com.allanbank.mongodb.client.state

Class Cluster

java.lang.Object

com.allanbank.mongodb.client.state.Cluster

All Implemented Interfaces:

ClusterStats

public class Cluster
extends Object
implements ClusterStats

Cluster tracks the state of the cluster of MongoDB servers. PropertyChangeEvents are fired when a server is added or marked writable/not writable.

This class uses brute force synchronization to protect its internal state. It is assumed that multiple connections will be concurrently updating the Cluster at once and that at any given time this class may not contain the absolute truth about the state of the cluster. Instead connections should keep querying for the state of the cluster via their connection until the view the server returned and the Cluster are consistent. Since this class will not fire a PropertyChangeEvent when the state is not truly modified the simplest mechanism is to keep querying for the cluster state on the connection until no addition change events are seen.

API Warning:

This class is NOT part of the drivers API. This class may be mutated in incompatible ways between any two releases of the driver.

Copyright ©:

2011-2013, Allanbank Consulting, Inc., All Rights Reserved

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected class	Cluster.ServerListener ServerListener provides a listener for the state updates of the Server.

Field Summary

Fields

Modifier and Type	Field and Description
protected MongoClientConfiguration	myConfig The configuration for connecting to the servers.
protected ConcurrentMap<String,Server>	myServers The complete list of servers.
protected VersionRange	myServerVersionRange The range of versions within the cluster.
protected int	mySmallestMaxBatchedWriteOperations The smallest maximum number of operations in a batch in the cluster.
protected long	mySmallestMaxBsonObjectSize The smallest maximum document size in the cluster.
static String	SERVER_PROP The property sued for adding a new server.
static String	WRITABLE_PROP The property name for if there is a writable server.

Constructor Summary

Constructors

Constructor and Description
Cluster(MongoClientConfiguration config, ClusterType type) Creates a new CLusterState.

Method Summary

Methods

Modifier and Type	Method and Description
Server	add(InetSocketAddress address) Adds a Server to the Cluster for the address provided if one does not already exist.
Server	add(String address) Adds a Server to the Cluster for the address provided if one does not already exist.
void	addListener(PropertyChangeListener listener) Adds a listener to the state.
protected double[]	cdf(List<Server> servers) Computes a relative CDF (cumulative distribution function) for the servers based on the latency from the client.
void	clear() Removes all of the servers from the cluster.
protected List<Server>	findCandidateServer(ReadPreference readPreference) Finds the candidate server, if known.
List<Server>	findCandidateServers(ReadPreference readPreference) Returns the set of servers that can be used based on the provided ReadPreference.
protected List<Server>	findNearestCandidates(ReadPreference readPreference) Returns the list of servers that match the read preference's tags.
protected List<Server>	findNonWritableCandidates(ReadPreference readPreference) Returns the list of non-writable servers that match the read preference's tags.
List<Server>	findServers(Message message1, Message message2) Locates the set of servers that can be used to send the specified messages.
protected List<Server>	findWritableCandidates(ReadPreference readPreference) Returns the list of writable servers that match the read preference's tags.
Server	get(String address) Returns the server state for the address provided.
List<Server>	getNonWritableServers() Returns a copy of the list of non-writable servers.
List<Server>	getServers() Returns a copy of the list of servers.
VersionRange	getServerVersionRange() Returns the range of versions that we currently see within the cluster.
int	getSmallestMaxBatchedWriteOperations() Returns smallest value for the maximum number of write operations allowed in a single write command.
long	getSmallestMaxBsonObjectSize() Returns the smallest value for the maximum BSON object size within the cluster.
ClusterType	getType() Returns the type of cluster.
List<Server>	getWritableServers() Returns a copy of the list of writable servers.
void	remove(Server server) Removes the specified server from the cluster.
void	removeListener(PropertyChangeListener listener) Removes a listener to the state.
protected void	sort(List<Server> servers) Sorts the servers based on the latency from the client.
protected void	updateVersions() Updates the min/max versions across all servers.

Methods inherited from class java.lang.Object

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

Field Detail

SERVER_PROP

public static final String SERVER_PROP

The property sued for adding a new server.

See Also:

Constant Field Values

WRITABLE_PROP

public static final String WRITABLE_PROP

The property name for if there is a writable server.

See Also:

Constant Field Values

myConfig

protected final MongoClientConfiguration myConfig

The configuration for connecting to the servers.

myServers

protected final ConcurrentMap<String,Server> myServers

The complete list of servers.

myServerVersionRange

protected VersionRange myServerVersionRange

The range of versions within the cluster.

mySmallestMaxBatchedWriteOperations

protected int mySmallestMaxBatchedWriteOperations

The smallest maximum number of operations in a batch in the cluster.

mySmallestMaxBsonObjectSize

protected long mySmallestMaxBsonObjectSize

The smallest maximum document size in the cluster.

Constructor Detail

Cluster

public Cluster(MongoClientConfiguration config,
       ClusterType type)

Creates a new CLusterState.

Parameters:

config - The configuration for the cluster.

type - The type of the cluster.

Method Detail

add

public Server add(InetSocketAddress address)

Adds a Server to the Cluster for the address provided if one does not already exist.

Parameters:

address - The address of the Server to return.

Returns:

The Server for the address.

add

public Server add(String address)

Adds a Server to the Cluster for the address provided if one does not already exist.

This method is equivalent to calling add(ServerNameUtils.parse(address)).

Parameters:

address - The address of the Server to return.

Returns:

The Server for the address.

addListener

public void addListener(PropertyChangeListener listener)

Adds a listener to the state.

Parameters:

listener - The listener for the state changes.

clear

public void clear()

Removes all of the servers from the cluster.

findCandidateServers

public List<Server> findCandidateServers(ReadPreference readPreference)

Returns the set of servers that can be used based on the provided ReadPreference.

Parameters:

readPreference - The ReadPreference to filter the servers.

Returns:

The List of servers that can be used. Servers will be ordered by preference to be used, most preferred to least preferred.

findServers

public List<Server> findServers(Message message1,
                       Message message2)

Locates the set of servers that can be used to send the specified messages.

Parameters:

message1 - The first message to send.

message2 - The second message to send. May be null.

Returns:

The servers that can be used.

get

public Server get(String address)

Returns the server state for the address provided. If the Server does not already exist a non-writable state is created and returned.

This method is equivalent to calling add(address).

Parameters:

address - The address of the Server to return.

Returns:

The Server for the address.

getNonWritableServers

public List<Server> getNonWritableServers()

Returns a copy of the list of non-writable servers. The list returned is a copy of the internal list and can be modified by the caller.

Returns:

The complete list of non-writable servers.

getServers

public List<Server> getServers()

Returns a copy of the list of servers. The list returned is a copy of the internal list and can be modified by the caller.

Returns:

The complete list of servers.

getServerVersionRange

public VersionRange getServerVersionRange()

Returns the range of versions that we currently see within the cluster.

Specified by:

getServerVersionRange in interface ClusterStats

Returns:

Tthe range of versions that we currently see within the cluster.

getSmallestMaxBatchedWriteOperations

public int getSmallestMaxBatchedWriteOperations()

Returns smallest value for the maximum number of write operations allowed in a single write command.

Specified by:

getSmallestMaxBatchedWriteOperations in interface ClusterStats

Returns:

The smallest value for maximum number of write operations allowed in a single write command.

getSmallestMaxBsonObjectSize

public long getSmallestMaxBsonObjectSize()

Returns the smallest value for the maximum BSON object size within the cluster.

Specified by:

getSmallestMaxBsonObjectSize in interface ClusterStats

Returns:

The smallest value for the maximum BSON object size within the cluster.

getType

public ClusterType getType()

Returns the type of cluster.

Returns:

The type of cluster.

getWritableServers

public List<Server> getWritableServers()

Returns a copy of the list of writable servers. The list returned is a copy of the internal list and can be modified by the caller.

Returns:

The complete list of writable servers.

remove

public void remove(Server server)

Removes the specified server from the cluster.

Parameters:

server - The server to remove from the cluster.

removeListener

public void removeListener(PropertyChangeListener listener)

Removes a listener to the state.

Parameters:

listener - The listener for the state changes.

cdf

protected final double[] cdf(List<Server> servers)

Computes a relative CDF (cumulative distribution function) for the servers based on the latency from the client.

The latency of each server is used to create a strict ordering of servers from lowest latency to highest. The relative latency of the i'th server is then calculated based on the function:

                                       latency[0]
                relative_latency[i] =  ----------
                                       latency[i]
 

The relative latencies are then then summed and the probability of selecting each server is then calculated by:

                                  relative_latency[i]
     probability[i] = -------------------------------------------------
                      sum(relative_latency[0], ... relative_latency[n])
 

The CDF over these probabilities is returned.

Parameters:

servers - The servers to compute the CDF for.

Returns:

The CDF for the server latencies.

findCandidateServer

protected List<Server> findCandidateServer(ReadPreference readPreference)

Finds the candidate server, if known.

Parameters:

readPreference - The read preference to match the server against.

Returns:

The Server found in a singleton list or an empty list if the server is not known.

findNearestCandidates

protected List<Server> findNearestCandidates(ReadPreference readPreference)

Returns the list of servers that match the read preference's tags.

Parameters:

readPreference - The read preference to match the server against.

Returns:

The servers found in order of preference. Generally this is in latency order but we randomly move one of the servers to the front of the list to distribute the load across more servers.

See Also:

sort(java.util.List<com.allanbank.mongodb.client.state.Server>)

findNonWritableCandidates

protected List<Server> findNonWritableCandidates(ReadPreference readPreference)

Returns the list of non-writable servers that match the read preference's tags.

Parameters:

readPreference - The read preference to match the server against.

Returns:

The servers found in order of preference. Generally this is in latency order but we randomly move one of the servers to the front of the list to distribute the load across more servers.

See Also:

sort(java.util.List<com.allanbank.mongodb.client.state.Server>)

findWritableCandidates

protected List<Server> findWritableCandidates(ReadPreference readPreference)

Returns the list of writable servers that match the read preference's tags.

Parameters:

readPreference - The read preference to match the server against.

Returns:

The servers found in order of preference. Generally this is in latency order but we randomly move one of the servers to the front of the list to distribute the load across more servers.

See Also:

sort(java.util.List<com.allanbank.mongodb.client.state.Server>)

sort

protected final void sort(List<Server> servers)

Sorts the servers based on the latency from the client.

To distribute the requests across servers more evenly the first server is replaced with a random server based on a single sided simplified Gaussian distribution.

Parameters:

servers - The servers to be sorted.

See Also:

cdf(List)

updateVersions

protected void updateVersions()

Updates the min/max versions across all servers. Since the max BSON object size is tied to the version we also update that value.