IMPLEMENTATION OF STREAM ALGEBRA OVER CLASS INSTANCES

• US 20090024622A1
• Filed: 07/18/2007
• Published: 01/22/2009
• Est. Priority Date: 07/18/2007
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Goldstein, Jonathan, Chkodrov, Gueorgui B., Ringseth, Paul F., Barga, Roger Shane, Tarnavski, Tihomir T., Shen, Andy
• Granted Patent: US 7,676,461 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 16/24542 Plan optimisation
• CPC Class Codes: G06F 16/24568 Data stream processing; Continuous queries
• CPC Class Codes: Y10S 707/99934 Query formulation, input preparation, or translation

Abstract

Creating and executing a distributed stream processing operator graph based on a query. The operator graph includes movable stream algebra operators for processing events received from high volume data streams. The operators are partially compiled and distributed to computing devices for completion of the compilation and subsequent execution. During execution, the operators maintain minimal state information associated with received events via an expiration time assigned to each of the event instances. Additional events are generated and aggregated by the operators for communication to a service responsible for the query.

Claims

1. A method of processing high-volume continuous streams of data while maintaining minimal state information associated with the data, said method comprising:

receiving a query comprising query data and operator semantics, said query representing a request for data;

translating the received query into a plurality of stream algebra operators;

defining an execution plan representing a data flow implemented by the stream algebra operators;

receiving a first event from a data stream;

assigning an expiration time to the received first event as a function of the query data;

receiving a plurality of second events from the data stream;

executing one or more of the stream algebra operators according to the defined execution plan and as a function of the operator semantics from the received query to find a match between the received first event and at least one of the received plurality of second events prior to expiration of the first event based on the assigned expiration time associated with the first event; and

producing, as a function of said executing, a third event to be executed according to the execution plan.

2. The method of claim 1, wherein translating the query comprises compiling a description of the stream algebra operators into assembly code for efficient execution.

3. The method of claim 1, further comprising distributing one of the stream algebra operators to a destination computing device by:

pausing execution of the stream algebra operator;

storing state information maintained by the stream algebra operator; and

sending the stream algebra operator and the stored state information to the destination computing device.

4. The method of claim 3, wherein distributing one of the stream algebra operators to a destination computing device comprises identifying the destination computing device and the one of the stream algebra operators based on the execution plan.

5. The method of claim 3, further comprising adjusting the expiration time assigned to the first event to minimize the quantity of state information maintained by the stream algebra operator.

6. The method of claim 1, further comprising assigning an expiration time to each of the received plurality of second events, wherein the assigned expiration time comprises infinity or zero.

7. The method of claim 1, wherein said producing the third event comprises producing the third event representing a combination of the first event and the matched one of the received plurality of second events.

8. The method of claim 1, further comprising maintaining a state of the first event only until the first event has expired based on the associated expiration time.

9. The method of claim 1, further comprising discarding the first event as a function of the assigned expiration time.

10. The method of claim 1, wherein receiving the first event comprises receiving a request for data, and wherein receiving the plurality of second events comprises receiving a plurality of responses.

11. A system for processing high-volume continuous streams of data while maintaining minimal state information associated with the data, said system comprising:

a memory area for storing a plurality of stream algebra operators for building a distributed stream processing operator graph, each of said stream algebra operators being adapted to perform one or more functions on data events from an event stream; and

a processor configured to execute computer-executable instructions for building a distributed operator graph using the stream algebra operators stored in the memory area by;

defining an object to include an expression, said expression representing the one or more functions to be performed on the data events from the event stream;

serializing the defined object including the expression into a message corresponding to one of the plurality of stream algebra operators stored in the memory area;

identifying one of a plurality of destination computing devices to host said one of the plurality of stream algebra operators;

transmitting the message to the identified destination computing device to build the distributed operator graph, wherein the destination computing device compiles the expression from the message into executable code representing said one of the plurality of stream algebra operators implementing a portion of the operator graph, wherein the executable code operates on the data events received from the event stream to produce aggregated events;

receiving the aggregated events from the destination computing device; and

processing the aggregated events in accordance with another portion of the operator graph implemented by the processor.

12. The system of claim 11, wherein the data events comprise one or more of the following:

a class instance, a C# event, and a message.

13. The system of claim 11, wherein the memory area further stores an alterlifetime operator for adjusting a timestamp associated with a data event received from the event stream.

14. The system of claim 11, further comprising one or more of the following:

means for building the distributed operator graph, means for generating the expression, and means for identifying the one of the plurality of destination computing devices to host said one of the plurality of stream algebra operators.

15. The system of claim 11, wherein the processor is configured to execute computer-executable instructions for identifying the one of the plurality of destination computing devices as a function of a placement algorithm.

16. The system of claim 11, wherein the data events comprise an insert event, and wherein processing of the insert event adds information associated with the insert event to a computation state associated with one of the stream algebra operators.

17. The system of claim 11, wherein receiving the aggregated events from the destination computing device comprises receiving locally aggregated events from each of a plurality of destination computing devices, and wherein the processor is further configured to execute computer-executable instructions for globally aggregating the received locally aggregated event in accordance with the operator graph implemented by the processor.

18. A method for configuring an operator graph to process a continuous stream of events, said method comprising:

defining an object to include an expression, said expression representing a function to be performed on events from an event stream;

generating an abstract syntax tree corresponding to the object;

serializing the generated abstract syntax tree into a message; and

sending the message representing the object to a destination machine, said destination machine being one of a plurality of machines, wherein the destination machine compiles the expression from the abstract syntax tree into executable code, wherein the executable code is executed on events received from the event stream.

19. The method of claim 18, wherein the event stream is a continuous stream of events.

20. The method of claim 18, wherein the executable code is represented as an operator in an operator graph.