HDFS-15202 Boost short circuit cache (rebase PR-1884) (#2016)

Added parameter dfs.client.short.circuit.num improving HDFS-client's massive reading performance by create few instances ShortCircuit caches instead of one. It helps avoid locks and lets CPU do job.

(cherry picked from commit 86e6aa8eec)
This commit is contained in:
pustota2009 2020-05-18 17:04:04 +03:00 committed by Wei-Chiu Chuang
parent 77587ffb1e
commit ad9a6a0ee3
9 changed files with 214 additions and 75 deletions

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@ -77,7 +77,7 @@ public class ClientContext {
/**
* Caches short-circuit file descriptors, mmap regions.
*/
private final ShortCircuitCache shortCircuitCache;
private final ShortCircuitCache[] shortCircuitCache;
/**
* Caches TCP and UNIX domain sockets for reuse.
@ -132,13 +132,23 @@ public class ClientContext {
*/
private DeadNodeDetector deadNodeDetector = null;
/**
* ShortCircuitCache array size.
*/
private final int clientShortCircuitNum;
private ClientContext(String name, DfsClientConf conf,
Configuration config) {
final ShortCircuitConf scConf = conf.getShortCircuitConf();
this.name = name;
this.confString = scConf.confAsString();
this.shortCircuitCache = ShortCircuitCache.fromConf(scConf);
this.clientShortCircuitNum = conf.getClientShortCircuitNum();
this.shortCircuitCache = new ShortCircuitCache[this.clientShortCircuitNum];
for (int i = 0; i < this.clientShortCircuitNum; i++) {
this.shortCircuitCache[i] = ShortCircuitCache.fromConf(scConf);
}
this.peerCache = new PeerCache(scConf.getSocketCacheCapacity(),
scConf.getSocketCacheExpiry());
this.keyProviderCache = new KeyProviderCache(
@ -228,7 +238,11 @@ public class ClientContext {
}
public ShortCircuitCache getShortCircuitCache() {
return shortCircuitCache;
return shortCircuitCache[0];
}
public ShortCircuitCache getShortCircuitCache(long idx) {
return shortCircuitCache[(int) (idx % clientShortCircuitNum)];
}
public PeerCache getPeerCache() {

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@ -144,6 +144,8 @@ public interface HdfsClientConfigKeys {
"dfs.short.circuit.shared.memory.watcher.interrupt.check.ms";
int DFS_SHORT_CIRCUIT_SHARED_MEMORY_WATCHER_INTERRUPT_CHECK_MS_DEFAULT =
60000;
String DFS_CLIENT_SHORT_CIRCUIT_NUM = "dfs.client.short.circuit.num";
int DFS_CLIENT_SHORT_CIRCUIT_NUM_DEFAULT = 1;
String DFS_CLIENT_SLOW_IO_WARNING_THRESHOLD_KEY =
"dfs.client.slow.io.warning.threshold.ms";
long DFS_CLIENT_SLOW_IO_WARNING_THRESHOLD_DEFAULT = 30000;

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@ -476,7 +476,8 @@ public class BlockReaderFactory implements ShortCircuitReplicaCreator {
"giving up on BlockReaderLocal.", this, pathInfo);
return null;
}
ShortCircuitCache cache = clientContext.getShortCircuitCache();
ShortCircuitCache cache =
clientContext.getShortCircuitCache(block.getBlockId());
ExtendedBlockId key = new ExtendedBlockId(block.getBlockId(),
block.getBlockPoolId());
ShortCircuitReplicaInfo info = cache.fetchOrCreate(key, this);
@ -527,7 +528,8 @@ public class BlockReaderFactory implements ShortCircuitReplicaCreator {
if (curPeer.fromCache) remainingCacheTries--;
DomainPeer peer = (DomainPeer)curPeer.peer;
Slot slot = null;
ShortCircuitCache cache = clientContext.getShortCircuitCache();
ShortCircuitCache cache =
clientContext.getShortCircuitCache(block.getBlockId());
try {
MutableBoolean usedPeer = new MutableBoolean(false);
slot = cache.allocShmSlot(datanode, peer, usedPeer,
@ -582,7 +584,8 @@ public class BlockReaderFactory implements ShortCircuitReplicaCreator {
*/
private ShortCircuitReplicaInfo requestFileDescriptors(DomainPeer peer,
Slot slot) throws IOException {
ShortCircuitCache cache = clientContext.getShortCircuitCache();
ShortCircuitCache cache =
clientContext.getShortCircuitCache(block.getBlockId());
final DataOutputStream out =
new DataOutputStream(new BufferedOutputStream(peer.getOutputStream(), SMALL_BUFFER_SIZE));
SlotId slotId = slot == null ? null : slot.getSlotId();

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@ -142,6 +142,7 @@ public class DfsClientConf {
private final long refreshReadBlockLocationsMS;
private final ShortCircuitConf shortCircuitConf;
private final int clientShortCircuitNum;
private final long hedgedReadThresholdMillis;
private final int hedgedReadThreadpoolSize;
@ -272,8 +273,6 @@ public class DfsClientConf {
HdfsClientConfigKeys.
DFS_CLIENT_REFRESH_READ_BLOCK_LOCATIONS_MS_DEFAULT);
shortCircuitConf = new ShortCircuitConf(conf);
hedgedReadThresholdMillis = conf.getLong(
HedgedRead.THRESHOLD_MILLIS_KEY,
HedgedRead.THRESHOLD_MILLIS_DEFAULT);
@ -296,6 +295,17 @@ public class DfsClientConf {
leaseHardLimitPeriod =
conf.getLong(HdfsClientConfigKeys.DFS_LEASE_HARDLIMIT_KEY,
HdfsClientConfigKeys.DFS_LEASE_HARDLIMIT_DEFAULT) * 1000;
shortCircuitConf = new ShortCircuitConf(conf);
clientShortCircuitNum = conf.getInt(
HdfsClientConfigKeys.DFS_CLIENT_SHORT_CIRCUIT_NUM,
HdfsClientConfigKeys.DFS_CLIENT_SHORT_CIRCUIT_NUM_DEFAULT);
Preconditions.checkArgument(clientShortCircuitNum >= 1,
HdfsClientConfigKeys.DFS_CLIENT_SHORT_CIRCUIT_NUM +
"can't be less then 1.");
Preconditions.checkArgument(clientShortCircuitNum <= 5,
HdfsClientConfigKeys.DFS_CLIENT_SHORT_CIRCUIT_NUM +
"can't be more then 5.");
}
@SuppressWarnings("unchecked")
@ -601,6 +611,13 @@ public class DfsClientConf {
return slowIoWarningThresholdMs;
}
/*
* @return the clientShortCircuitNum
*/
public int getClientShortCircuitNum() {
return clientShortCircuitNum;
}
/**
* @return the hedgedReadThresholdMillis
*/

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@ -4178,6 +4178,16 @@
</description>
</property>
<property>
<name>dfs.client.short.circuit.num</name>
<value>1</value>
<description>
Number of short-circuit caches. This setting should
be in the range 1 - 5. Lower values will result in lower CPU consumption; higher
values may speed up massive parallel reading files.
</description>
</property>
<property>
<name>dfs.client.read.striped.threadpool.size</name>
<value>18</value>

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@ -358,7 +358,7 @@ public class TestEnhancedByteBufferAccess {
fsIn.close();
fsIn = fs.open(TEST_PATH);
final ShortCircuitCache cache = ClientContext.get(
CONTEXT, conf).getShortCircuitCache();
CONTEXT, conf).getShortCircuitCache(0);
cache.accept(new CountingVisitor(0, 5, 5, 0));
results[0] = fsIn.read(null, BLOCK_SIZE,
EnumSet.of(ReadOption.SKIP_CHECKSUMS));
@ -654,12 +654,12 @@ public class TestEnhancedByteBufferAccess {
BLOCK_SIZE), byteBufferToArray(result2));
fsIn2.releaseBuffer(result2);
fsIn2.close();
// check that the replica is anchored
final ExtendedBlock firstBlock =
DFSTestUtil.getFirstBlock(fs, TEST_PATH);
final ShortCircuitCache cache = ClientContext.get(
CONTEXT, conf).getShortCircuitCache();
CONTEXT, conf).getShortCircuitCache(0);
waitForReplicaAnchorStatus(cache, firstBlock, true, true, 1);
// Uncache the replica
fs.removeCacheDirective(directiveId);

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@ -389,7 +389,7 @@ public class TestBlockReaderFactory {
try (FSDataInputStream in = dfs.open(testFile)) {
Assert.assertEquals(0,
dfs.getClient().getClientContext().getShortCircuitCache()
dfs.getClient().getClientContext().getShortCircuitCache(0)
.getReplicaInfoMapSize());
final byte[] buf = new byte[testFileLen];
@ -398,12 +398,12 @@ public class TestBlockReaderFactory {
// Set cache size to 0 so the replica marked evictable by unbuffer
// will be purged immediately.
dfs.getClient().getClientContext().getShortCircuitCache()
dfs.getClient().getClientContext().getShortCircuitCache(0)
.setMaxTotalSize(0);
LOG.info("Unbuffering");
in.unbuffer();
Assert.assertEquals(0,
dfs.getClient().getClientContext().getShortCircuitCache()
dfs.getClient().getClientContext().getShortCircuitCache(0)
.getReplicaInfoMapSize());
DFSTestUtil.appendFile(dfs, testFile, "append more data");
@ -432,7 +432,7 @@ public class TestBlockReaderFactory {
final int expectedScrRepMapSize) {
Assert.assertThat(expected, CoreMatchers.is(actual));
Assert.assertEquals(expectedScrRepMapSize,
dfs.getClient().getClientContext().getShortCircuitCache()
dfs.getClient().getClientContext().getShortCircuitCache(0)
.getReplicaInfoMapSize());
}
@ -467,7 +467,7 @@ public class TestBlockReaderFactory {
calculateFileContentsFromSeed(SEED, TEST_FILE_LEN);
Assert.assertTrue(Arrays.equals(contents, expected));
final ShortCircuitCache cache =
fs.getClient().getClientContext().getShortCircuitCache();
fs.getClient().getClientContext().getShortCircuitCache(0);
final DatanodeInfo datanode = new DatanodeInfoBuilder()
.setNodeID(cluster.getDataNodes().get(0).getDatanodeId())
.build();
@ -516,7 +516,7 @@ public class TestBlockReaderFactory {
calculateFileContentsFromSeed(SEED, TEST_FILE_LEN);
Assert.assertTrue(Arrays.equals(contents, expected));
final ShortCircuitCache cache =
fs.getClient().getClientContext().getShortCircuitCache();
fs.getClient().getClientContext().getShortCircuitCache(0);
Assert.assertEquals(null, cache.getDfsClientShmManager());
cluster.shutdown();
sockDir.close();
@ -548,7 +548,7 @@ public class TestBlockReaderFactory {
calculateFileContentsFromSeed(SEED, TEST_FILE_LEN);
Assert.assertTrue(Arrays.equals(contents, expected));
final ShortCircuitCache cache =
fs.getClient().getClientContext().getShortCircuitCache();
fs.getClient().getClientContext().getShortCircuitCache(0);
cache.close();
Assert.assertTrue(cache.getDfsClientShmManager().
getDomainSocketWatcher().isClosed());

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@ -116,7 +116,7 @@ public class TestBlockReaderLocal {
}
private static class BlockReaderLocalTest {
final static int TEST_LENGTH = 12345;
final static int TEST_LENGTH = 1234567;
final static int BYTES_PER_CHECKSUM = 512;
public void setConfiguration(HdfsConfiguration conf) {
@ -130,10 +130,14 @@ public class TestBlockReaderLocal {
throws IOException {
// default: no-op
}
}
public void doTest(BlockReaderLocal reader, byte[] original, int shift)
throws IOException {
// default: no-op
} }
public void runBlockReaderLocalTest(BlockReaderLocalTest test,
boolean checksum, long readahead) throws IOException {
boolean checksum, long readahead, int shortCircuitCachesNum)
throws IOException {
Assume.assumeThat(DomainSocket.getLoadingFailureReason(), equalTo(null));
MiniDFSCluster cluster = null;
HdfsConfiguration conf = new HdfsConfiguration();
@ -143,10 +147,13 @@ public class TestBlockReaderLocal {
BlockReaderLocalTest.BYTES_PER_CHECKSUM);
conf.set(DFSConfigKeys.DFS_CHECKSUM_TYPE_KEY, "CRC32C");
conf.setLong(HdfsClientConfigKeys.DFS_CLIENT_CACHE_READAHEAD, readahead);
conf.setInt(HdfsClientConfigKeys.DFS_CLIENT_SHORT_CIRCUIT_NUM,
shortCircuitCachesNum);
test.setConfiguration(conf);
FileInputStream dataIn = null, metaIn = null;
final Path TEST_PATH = new Path("/a");
final long RANDOM_SEED = 4567L;
final int blockSize = 10 * 1024;
BlockReaderLocal blockReaderLocal = null;
FSDataInputStream fsIn = null;
byte original[] = new byte[BlockReaderLocalTest.TEST_LENGTH];
@ -158,8 +165,8 @@ public class TestBlockReaderLocal {
cluster = new MiniDFSCluster.Builder(conf).numDataNodes(1).build();
cluster.waitActive();
fs = cluster.getFileSystem();
DFSTestUtil.createFile(fs, TEST_PATH,
BlockReaderLocalTest.TEST_LENGTH, (short)1, RANDOM_SEED);
DFSTestUtil.createFile(fs, TEST_PATH, 1024,
BlockReaderLocalTest.TEST_LENGTH, blockSize, (short)1, RANDOM_SEED);
try {
DFSTestUtil.waitReplication(fs, TEST_PATH, (short)1);
} catch (InterruptedException e) {
@ -174,47 +181,52 @@ public class TestBlockReaderLocal {
BlockReaderLocalTest.TEST_LENGTH);
fsIn.close();
fsIn = null;
ExtendedBlock block = DFSTestUtil.getFirstBlock(fs, TEST_PATH);
File dataFile = cluster.getBlockFile(0, block);
File metaFile = cluster.getBlockMetadataFile(0, block);
for (int i = 0; i < shortCircuitCachesNum; i++) {
ExtendedBlock block = DFSTestUtil.getAllBlocks(
fs, TEST_PATH).get(i).getBlock();
File dataFile = cluster.getBlockFile(0, block);
File metaFile = cluster.getBlockMetadataFile(0, block);
ShortCircuitCache shortCircuitCache =
ClientContext.getFromConf(conf).getShortCircuitCache();
ShortCircuitCache shortCircuitCache =
ClientContext.getFromConf(conf).getShortCircuitCache(
block.getBlockId());
test.setup(dataFile, checksum);
FileInputStream[] streams = {
new FileInputStream(dataFile),
new FileInputStream(metaFile)
};
dataIn = streams[0];
metaIn = streams[1];
ExtendedBlockId key = new ExtendedBlockId(block.getBlockId(),
block.getBlockPoolId());
raf = new RandomAccessFile(
new File(sockDir.getDir().getAbsolutePath(),
UUID.randomUUID().toString()), "rw");
raf.setLength(8192);
FileInputStream shmStream = new FileInputStream(raf.getFD());
shm = new ShortCircuitShm(ShmId.createRandom(), shmStream);
ShortCircuitReplica replica =
new ShortCircuitReplica(key, dataIn, metaIn, shortCircuitCache,
Time.now(), shm.allocAndRegisterSlot(
ExtendedBlockId.fromExtendedBlock(block)));
blockReaderLocal = new BlockReaderLocal.Builder(
new DfsClientConf.ShortCircuitConf(conf)).
setFilename(TEST_PATH.getName()).
setBlock(block).
setShortCircuitReplica(replica).
setCachingStrategy(new CachingStrategy(false, readahead)).
setVerifyChecksum(checksum).
build();
dataIn = null;
metaIn = null;
test.doTest(blockReaderLocal, original, i * blockSize);
// BlockReaderLocal should not alter the file position.
Assert.assertEquals(0, streams[0].getChannel().position());
Assert.assertEquals(0, streams[1].getChannel().position());
}
cluster.shutdown();
cluster = null;
test.setup(dataFile, checksum);
FileInputStream streams[] = {
new FileInputStream(dataFile),
new FileInputStream(metaFile)
};
dataIn = streams[0];
metaIn = streams[1];
ExtendedBlockId key = new ExtendedBlockId(block.getBlockId(),
block.getBlockPoolId());
raf = new RandomAccessFile(
new File(sockDir.getDir().getAbsolutePath(),
UUID.randomUUID().toString()), "rw");
raf.setLength(8192);
FileInputStream shmStream = new FileInputStream(raf.getFD());
shm = new ShortCircuitShm(ShmId.createRandom(), shmStream);
ShortCircuitReplica replica =
new ShortCircuitReplica(key, dataIn, metaIn, shortCircuitCache,
Time.now(), shm.allocAndRegisterSlot(
ExtendedBlockId.fromExtendedBlock(block)));
blockReaderLocal = new BlockReaderLocal.Builder(
new DfsClientConf.ShortCircuitConf(conf)).
setFilename(TEST_PATH.getName()).
setBlock(block).
setShortCircuitReplica(replica).
setCachingStrategy(new CachingStrategy(false, readahead)).
setVerifyChecksum(checksum).
build();
dataIn = null;
metaIn = null;
test.doTest(blockReaderLocal, original);
// BlockReaderLocal should not alter the file position.
Assert.assertEquals(0, streams[0].getChannel().position());
Assert.assertEquals(0, streams[1].getChannel().position());
} finally {
if (fsIn != null) fsIn.close();
if (fs != null) fs.close();
@ -227,6 +239,12 @@ public class TestBlockReaderLocal {
}
}
public void runBlockReaderLocalTest(BlockReaderLocalTest test,
boolean checksum, long readahead) throws IOException {
runBlockReaderLocalTest(BlockReaderLocalTest test,
boolean checksum, long readahead, 1);
}
private static class TestBlockReaderLocalImmediateClose
extends BlockReaderLocalTest {
}
@ -242,7 +260,7 @@ public class TestBlockReaderLocal {
@Override
public void doTest(BlockReaderLocal reader, byte original[])
throws IOException {
byte buf[] = new byte[TEST_LENGTH];
byte[] buf = new byte[TEST_LENGTH];
reader.readFully(buf, 0, 512);
assertArrayRegionsEqual(original, 0, buf, 0, 512);
reader.readFully(buf, 512, 512);
@ -291,7 +309,7 @@ public class TestBlockReaderLocal {
@Override
public void doTest(BlockReaderLocal reader, byte original[])
throws IOException {
byte buf[] = new byte[TEST_LENGTH];
byte[] buf = new byte[TEST_LENGTH];
reader.readFully(buf, 0, 10);
assertArrayRegionsEqual(original, 0, buf, 0, 10);
reader.readFully(buf, 10, 100);
@ -369,7 +387,7 @@ public class TestBlockReaderLocal {
public void testBlockReaderLocalByteBufferReadsNoReadahead()
throws IOException {
runBlockReaderLocalTest(new TestBlockReaderLocalByteBufferReads(),
true, 0);
true, 0);
}
@Test
@ -468,7 +486,7 @@ public class TestBlockReaderLocal {
public void doTest(BlockReaderLocal reader, byte original[])
throws IOException {
byte buf[] = new byte[TEST_LENGTH];
byte[] buf = new byte[TEST_LENGTH];
if (usingChecksums) {
try {
reader.readFully(buf, 0, 10);
@ -508,7 +526,7 @@ public class TestBlockReaderLocal {
public void doTest(BlockReaderLocal reader, byte original[])
throws IOException {
byte buf[] = new byte[TEST_LENGTH];
byte[] buf = new byte[TEST_LENGTH];
try {
reader.readFully(buf, 0, 10);
assertArrayRegionsEqual(original, 0, buf, 0, 10);
@ -845,4 +863,78 @@ public class TestBlockReaderLocal {
}
}
}
private static class TestBlockReaderFiveShortCircutCachesReads
extends BlockReaderLocalTest {
@Override
public void doTest(BlockReaderLocal reader, byte[] original, int shift)
throws IOException {
byte[] buf = new byte[TEST_LENGTH];
reader.readFully(buf, 0, 512);
assertArrayRegionsEqual(original, shift, buf, 0, 512);
reader.readFully(buf, 512, 512);
assertArrayRegionsEqual(original, 512 + shift, buf, 512, 512);
reader.readFully(buf, 1024, 513);
assertArrayRegionsEqual(original, 1024 + shift, buf, 1024, 513);
reader.readFully(buf, 1537, 514);
assertArrayRegionsEqual(original, 1537 + shift, buf, 1537, 514);
// Readahead is always at least the size of one chunk in this test.
Assert.assertTrue(reader.getMaxReadaheadLength() >=
BlockReaderLocalTest.BYTES_PER_CHECKSUM);
}
}
@Test
public void testBlockReaderFiveShortCircutCachesReads() throws IOException {
runBlockReaderLocalTest(new TestBlockReaderFiveShortCircutCachesReads(),
true, HdfsClientConfigKeys.DFS_DATANODE_READAHEAD_BYTES_DEFAULT,
5);
}
@Test
public void testBlockReaderFiveShortCircutCachesReadsShortReadahead()
throws IOException {
runBlockReaderLocalTest(new TestBlockReaderFiveShortCircutCachesReads(),
true, BlockReaderLocalTest.BYTES_PER_CHECKSUM - 1,
5);
}
@Test
public void testBlockReaderFiveShortCircutCachesReadsNoChecksum()
throws IOException {
runBlockReaderLocalTest(new TestBlockReaderFiveShortCircutCachesReads(),
false, HdfsClientConfigKeys.DFS_DATANODE_READAHEAD_BYTES_DEFAULT,
5);
}
@Test
public void testBlockReaderFiveShortCircutCachesReadsNoReadahead()
throws IOException {
runBlockReaderLocalTest(new TestBlockReaderFiveShortCircutCachesReads(),
true, 0, 5);
}
@Test
public void testBlockReaderFiveShortCircutCachesReadsNoChecksumNoReadahead()
throws IOException {
runBlockReaderLocalTest(new TestBlockReaderFiveShortCircutCachesReads(),
false, 0, 5);
}
@Test(expected = IllegalArgumentException.class)
public void testBlockReaderShortCircutCachesOutOfRangeBelow()
throws IOException {
runBlockReaderLocalTest(new TestBlockReaderFiveShortCircutCachesReads(),
true, HdfsClientConfigKeys.DFS_DATANODE_READAHEAD_BYTES_DEFAULT,
0);
}
@Test(expected = IllegalArgumentException.class)
public void testBlockReaderShortCircutCachesOutOfRangeAbove()
throws IOException {
runBlockReaderLocalTest(new TestBlockReaderFiveShortCircutCachesReads(),
true, HdfsClientConfigKeys.DFS_DATANODE_READAHEAD_BYTES_DEFAULT,
555);
}
}

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@ -431,7 +431,7 @@ public class TestShortCircuitCache {
cluster.waitActive();
DistributedFileSystem fs = cluster.getFileSystem();
final ShortCircuitCache cache =
fs.getClient().getClientContext().getShortCircuitCache();
fs.getClient().getClientContext().getShortCircuitCache(0);
cache.getDfsClientShmManager().visit(new Visitor() {
@Override
public void visit(HashMap<DatanodeInfo, PerDatanodeVisitorInfo> info)
@ -501,7 +501,7 @@ public class TestShortCircuitCache {
cluster.waitActive();
DistributedFileSystem fs = cluster.getFileSystem();
final ShortCircuitCache cache =
fs.getClient().getClientContext().getShortCircuitCache();
fs.getClient().getClientContext().getShortCircuitCache(0);
String TEST_FILE = "/test_file";
final int TEST_FILE_LEN = 8193;
final int SEED = 0xFADED;
@ -565,7 +565,7 @@ public class TestShortCircuitCache {
cluster.waitActive();
DistributedFileSystem fs = cluster.getFileSystem();
final ShortCircuitCache cache =
fs.getClient().getClientContext().getShortCircuitCache();
fs.getClient().getClientContext().getShortCircuitCache(0);
cache.getDfsClientShmManager().visit(new Visitor() {
@Override
public void visit(HashMap<DatanodeInfo, PerDatanodeVisitorInfo> info)
@ -877,19 +877,20 @@ public class TestShortCircuitCache {
return peerCache;
});
Mockito.when(clientContext.getShortCircuitCache()).thenAnswer(
Mockito.when(clientContext.getShortCircuitCache(
blk.getBlock().getBlockId())).thenAnswer(
(Answer<ShortCircuitCache>) shortCircuitCacheCall -> {
ShortCircuitCache cache = Mockito.mock(ShortCircuitCache.class);
Mockito.when(cache.allocShmSlot(
ShortCircuitCache cache = Mockito.mock(ShortCircuitCache.class);
Mockito.when(cache.allocShmSlot(
Mockito.any(DatanodeInfo.class),
Mockito.any(DomainPeer.class),
Mockito.any(MutableBoolean.class),
Mockito.any(ExtendedBlockId.class),
Mockito.anyString()))
.thenAnswer((Answer<Slot>) call -> null);
.thenAnswer((Answer<Slot>) call -> null);
return cache;
}
return cache;
}
);
DatanodeInfo[] nodes = blk.getLocations();