Interplay between LCG and ALICE Environment

INFSO-RI-508833

Enabling Grids for E-sciencE

www.eu-egee.org

Interplay between LCG and ALICE Environment

Patricia Méndez Lorenzo

CERN IT-ED-PSS

ALICE-CIEMAT MeetingMadrid4th May 2006

FZK 20th October Patricia Mendez Lorenzo


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Introduction and Outlook

After seeing the ALICE Computing Model, now we will see the interplay with LCG

The central point of the presentation: VOBOX

Now we will see:◘ General introduction to the VOBOX service◘ How ALICE uses it◘ How ALICE-LCG works together to set them up

➸ Requirements➸ Current Status



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1st PART: GENERAL OUTLOOK OF THE VOBOX SERVICE



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General Introduction to the VOBOX Service

New LCG Service (from v2.6.0)Motivation:◘ Several experiments run service jobs in the production sites ➸ In some cases using the Fork Jobmanager in the gatekeeper node

◘ The BaseLine service workgroup identified the need of the experiments to run specific services in the sites◘ The solution has to be acceptable for experiments and for the sitesSolution: ◘ A separate service where experiments can run their agents and experiments ➸ Specific agents not provided by the LCG middleware



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General Introduction to the VOBOX Service (cont)

General Characteristics for any VOBOX:

◘ Only sgm users of each VO have access to the node ◘ From LCGv.7.0 it run the UI service inside (asked by ALICE and provided for all experiments)◘ It provides direct access to the software area ➸ Area mounted and accessible in the filesystem ➸ VO_ALICE_SW_DIR variable mandatory◘ Contains a GSISSH server (port 1975) ➸ ssh connection authorized through user proxies◘ Proxy renewal service included◘ If needed GSSKLOG client ➸ Needed if the software area is placed in AFS◘ It runs a local GRIS ➸ The Service must be published in the information system



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General Introduction to the VOBOX Service (cont)

General Requirements for any VOBOX:

◘ OS: Scientific Linux (usually) ◘ WN type host + experiment specific requirements◘ Outbound connectivity ➸ It is a UI (globus range 20000-25000)

◘ Inbound connectivity ➸ As for a CE plus experiment requirements

◘ Access to local accounts via gsissh (port 1975)◘ Write access to the software area◘ At this moment a gridftp server is included (port 2811)



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2nd PART: HOW DOES ALICE USE THE VOBOX



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Interfacing AliEn and LCG

ALICE SC3 layout

User(ProductionManager)

LCG site (T1)

LCG CEWN

VO-Box (UI)

TaskQueue

LFC FileCatalogue

RB (external)CElist

T1 SE

(local)

T2

VO-BOX

(UI)

CeList T2

T2

VO-BOX

(UI)

CeList T2

ALICE Layout in terms of LCG

ALICE Central

Services LCG WORLD

ENTRY DOOR



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General Outlook of the Services

1. CENTRAL ALICE SERVICES

◘ OUTSIDE of the LCG environment➸ Central TQ, central FC, VOMS, FTD

◘ Their experts take care of them2. LCG SERVICES USED BY ALICE

◘ All of them!: RB/WMS, VOMS, FTS/SRM, LFC◘ No experience up to now with dCACHE and DPM3. ALICE SITE VOBOX SERVICES

◘ Specific ALICE site services all run in VOBOXES◘ Supported together by LCG and ALICE experts

➸ PackMan, MonaLisa, Site Computing Agent, Storage Adaptor, xrootd, site proxy, proofd, agent monitoring service



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Outlook of ALICE Site services

PackMan◘ It distributes, installs and configures the software needed by ALICE jobs◘ Includes versioning and test tools◘ Integrated with the TQ central service, it takes care of the matchmaking◘ If a job needs a certain software to run, this service automatically install it before pulling it from the TQ◘ It is a complex and reliable service needed by the ALICE architecture◘ It writes the software under VO_ALICE_SW_DIR

➸ It must therefore run in the VOBOX to access this area



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MonAlisa◘ It monitors the job status, the storage and the traffic◘ It includes specific ALICE monitoring◘ ALICE would like to have it as BS service following other experiment initiatives◘ It is installed in the VOBOX because:

➸ It runs specific LCG test suites which must be executed from the VOBOX (monitoring of the VO-BOX itself) ➸ If a previous local aggregation is performed it will minimize the monitoring traffic



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Site Computing Agent◘ Interfaces different WMS (LCG, OSG, etc)◘ It performs the matchmaking with the ALICE TQ◘ This service in principle could be run centrally but scaling and size problems of the CERN ALICE installation would appear

Agent Monitoring Service◘ Control of all VOBOX services◘ As long as the VOBOX exists, the service will run there



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Storage Adaptor◘ Handles the communication with LFC to translate GUID to TURL/SURL◘ Builds the TURL◘ Can act as a volume manager◘ Starts up xrootd services◘ Handles communication with FTD◘ Monitor site storage configuration◘ It must run in the VOBOX because ➸ To avoid communication with the central service (catalog)

➸ Need to communicate with the local LFC

➸ Need to be local to start xrootd and to monitor the storage



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Site Proxy◘ Communication between job agent and central services in case WN do not have incoming/outgoing connectivity◘ It runs in the VOBOX because ➸ Needs to communicate with the local services ➸ Essential to handle local VO-Specific services

Proofd◘ Handle communication between local master and workers when using proof on wide area◘ It runs in the VOBOX because: ➸ Needs to communicate with the local WN ➸ At this moment is part of xrootd



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Xrootd◘ Posix I/O ◘ Insulates application from local storage systems◘ Efficient handling of storage◘ Handles user-level file authorization◘ It runs in the VOBOX because: ➸ It needs to communicate with the local SE

◘ An official requirement of ALICE to include it in the middleware ongoing



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3rd PART: SETTING THE VOBOX UP



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Specific ALICE Requirements

Document: “VOBOX Security and Operations Questionnaires v-0.5”

LCG Configuration requirements◘ Full LCG UI (included in default)

◘ FTS client (Perl APIs) (included in the UI)

◘ lcg-infosites (included in the UI)

◘ Local LFC Server with ALICE access◘ Access to the local RB (default gdrb11.cern.ch)

ALICE Configuration◘ The ALICE experts will take care of the installation◘ The site manager should take care of the ALICE ports ◘ The VOBOX must be Alice specific used onlyBACKUP◘ Local directory of the alicesgm user◘ /opt/vobox directory



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Setting up a new VOBOX

You are providing a VOBOX for ALICE:◘ Get a host certificate for the machine and send me the subject back ➸ Registration in the myproxy server at CERN

◘ Perform the LCG VOBOX installation and configuration http://goc.grid.sinica.edu.tw/gocwiki/VO-box_HowTo

◘ As site manager, configure the connection requirements of ALICE following VOBOX questionnaire document◘ Announce the [email protected] list that the VOBOX is ready for testing◘ Now we will test it from the LCG point of view and then open it to the ALICE installation and configuration http://alien.cern.ch/twiki/bin/view/AliEn/HowToInstallLcgVoBox



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Conclusions

◘ ALICE has a well defined infrastructure of Services included in the VOBOX◘ This node is the ALICE entry door to the LCG

➸ Mandatory to provide for Alice exclusive use only

◘ At this moment more than 20 VOBOXES in production ➸ No site is opened until the full configuration of the VOBOX

◘ Well defined infrastructure of deployment and testing◘ Before installing the VOBOX read the documentation:

➸ ALICE VOBOX Requirements

➸ VOBOX installation ➸ AliEn installation in the VOBOX

◘ You have a well defined set of persons providing you support from ALICE and LCG

Documents

Interplay between LCG and ALICE Environment