Determining a backup server for a session based on a deterministic mechanism and the session's key value
A mechanism is disclosed for determining, based on a deterministic mechanism and a session's key value, a backup server for the session. In one embodiment, each session has a different key value, and each key value can be processed through the deterministic mechanism to give rise to a separate ordering of a result value set. Each server of a plurality of servers is associated with a different one of the set's values. A request pertaining to a particular session is received. The request indicates the particular session's key value. The deterministic mechanism can generate result values, in a particular order to which the session's key value gives rise, until a result value associated with a currently operational server is generated. The request is sent to that server if the request's primary server is not currently operational. A pseudo-random number generator seeded with the key value may generate the result values.
1. A machine-implemented method, comprising:
receiving, by a first backup server, a first request comprising a first session key value and a first primary server identifier, wherein the first backup server is one of a plurality of servers;
making a first determination, by the first backup server, that the first request is associated with a first primary server based on the first primary server identifier, wherein the first primary server is one of the plurality of servers;
making a second determination, by the first backup server, that the first primary server is not currently operational;
generating, by the first backup server based on the second determination, a first ordering of potential backup servers by applying a deterministic algorithm to the first session key value;
selecting, by the first backup server, a second backup server based on a first-ordered value from the first ordering of potential backup servers, wherein the second backup server is one of the plurality of servers;
sending, by the first backup server based on the selecting, the first request to the second backup server;
receiving, by the second backup server, the first request;
making a third determination, by the second backup server, that the first request is associated with the first primary server based on the first primary server identifier;
making a fourth determination, by the second backup server, that the first primary server is not currently operational;
generating, by the second backup server based on the fourth determination, the first ordering of potential backup servers by applying the deterministic algorithm to the first session key value;
obtaining the first-ordered value from the first ordering of potential backup servers; and
processing, by the second backup server, the first request based on a determination that the first-ordered value from the first ordering of potential backup servers is associated with the second backup server.
2. The method of claim 1 , further comprising:
receiving, by the first backup server, a second request comprising a second session key value and a second primary server identifier;
making a fifth determination, by the first backup server, that the second request is associated with a second primary server based on the second primary server identifier, wherein the second primary server is one of the plurality of servers;
making a sixth determination, by the first backup server, that the second primary server is not currently operational;
generating, by the first backup server based on the sixth determination, a second ordering of potential backup servers by applying the deterministic algorithm to the second session key value;
obtaining, by the first backup server, a first-ordered value from the second ordering of potential backup servers; and
processing, by the first backup server, the second request based on a determination that the first-ordered value from the second ordering of potential backup servers is associated with the first backup server.
3. A non-transitory machine-readable medium, comprising instructions, which when executed by a processor perform a method, the method comprising:
receiving, by a first backup server, a first request comprising a first session key value and a first primary server identifier, wherein the first backup server is one of a plurality of servers;
making a first determination, by the first backup server, that the first request is associated with a first primary server based on the first primary server identifier, wherein the first primary server is one of the plurality of servers;
making a second determination, by the first backup server, that the first primary server is not currently operational;
generating, by the first backup server based on the second determination, a first ordering of potential backup servers by applying a deterministic algorithm to the first session key value;
selecting, by the first backup server, a second backup server based on a first-ordered value from the first ordering of potential backup servers, wherein the second backup server is one of the plurality of servers;
sending, by the first backup server based on the selecting, the first request to the second backup server;
receiving, by the second backup server, the first request;
making a third determination, by the second backup server, that the first request is associated with the first primary server based on the first primary server identifier;
making a fourth determination, by the second backup server, that the first primary server is not currently operational;
generating, by the second backup server based on the fourth determination, the first ordering of potential backup servers by applying the deterministic algorithm to the first session key value;
obtaining, the first-ordered value from the first ordering of potential backup servers; and
processing, by the second backup server, the first request based on a determination that the first-ordered value is associated with the second backup server.
4. The non-transitory machine-readable medium of claim 3 , the method further comprising:
receiving, by the first backup server, a second request comprising a second session key value and a second primary server identifier;
making a fifth determination, by the first backup server, that the second request is associated with a second primary server based on the second primary server identifier, wherein the second primary server is one of the plurality of servers;
making a sixth determination, by the first backup server, that the second primary server is not currently operational;
generating, by the first backup server, a second ordering of potential backup servers by applying the deterministic algorithm to the second session key value;
obtaining, by the first backup server, a first-ordered value from the second ordering of potential backup servers; and
processing, by the first backup server, the second request based on a determination that the first-ordered value from the second ordering of potential backup servers is associated with the first backup server.
5. An apparatus comprising:
a first backup server configured to:
receive a first request comprising a first session key value and a first primary server identifier;
make a first determination that the first request is associated with a first primary server based on the first primary server identifier, wherein the first primary server is one of a plurality of servers;
make a second determination that the first primary server is not currently operational;
generate a first ordering of potential backup servers by applying a deterministic algorithm to the first session key value;
select a second backup server based on a first-ordered value from the first ordering of potential backup servers;
send the first request to the second backup server;
the second backup server configured to:
receive the first request;
make a third determination that the first request is associated with the first primary server based on the first primary server identifier;
make a fourth determination that the first primary server is not currently operational;
generate, based on the fourth determination, the first ordering of potential backup servers by applying the deterministic algorithm to the first session key value;
obtain the first-ordered value from the first ordering of potential backup servers; and
process the first request based on a determination that the first-ordered value is associated with the second backup server.
6. The apparatus of claim 5 , wherein the first backup server is further configured to;
receive a second request comprising a second session key value and a second primary server identifier;
make a fifth determination that the second request is associated with a second primary server based on the second primary server identifier, wherein the second primary server is one of the plurality of servers;
make a sixth determination that the second primary server is not currently operational; based on the determination that the second primary server is not currently operational: obtain the set of values; seed the deterministic pseudo-random number generator with the second session key value;
generate, based on the sixth determination, a second ordering of potential backup servers by applying the deterministic algorithm to the second session key value;
obtain a first-ordered value from the second ordering of potential backup servers; and
process the second request based on a determination that the first-ordered value from the second ordering of potential backup servers is associated with the first backup server.
7. The method of claim 1 , wherein the first primary server is a third backup server.
8. The method of claim 1 , wherein making the first determination comprises:
making a third determination, by the first backup server, that session state information associated with the first session key value is not stored in a session table on the first backup server.
9. The method of claim 1 , further comprising:
receiving, by the first backup server, a second request comprising a second session key value and a second primary server identifier;
making a fifth determination, by the first backup server, that the second request is associated with a second primary server based on the second primary server identifier, wherein the second primary server is one of the plurality of servers;
making a sixth determination, by the first backup server, that the second backup server is operational; and
sending the second request to the second backup server based on the sixth determination.
10. The non-transitory machine-readable medium of claim 3 , wherein the first primary server is a third backup server.
11. The non-transitory machine-readable medium of claim 3 , wherein making the first determination a first comprises:
making a third determination, by the first backup server, that session state information associated with the first session key value is not stored in a session table on the first backup server.
12. The non-transitory machine-readable medium of claim 3 , the method further comprising:
receiving, by the first backup server, a second request comprising a second session key value and a second primary server identifier;
making a fifth determination, by the first backup server, that the second request is associated with a second primary server based on the second primary server identifier, wherein the second primary server is one of the plurality of servers;
making a sixth determination, by the first backup server, that the second backup server is operational; and
sending the second request to the second backup server based on the sixth determination.
13. The apparatus of claim 5 , wherein the first primary server is a third backup server.
14. The apparatus of claim 5 , wherein making the first determination comprises:
making a third determination, by the first backup server, that session state information associated with the first session key value is not stored in a session table on the first backup server.
15. The apparatus of claim 5 , wherein the first backup server is further configured to:
receive a second request comprising a second session key value and a second primary server identifier;
make a fifth determination, by the first backup server, that the second request is associated with a second primary server based on the second primary server identifier, wherein the second primary server is one of the plurality of servers;
make a sixth determination, that the second backup server is operational; and send the second request to the second backup server based on the sixth determination.