REDUCED BANDWIDTH CACHE COHERENCY VIA CHECKSUM EXCHANGE

• US 20100257148A1
• Filed: 04/03/2009
• Published: 10/07/2010
• Est. Priority Date: 04/03/2009
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Google Inc. (Alphabet Inc.)
• Inventors: Phillips, Derek J., KROEGER, ROBERT J.
• Granted Patent: US 8,666,954 B2
• Time in Patent Office: Days
• US Class Current: 707/697
• CPC Class Codes: G06F 11/1004 to protect a block of data words, e.g. CRC or checksum G06F11/1076 takes precedence; security arrangements for protecting computers or computer systems against unauthorized activity G06F21/00

Abstract

A server system receives a first request for a data item from a web application on a client device, wherein the first request includes an identifier of the data item. In response to the first request, the server system calculates a first checksum of the data item and sends the data item and the first checksum to the web application, for storage in the local database. The server system receives a second request for the data item from the web application, calculates a second checksum of the data item and compares the first and second checksums. The server system, determines that the data item has been updated by comparing the first checksum to the second checksum; and in response to determining that the data item has been updated, the server system a reply to the web application a indicating that the data item has been updated.

Claims

1. A computer-implemented method for updating a local database, comprising at a server system:

receiving a first request for a data item from a web application on a client device, wherein the first request includes an identifier of the data item;

in response to the first request;

calculating a first checksum of the data item;

sending the data item and the first checksum to the web application, for storage in the local database;

receiving a second request for the data item from the web application, wherein the second request includes the identifier of the data item and the first checksum;

in response to the second request;

calculating a second checksum of the data item;

comparing the first checksum and the second checksum;

determining that the data item has been updated by comparing the first checksum to the second checksum; and

in response to determining that the data item has been updated, sending to the web application a reply indicating that the data item has been updated.

2. The method of claim 1, wherein the reply indicating that the data item has been updated includes the updated data item and the second checksum.

3. The method of claim 1, wherein:

the second request further includes a plurality of identifiers each corresponding to a component of the data item;

determining that the data item has been updated includes determining that a respective component of the plurality of components is a new component; and

the reply indicating that the data item has been updated includes;

the new component that and the second checksum.

4. The method of claim 1, wherein the reply indicating that the data item has been updated includes a request for a first plurality of identifiers each corresponding to a component of the data item stored in the local database, and the method further includes:

receiving a communication from the web application, wherein the communication includes the first plurality of identifiers;

in response to the second request, comparing the first plurality of identifiers received from the web application with a second plurality of identifiers associated a second plurality of components of the data item;

determining a respective identifier in the second plurality of identifiers that is not in the first plurality of identifiers;

in response to determining the respective identifier, sending the respective component that is associated with the respective identifier and the second checksum to the web application.

5. The method of claim 1, wherein the web application is configured to operate in an offline mode, wherein operating in the offline mode includes:

accessing the data item from the local database;

detecting an operation performed on the data item;

writing information characterizing the operation to a write queue along with the identifier of the data item;

detecting a network connection between the web application and the server system; and

in response to detecting the network connection, draining the write queue to the server system.

6. The method of claim 5, including, prior to calculating a second checksum of the data item:

performing the operations from the write queue of the web application.

7. The method of claim 1, including:

in response to determining that the data item has not been updated, sending a message to the web application indicating that the data item has not been updated.

8. The method of claim 1, wherein the web application is a mobile email application and the data item includes one of the list comprising:

a conversation that includes a list of email messages and a thread list that includes a list of conversations.

9. The method of claim 1, wherein the identifier of the data item includes a data item type indicator and a data item identifier.

10. The method of claim 1, wherein the sending operation performed by the web application comprises periodically sending the first checksum to the server system.

11. A server system for updating a local database, comprising:

memory

one or more processors; and

one or more modules stored in the memory, the one or more modules including instructions which when executed by the one or more processors cause the system to;

receive a first request for a data item from a web application on a client device, wherein the first request includes an identifier of the data item;

in response to the first request;

calculate a first checksum of the data item;

send the data item and the first checksum to the web application, for storage in the local database;

receive a second request for the data item from the web application, wherein the second request includes the identifier of the data item and the first checksum;

in response to the second request;

calculate a second checksum of the data item;

compare the first checksum and the second checksum;

determine that the data item has been updated by comparing the first checksum to the second checksum; and

in response to determining that the data item has been updated, send to the web application a reply indicating that the data item has been updated.

12. The system of claim 11, wherein the reply indicating that the data item has been updated includes the updated data item and the second checksum.

13. The system of claim 11, wherein:

the second request further includes a plurality of identifiers each corresponding to a component of the data item;

determining that the data item has been updated includes determining that a respective component of the plurality of components is a new component; and

the reply indicating that the data item has been updated includes;

the new component that and the second checksum.

14. The system of claim 11, wherein the reply indicating that the data item has been updated includes a request for a first plurality of identifiers each corresponding to a component of the data item stored in the local database, and the instructions further include instructions which when executed by the one or more processors cause the system to:

receive a communication from the web application, wherein the communication includes the first plurality of identifiers;

in response to the second request, compare the first plurality of identifiers received from the web application with a second plurality of identifiers associated a second plurality of components of the data item;

determine a respective identifier in the second plurality of identifiers that is not in the first plurality of identifiers;

in response to determining the respective identifier, send the respective component that is associated with the respective identifier and the second checksum to the web application.

15. A computer readable storage medium storing one or more programs for execution by one or more processors of a computer system, the one or more programs comprising instructions to:

receive a first request for a data item from a web application on a client device, wherein the first request includes an identifier of the data item;

in response to the first request;

calculate a first checksum of the data item;

send the data item and the first checksum to the web application, for storage in the local database;

receive a second request for the data item from the web application, wherein the second request includes the identifier of the data item and the first checksum;

in response to the second request;

calculate a second checksum of the data item;

compare the first checksum and the second checksum;

determine that the data item has been updated by comparing the first checksum to the second checksum; and

send, in response to determining that the data item has been updated, to the web application a reply indicating that the data item has been updated.

16. The computer readable storage medium of claim 15, wherein the reply indicating that the data item has been updated includes the updated data item and the second checksum.

17. The computer readable storage medium of claim 15, wherein:

the second request further includes a plurality of identifiers each corresponding to a component of the data item;

instructions to determine that the data item has been updated includes instructions to determine that a respective component of the plurality of components is a new component; and

the reply indicating that the data item has been updated includes;

the new component that and the second checksum.

18. The computer readable storage medium of claim 15, wherein the reply indicating that the data item has been updated includes a request for a first plurality of identifiers each corresponding to a component of the data item stored in the local database, and the instructions further include instructions to:

receive a communication from the web application, wherein the communication includes the first plurality of identifiers;

compare, in response to the second request, the first plurality of identifiers received from the web application with a second plurality of identifiers associated a second plurality of components of the data item;

determine a respective identifier in the second plurality of identifiers that is not in the first plurality of identifiers;

send, in response to determining the respective identifier, the respective component that is associated with the respective identifier and the second checksum to the web application.

19. A computer-implemented method for updating a local database, comprising at a client device:

receiving a request to perform an operation on a data item;

sending, a request to a server system, wherein the request includes an identifier of the data item and an associated checksum;

while waiting for a reply from the server system, performing the operation on the data item;

receiving a reply from the server system including an updated data item; and

performing the same operation on the updated data item.

20. The method of claim 19, wherein the operation is a display operation.

21. The method of claim 19, further comprising, prior to receiving the request to perform the operation on the data item, displaying a compressed representation of the data item;

and

wherein the performing the operation on the data item includes displaying an uncompressed representation of the data item; and

performing the operation on the updated data item includes replacing the display of the uncompressed representation of the data item with an uncompressed representation of the updated data item.

22. The method of claim 21, further comprising:

displaying a compressed representation of a plurality of data items;

sending a plurality of requests, wherein each of the requests includes an associated checksum and identifier for one of the plurality of data items.

23. A client device for updating a local database, comprising:

memory

one or more processors; and

one or more modules stored in the memory, the one or more modules including instructions which when executed by the one or more processors cause the system to;

receive a request to perform an operation on a data item;

send, a request to a server system, wherein the request includes an identifier of the data item and an associated checksum;

while waiting for a reply from the server system, perform the operation on the data item;

receive a reply from the server system including an updated data item; and

perform the same operation on the updated data item.

24. A computer readable storage medium storing one or more programs for execution by one or more processors of a computer system, the one or more programs comprising instructions to:

receive a request to perform an operation on a data item;

send, a request to a server system, wherein the request includes an identifier of the data item and an associated checksum;

perform, while waiting for a reply from the server system, the operation on the data item;

receive a reply from the server system including an updated data item; and

perform the operation on the updated data item.