org.osgi.service.monitor

Interface MonitorAdmin

public interface MonitorAdmin

The MonitorAdmin service is a singleton service that handles StatusVariable query requests and measurement job control requests.

Note that an alternative but not recommended way of obtaining StatusVariables is that applications having the required ServicePermissions can query the list of Monitorable services from the service registry and then query the list of StatusVariable names from the Monitorable services. This way all services which publish StatusVariables will be returned regardless of whether they do or do not hold the necessary MonitorPermission for publishing StatusVariables. By using the MonitorAdmin to obtain the StatusVariables it is guaranteed that only those Monitorable services will be accessed who are authorized to publish StatusVariables. It is the responsibility of the MonitorAdmin implementation to check the required permissions and show only those variables which pass this check.

The events posted by MonitorAdmin contain the following properties:

• mon.monitorable.pid: The identifier of the Monitorable
• mon.statusvariable.name: The identifier of the StatusVariable within the given Monitorable
• mon.statusvariable.value: The value of the StatusVariable , represented as a String
• mon.listener.id: The identifier of the initiator of the monitoring job (only present if the event was generated due to a monitoring job)

Most of the methods require either a Monitorable ID or a Status Variable path parameter, the latter in [Monitorable_ID]/[StatusVariable_ID] format. These parameters must not be null, and the IDs they contain must conform to their respective definitions in Monitorable and StatusVariable. If any of the restrictions are violated, the method must throw an IllegalArgumentException.

Method Summary

Methods

Modifier and Type	Method and Description
String	getDescription(String path) Returns a human readable description of the given StatusVariable.
String[]	getMonitorableNames() Returns the names of the Monitorable services that are currently registered.
MonitoringJob[]	getRunningJobs() Returns the list of currently running MonitoringJobs.
StatusVariable	getStatusVariable(String path) Returns a StatusVariable addressed by its full path.
String[]	getStatusVariableNames(String monitorableId) Returns the list of StatusVariable names published by a Monitorable instance.
StatusVariable[]	getStatusVariables(String monitorableId) Returns the StatusVariable objects published by a Monitorable instance.
boolean	resetStatusVariable(String path) Issues a request to reset a given StatusVariable.
MonitoringJob	startJob(String initiator, String[] statusVariables, int count) Starts a change based MonitoringJob with the parameters provided.
MonitoringJob	startScheduledJob(String initiator, String[] statusVariables, int schedule, int count) Starts a time based MonitoringJob with the parameters provided.
void	switchEvents(String path, boolean on) Switches event sending on or off for the specified StatusVariable s.

Method Detail

getStatusVariable

StatusVariable getStatusVariable(String path)
                                 throws IllegalArgumentException,
                                        SecurityException

Returns a StatusVariable addressed by its full path. The entity which queries a StatusVariable needs to hold MonitorPermission for the given target with the read action present.

Parameters:

path - the full path of the StatusVariable in [Monitorable_ID]/[StatusVariable_ID] format

Returns:

the StatusVariable object

Throws:

IllegalArgumentException - if path is null or otherwise invalid, or points to a non-existing StatusVariable

SecurityException - if the caller does not hold a MonitorPermission for the StatusVariable specified by path with the read action present

getMonitorableNames

String[] getMonitorableNames()

Returns the names of the Monitorable services that are currently registered. The Monitorable instances are not accessible through the MonitorAdmin, so that requests to individual status variables can be filtered with respect to the publishing rights of the Monitorable and the reading rights of the caller.

The returned array contains the names in alphabetical order. It cannot be null, an empty array is returned if no Monitorable services are registered.

Returns:

the array of Monitorable names

getStatusVariables

StatusVariable[] getStatusVariables(String monitorableId)
                                    throws IllegalArgumentException

Returns the StatusVariable objects published by a Monitorable instance. The StatusVariables will hold the values taken at the time of this method call. Only those status variables are returned where the following two conditions are met:

• the specified Monitorable holds a MonitorPermission for the status variable with the publish action present
• the caller holds a MonitorPermission for the status variable with the read action present

All other status variables are silently ignored, they are omitted from the result.

The elements in the returned array are in no particular order. The return value cannot be null, an empty array is returned if no (authorized and readable) Status Variables are provided by the given Monitorable.

Parameters:

monitorableId - the identifier of a Monitorable instance

Returns:

a list of StatusVariable objects published by the specified Monitorable

Throws:

IllegalArgumentException - if monitorableId is null or otherwise invalid, or points to a non-existing Monitorable

getStatusVariableNames

String[] getStatusVariableNames(String monitorableId)
                                throws IllegalArgumentException

Returns the list of StatusVariable names published by a Monitorable instance. Only those status variables are listed where the following two conditions are met:

• the specified Monitorable holds a MonitorPermission for the status variable with the publish action present
• the caller holds a MonitorPermission for the status variable with the read action present

All other status variables are silently ignored, their names are omitted from the list.

The returned array does not contain duplicates, and the elements are in alphabetical order. It cannot be null, an empty array is returned if no (authorized and readable) Status Variables are provided by the given Monitorable.

Parameters:

monitorableId - the identifier of a Monitorable instance

Returns:

a list of StatusVariable objects names published by the specified Monitorable

Throws:

IllegalArgumentException - if monitorableId is null or otherwise invalid, or points to a non-existing Monitorable

switchEvents

void switchEvents(String path,
                boolean on)
                  throws IllegalArgumentException,
                         SecurityException

Switches event sending on or off for the specified StatusVariable s. When the MonitorAdmin is notified about a StatusVariable being updated it sends an event unless this feature is switched off. Note that events within a monitoring job can not be switched off. The event sending state of the StatusVariables must not be persistently stored. When a StatusVariable is registered for the first time in a framework session, its event sending state is set to ON by default.

Usage of the "*" wildcard is allowed in the path argument of this method as a convenience feature. The wildcard can be used in either or both path fragments, but only at the end of the fragments. The semantics of the wildcard is that it stands for any matching StatusVariable at the time of the method call, it does not affect the event sending status of StatusVariables which are not yet registered. As an example, when the switchEvents("MyMonitorable/*", false) method is executed, event sending from all StatusVariables of the MyMonitorable service are switched off. However, if the MyMonitorable service starts to publish a new StatusVariable later, it's event sending status is on by default.

Parameters:

path - the identifier of the StatusVariable(s) in [Monitorable_id]/[StatusVariable_id] format, possibly with the "*" wildcard at the end of either path fragment

on - false if event sending should be switched off, true if it should be switched on for the given path

Throws:

SecurityException - if the caller does not hold MonitorPermission with the switchevents action or if there is any StatusVariable in the path field for which it is not allowed to switch event sending on or off as per the target field of the permission

IllegalArgumentException - if path is null or otherwise invalid, or points to a non-existing StatusVariable

resetStatusVariable

boolean resetStatusVariable(String path)
                            throws IllegalArgumentException,
                                   SecurityException

Issues a request to reset a given StatusVariable. Depending on the semantics of the StatusVariable this call may or may not succeed: it makes sense to reset a counter to its starting value, but e.g. a StatusVariable of type String might not have a meaningful default value. Note that for numeric StatusVariables the starting value may not necessarily be 0. Resetting a StatusVariable triggers a monitor event if the StatusVariable supports update notifications.

The entity that wants to reset the StatusVariable needs to hold MonitorPermission with the reset action present. The target field of the permission must match the StatusVariable name to be reset.

Parameters:

path - the identifier of the StatusVariable in [Monitorable_id]/[StatusVariable_id] format

Returns:

true if the Monitorable could successfully reset the given StatusVariable, false otherwise

Throws:

IllegalArgumentException - if path is null or otherwise invalid, or points to a non-existing StatusVariable

SecurityException - if the caller does not hold MonitorPermission with the reset action or if the specified StatusVariable is not allowed to be reset as per the target field of the permission

getDescription

String getDescription(String path)
                      throws IllegalArgumentException,
                             SecurityException

Returns a human readable description of the given StatusVariable. The null value may be returned if there is no description for the given StatusVariable.

The entity that queries a StatusVariable needs to hold MonitorPermission for the given target with the read action present.

Parameters:

path - the full path of the StatusVariable in [Monitorable_ID]/[StatusVariable_ID] format

Returns:

the human readable description of this StatusVariable or null if it is not set

Throws:

IllegalArgumentException - if path is null or otherwise invalid, or points to a non-existing StatusVariable

SecurityException - if the caller does not hold a MonitorPermission for the StatusVariable specified by path with the read action present

startScheduledJob

MonitoringJob startScheduledJob(String initiator,
                              String[] statusVariables,
                              int schedule,
                              int count)
                                throws IllegalArgumentException,
                                       SecurityException

Starts a time based MonitoringJob with the parameters provided. Monitoring events will be sent according to the specified schedule. All specified StatusVariables must exist when the job is started. The initiator string is used in the mon.listener.id field of all events triggered by the job, to allow filtering the events based on the initiator.

The schedule parameter specifies the time in seconds between two measurements, it must be greater than 0. The first measurement will be taken when the timer expires for the first time, not when this method is called.

The count parameter defines the number of measurements to be taken, and must either be a positive integer, or 0 if the measurement is to run until explicitly stopped.

The entity which initiates a MonitoringJob needs to hold MonitorPermission for all the specified target StatusVariables with the startjob action present. If the permission's action string specifies a minimal sampling interval then the schedule parameter should be at least as great as the value in the action string.

Parameters:

initiator - the identifier of the entity that initiated the job

statusVariables - the list of StatusVariables to be monitored, with each StatusVariable name given in [Monitorable_PID]/[StatusVariable_ID] format

schedule - the time in seconds between two measurements

count - the number of measurements to be taken, or 0 for the measurement to run until explicitly stopped

Returns:

the successfully started job object, cannot be null

Throws:

IllegalArgumentException - if the list of StatusVariable names contains an invalid or non-existing StatusVariable; if initiator is null or empty; or if the schedule or count parameters are invalid

SecurityException - if the caller does not hold MonitorPermission for all the specified StatusVariables, with the startjob action present, or if the permission does not allow starting the job with the given frequency

startJob

MonitoringJob startJob(String initiator,
                     String[] statusVariables,
                     int count)
                       throws IllegalArgumentException,
                              SecurityException

Starts a change based MonitoringJob with the parameters provided. Monitoring events will be sent when the StatusVariables of this job are updated. All specified StatusVariables must exist when the job is started, and all must support update notifications. The initiator string is used in the mon.listener.id field of all events triggered by the job, to allow filtering the events based on the initiator.

The count parameter specifies the number of changes that must happen to a StatusVariable before a new notification is sent, this must be a positive integer.

The entity which initiates a MonitoringJob needs to hold MonitorPermission for all the specified target StatusVariables with the startjob action present.

Parameters:

initiator - the identifier of the entity that initiated the job

statusVariables - the list of StatusVariables to be monitored, with each StatusVariable name given in [Monitorable_PID]/[StatusVariable_ID] format

count - the number of changes that must happen to a StatusVariable before a new notification is sent

Returns:

the successfully started job object, cannot be null

Throws:

IllegalArgumentException - if the list of StatusVariable names contains an invalid or non-existing StatusVariable, or one that does not support notifications; if the initiator is null or empty; or if count is invalid

SecurityException - if the caller does not hold MonitorPermission for all the specified StatusVariables, with the startjob action present

getRunningJobs

MonitoringJob[] getRunningJobs()

Returns the list of currently running MonitoringJobs. Jobs are only visible to callers that have the necessary permissions: to receive a Monitoring Job in the returned list, the caller must hold all permissions required for starting the job. This means that if the caller does not have MonitorPermission with the proper startjob action for all the Status Variables monitored by a job, then that job will be silently omitted from the results.

The returned array cannot be null, an empty array is returned if there are no running jobs visible to the caller at the time of the call.

Returns:

the list of running jobs visible to the caller