Performing composable transactions in a dispersed storage network

A processing system of a dispersed storage and task (DST) processing unit comprises:

• at least one processor;
• a memory that stores operational instructions, that when executed by the at least one processor cause the processing system to:
• initialize a composite operation from a plurality of operations;
• create an empty transaction context by performing an evaluation of the composite operation;
• create a multi-source compare and swap (CASN) transaction from resulting expected values determined by evaluating the composite operation in the empty transaction context;
• execute the CASN transaction against a dispersed storage network (DSN) memory;
• when execution of the CASN transaction is successful, commit the transaction to the DSN memory;
• and
• when the execution failed due to at least one conflicting value stored in the DSN memory:
• create a new transaction context pre-populated with the at least one conflicting value;
• and
• execute an updated CASN for the composite operation that utilizes the new transaction context,
• wherein the DSN memory includes a plurality of storage units;
• and
• the DST processing unit is configured to store a data object in the DSN memory by:
• dividing the data object into plural segments;
• producing a plurality of sets of encoded data slices from the plural segments;
• and providing the plurality of sets of encoded data slices with their respective slice names to the plurality of storage units for storage.

A computer readable storage medium comprises:

• at least one memory section that stores operational instructions that, when executed by a processing system of a dispersed storage network (DSN) that includes a processor and a memory, causes the processing system to:
• initialize a composite operation from a plurality of operations;
• create an empty transaction context by performing an evaluation of the composite operation;
• create a multi-source compare and swap (CASN) transaction from resulting expected values determined by evaluating the composite operation in the empty transaction context;
• execute the CASN transaction against the dispersed storage network;
• when execution of the CASN transaction is successful, commit the transaction to the DSN;
• and
• when the execution failed due to at least one conflicting value stored in the DSN:
• create a new transaction context pre-populated with the at least one conflicting value;
• and
• execute an updated CASN for the composite operation that utilizes the new transaction context,
• wherein the DSN memory includes a plurality of storage units;
• and
• the DST processing unit is configured to store a data object in the DSN memory by:
• dividing the data object into plural segments;
• producing a plurality of sets of encoded data slices from the plural segments;
• and providing the plurality of sets of encoded data slices with their respective slice names to the plurality of storage units for storage.