package com.datasift.dropwizard.hbase;
import com.datasift.dropwizard.hbase.scanner.BoundedRowScanner;
import com.datasift.dropwizard.hbase.scanner.RowScanner;
import com.datasift.dropwizard.hbase.util.*;
import com.stumbleupon.async.Deferred;
import io.dropwizard.util.Duration;
import io.dropwizard.util.Size;
import org.hbase.async.*;
import org.jboss.netty.util.Timer;
import java.util.ArrayList;
import java.util.concurrent.Semaphore;
/**
* An {@link HBaseClient} that constrains the maximum number of concurrent asynchronous requests.
* <p/>
* This client places an upper-bounds on the number of concurrent asynchronous requests awaiting
* completion. When this limit is reached, subsequent requests will block until an existing request
* completes.
* <p/>
* This behaviour is particularly useful for throttling high-throughput applications where HBase is
* the bottle-neck. Without backing-off, such an application may run out of memory. By constraining
* the maximum number of requests to a sufficiently high limit, but low enough so that it can be
* reached without running out of memory, such applications can organically throttle and back-off
* their requests.
* <p/>
* Book-keeping of in-flight requests is done using a {@link Semaphore} which is configured as
* "non-fair" to reduce its impact on request throughput.
*/
public class BoundedHBaseClient implements HBaseClient {
/**
* The underlying {@link HBaseClient} to dispatch requests.
*/
private final HBaseClient client;
/**
* The {@link Semaphore} constraining the maximum number of concurrent
* asynchronous requests.
*/
private final Semaphore semaphore;
/**
* Create a new instance with the given limit on concurrent requests for the given underlying
* {@link HBaseClient} implementation.
*
* @param client the underlying {@link HBaseClient} implementation
* @param maxRequests the maximum number of concurrent requests
*/
public BoundedHBaseClient(final HBaseClient client, final int maxRequests) {
this(client, new Semaphore(maxRequests));
}
/**
* Create a new instance with the given semaphore for the given underlying {@link HBaseClient}
* implementation.
* <p/>
* <i>Note: this is only really useful for sharing a {@link Semaphore} between two {@link
* BoundedHBaseClient} instances, which only really makes sense for instances configured for
* the same cluster, but with different client-side settings. <b>Use with caution!!</b></i>
*
* @param client the underlying {@link HBaseClient} implementation.
* @param semaphore the {@link Semaphore} to track concurrent asynchronous requests with.
*/
public BoundedHBaseClient(final HBaseClient client, final Semaphore semaphore) {
this.client = client;
this.semaphore = semaphore;
}
/**
* Get the maximum time for which edits may be buffered before being flushed.
*
* @return the maximum time for which edits may be buffered.
*
* @see HBaseClient#getFlushInterval()
*/
public Duration getFlushInterval() {
return client.getFlushInterval();
}
/**
* Get the capacity of the increment buffer.
*
* @return the capacity of the increment buffer.
*
* @see HBaseClient#getIncrementBufferSize()
*/
public Size getIncrementBufferSize() {
return client.getIncrementBufferSize();
}
/**
* Sets the maximum time for which edits may be buffered before being flushed.
*
* @param flushInterval the maximum time for which edits may be buffered.
*
* @return the previous flush interval.
*
* @see HBaseClient#setFlushInterval(Duration)
*/
public Duration setFlushInterval(final Duration flushInterval) {
return client.setFlushInterval(flushInterval);
}
/**
* Sets the capacity of the increment buffer.
*
* @param incrementBufferSize the capacity of the increment buffer.
*
* @return the previous increment buffer capacity.
*
* @see HBaseClient#setIncrementBufferSize(Size)
*/
public Size setIncrementBufferSize(final Size incrementBufferSize) {
return client.setIncrementBufferSize(incrementBufferSize);
}
/**
* Atomically creates a cell if, and only if, it doesn't already exist.
*
* @param edit the new cell to create.
*
* @return true if the cell was created, false if the cell already exists.
*
* @see HBaseClient#create(PutRequest)
*/
public Deferred<Boolean> create(final PutRequest edit) {
semaphore.acquireUninterruptibly();
return client.create(edit)
.addBoth(new PermitReleasingCallback<Boolean>(semaphore));
}
/**
* Buffer a durable increment for coalescing.
*
* @param request the increment to buffer.
*
* @return the new value of the cell, after the increment.
*
* @see HBaseClient#bufferIncrement(AtomicIncrementRequest)
*/
public Deferred<Long> bufferIncrement(final AtomicIncrementRequest request) {
semaphore.acquireUninterruptibly();
return client.bufferIncrement(request)
.addBoth(new PermitReleasingCallback<Long>(semaphore));
}
/**
* Atomically and durably increment a cell value.
*
* @param request the increment to make.
*
* @return the new value of the cell, after the increment.
*
* @see HBaseClient#increment(AtomicIncrementRequest)
*/
public Deferred<Long> increment(final AtomicIncrementRequest request) {
semaphore.acquireUninterruptibly();
return client.increment(request).addBoth(new PermitReleasingCallback<Long>(semaphore));
}
/**
* Atomically increment a cell value, with optional durability.
*
* @param request the increment to make.
* @param durable whether to guarantee this increment succeeded durably.
*
* @return the new value of the cell, after the increment.
*
* @see HBaseClient#increment(AtomicIncrementRequest, Boolean)
*/
public Deferred<Long> increment(final AtomicIncrementRequest request,
final Boolean durable) {
semaphore.acquireUninterruptibly();
return client.increment(request, durable)
.addBoth(new PermitReleasingCallback<Long>(semaphore));
}
/**
* Atomically compares and sets (CAS) a single cell
*
* @param edit the cell to set.
* @param expected the expected current value.
*
* @return true if the expectation was met and the cell was set; otherwise, false.
*
* @see HBaseClient#compareAndSet(PutRequest, byte[])
*/
public Deferred<Boolean> compareAndSet(final PutRequest edit,
final byte[] expected) {
semaphore.acquireUninterruptibly();
return client.compareAndSet(edit, expected)
.addBoth(new PermitReleasingCallback<Boolean>(semaphore));
}
/**
* Atomically compares and sets (CAS) a single cell.
*
* @param edit the cell to set.
* @param expected the expected current value.
*
* @return true if the expectation was met and the cell was set; otherwise, false.
*
* @see HBaseClient#compareAndSet(PutRequest, String)
*/
public Deferred<Boolean> compareAndSet(final PutRequest edit,
final String expected) {
semaphore.acquireUninterruptibly();
return client.compareAndSet(edit, expected)
.addBoth(new PermitReleasingCallback<Boolean>(semaphore));
}
/**
* Deletes the specified cells.
*
* @param request the cell(s) to delete.
*
* @return a {@link Deferred} indicating when the deletion completes.
*
* @see HBaseClient#delete(DeleteRequest)
*/
public Deferred<Object> delete(final DeleteRequest request) {
semaphore.acquireUninterruptibly();
return client.delete(request).addBoth(new PermitReleasingCallback<>(semaphore));
}
/**
* Ensures that a specific table exists.
*
* @param table the table to check.
*
* @return a {@link Deferred} indicating the completion of the assertion.
*
* @throws TableNotFoundException (Deferred) if the table does not exist.
*
* @see HBaseClient#ensureTableExists(byte[])
*/
public Deferred<Object> ensureTableExists(final byte[] table) {
semaphore.acquireUninterruptibly();
return client.ensureTableExists(table)
.addBoth(new PermitReleasingCallback<>(semaphore));
}
/**
* Ensures that a specific table exists.
*
* @param table the table to check.
*
* @return a {@link Deferred} indicating the completion of the assertion.
*
* @throws TableNotFoundException (Deferred) if the table does not exist.
*
* @see HBaseClient#ensureTableExists(String)
*/
public Deferred<Object> ensureTableExists(final String table) {
semaphore.acquireUninterruptibly();
return client.ensureTableExists(table)
.addBoth(new PermitReleasingCallback<>(semaphore));
}
/**
* Ensures that a specific table exists.
*
* @param table the table to check.
*
* @return a {@link Deferred} indicating the completion of the assertion.
*
* @throws TableNotFoundException (Deferred) if the table does not exist.
* @throws NoSuchColumnFamilyException (Deferred) if the family doesn't exist.
*
* @see HBaseClient#ensureTableFamilyExists(byte[], byte[])
*/
public Deferred<Object> ensureTableFamilyExists(final byte[] table,
final byte[] family) {
semaphore.acquireUninterruptibly();
return client.ensureTableFamilyExists(table, family)
.addBoth(new PermitReleasingCallback<>(semaphore));
}
/**
* Ensures that a specific table exists.
*
* @param table the table to check.
*
* @return a {@link Deferred} indicating the completion of the assertion.
*
* @throws TableNotFoundException (Deferred) if the table does not exist.
* @throws NoSuchColumnFamilyException (Deferred) if the family doesn't exist.
*
* @see HBaseClient#ensureTableFamilyExists(String, String)
*/
public Deferred<Object> ensureTableFamilyExists(final String table,
final String family) {
semaphore.acquireUninterruptibly();
return client.ensureTableFamilyExists(table, family)
.addBoth(new PermitReleasingCallback<>(semaphore));
}
/**
* Flushes all requests buffered on the client-side
*
* @return a {@link Deferred} indicating the completion of the flush.
*
* @see HBaseClient#flush()
*/
public Deferred<Object> flush() {
semaphore.acquireUninterruptibly();
return client.flush().addBoth(new PermitReleasingCallback<>(semaphore));
}
/**
* Retrieves the specified cells
*
* @param request the cells to get.
*
* @return the requested cells.
*
* @see HBaseClient#get(GetRequest)
*/
public Deferred<ArrayList<KeyValue>> get(final GetRequest request) {
semaphore.acquireUninterruptibly();
return client.get(request)
.addBoth(new PermitReleasingCallback<ArrayList<KeyValue>>(semaphore));
}
/**
* Aqcuire an explicit row lock.
*
* @param request the row(s) to lock.
*
* @return the row lock.
*
* @see HBaseClient#lockRow(RowLockRequest)
*/
public Deferred<RowLock> lockRow(final RowLockRequest request) {
semaphore.acquireUninterruptibly();
return client.lockRow(request).addBoth(new PermitReleasingCallback<RowLock>(semaphore));
}
/**
* Create a new {@link RowScanner} for a table.
*
* @param table the table to scan.
*
* @return a new {@link RowScanner} for the specified table.
*
* @see HBaseClient#scan(byte[])
*/
public RowScanner scan(final byte[] table) {
return new BoundedRowScanner(client.scan(table), semaphore);
}
/**
* Create a new {@link RowScanner} for a table.
*
* @param table the table to scan.
*
* @return a new {@link RowScanner} for the specified table.
*
* @see HBaseClient#scan(String)
*/
public RowScanner scan(final String table) {
return new BoundedRowScanner(client.scan(table), semaphore);
}
/**
* Store the specified cell(s).
*
* @param request the cell(s) to store.
*
* @return a {@link Deferred} indicating the completion of the put operation.
*
* @see HBaseClient#put(PutRequest)
*/
public Deferred<Object> put(final PutRequest request) {
semaphore.acquireUninterruptibly();
return client.put(request).addBoth(new PermitReleasingCallback<>(semaphore));
}
/**
* Performs a graceful shutdown of this client, flushing any pending requests.
*
* @return a {@link Deferred} indicating the completion of the shutdown operation.
*
* @see HBaseClient#shutdown()
*/
public Deferred<Object> shutdown() {
return client.shutdown();
}
/**
* Get an immutable snapshot of client usage statistics.
*
* @return an immutable snapshot of client usage statistics.
*
* @see HBaseClient#stats()
*/
public ClientStats stats() {
return client.stats();
}
/**
* Get the underlying {@link org.jboss.netty.util.Timer} used by the client.
*
* @return the underlying {@link org.jboss.netty.util.Timer} used by the async client.
*
* @see HBaseClient#getTimer()
*/
public Timer getTimer() {
return client.getTimer();
}
/**
* Release an explicit row lock.
*
* @param lock the lock to release.
*
* @return a {@link Deferred} indicating the completion of the unlock operation.
*
* @see HBaseClient#unlockRow(RowLock)
*/
public Deferred<Object> unlockRow(final RowLock lock) {
semaphore.acquireUninterruptibly();
return client.unlockRow(lock).addBoth(new PermitReleasingCallback<>(semaphore));
}
}