AU6575500A

AU6575500A - Method for distributing the load of a communication channel

Info

Publication number: AU6575500A
Application number: AU65755/00A
Authority: AU
Inventors: Laurent Clevy; Ramzi Karoui; Michel Ruffin; Simone Sedillot
Original assignee: Alcatel CIT SA; Alcatel SA
Current assignee: Alcatel Lucent SAS
Priority date: 1999-07-15
Filing date: 2000-07-13
Publication date: 2001-02-05
Also published as: EP1114544B1; ES2265961T3; DE60028715T2; EP1114544A1; ATE330407T1; DE60028715D1; JP2003505935A; WO2001006730A1

Abstract

The invention concerns a method for distributing the load of a communication channel (4) in a transaction exchange between two communication channels, in conformity with the transactions between the providers (2, 7) and the channel and the transactions between the channel and the consumers (6), comprising steps which consist in: creating a twin communication channel; transferring part of the data providers on the twin channel, when their current transactions (3, 13) with the initial channel are completed.

Description

ATOMIC SWITCHING OF THE DESTINATION OBJECT BETWEEN TWO TRANSACTIONAL INVOCATIONS The field of the invention is that of transactional communications between objects that supply data and 5 objects that consume the data, such communication using communication channels and internal or external managers of the various relations between the aforementioned objects. The mechanism is implemented by an intermediate object, namely the communication channel. 10 Suppliers can overload a channel if they transfer too great a quantity of data or if a large number of suppliers are connected to the channel. In the art, one known way of limiting overload consists of providing the communication channel with an 15 activity limit threshold from which it refuses any new transaction until the transactions in progress have terminated. However, that solution is too costly in terms of execution time. The slightest overrun entails the risk of blocking an entire channel, even if the 20 overrun is only temporary. It is possible to improve the above solution by implementing a dynamic system for determining overruns which takes account of their context. The above solution necessarily reduces the reaction time of the system as a whole. 25 A transaction must satisfy four properties grouped together under the acronym ACID signifying: Atomicity, Consistency, Isolation, and Durability. The four properties are closely interrelated. The objective of restart and competition control mechanisms used by a 30 transactional engine is to ensure conformance to them. Atomicity guarantees that either all the updates of a transaction are effected or none of them. Non conformance to this property can change the set of data from the initial consistent state to an inconsistent 35 state. In order to conform to this property, any series of actions constituting a transaction is marked by a start 2 and an end. The start of a transaction signals the start event of a transaction to the transactional engine. Two instructions are provided for marking the end of a transaction: "Commit" enables the transaction to signal 5 to the transactional monitor that from the isolated point of the transaction all its actions have been completed successfully and "Abort" enables the transaction to signal to the transactional monitor that one or more of its actions have failed and that it does not wish to be 10 validated (the data modified by the transaction must be returned to its preceding state). Depending on the end of transaction event received by the transactional monitor and on its overview of the system (interaction between transactions), the transactional monitor decides 15 whether or not to validate the transaction, i.e. whether or not to make the modifications effected by it permanent. If a system fault occurs before the end of a transaction, then the transaction is considered to be aborted. One mechanism for conforming to the atomicity 20 property entails retaining the preceding image of any data updated for each transaction in progress. If a transaction is aborted, it is possible to undo the transaction by applying all the preceding images of the transaction. 25 The consistency property concerns the semantic consistency of a set of data. It can be maintained partly by mechanisms assuring integrity constraint control and by maintaining the property of the transactions. Isolation is indispensable in a 30 multitasking environment, to guarantee that each transaction sees a consistent state of the set of data. Isolation entails guaranteeing that, if the transaction executes in parallel with other transactions accessing a common set of data, then serial execution of the same 35 transactions would produce the same changes on the set of data accessed by the transactions. In this case, the isolation property is satisfied for that set of 3 transactions. Durability guarantees that the updates of a validated transaction are permanent. The only action that should enable the updates of a validated transaction to be undone is executing a compensation transaction. 5 This property goes hand in hand with the atomicity property stipulating that the updates of a transaction form a consistent whole which is either aborted entirely or validated permanently. One way to deal with a memory or hard disc failure leading to loss of information from 10 the database is to provide a restart mechanism to recover the lost information. The object of the invention is to propose a solution which reduces the overloading of a communication channel, conforms to reliability ACID properties and does not 15 degrade the capacities of the system. To reduce the overload, an additional twin channel is created and some of the data is directed onto the new channel. The invention provides a method of distributing the 20 load of a communication channel in transactional communication between two communication channels conforming to transactions between suppliers and the channel and transactions between the channel and consumers. The method includes the following steps: 25 - a twin communication channel is created; - some data suppliers are transferred to the twin channel as soon as their transactions in progress with the original channel have terminated. The invention also relates to the disconnection 30 mechanism. It provides a method of distributing the load of a communication channel in transactional communication between two communication channels conforming to transactions between suppliers and the channel and transactions between the channel and consumers. The 35 method including the following steps: - a twin communication channel is created; - some data suppliers are transferred to the twin 4 channel as soon as their transactions in progress with the original channel have terminated. The method preferably includes a step of identifying suppliers to be transferred to the twin channel. No new 5 transaction is undertaken between the suppliers so identified and the original channel after the step of identifying those suppliers. The invention also relates to the disconnection mechanism. It provides a method of distributing the load 10 of two communication channels conforming to transactions between suppliers and the channels and transactions between the channels and consumers, said method including the following steps: - a main channel and a secondary channel are 15 defined; - the data suppliers are transferred from the secondary channel to the main channel as soon as their transactions in progress with the secondary channel have terminated. 20 The consumers are advantageously disconnected from the secondary channel when all the transactions involving said secondary channel have been effected. The secondary channel can be determined by a minimum traffic threshold. In one variant, whether the main 25 channel is managing traffic below a predetermined threshold is tested beforehand. To guarantee reliable delivery of data between a supplier and one or more consumers, the data can propagate between two contiguous objects under the 30 control of a transaction. In this case a supplier initiates a transaction in order to ensure transfer with the communication channel is reliable. The supplier is released when the channel supplier transaction has terminated correctly. A second 35 transaction is initiated by the channel for reliable transfer to the consumer. The second transaction, which makes the propagation between the channel and the 5 consumer reliable, is terminated when the client has received the data correctly. An empty copy of the communication channel is created when the channel is overloaded. The copy is 5 connected to all the clients connected to the original channel. A supplier is not switched to the new channel unless its transactions in progress on the original channel have terminated. 10 To distribute the load some suppliers are disconnected from the original channel one by one and connected to the twin channel. The supplier has a field that can be interrogated and that indicates whether it can be disconnected or not, 15 i.e. whether the supplier has a transaction in progress or not. When the load decreases, a similar mechanism switches the suppliers back to the original channel and destroys the twin channel, which is no longer of any 20 utility. A supplier is not switched until there is no transaction in progress. To prevent the supplier from beginning new transactions indefinitely, new transactions are prohibited for the supplier. When migration becomes 25 possible, the supplier is given the reference of the new channel so that it can connect. It can then begin new transactions on the original channel. All the clients are connected to the new channel before a supplier migrates in order to ensure that no 30 data is lost and that no data is transmitted more than once. The converse operation is similar: all the suppliers must be moved from the twin channel to the original channel before the clients are disconnected. Also, all 35 the transactions in progress must terminate before an object migrates. Figure 1 shows the overloaded system before the twin 6 channel starts to operate. The suppliers (1 and 7) each have a specific interface (1) that the communication managers interrogate to find out if transactions are in progress. The 5 supplier (1) has a transaction (3) with the communication channel (4) in progress but the supplier (7) is not doing anything and can be transferred to a twin channel. The consumers (6) are in constant communication (5) with the communication channel. 10 Figure 2 shows a twin channel after it has been set up. The twin channel (12) has transactions (13) with the supplier (7) in progress. The consumers (6) are in communication with all the communication channels (11).

Claims

1. A method of distributing the load of a communication channel (4) in transactional communication between two communication channels conforming to transactions between 5 suppliers (2,7) and the channel and transactions between the channel and consumers (6), said method including the following steps: - a twin communication channel (12) is created; - some data suppliers are transferred to the twin 10 channel as soon as their transactions in progress with the original channel have terminated.

2. A method according to claim 1 of distributing the load of a communication channel, including a step of identifying suppliers (7) to be transferred to the twin 15 channel, and characterized in that no new transaction is undertaken between the suppliers (7) so identified and the original channel (4) after the step of identifying those suppliers.

3. A method of distributing the load of two 20 communication channels conforming to transactions between suppliers and the channels and transactions between the channels and consumers, said method including the following steps: - a main channel and a secondary channel are 25 defined; - the data suppliers are transferred from the secondary channel to the main channel as soon as their transactions in progress with the secondary channel have terminated. 30

4. A method according to claim 3 of distributing the loads of two communication channels, characterized in that the consumers are disconnected from the secondary channel when all the transactions involving said secondary channel have been effected. 8

5. A method in accordance with claim 3 or claim 4 of distributing the load of two communication channels, characterized in that the secondary channel is determined by a minimum traffic threshold. 5

6. A method according to claim 5 of distributing the load of two communication channels, characterized in that whether the main channel is managing traffic below a predetermined threshold is tested beforehand.