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Grid Computing Environment Shell

GCEShell provides a user view of computational Grid technologies through a shell-like system portal inspired by Unix environments. Learn about GCEShell Engine, Components, Tasks, Commands, and Exception Handling.

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Grid Computing Environment Shell

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  1. Grid Computing Environment Shell By Mehmet Nacar Las Vegas, June 2003

  2. GCEShell (Grid Computing Environment Shell) provides a user view of computational Grid technologies. GCEShell is a shell-like system portal. It is inspired by Unix shell environments Using Web Services and OGSA infrastructure as a global operating system. Shell commands for manipulating remote files, for listing system resources. GCEShell engine is simple, well defined mechanism for adding new shell commands. Overview

  3. GCEShell Engine • The shell engine is the core application • runs client commands • communicates with applications and registries • manages application lifecycles • The engine spawns a new thread for each shell command • GCEShell involves both local and remote commands. • If given argument is a URL, the command known as remote and WSDL interfaces gives description of the service. • Otherwise, it is local like history, kill, exit etc.

  4. GCEShell Engine cont. • The shell engine aggregates all the objects that perform functionality to the shell container. • Objects are commands, tasks and workflows • If the server is down, the request may be repeated according to service priority and importance. • if a part of command arguments fails, either entire command fails or partial result given on demand.

  5. GCEShell Engine cont. • The base shell context is responsible for creating child shell contexts to hold individual commands and for managing the lifecycle of these child contexts. • It also manages communications between the child contexts; that is, the pipes and redirects are functions of the base context. • The child context will need to implement a listener that gets notified when the command completes on the server.

  6. Components • Figure shows the shell engine’s principal components. • Each component in our implementation is a Java interface with an implementing class. The shell interface has the following components. • Base Shell • Parser • Workflow Manager • Exception Handler

  7. GCE Interface (User Commands) (1) GCE Shell Engine (2) Base Shell Parser Exception Handler (3) (4a) Local Clients Workflow Manager Exception Thrown (4b) WS Clients (5) SOAP Remote Services WS OGSA

  8. Execution Steps • A command is caught by the shell engine and divided into the tokens by the Parser. • The workflow manager is responsible for managing the execution of the clients and their arguments. • Arguments may indicate either local applications such as shell history command, or services that must connect to remote applications. In the latter case, the client must then interact with the remote Web Service as next step.

  9. GCEShell Tasks • GCEShell contains command and context interfaces which must be implemented by new commands. • The shell interface has the following methods. • For each attribute, write accessor (get and set) methods. • For execution directions, execute() method. • To kill the command or process, exit() method. • Allowing process to sleep, suspend() method.

  10. GCEShell Commands • gce-list is based on WSIL • gce-copy is Grid FTP • gce-ls could be local and remote • gce-ps could be local and remote • gce-set is a local command • gce-history is a local command • gce-man is a local command • gce-kill is a local command • gce-help is a local command

  11. Adding New Commands • Commands are similar to jakarta-ant tasks and JXTA ShellCommands in terms of adding new functionalities. • Commands will be well defined by interfaces, so a developer might want to add more commands. • To plug a new command into shell container, updating property file giving command name and package name pairs.

  12. Exception Handling • GCEShell has modular and integrated design, to prevent conflicts in terms of using services and crashes. • GCEShell, which interact with distributed resources that may become unavailable for a number of reasons. • Each exception interacted with related module, but most of them are handled by the workflow manager and base shell.

  13. Exceptions • ParserException is thrown, when the command stream consist of unknown syntax parameters or characters. • CommandNotFound exception is thrown, if the given command name is not specified in the properties file. • LocalClientException is thrown when a local command has an internal error, perhaps caused by improper input. • RemoteClientExceptions may be thrown either if the remote command was sent improper input or the remote server is unreachable for any number of reasons.

  14. Discovering Information Systems • The Shell Commands are responsible for discovering the service that they need and for communicating with that service. • Workflow manager coordinates all negotiations with services and adjust timeouts according to priority of specified services. • The shell container is eligible to deal with some possible failures.

  15. Inspection of Services • The purpose of involving WSIL is that the base shell needs to inspect web services instantly. gce-list http://fuji.ucs.indiana.edu:8080/axis/services The gce-list command examines the inspection.wsil at this location and inspects what WS running and gets back the list of WSDL interfaces.

  16. Inspection of Services cont. >> gcelist $TORO GCE List http://toro.ucs.indiana.edu:8080 Display list of WSDL service description references... Service: Version [1] http://complexity:8282/GCWS/services/Version?wsdl Service: AdminService [1] http://complexity:8282/GCWS/services/AdminService?wsdl Service: Submitjob [1] http://complexity:8282/GCWS/services/Submitjob?wsdl Service: ApplicationDescriptor3 [1] http://complexity:8282/GCWS/services/ApplicationDescriptor3?wsdl Service: Submitjob [1] http://judi.ucs.indiana.edu:8787/GCWS/services/Submitjob?wsdl Service: AdminService [1] http://judi.ucs.indiana.edu:8787/GCWS/services/AdminService?wsdl Service: Version [1] http://judi.ucs.indiana.edu:8787/GCWS/services/Version?wsdl Service: ApplicationDescriptor3 [1] http://judi.ucs.indiana.edu:8787/GCWS/services/ApplicationDescriptor3?wsdl >>

  17. Future Work • Dynamic class loading needed so that grid users could place new features on run time. • Support for shell command composition and scripting. • XML-based BPEL4WS for workflow • Python • One of the powers of the shell environment is that new, specialized commands may be created as needed from the basic library of shell commands.

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