com.sleepycat.je.rep.ReplicaConsistencyException Maven / Gradle / Ivy
/*-
* Copyright (C) 2002, 2018, Oracle and/or its affiliates. All rights reserved.
*
* This file was distributed by Oracle as part of a version of Oracle Berkeley
* DB Java Edition made available at:
*
* http://www.oracle.com/technetwork/database/database-technologies/berkeleydb/downloads/index.html
*
* Please see the LICENSE file included in the top-level directory of the
* appropriate version of Oracle Berkeley DB Java Edition for a copy of the
* license and additional information.
*/
package com.sleepycat.je.rep;
import java.util.concurrent.TimeUnit;
import com.sleepycat.je.OperationFailureException;
import com.sleepycat.je.ReplicaConsistencyPolicy;
/**
* This exception is thrown by a Replica to indicate it could not meet the
* consistency requirements as defined by the
* ReplicaConsistencyPolicy in effect for the transaction, within
* the allowed timeout period.
*
* A Replica will typically keep current with its Master. However, network
* problems, excessive load on the Master, or Replica, may prevent the Replica
* from keeping up and the Replica may fall further behind than is permitted by
* its consistency policy. If the Replica cannot catch up in the time defined
* by its ReplicaConsistencyPolicy, it will throw this exception
* from the {@link com.sleepycat.je.Environment#beginTransaction
* Environment.beginTransaction} method, thus preventing the transaction from
* accessing data that does not meet its consistency requirements.
*
* If this exception is encountered frequently, it indicates that the
* consistency policy requirements are too strict and cannot be met routinely
* given the load being placed on the system and the hardware resources that
* are available to service the load. The exception may also indicate that
* there is a network related issue that is preventing the Replica from
* communicating with the master and keeping up with the replication stream.
*
* The application can choose to retry the transaction, until the underlying
* system problem has been resolved. Or it can try relaxing the consistency
* constraints, or choose the {@link NoConsistencyRequiredPolicy} so that the
* constraints can be satisfied more easily.
* For example, in a two node
* replication group, if the primary goes down, the application may want
* the secondary node to continue to service read requests, and will lower the
* consistency requirement on that node in order to maintain read availability.
*
* @see ReplicaConsistencyPolicy
* @see Managing Consistency
*/
public class ReplicaConsistencyException extends OperationFailureException {
private static final long serialVersionUID = 1;
final ReplicaConsistencyPolicy consistencyPolicy;
/**
* @hidden
* For internal use only.
*/
public ReplicaConsistencyException(ReplicaConsistencyPolicy
consistencyPolicy,
String rnName,
boolean unknownMaster) {
/* No need to set abortOnly, beginTransaction will fail. */
super(null /*locker*/, false /*abortOnly*/,
"Unable to achieve consistency at rep node:" + rnName +
", despite waiting for " +
consistencyPolicy.getTimeout(TimeUnit.MILLISECONDS) + " ms." +
(unknownMaster ?
" The node is not currently in contact with a master." :
""),
null /*cause*/);
this.consistencyPolicy = consistencyPolicy;
}
public ReplicaConsistencyException(String message,
ReplicaConsistencyPolicy
consistencyPolicy) {
/* No need to set abortOnly, beginTransaction will fail. */
super(null /*locker*/, false /*abortOnly*/,
message,
null /*cause*/);
this.consistencyPolicy = consistencyPolicy;
}
/**
* For internal use only.
* @hidden
*/
private ReplicaConsistencyException(String message,
ReplicaConsistencyException cause) {
super(message, cause);
this.consistencyPolicy = cause.consistencyPolicy;
}
/**
* For internal use only.
* @hidden
*/
@Override
public OperationFailureException wrapSelf(String msg) {
return new ReplicaConsistencyException(msg, this);
}
/**
* Returns the Replica consistency policy that could not be satisfied.
*
* @return the Replica consistency policy
*/
public ReplicaConsistencyPolicy getConsistencyPolicy() {
return consistencyPolicy;
}
}