Compensating transaction
Encyclopedia
The execution of a business process consists of one or more transactions
. Each transaction may consist of several individual operations yet, as a whole, it moves the system between consistent states.
There are two groups of systems where compensating transaction may be applied:
1. In the context of a database
this is often easily achieved using transactions
and the commit
/rollback
mechanism . Compensating transaction logic could be implemented as additional on top of database supporting commit
/rollback
. In that case we can decrease business transaction granularity.
2. For systems without a commit
/rollback
mechanism available, one can undo a failed transaction with a compensating transaction, which will bring the system back to its initial state. Typically, this is only a workaround which has to be implemented manually and cannot guarantee that the system always ends in a consistent state. The system designer may need to consider what happens if the compensating transaction also fails.
Compensating transactions are also used in case where a transaction is long lived (commonly called Saga Transactions), for instance in a business process requiring user input. In such cases data will be committed to permanent storage, but may subsequently need to be rolled back, perhaps due to the user opting to cancel the operation. Unlike conventional rollbacks, specific business logic will typically be required to rollback a long lived transaction and restore the system to its original state. This type of transaction differs from distributed transaction
s (often implemented using the two-phase-commit protocol), because although both types of transactions can result in multiple data stores being updated, compensating transactions allows for the updates to span a long period of time.
Compensating transactions are often designed into Web service
s that participate in the execution of business processes that are part of a service-oriented architecture
solution.
Transaction processing
In computer science, transaction processing is information processing that is divided into individual, indivisible operations, called transactions. Each transaction must succeed or fail as a complete unit; it cannot remain in an intermediate state...
. Each transaction may consist of several individual operations yet, as a whole, it moves the system between consistent states.
There are two groups of systems where compensating transaction may be applied:
1. In the context of a database
Database
A database is an organized collection of data for one or more purposes, usually in digital form. The data are typically organized to model relevant aspects of reality , in a way that supports processes requiring this information...
this is often easily achieved using transactions
Database transaction
A transaction comprises a unit of work performed within a database management system against a database, and treated in a coherent and reliable way independent of other transactions...
and the commit
Commit (data management)
In the context of computer science and data management, commit refers to the idea of making a set of tentative changes permanent. A popular usage is at the end of a transaction. A commit is an act of committing.-Data management:...
/rollback
Rollback (data management)
In database technologies, a rollback is an operation which returns the database to some previous state. Rollbacks are important for database integrity, because they mean that the database can be restored to a clean copy even after erroneous operations are performed...
mechanism . Compensating transaction logic could be implemented as additional on top of database supporting commit
Commit (data management)
In the context of computer science and data management, commit refers to the idea of making a set of tentative changes permanent. A popular usage is at the end of a transaction. A commit is an act of committing.-Data management:...
/rollback
Rollback (data management)
In database technologies, a rollback is an operation which returns the database to some previous state. Rollbacks are important for database integrity, because they mean that the database can be restored to a clean copy even after erroneous operations are performed...
. In that case we can decrease business transaction granularity.
2. For systems without a commit
Commit (data management)
In the context of computer science and data management, commit refers to the idea of making a set of tentative changes permanent. A popular usage is at the end of a transaction. A commit is an act of committing.-Data management:...
/rollback
Rollback (data management)
In database technologies, a rollback is an operation which returns the database to some previous state. Rollbacks are important for database integrity, because they mean that the database can be restored to a clean copy even after erroneous operations are performed...
mechanism available, one can undo a failed transaction with a compensating transaction, which will bring the system back to its initial state. Typically, this is only a workaround which has to be implemented manually and cannot guarantee that the system always ends in a consistent state. The system designer may need to consider what happens if the compensating transaction also fails.
Compensating transactions are also used in case where a transaction is long lived (commonly called Saga Transactions), for instance in a business process requiring user input. In such cases data will be committed to permanent storage, but may subsequently need to be rolled back, perhaps due to the user opting to cancel the operation. Unlike conventional rollbacks, specific business logic will typically be required to rollback a long lived transaction and restore the system to its original state. This type of transaction differs from distributed transaction
Distributed transaction
A distributed transaction is an operations bundle, in which two or more network hosts are involved. Usually, hosts provide transactional resources, while the transaction manager is responsible for creating and managing a global transaction that encompasses all operations against such resources...
s (often implemented using the two-phase-commit protocol), because although both types of transactions can result in multiple data stores being updated, compensating transactions allows for the updates to span a long period of time.
Compensating transactions are often designed into Web service
Web service
A Web service is a method of communication between two electronic devices over the web.The W3C defines a "Web service" as "a software system designed to support interoperable machine-to-machine interaction over a network". It has an interface described in a machine-processable format...
s that participate in the execution of business processes that are part of a service-oriented architecture
Service-oriented architecture
In software engineering, a Service-Oriented Architecture is a set of principles and methodologies for designing and developing software in the form of interoperable services. These services are well-defined business functionalities that are built as software components that can be reused for...
solution.
See also
- Commit (data management)Commit (data management)In the context of computer science and data management, commit refers to the idea of making a set of tentative changes permanent. A popular usage is at the end of a transaction. A commit is an act of committing.-Data management:...
- Business Process Execution LanguageBusiness Process Execution LanguageBusiness Process Execution Language , short for Web Services Business Process Execution Language is an OASIS standard executable language for specifying actions within business processes with web services...