Interplay between LCG and ALICE Environment

1
Interplay between LCG and ALICE Environment

• Patricia Méndez Lorenzo
• CERN IT-ED-PSS
• ALICE-CIEMAT Meeting
• Madrid
• 4th May 2006

2
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

3
1st PART GENERAL OUTLOOK OF THE VOBOX SERVICE
4
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 sites
• Solution
• ? A separate service where experiments can run
  their agents and experiments
• ? Specific agents not provided by the LCG
  middleware

5
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

6
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)

7
2nd PART HOW DOES ALICE USE THE VOBOX
8
Interfacing AliEn and LCG
ALICE SC3 layout
LCG site (T1)
ALICE Layout in terms of LCG
WN
LCG CE
User (Production Manager)
VO-Box (UI)
RB (external)
SE (local)
CElist T1
ENTRY DOOR
T2 VO-BOX (UI) CeList T2
LCG WORLD
T2 VO-BOX (UI) CeList T2
ALICE Central Services
9
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 them
• 2. LCG SERVICES USED BY ALICE
• ? All of them! RB/WMS, VOMS, FTS/SRM, LFC
• ? No experience up to now with dCACHE and DPM
• 3. 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

10
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

11
Outlook of ALICE Site services

• 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

12
Outlook of ALICE Site services

• 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

13
Outlook of ALICE Site services

• 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

14
Outlook of ALICE Site services

• 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

15
Outlook of ALICE Site services

• 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

16
3rd PART SETTING THE VOBOX UP
17
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 only
• BACKUP
• ? Local directory of the alicesgm user
• ? /opt/vobox directory

18
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_Ho
  wTo
• ? As site manager, configure the connection
  requirements of ALICE following VOBOX
  questionnaire document
• ? Announce the alice-lcg-task-force_at_cern.ch
  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/HowTo
  InstallLcgVoBox

19
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