Multi-Part Aggregated Variable in Structured External Storage

• US 20110302375A1
• Filed: 06/07/2010
• Published: 12/08/2011
• Est. Priority Date: 06/07/2010
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Elko, David A., Palmer, Stewart L., Storm, Adam J., Crosmas, Ronen
• Granted Patent: US 8,838,910 B2
• Time in Patent Office: Days
• US Class Current: 711/147
• CPC Class Codes: G06F 16/2308 Concurrency control transaction processing G06F9/466
• CPC Class Codes: G06F 16/2315 Optimistic concurrency control

Abstract

A mechanism is provided for multi-part aggregated variables in structured external storage. The shared external storage provides a serialized, aggregated structure update capability. The shared external storage identifies each local value for which a group value is needed by name. Each time a member writes out its value, the member specifies the name of the object, the member'"'"'s current value, and the type of aggregate function to apply (e.g., minimum, maximum, etc.). The structured external storage in one atomic operation updates the member'"'"'s value, recalculates the aggregate of all of the individual values, and returns the aggregate to the member. The advantage of this approach is that it requires only one write operation to the structured external storage. The update operation does not require locking, because the operation is atomic.

Claims

1. A method, in a shared external storage device, for multi-part aggregate variables in shared external storage structures, the method comprising:

receiving, by the shared external storage device, a request to write a value to a multi-part aggregate variable from a first member client;

creating, by the shared external storage device, a first entry, wherein the first entry comprises a primary key identifying the multi-part aggregate variable, a member identifier identifying the first member client, an identification of the aggregate function for the multi-part aggregate variable, and the value being written by the first member client;

determining, by the shared external storage device, an aggregate value for the multi-part aggregate variable based on the aggregate function for the multi-part aggregate variable;

writing, by the shared external storage device, the aggregate value for the multi-part aggregate variable in a predetermined entry for the multi-part aggregate variable; and

returning the aggregate value to the first member client.

2. The method of claim 1, wherein the method is performed as one atomic operation.

3. The method of claim 1, wherein the shared external storage structures comprise an index that indexes the list structure, the method further comprising:

updating the index such that for the primary key, the index points to the first entry as a first entry of the multi-part aggregate variable.

4. The method of claim 1, further comprising:

updating a list header to point to the first entry as a first entry in the list structure.

5. The method of claim 1, further comprising:

receiving a request to write a subsequent value to the multi-part aggregate variable from a second member client;

creating a second entry, wherein the second entry comprises the primary key identifying the multi-part aggregate variable, a member identifier identifying the second member client, the identification of the aggregate function for the multi-part aggregate variable, and the subsequent value being written by the second member client;

determining a new aggregate value for the multi-part aggregate variable based on the aggregate function for the multi-part aggregate variable, the value written by the first member client, and the subsequent value written by the second member client;

writing the new aggregate value for the multi-part aggregate variable in the predetermined entry; and

returning the new aggregate value to the second member client.

6. The method of claim 5, wherein the shared external storage comprises an index that indexes the list structure, the method further comprises:

updating the index such that for the primary key the index points to the first entry as a first entry of the multi-part aggregate variable and points to the second entry as a last entry of the multi-part aggregate variable.

7. The method of claim 5, wherein the request to write the subsequent value is a request to create a new entry for the second member client, the method further comprising:

determining whether an entry exists for the second member client in the list structure for the multi-part aggregate variable; and

responsive to an entry already existing for the second member client in the us structure for the multi-part aggregate variable, rejecting the request to write the subsequent value.

8. The method of claim 1, further comprising:

receiving a request to update a value of the multi-part aggregate variable for a given member client;

determining whether an entry exists for the given member client in the list structure for the multi-part aggregate variable;

responsive to an entry not existing for the given member for the multi-part aggregate variable, creating a second entry, wherein the second entry comprises the primary key identifying the multi-part aggregate variable, a member identifier identifying the second member client, the identification of the aggregate function for the multi-part aggregate variable, and the subsequent value being written by the second member client;

determining a new aggregate value for the multi-part aggregate variable based on the aggregate function for the multi-part aggregate variable, the value written by the first member client, and the subsequent value written by the second member client;

writing the new aggregate value for the multi-part aggregate variable in the predetermined entry; and

returning the new aggregate value to the given member client.

9. The method of claim 8, further comprising:

responsive to an entry existing for the given member for the multi-part aggregate variable, updating the existing entry to overwrite the value with the value being written by the given member client;

determining a new aggregate value for the multi-part aggregate variable based on the aggregate function for the multi-part aggregate variable;

writing the new aggregate value for the multi-part aggregate variable in the predetermined entry; and

returning the new aggregate value to the given member client.

10. The method of claim 1, further comprising:

receiving a request to remove an entry for the multi-part aggregate variable from a given member client;

removing an entry of the given member client;

determining a new aggregate value for the multi-part aggregate variable;

writing the new aggregate value for the multi-part aggregate variable in the predetermined entry for the multi-part aggregate variable; and

returning the new aggregate value to the given member client.

11. The method of claim 1, wherein the aggregate function comprises a minimum function, a maximum function, or an average function.

12. The method of claim 1, further comprising:

receiving a bulk read request from a requesting client;

reading multi-part aggregate variable values from the list structure to a read buffer;

returning contents of the read buffer to the requesting client; and

repeating receiving a bulk read request, reading multi-part aggregate variables to the read buffer, and returning contents of the read buffer until all items are read.

13. The method of claim 12, wherein the bulk read request comprises a buffer length and wherein the read buffer has a length equal to the buffer length.

14. The method of claim 12, further comprising:

responsive to a timeout condition, returning partial results with a response code that notifies the requesting client of the timeout condition and a restart token that indicates how far into the bulk read the shared external storage device progressed.

15. The method of claim 12, further comprising:

responsive to filling the read buffer, returning contents of the read buffer with a response code that notifies the requesting client that the buffer is full.

16. The method of claim 1, further comprising:

receiving a bulk write request comprising a write buffer of write values; and

writing values from the write buffer to the shared external storage.

17. A computer program product comprising a computer readable storage medium having a computer readable program stored therein, wherein the computer readable program, when executed on a computing device, causes the computing device to:

receive a request to write a value to a multi-part aggregate variable from a first member client;

create a first entry, wherein the first entry comprises a primary key identifying the multi-part aggregate variable, a member identifier identifying the first member client, an identification of the aggregate function for the multi-part aggregate variable, and the value being written by the first member client;

determine an aggregate value for the multi-part aggregate variable based on the aggregate function for the multi-part aggregate variable;

write the aggregate value for the multi-part aggregate variable in a predetermined entry for the multi-part aggregate variable; and

return the aggregate value to the first member client.

18. The computer program product of claim 17, wherein the computer readable program is stored in a computer readable storage medium in a data processing system and wherein the computer readable program was downloaded over a network from a remote data processing system.

19. The computer program product of claim 17, wherein the computer readable program is stored in a computer readable storage medium in a server data processing system and wherein the computer readable program is downloaded over a network to a remote data processing system for use in a computer readable storage medium with the remote system.

20. An apparatus, comprising:

a processor; and

a memory coupled to the processor, wherein the memory comprises instructions which, when executed by the processor, cause the processor to;

receive a request to write a value to a multi-part aggregate variable from a first member client;

create a first entry, wherein the first entry comprises a primary key identifying the multi-part aggregate variable, a member identifier identifying the first member client, an identification of the aggregate function for the multi-part aggregate variable, and the value being written by the first member client;

determine an aggregate value for the multi-part aggregate variable based on the aggregate function for the multi-part aggregate variable;

write the aggregate value for the multi-part aggregate variable in a predetermined entry for the multi-part aggregate variable; and

return the aggregate value to the first member client.