// Selects a dir with enough space (including space evictable) from all tiers
private StorageDirView selectEvictableDirFromAnyTier(
BlockMetadataManagerView view, long availableBytes) {
for (StorageTierView tierView : view.getTierViews()) {
for (StorageDirView dirView : tierView.getDirViews()) {
if (canEvictBlocksFromDir(dirView, availableBytes)) {
return dirView;
}
}
}
return null;
}
private StorageDirView selectAvailableDir(
BlockMeta block,
List<StorageTierView> candidateTiers,
Map<StorageDirView, Long> pendingBytesInDir) {
for (StorageTierView candidateTier : candidateTiers) {
for (StorageDirView candidateDir : candidateTier.getDirViews()) {
long pendingBytes = 0;
if (pendingBytesInDir.containsKey(candidateDir)) {
pendingBytes = pendingBytesInDir.get(candidateDir);
}
if (candidateDir.getAvailableBytes() - pendingBytes >= block.getBlockSize()) {
return candidateDir;
}
}
}
return null;
}
@Override
public EvictionPlan freeSpaceWithView(
long availableBytes, BlockStoreLocation location, BlockMetadataManagerView view) {
Preconditions.checkNotNull(location);
Preconditions.checkNotNull(view);
// 1. Select a StorageDirView that has enough capacity for required bytes.
StorageDirView selectedDirView = null;
if (location.equals(BlockStoreLocation.anyTier())) {
selectedDirView = selectEvictableDirFromAnyTier(view, availableBytes);
} else {
String tierAlias = location.tierAlias();
StorageTierView tierView = view.getTierView(tierAlias);
if (location.equals(BlockStoreLocation.anyDirInTier(tierAlias))) {
selectedDirView = selectEvictableDirFromTier(tierView, availableBytes);
} else {
int dirIndex = location.dir();
StorageDirView dir = tierView.getDirView(dirIndex);
if (canEvictBlocksFromDir(dir, availableBytes)) {
selectedDirView = dir;
}
}
}
if (selectedDirView == null) {
LOG.error(
"Failed to freeSpace: No StorageDirView has enough capacity of {} bytes", availableBytes);
return null;
}
// 2. Check if the selected StorageDirView already has enough space.
List<BlockTransferInfo> toTransfer = new ArrayList<>();
List<Pair<Long, BlockStoreLocation>> toEvict = new ArrayList<>();
long bytesAvailableInDir = selectedDirView.getAvailableBytes();
if (bytesAvailableInDir >= availableBytes) {
// No need to evict anything, return an eviction plan with empty instructions.
return new EvictionPlan(toTransfer, toEvict);
}
// 3. Collect victim blocks from the selected StorageDirView. They could either be evicted or
// moved.
List<BlockMeta> victimBlocks = new ArrayList<>();
for (BlockMeta block : selectedDirView.getEvictableBlocks()) {
victimBlocks.add(block);
bytesAvailableInDir += block.getBlockSize();
if (bytesAvailableInDir >= availableBytes) {
break;
}
}
// 4. Make best effort to transfer victim blocks to lower tiers rather than evict them.
Map<StorageDirView, Long> pendingBytesInDir = new HashMap<>();
for (BlockMeta block : victimBlocks) {
// TODO(qifan): Should avoid calling getParentDir.
String fromTierAlias = block.getParentDir().getParentTier().getTierAlias();
List<StorageTierView> candidateTiers = view.getTierViewsBelow(fromTierAlias);
StorageDirView dstDir = selectAvailableDir(block, candidateTiers, pendingBytesInDir);
if (dstDir == null) {
// Not possible to transfer
toEvict.add(new Pair<>(block.getBlockId(), block.getBlockLocation()));
} else {
StorageTierView dstTier = dstDir.getParentTierView();
toTransfer.add(
new BlockTransferInfo(
block.getBlockId(),
block.getBlockLocation(),
new BlockStoreLocation(dstTier.getTierViewAlias(), dstDir.getDirViewIndex())));
if (pendingBytesInDir.containsKey(dstDir)) {
pendingBytesInDir.put(dstDir, pendingBytesInDir.get(dstDir) + block.getBlockSize());
} else {
pendingBytesInDir.put(dstDir, block.getBlockSize());
}
}
}
return new EvictionPlan(toTransfer, toEvict);
}