
+ */
+ public RegionLocations findForBeforeRow(byte[] row) {
+ boolean isEmptyStopRow = isEmptyStopRow(row);
+ Map.Entry<byte[], RegionLocations> entry =
+ isEmptyStopRow ? cache.lastEntry() : cache.lowerEntry(row);
+ if (entry == null) {
+ return null;
+ }
+ return entry.getValue();
+ }
+
+ /**
+ * Removes the location from the cache if it exists and can be removed.
Once a change is deemed
+ * possible, calls beforeUpdate callback prior to making a change. Calls
afterUpdate callback
+ * after making a change.
+ */
+ public synchronized void remove(HRegionLocation loc, Runnable beforeUpdate,
Review Comment:
Let me see if I can remove the callbacks. I was trying to keep the
metaLocation.onError stuff out of here. I wasn't sure if the onError call
needed to happen at the exact point
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