Running complex workflows in distributed systems while protecting consistency and ensuring progress despite failures

A method implemented by a computing system for executing a workflow composed of a plurality of idempotent actions, the method comprising:

• accessing the workflow composed of the plurality of idempotent actions, each idempotent action comprising a corresponding action name, a corresponding guard that specifies one or more guard conditions for triggering execution of the idempotent action, idempotent code that is atomically executable in the workflow, and a record reflecting a state of execution;
• and
• for each idempotent action defined in the workflow, iteratively
• attempting to execute the idempotent action at least until it is executed and by at least iteratively determining whether or not the one or more guard conditions are satisfied for triggering execution of the corresponding idempotent code and,
• based at least on determining the one or more guard conditions are satisfied for triggering execution of the corresponding idempotent code,
• taking a lock on one or more resources used for executing the idempotent code of the idempotent action and initiating executing the idempotent code;
• upon successfully executing the idempotent code for the idempotent action, updating the record to reflect execution of the idempotent action;
• and
• releasing the lock;
• or
• based at least on determining that the one or more guard conditions are not satisfied for triggering execution of the corresponding idempotent action,
• refraining from initiating execution of the idempotent code;
• updating the record to log an exception;
• and
• repeating the determining whether the one or more guard conditions are satisfied again at a predetermined interval,
• wherein the plurality of idempotent actions are executable without an ordering restriction, and at least one failure of at least one idempotent action is independent of an execution of another idempotent action.

A computer program product comprising one or more storage devices having stored computer-executable instructions which are executable by the one or more processors of a computing system for implementing a method with the computing system for executing a workflow, the method comprising:

• accessing the workflow, the workflow comprised of a plurality of idempotent actions, wherein each idempotent action comprises a corresponding action name, a corresponding guard that specifies one or more guard conditions for triggering execution of the idempotent action, idempotent code that is atomically executable in the workflow, and a record reflecting a state of execution;
• and
• for each idempotent action defined in the workflow, iteratively, and at a predetermined interval,
• determining whether or not the one or more guard conditions are satisfied for triggering processing of the corresponding idempotent action and,
• based at least on determining the one or more guard conditions are satisfied for triggering processing of the corresponding idempotent action,
• taking a lock on one or more resources used for executing the idempotent code of the idempotent action and initiating executing the idempotent code;
• upon successfully executing the idempotent code for the idempotent action, updating the record to reflect execution of the idempotent action;
• and
• releasing the lock;
• or
• based at least on determining that the one or more guard conditions are not satisfied for triggering execution of the corresponding idempotent action,
• refraining from initiating execution of the idempotent code;
• updating the record to log an exception;
• and
• repeating the determining whether the one or more guard conditions are satisfied again at a predetermined interval,
• wherein the plurality of idempotent actions are executable without an ordering restriction, and at least one failure of at least one idempotent action is independent of an execution of another idempotent action.