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Torrent-based software distribution

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Presentation on theme: "Torrent-based software distribution"— Presentation transcript:

1 Torrent-based software distribution

2 Shared area software deployment
Build servers AliEn, AliRoot & deps SLC5 32bit SLC5 64bit Mac 64bit Ubuntu 64bit Catalogue ALICE::CERN::SE AliEn Shared software area NFS/AFS/... VoBox PackMan Worker nodes Site X T1/T2 Karlsruhe

3 Shared area software deployment
Advantages One service/site managing the installation of required packages Disadvantages Shared software area is a single point of failure / bottleneck Difficult to redeploy rebuilds of the same version Need to keep a short list of active software packages T1/T2 Karlsruhe

4 T1/T2 Workshop @ Karlsruhe
Preparing for torrent package.tar.bz2 Chunks of equal size package.tar.bz2.torrent (tens of KB) Metadata info of the original file: - SHA1 hashes of chunks - SHA1 hash of the entire file * uniquely identifies the file - Tracker location (entry point) T1/T2 Karlsruhe

5 Data flow in torrent networks
Tracker Discovery service: keeps track of who has which files/chunks. HTTP-based protocol Seeder Seeder Leech Leech Peers that have the complete file and serve it Peers that are in the process of downloading the file, cooperating to finish faster. T1/T2 Karlsruhe

6 Implementation in AliEn
SLC5 32bit SLC5 64bit Mac 64bit Ubuntu 64bit Build servers AliEn, AliRoot & deps Catalogue torrent://... Seeder alitorrent:8092 Tracker alitorrent:8088 AliEn CERN::SE VoBox Worker nodes Site X T1/T2 Karlsruhe

7 Implementation in AliEn
Worker nodes keep seeding the packages that they have downloaded Other worker nodes will fetch the content mostly from local nodes, if available Worker nodes from site A are usually firewalled from site B, so no inter-site traffic If initial download is not possible via torrent, fall back to wget and then seed the fetched files T1/T2 Karlsruhe

8 T1/T2 Workshop @ Karlsruhe
Current status AliEn itself is packaged in a small (35MB) archive AliRoot, Root & deps. : max. 300MB/job Activated by a flag in LDAP LDAP flag to switch modes: name=<CE_NAME>,ou=CE,ou=Services,ou=<SITE>,ou=Sites,o=alice,dc=cern,dc=ch installMethod=Torrent Stable running at CERN, 2 T1s and a few T2s Integrated in the alien-installer and T1/T2 Karlsruhe

9 Special features of aria2c we use
DHT (Distributed Hash Table) Decentralized distributed lookup system Peer exchange Information about local peers will be quickly propagated between peers LPD (Local Peer Discovery) Multicast mechanism to find out other peers in the local network So the system can work even without access to the central seeder and tracker T1/T2 Karlsruhe

10 Firewall requirements
Outgoing access from the WNs to alitorrent.cern.ch:{8088, 8092} Please don't allow incoming connection requests from the world to the WNs But don't be surprised if they do talk to other outside nodes (users that have the package...) Allow WN-to-WN connections on at least TCP,UDP/6881:6999 – aria2c listening ports UDP,IGMP → /4 – local peer discovery T1/T2 Karlsruhe

11 T1/T2 Workshop @ Karlsruhe
Other considerations You can install your own aria2c client on the system to avoid downloading it for bootstrap In the default configuration file you can tune it more to your liking Enabling JSON/XML-RPC for local activity monitoring … Custom ports HTTP proxies Bandwidth limits T1/T2 Karlsruhe

12 FAQ: Bandwidth worries
CERN seeder limited to 50MB/s In practice the machine has an average of 8MB/s outgoing So the fraction that goes to any particular site is negligible Even the internal network traffic should reduce and not saturate any particular segment any more T1/T2 Karlsruhe

13 T1/T2 Workshop @ Karlsruhe
Plans Very soon enable this option for all sites One site at a time We will contact in advance Please ensure the firewall allows smooth running of this Please be ready to support one service less for ALICE :) T1/T2 Karlsruhe


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