Method and System to Maintain Strong Consistency of Distributed Replicated Contents in a Client/Server System

• US 20130036092A1
• Filed: 08/04/2011
• Published: 02/07/2013
• Est. Priority Date: 08/03/2011
• Status: Active Grant

• Current Assignee: Amadeus (Amadeus Global Travel Distribution S.A.)
• Original Assignee: Amadeus (Amadeus Global Travel Distribution S.A.)
• Inventors: Touffait, Guillaume, Defayet, Christophe, Amar, Virginie, Lafont, Caroline, Collendavelloo, Yan
• Granted Patent: US 8,495,017 B2
• Time in Patent Office: Days
• US Class Current: 707/634
• CPC Class Codes: G06F 16/172 Caching, prefetching or hoarding of files
• CPC Class Codes: G06F 16/178 Techniques for file synchronisation in file systems
• CPC Class Codes: G06F 16/184 implemented as replicated file system

Abstract

A method and a system for maintaining consistency of replicated files distributed over a plurality of independent processing slave nodes part of an application tier of a multi-tier client/server data processing system are described. The replicated files are distributed from a master node of a master tier. Upon reception of an update request to update a master database a new version of a replicated file is first generated and stored in a shared file system. A notification of availability of the new version is forwarded to a synchronizing slave node and broadcasted to all slave nodes. Each slave node preloads the new version of the replicated file from the shared file system and acknowledges successful completion. Upon reception of all acknowledgments in the synchronization slave node a notification of preloading achievement is forwarded to the master server which updates the master database.

Claims

1. A method of maintaining consistency of replicated files distributed over a plurality of independent processing slave nodes part of an application tier of a multi-tier client/server data processing system, the replicated files being distributed from a master node (110) of a master tier, wherein the method comprises the following steps performed with at least one data processor:

receiving an update request in at least a master server of the master tier to update a master database of the data processing system;

based on said update generating and storing a new version of a replicated file stored in a shared file system of the master tier;

providing a notification of availability of the new version of the replicated file to all slave nodes;

in each slave node, starting preloading from the shared file system the new version of the replicated file and upon completion of the preloading, acknowledging successful completion of the preloading;

only if all slave nodes acknowledge successful completion of the preloading then performing the following steps;

receiving at the master server a notification of preloading achievement;

from the master server, updating the master database with data of the new version of the replicated file thus committing the use of the new version of the replicated file by the master tier;

committing the use of the new version of the replicated file in a slave database of the application tier arranged for keeping track of all replicated file versions;

forwarding to the master server a notification of commitment of all slave nodes;

from master server, acknowledging achievement of the update in response to the received update request,

if not all the slave nodes acknowledge successful completion of the preloading, then receiving at the master node a notification of error.

2. The method according to claim 1 wherein the step of providing a notification of availability of the new version of the replicated file to all slave nodes comprises the following steps:

forwarding, from the master server, a notification of availability of the new version of the replicated file to a synchronizing slave node taken among the slave nodes;

broadcasting from the synchronizing slave node said notification of availability to all other slave nodes.

3. The method according to claim 2 wherein the step of acknowledging successful completion of the preloading comprises a step wherein the slave nodes acknowledge successful completion of the preloading to a server process of the synchronizing slave node.

4. The method according to claim 3 wherein once all slave nodes acknowledge successful completion of the preloading to the server process of the synchronizing slave node and before the step of receiving at the master server a notification of preloading achievement, the synchronizing slave node forwards to the master server said notification of preloading achievement.

5. The method according to claim 2 wherein upon completion of the step of committing the use of the new version of the replicated file by the master tier, the master node forwards a commitment notification to the synchronizing slave node and then the synchronizing slave node triggers the step of committing the use of the new version of the replicated file in the slave database.

6. The method according to claim 1 wherein at beginning of a transaction initiated by a query for information from a user, at least in each slave node involved in said transaction an applicative process interrogates the slave database and is instructed whether to switch from a current version of the replicated file to the preloaded new version of the replicated file.

7. The method according to claim 1 wherein at beginning of a transaction initiated by a query for information from a user, in each slave node involved in said transaction an applicative process reads a tag of a current version of the replicated file, said tag indicating if a new version of the replicated file is available, and wherein if the tag indicates that a new version of the replicated file is available, then the applicative process interrogates the slave database and is instructed whether to switch from the current version of the replicated file to the new version of the replicated file.

8. The method according to claim 7 wherein the tag is set at successful completion of preloading (51) of a new version of the replicated file and is reset at first reading by the applicative process.

9. The method according to claim 1 wherein the received update request comprises at least an update and wherein the steps of generating and storing a new version of a replicated file in the shared file system is an incremental process including, in the master server, the steps of:

retrieving from the shared file system a current version of a replicated file and converting to an appropriate format the current version of the replicated file to be updated;

applying the update onto the current version and converting and storing the new version of the replicated file into the shared file system.

10. The method according to claim 9 wherein the replicated files are compressed when stored in the shared file system and wherein the replicated files stored in the shared file system are decompressed and converted into an appropriate format by the master server when performing the incremental update, and by the slave nodes upon preloading.

11. The method according to claim 1 wherein if not all slave nodes acknowledge successful completion of the preloading, then the master node sends a notification of error to an administrator that sent said update request.

12. The method according to claim 1 wherein the shared file system is a network-attached storage (NAS).

13. The method according to claim 1 wherein the slave database only stores data related to the version of replicated files.

14. Computer program product stored in a non-transitory computer-readable memory medium and performing the method according to claim 1.

19. The method according to claim 1 wherein the multi-tier client/server data processing system is part of an inventory of a travel provider.

15. A method of maintaining consistency of replicated files containing business rules, said replicated files being distributed over a plurality of independent processing slave nodes forming a part of an application tier of a multi-tier client/server data processing system, the replicated files being distributed from a master node of a master tier, wherein the method comprises the following steps performed with at least a data processor:

receiving an update request in at least a master server of the master tier to update business rules stored in a master database of the data processing system;

based on said update generating and storing a new version of a replicated file stored in a shared file system of the master tier;

providing a notification of availability of the new version of the replicated file to all slave nodes;

in each slave node, starting preloading from the shared file system the new version of the replicated file and upon completion of the preloading, acknowledging successful completion of the preloading;

only if all slave nodes acknowledge successful completion of the preloading then performing the following steps;

receiving at the master server a notification of preloading achievement;

from the master server, updating the master database with data of the new version of the replicated file thus committing the use of the new version of the replicated file by the master tier;

if not all the slave nodes acknowledge successful completion of the preloading, then receiving at the master node a notification of error.

16. The method according to claim 15 wherein each business rule comprises a set of criterion and a content.

17. The method according to claim 16 wherein each criterion is associated to a weight.

18. The method according to claim 15 wherein the set of criterion comprises at least one of:

a point of sale, a country, a group of countries, a country of origin of a flight, a destination of a flight, a customer profile.

20. The method according to claim 15 wherein the slave nodes are connected to at least one of:

an inventory of an airline, a departure control system of an airline, a revenue management system of an airline, a revenue accounting system of an airline, an electronic ticket server of an airline.

21. The method according to claim 15 wherein only if all slave nodes acknowledge successful completion of the preloading then performing the following additional steps:

committing the use of the new version of the replicated file in a slave database of the application tier arranged for keeping track of all replicated file versions;

forwarding to the master server a notification of commitment of all slave nodes;

from master server, acknowledging achievement of the update in response to the received update request.

22. A distributed multi-tier client/server data processing system comprising an application tier and a master tier, the application tier comprising a plurality of independent processing slave nodes and the master tier comprising a master node arranged for distributing replicated files to the slave nodes, a master database and a master server, wherein:

the master tier comprises a shared file system, the master server being arranged for receiving an update request to update the master database, to generate a new version of a replicated file stored in the shared file system and to store said new version in the shared file system;

in that it comprises a slave database connected to all slave nodes and arranged for keeping track of all replicated file versions; and

in that the system is configured for;

providing a notification of availability of the new version of the replicated file to all slave nodes;

in each slave node, starting preloading from the shared file system the new version of the replicated file and upon completion of the preloading, acknowledging successful completion of the preloading;

only if all slave nodes acknowledge successful completion of the preloading then performing the following steps;

receiving at the master server a notification of preloading achievement;

from the master server, updating the master database with data of the new version of the replicated file thus committing the use of the new version of the replicated file by the master tier;

committing the use of the new version of the replicated file in the slave database;

forwarding to the master server a notification of commitment of all slave nodes;

from master server, acknowledging achievement of the update in response to the received update request,

if not all the slave nodes acknowledge successful completion of the preloading, then receiving at the master node a notification of error.