com.sleepycat.je.rep
Class NetworkRestore

java.lang.Object
  com.sleepycat.je.rep.NetworkRestore

public class NetworkRestore
extends Object

Obtains log files for a Replica from other members of the replication group. A Replica may need to do so if it has been offline for some time, and has fallen behind in its execution of the replication stream.

During that time, the connected nodes may have reduced their log files by doing log cleaning. When this node rejoins the group, it is possible that the current Master's log files do not go back far enough to adequately sync up this node. In that case, the node can use a NetworkRestore object to copy the log files from one of the nodes in the group.

A Replica discovers the need for a NetworkRestore operation when a call to ReplicatedEnvironment() fails with a InsufficientLogException.

A call to NetworkRestore.execute() will copy the required log files from a member of the group who owns the files and seems to be the least busy. For example:

  try {
     node = new ReplicatedEnvironment(envDir, envConfig, repConfig);
 } catch (InsufficientLogException insufficientLogEx) {

     NetworkRestore restore = new NetworkRestore();
     NetworkRestoreConfig config = new NetworkRestoreConfig();
     config.setRetainLogFiles(false); // delete obsolete log files.

     // Use the members returned by insufficientLogEx.getLogProviders() to
     // select the desired subset of members and pass the resulting list
     // as the argument to config.setLogProviders(), if the default selection
     // of providers is not suitable.

     restore.execute(insufficientLogEx, config);

     // retry
     node = new ReplicatedEnvironment(envDir, envConfig, repConfig);
 }
 

See Also:

Restoring Log Files

Constructor Summary

NetworkRestore()
Creates an instance of NetworkRestore suitable for restoring the logs at this node.

Method Summary

void	execute(InsufficientLogException logException, NetworkRestoreConfig config) Restores the log files from one of the members of the replication group.

Methods inherited from class java.lang.Object

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

Constructor Detail

NetworkRestore

public NetworkRestore()

Creates an instance of NetworkRestore suitable for restoring the logs at this node. After the logs are restored, the node can create a new ReplicatedEnvironment and join the group

Method Detail

execute

public void execute(InsufficientLogException logException,
                    NetworkRestoreConfig config)
             throws EnvironmentFailureException,
                    IllegalArgumentException

Restores the log files from one of the members of the replication group.

If config.getLogProviders() returns null, or an empty list, it uses the member that is least busy as the provider of the log files. Otherwise it selects a member from the list, choosing the first member that's available, to provide the log files. If the members in this list are not present in logException.getLogProviders(), it will result in an IllegalArgumentException being thrown. Exceptions handlers for InsufficientLogException will typically use InsufficientLogException.getLogProviders() as the starting point to compute an appropriate list, with which to set up the config argument.

Log files that are currently at the node will be retained if they are part of a consistent set of log files. Obsolete log files are either deleted, or are renamed based on the the configuration of config.getRetainLogFiles().

Parameters:

logException - the exception thrown by ReplicatedEnvironment() that necessitated this log refresh operation

config - configures the execution of the network restore operation

Throws:

EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.

IllegalArgumentException - if the config is invalid

See Also:

NetworkRestoreConfig