Package org.apache.solr.cloud

Class ZkDistributedQueue

java.lang.Object

org.apache.solr.cloud.ZkDistributedQueue

All Implemented Interfaces:

DistributedQueue

Direct Known Subclasses:

OverseerTaskQueue

public class ZkDistributedQueue
extends Object
implements DistributedQueue

A ZK-based distributed queue. Optimized for single-consumer, multiple-producer: if there are multiple consumers on the same ZK queue, the results should be correct but inefficient.

This implementation (with help from subclass OverseerTaskQueue) is used for the /overseer/collection-queue-work queue used for Collection and Config Set API calls to the Overseer.

Implementation note: In order to enqueue a message into this queue, a CreateMode.EPHEMERAL_SEQUENTIAL response node is created and watched at /overseer/collection-queue-work/qnr-monotonically_increasng_id, then a corresponding CreateMode.PERSISTENT request node reusing the same id is created at /overseer/collection-queue-work/qn-response_id.

Constructor Summary

Constructors

Constructor	Description
ZkDistributedQueue(SolrZkClient zookeeper, String dir)
ZkDistributedQueue(SolrZkClient zookeeper, String dir, Stats stats)
ZkDistributedQueue(SolrZkClient zookeeper, String dir, Stats stats, int maxQueueSize)
ZkDistributedQueue(SolrZkClient zookeeper, String dir, Stats stats, int maxQueueSize, ConnectionManager.IsClosed higherLevelIsClosed)

Method Summary

Modifier and Type	Method	Description
Map<String,Object>	getStats()
Stats	getZkStats()
void	offer(byte[] data)	Inserts data into queue.
byte[]	peek()	Returns the data at the first element of the queue, or null if the queue is empty.
byte[]	peek(boolean block)	Returns the data at the first element of the queue, or null if the queue is empty and block is false.
byte[]	peek(long wait)	Returns the data at the first element of the queue, or null if the queue is empty after wait ms.
Collection<Pair<String,byte[]>>	peekElements(int max, long waitMillis, Predicate<String> acceptFilter)	Return the currently-known set of elements, using child names from memory.
byte[]	poll()	Attempts to remove the head of the queue and return it.
byte[]	remove()	Attempts to remove the head of the queue and return it.
void	remove(Collection<String> paths)
byte[]	take()	Removes the head of the queue and returns it, blocks until it succeeds.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ZkDistributedQueue

public ZkDistributedQueue(SolrZkClient zookeeper,
                          String dir)

ZkDistributedQueue

public ZkDistributedQueue(SolrZkClient zookeeper,
                          String dir,
                          Stats stats)

ZkDistributedQueue

public ZkDistributedQueue(SolrZkClient zookeeper,
                          String dir,
                          Stats stats,
                          int maxQueueSize)

ZkDistributedQueue

public ZkDistributedQueue(SolrZkClient zookeeper,
                          String dir,
                          Stats stats,
                          int maxQueueSize,
                          ConnectionManager.IsClosed higherLevelIsClosed)

Method Detail

peek

public byte[] peek()
            throws org.apache.zookeeper.KeeperException,
                   InterruptedException

Returns the data at the first element of the queue, or null if the queue is empty.

Specified by:

peek in interface DistributedQueue

Returns:

data at the first element of the queue, or null.

Throws:

org.apache.zookeeper.KeeperException

InterruptedException

peek

public byte[] peek(boolean block)
            throws org.apache.zookeeper.KeeperException,
                   InterruptedException

Returns the data at the first element of the queue, or null if the queue is empty and block is false.

Specified by:

peek in interface DistributedQueue

Parameters:

block - if true, blocks until an element enters the queue

Returns:

data at the first element of the queue, or null.

Throws:

org.apache.zookeeper.KeeperException

InterruptedException

peek

public byte[] peek(long wait)
            throws org.apache.zookeeper.KeeperException,
                   InterruptedException

Returns the data at the first element of the queue, or null if the queue is empty after wait ms.

Specified by:

peek in interface DistributedQueue

Parameters:

wait - max wait time in ms.

Returns:

data at the first element of the queue, or null.

Throws:

org.apache.zookeeper.KeeperException

InterruptedException

poll

public byte[] poll()
            throws org.apache.zookeeper.KeeperException,
                   InterruptedException

Attempts to remove the head of the queue and return it. Returns null if the queue is empty.

Specified by:

poll in interface DistributedQueue

Returns:

Head of the queue or null.

Throws:

org.apache.zookeeper.KeeperException

InterruptedException

remove

public byte[] remove()
              throws NoSuchElementException,
                     org.apache.zookeeper.KeeperException,
                     InterruptedException

Attempts to remove the head of the queue and return it.

Specified by:

remove in interface DistributedQueue

Returns:

The former head of the queue

Throws:

NoSuchElementException

org.apache.zookeeper.KeeperException

InterruptedException

remove

public void remove(Collection<String> paths)
            throws org.apache.zookeeper.KeeperException,
                   InterruptedException

Throws:

org.apache.zookeeper.KeeperException

InterruptedException

take

public byte[] take()
            throws org.apache.zookeeper.KeeperException,
                   InterruptedException

Removes the head of the queue and returns it, blocks until it succeeds.

Specified by:

take in interface DistributedQueue

Returns:

The former head of the queue

Throws:

org.apache.zookeeper.KeeperException

InterruptedException

offer

public void offer(byte[] data)
           throws org.apache.zookeeper.KeeperException,
                  InterruptedException

Inserts data into queue. If there are no other queue consumers, the offered element will be immediately visible when this method returns.

Specified by:

offer in interface DistributedQueue

Throws:

org.apache.zookeeper.KeeperException

InterruptedException

getZkStats

public Stats getZkStats()

getStats

public Map<String,Object> getStats()

Specified by:

getStats in interface DistributedQueue

peekElements

public Collection<Pair<String,byte[]>> peekElements(int max,
                                                          long waitMillis,
                                                          Predicate<String> acceptFilter)
                                                   throws org.apache.zookeeper.KeeperException,
                                                          InterruptedException

Return the currently-known set of elements, using child names from memory. If no children are found, or no children pass acceptFilter, waits up to waitMillis for at least one child to become available.

Package-private to support OverseerTaskQueue specifically.

Specified by:

peekElements in interface DistributedQueue

Throws:

org.apache.zookeeper.KeeperException

InterruptedException