Globus Toolkit 4
Globus is an open source software toolkit currently used by thousands of sites in business and academia. It provides the basic building blocks for building a Web service (naming and binding, lifecycle management, fault handling, subscription and notification of basic monitoring data) so users can build their own services easily, either by hand or using helper tools, such as provided by Introduce. Globus also provides a range of higher level services including software for security, information infrastructure, resource management, data management, and fault detection. These services are extensively tested and pass a high documentation standard in order to be included in a release.
Maintained By
The Globus Alliance, a set of over 100 committers around the globe.
License
The Globus Toolkit Public License (GTPL), which is Apache-2 compliant, and allows software to be used by anyone and for any purpose, without restriction.
Status
Released and in production on thousands of sites. Over 15,000 people download each new release.
Security
GT4 has an extensive security component. This allows for security policies to be set at a number of levels which provides fine grained access control. There is support for X.509 certificates which allows secure communication. Authentication is supported in three different ways: secure messaging, secure conversation and secure transport. There is also support for authorization which allows control over who can access what. For more advanced use, there is support for delegation of credentials to allow services to act on behalf of the user. Interfaces exist for both Kerberos and Shibboleth on the local sites, and interactions with firewalls are well documented.
SLA
There is no current support for SLAs in the Globus Toolkit. However they are involved in the WS-Agreement specification effort.
Data Management
Data management in Globus is supported through a number of mechanisms. At the low level, GridFTP provides fast data movement through parallelisation and striping, including partial file transfer support, as well as interfaces to SRM and SRB. There is a Web service front end, the reliable file transfer service (RFT), which provides reliability especially in the case of tens of thousands of file transfers occurring, or very large file transfers over unreliable networks. This is also the service used for file staging for job management. In addition, OGSA-DAI provides access to relational and xml databases, as well as files via Web services. There is work in progress to provide a WS-DAIS interface on top of OGSA-DAI. There is also support for replication of data through the Replica Location Service which provides a record of the location of data replicas and allows discovery of replicas.
User Integration
Globus provides a command line interface as well as API’s for Java, C, and Python for all of its services. These interfaces are also guaranteed not to change within a major version (GT4.0.x and 4.0.y are fully compatible).
Many user communities have also built their own GUI based access methods, and Globus has two incubator projects to help build portals, OGCE and UGP (http://dev.globus.org/wiki/Welcome).
Core Functionalities
- Workflow: There is no current support for workflow in Globus, although several are in development, including the Virtual Data System, part of OSG, and the workflow engine based on BPEL and GT4 in CAGrid.
- Brokering: GridWay is a Globus incubator project which provides full brokering support across multiple sites, using either pre-WS or WS GRAM for the final job submission, and MDS2 or MDS4 for the discovery and selection data.
- Monitoring:Every service built on top of the GT4 core includes basic monitoring support on the basis of a notification (publish/subscribe) specification, as well as the according link to resource properties. These are aggregated using the MDS4 registry (the Index service), which also caches the last value for higher performance. In addition, errors and warnings based on this data are available using the trigger service (basing on notifications).
- Accounting: There is no current support for accounting, although several groups (including KTH) have written Globus-compliant account systems.
- Steering: No explicit support.
- Interactive access: Users can access Globus services through command line, Java, Python and C APIs. In addition, several services have their own GUIs, including RFT and the MDS Index Service (WebMDS). Many client applications have built their own GUIS and Portals to Globus services as well and there are tools to aid this, including a set for interacting with Eclipse. For users wanting to build their own service, there is an IDE called “Introduce” which simplifies the production of Web services built using the Globus core to a five minute process, hiding most of the lower level details from the user.
- Addressing (WS-Addressing compliant?)Yes.
- Transactions: No specific support for transactions.
- WS-RF compliant? Yes
- Charging: No explicit support
