Purpose
To provide, through a standard web-service interface, a tuple-space-like capability which can be used by other services and by applications running in the ELF container.
We have chosen to implement this service instead of using JavaSpaces, the tuple-space which has long been part of the Jini Technology package (see http://java.sun.com/developer/products/jini and also http://javaspaces.org), for the following reasons:
- There are serious problems with using multicast technologies on NCSA's production resource subnets.
- We do not require the full generality of JavaSpaces with respect to serializable classes; our service accepts an open-ended (i.e., basically untyped) wrapper object containing a serialized xml blob corresponding to the
ncsa.tools.common.types.Configuration
object as its payload element. - We do not require the full peer-to-peer capabilities offered by Jini.
API
Service WSDL
IConfigurationSpace
public interface IConfigurationSpace { void write( String entryXML ) throws Throwable; String[] read( String matchXML, int max ) throws Throwable; String[] take( String matchXML, int max, long timeout ) throws Throwable; String[] takeNB( String matchXML, int max ) throws Throwable; }
NOTES
write
takes a serialized string representing thencsa.service.vizier.tspace.ConfigurationEntry
object (see below).read
andtake
are batch methods, both requiring a serialized string representing thencsa.service.vizier.tspace.ConfigurationMatchRequest
object (see below), along with an integer indicating the maximum number of tuples to return (default is 10; it is advisable not to set this number too high, as Axis will have trouble managing extremely large SOAP packets); the array returned contains serializedncsa.service.vizier.tspace.ConfigurationEntry
objects.take
also requires a timeout (if set to t <= 0, the non-blocking method is called), whereastakeNB
will return immediately subsequent to issuing the request against the data store.takeNB
can returnnull
if no tuples satisfy the request constraints.take
will not returnnull
unless timeout <= 0.take
may return an empty array (length 0) if its timeout has been exceeded.
ncsa.service.vizier.tspace.ConfigurationEntry
The object stored in the service's data store and which can be retrieved through the read
or take
ports. A fuller description of the object is found on the ncsa.tools.ogrscript.tspace page.
ncsa.service.vizier.tspace.ConfigurationMatchRequest
The object used to express the match query parameter required by the read
or take
ports. A fuller description of the object is found on the ncsa.tools.ogrscript.tspace page.