During initialisation, the GraphDB-Enterprise master node registers a JMX Bean component, which provides methods for monitoring and managing the running cluster. It is registered under "ReplicationCluster:name=ClusterInfo" signature and can be accessed through the standard Java instrumentation tools, e.g. JConsole. The rest of this section provides details about the attributes and operations available.
Attributes
Name
AutoReplication
Type
Boolean
Description
Indicates whether the cluster has the auto-replication enabled.
Possible values
Any non-negative integer.
Interface method
public int getAutoReplication(); public void setAutoReplication(boolean enabled);
Name
AverageReadTime
Type
Integer
Description
Indicates the average time required across the whole cluster for processing a read request in milliseconds.
Possible values
Any non-negative integer.
Interface method
public int getAverageReadTime();
Name
AverageTaskTimes
Type
Integer array
Description
Indicates the average time required for each node for processing a read request in milliseconds.
Possible values
An array of non-negative integer.
Interface method
public int[] getAverageTaskTimes();
Name
CompletedReads
Type
Integer
Description
Indicates the total number of successfully processed read requests.
Possible values
The value is not persistent and will be 0 after initialisation.
Interface method
public int getCompletedReads();
Name
CompletedTasks
Type
Integer array
Description
A list of values indicating the number of successful read requests for each node in the cluster, provided in the same order as NodeStatus.
Possible values
A list of non-negative integers
Interface method
public int[] getCompletedTasks();
Name
CompletedWrites
Type
Integer
Description
Indicates the total number of successful updates processed by the cluster. This value is not persistent and is set to 0 after each cluster initialisation.
Possible values
Any non-negative integer value
Interface method
public int getCompletedWrites();
Name
ConfiguredWritable
Type
Boolean
Description
Indicates if the cluster is configured to process update requests.
Possible values
True or false
Interface method
public boolean getConfiguredWritable(); public void setConfiguredWritable(boolean writable);
Name
FailedReads
Type
Integer
Description
Indicates the total number of failed read requests for the cluster. The value is not persistent and will be 0 after initialisation.
Possible values
Any non-negative integer
Interface method
public int getFailedReads();
Name
FailedTasks
Type
Integer array
Description
Indicates the total number of failed read requests for each node in the cluster.
Possible values
A list of non-negative integers
Interface method
public int[] getFailedTasks();
Name
FailedWrites
Type
Integer
Description
Indicates the total number of failed updates. An update may fail if there is a problem with the control node on which the update is first probed. The value may also reflect the number of rejected updates, because some node is not available or needs replication.
Possible values
Any non-negative integer value
Interface method
public int getFailedWrites();
Name
Fingerprints
Type
String array
Description
Retrieve a list of values representing the fingerprints of the individual nodes in the cluster.
Possible values
Unspecified
Interface method
public String[] getFingerprints();
Name
IsWritable
Type
Boolean
Description
Indicates whether the current state of the cluster allows for the processing of update requests.
Possible values
True or false
Interface method
public boolean getIsWritable();
Name
MasterReplicationPort
Type
Integer
Description
The port number used by the master node for replication (for online backup/restore or remote replication)
Possible values
1 to 65536
Interface method
public int getMasterReplicationPort(); public void setMasterReplicationPort(int value);
Name
MasterUrl
Type
String
Description
The repository URL used by the master node for replication (for online backup/restore or remote replication)
Possible values
Any valid URL
Interface method
public String getMasterUrl(); public void setMasterUrl(String value);
Name
NodeStatus
Type
String array
Description
Indicates the status of the registered nodes in the cluster as an array of strings, where values have the following format:
"[<node status>] <node URI>"
Possible values
[OK] - up to date and available for serving requests
[NEEDS-UPDATE] - the finger-print of the node is not the most recent - should be replicated but still be able to serve requests
[MASTER] - indicate that the node is a SERVER of an undergoing replication procedure and could not serve requests until is available again
[SLAVE] - indicate that the node is being replicated from a healthy node. Could not serve requests
[DISABLED] - the node do not respond on status requests - either not connected or not running at all
Interface method
public String[] getNodeStatus();
Name
NumberOfExplicitTriples
Type
Long
Description
Indicates the number of explicit triples asserted in the cluster.
Possible values
Any non-negative long integer value
Interface method
public long getNumberOfExplicitTriples();
Name
NumberOfTriples
Type
Long
Description
Indicates the total number of statements indexed with regard to the most recent update.
Possible values
Any non-negative long integer value
Interface method
public long getNumberOfTriples();
Name
PendingWrites
Type
Integer
Description
Indicates the number of updates in the queue waiting to be processed by the cluster.
Possible values
Any non-negative integer.
Interface method
public int getPendingWrites();
Name
PendingWritesLimit
Type
Integer
Description
Indicates the maximum number of updates that can be queued for processing by the cluster.
Possible values
Any non-negative integer.
Interface method
public int getPendingWritesLimit(); public void setPendingWritesLimit(int limit);
Name
RemoteMaster
Type
Boolean
Description
Indicates if this cluster master can be used for 'remote replication', i.e. whether or not it accepts updates from another cluster master.
Possible values
True or false
Interface method
public boolean getRemoteMaster(); public void setRemoteMaster(boolean value);
Name
RunningReads
Type
Integer array
Description
Indicates the total number of read requests currently being processed by the whole cluster.
Possible values
An array of any non-negative integers.
Interface method
public int getRunningReads();
Name
RunningTasks
Type
Integer array
Description
Indicates the number of read requests currently being processed by each node in the cluster.
Possible values
An array of any non-negative integers.
Interface method
public int getRunningTasks();
Name
RunningWrites
Type
Integer
Description
Indicates the number of updates currently being processed by the cluster.
Possible values
Currently only a single update could be processed at given point of time so the only possible values are 0 or 1.
Interface method
public int getRunningWrites();
Name
Status
Type
Integer
Description
Indicates the current status of the cluster.
Possible values
0 - available, all nodes up to date and in synch;
1 - needs attention, the attached worker nodes are not in synch or need to be updated
2 - not available - no worker nodes are available for processing requests
Interface method
public int getStatus();
Name
StatusAsText
Type
String
Description
Indicates the current status of the cluster in text form.
Possible values
"AVAILABLE" - all nodes up to date and in synch;
"NEEDS_ATTENTION" - the attached worker nodes are not in synch or need to be updated
"UNAVAILABLE" - no worker nodes are available for processing requests
Interface method
public String getStatusAsText();
Name
Timeout
Type
Integer
Description
The cluster timeout period used when executing update operations in seconds.
Possible values
Any non-negative integer value
Interface method
public long getTimeout(); public void setTimeout(int timeout);
replicationPort: int - The port number to use for replication activity.
remoteNotificationsPort: int - The port number used for emitting remote notifications, this can be left blank if it is not required, see remote notifications.
readable: boolean - If set to false (the default is true), then this worker node will receive only updates and will not particpate in sharing the cluster's query load.
Description
Add a new worker node to the cluster. If the node is a duplicate of an existing one then no error is logged. The same will also happen if the node pointed by the argument is not available.
Interface method
public void addClusterNode(String nodeURI, int replicationPort);
Name
backup
Parameters
backupDirectory : String - The full path to a directory on the master node where a backup image will be stored
Description
Initiates a backup from a healthy, in-synch worker node to the given directory on the master node.
Interface method
public void backup(String backupDirectory);
Name
cancelReplication
Parameters
none
Description
Cancels a full replication operation. This can be useful for recovering from stalled replication events, such as when two workers start replicating between themselves, but a network failure prevents this from finishing.
Interface method
public void cancelReplication();
Name
changeSystemTransactionPassword
Parameters
oldPassword : String - The old password
newPassword : String - The new password
newPasswordRetype : String - The new password repeated
Description
Change the system transaction password. System transactions include a statement with a special predicate that instructs GraphDB to allow modifications to the imported, read-only schemas/ontologies. The replication cluster introduces a password for such transactions and this must appear in the object position of the 'special' statement, e.g.
nodeURI : String - A string holding the full URI of the Sesame end point of the node to be removed.
Description
Removes a node from the cluster. Invoking this operation will neither generate an exception nor log an error message.
Interface method
public void removeClusterNode(String message);
Name
restoreFromImage
Parameters
backupDirectory : String - The full path to a directory on the master node where a backup image will be restored from.
Description
Initiates a restore from the given directory on the master node. The image will be replicated to each worker node in turn.
Interface method
public void restoreFromImage(String backupDirectory);
Name
startReplication
Parameters
none
Description
Manually initiate a replication procedure. A random node with the most recent state is selected to propagate its state to those that are in [NEEDS-UPDATE] state. During the operation the node that replicates its state is excluded from available nodes and does not process read requests until it is finished with the replication.
Interface method
public void startReplication();
Notifications
The ReplicationCluster MBean generates notifications for certain events. Users can receive these notifications by subscribing to this MBean (using jconsole, click on the notifications element, then click subscribe). The type and text of these notifications varies, but the following kinds of events are notified:
A control query has completed or failed to complete;
An RDF statement update has failed, been delayed or timed-out;
An RDF read event could not occur (no available workers);
A cluster worker node has been added or removed;
A worker node status has changed;
A worker node update has failed;
A worker node is low on disk space;
Replication (full/incremental) has started, stopped, failed.
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