Method Of Selecting One Server Out Of A Server Set
A method of selecting one server (S 1 -S 4 ) out of a server set for the purpose of requesting one or more service/s, for example related to an internet- and session-based application, each of the servers (S 1 -S 4 ) of the server set being capable of supporting the service/s, whereby a status vector is maintained which comprises a timestamp value (t 1 -t 4 ) indicating a point of time at which the status of the corresponding server (S 1 -S 4 ) is determined, to improve over existing server selection policies in its ability to reduce transaction control times.
1 . A method of selecting one server out of a server set for the purpose of requesting one or more service/s, for example related to at least one internet- and session-based application, each of the servers of the server set being capable of supporting the service/s, the method comprising:
maintaining a status vector, thereby assigning at least two elements of the status vector a status information, each status information representing a status of one of the servers of the server set,
selecting a server by applying a predetermined selection rule to the status information of elements of the status vector and
requesting the service/s from the selected server,
wherein at least one type of status information comprises a timestamp value indicating a point of time at which the status of the corresponding server is determined and the section rule comprises the step of determining the maximum timestamp value in the status vector and of selecting the corresponding server.
2 . The method according to claim 1 , wherein the status information comprises an availability information, indicating the availability of the corresponding server, associated to the timestamp value.
3 . The method according to claim 2 , wherein the availability information is represented by a minus sign in case the corresponding server is not available.
4 . The method according to claim 1 , wherein the step of assigning status information to a particular element of the status vector in response to completion or failure of a transaction with the corresponding server
5 . The method according to claim 1 , wherein the step of assigning status information to a particular element of the status vector in response to completion of failure of a heartbeat interconnection to the corresponding server.
6 . The method according to claim 1 , wherein the step of assigning status information to a particular element or elements of the status vector in response to a reception of third party status information from a third party for one or more servers of the server set.
7 . The method according to claim 1 , wherein the status information further comprises a delay value indicating an application response time of the corresponding server.
8 . The method according to claim 7 , wherein the section rule comprises the step of determining a subset of the elements of the status vector, the subset including those elements the delay value of which are below a predetermined delay threshold value.
9 . The method according to claim 8 , wherein the selection rule comprises the step of determining the maximum timestamp value in the subset of the status vector elements and of selecting the corresponding server.
10 . The method according to claim 7 , characterized wherein the selection rule comprises the step of determining a subset of the elements of the status vector, the subset including those elements the timestamp values of which are a positive number and, when subtracted from a maximum of the timestamp values, lead to a value less than a predetermined time stamp range value.
11 . The method according to claim 10 , wherein the selection rule comprises the step of determining the minimum delay value in the subset of the status vector elements and of selecting the corresponding server.
12 . The client device for implementation of a method according to claim 1 , comprising
a control module for controlling further modules of the client device,
a memory for storing a status vector, thereby assigning at least two elements of the status vector a status information, each status information representing a status of one of the servers of the server set,
a status vector management module for maintaining the status vector by writing status information to the memory,
a server selection module for reading the status vector from the memory, applying a predetermined selection rule to elements of the status vector and determining thereby a server to be selected,
a client module for requesting the service from the selected server,
wherein the memory is adapted to store at least one type of status information comprises a timestamp value indicating a point of time at which the status of the corresponding server is determined and the status vector management module is adapted to write such status information to the memory and the server selection module is adapted to determine the maximum timestamp value in the status vector and the corresponding server.
13 . The client device of claim 12 , wherein the status vector management module is adapted to assign an availability information to the timestamp value and to write availability information and timestamp value as the status information to the memory.
14 . The client device of claim 12 , wherein the memory is adapted to store status information comprising a delay value and the status vector management module is adapted to write such status information to the memory.
15 . The client device of claim 12 , wherein the server selection module is adapted to determine subsets of elements of the status vector based on discrimination of status information according to one or more predetermined constants, for example a delay threshold value or a timestamp range value.