Method and apparatus for enhanced client persistence in multi-site GSLB deployments
Some embodiments provide a method that, at a first domain name system (DNS) cluster of a set of DNS clusters, receives a DNS request from a client. The first DNS cluster identifies, based on an identifier of the client in the DNS request, a home DNS cluster of the client. The method forwards the DNS request to the home DNS cluster. The home DNS cluster supplies a DNS response to the client. Identifying the home DNS cluster, in some embodiments, includes performing a hash on the identifier of the client. Supplying the DNS response, in some embodiments, includes receiving a virtual IP (VIP) address associated with one of a plurality of sets of application servers to the client and providing the received VIP address to the client in the DNS response.
1. A method comprising:
at a first domain name system (DNS) cluster of a set of DNS clusters:
receiving, from a client, a DNS request for a domain name;
performing a hashing operation to produce a hash value from an identifier that identifies the client;
using the hash value to identify a home DNS cluster for the client; and
forwarding the DNS request to the home DNS cluster, wherein the home DNS cluster supplies, to the client, a DNS response that includes a virtual Internet Protocol (VIP) address associated with the domain name.
2. The method of claim 1 , wherein
the VIP address is associated with one of a plurality of sets of application servers.
3. The method of claim 2 , wherein the supplied VIP address is a VIP address of a load balancer or a network address translation (NAT) engine that:
assigns, to the client, an IP address of an application server in the set of application servers associated with the VIP address; and
creates a record that associates the IP address with the client.
4. The method of claim 2 further comprising creating, in a persistence table of the home DNS cluster, an entry associating the VIP address with the client.
5. The method of claim 4 , wherein the DNS request is a first DNS request from the client, the domain name is a first domain name, the VIP address is a first VIP address, and the DNS response is a first DNS response, the method further comprising:
at a second DNS cluster of the set of DNS clusters:
receiving, from the client, a second DNS request for a second domain name;
performing the hashing operation to produce the hash value from the identifier that identifies the client;
using the hash value to identify the home DNS cluster for the client; and
forwarding the second DNS request to the home DNS cluster, wherein the home DNS cluster supplies, to the client, a second DNS response that includes a second VIP address.
6. The method of claim 5 , wherein supplying the second DNS response comprises finding, based on the client identifier, the entry in the persistence table of the home DNS cluster.
7. The method of claim 6 , wherein finding the entry in the persistence table comprises applying a counting bloom filter and bloom collision hash to the identifier.
8. The method of claim 4 , wherein the home DNS cluster is a home DNS cluster to a plurality of clients, wherein the persistence table includes a persistence table entry for each client in the plurality of clients, the method further comprising:
assigning a set of backup home DNS clusters to the home DNS cluster;
backing up the persistence table of the home DNS cluster with each DNS cluster in the set of backup home DNS clusters.
9. The method of claim 8 , wherein each DNS cluster in the set of DNS clusters is a home DNS cluster to a plurality of clients, and each DNS cluster maintains a persistence table for that DNS cluster's clients and clients of a set of DNS clusters that that DNS cluster is assigned as a backup home DNS cluster for.
10. The method of claim 2 , wherein the VIP address is received from a load balancer that selects the VIP address from a set of VIP addresses, each VIP address associated with a set of application servers.
11. A non-transitory machine readable medium storing a program that when executed by one or more processing units responds to a domain name system (DNS) request, the program comprising sets of instructions for:
at a first DNS cluster of a set of DNS clusters:
receiving, from a client, a DNS request for a domain name;
performing a hashing operation to produce a hash value from an identifier that identifies the client;
using the hash value to identify a home DNS cluster for the client; and
forwarding the DNS request to the home DNS cluster, wherein the home DNS cluster supplies, to the client, a DNS response that includes a virtual Internet Protocol (VIP) address associated with the domain name.
12. The non-transitory machine readable medium of claim 11 , wherein
the VIP address is associated with one of a plurality of sets of application servers.
13. The non-transitory machine readable medium of claim 12 , wherein the supplied VIP address is a VIP address of a load balancer or a network address translation (NAT) engine that:
assigns, to the client, an IP address of an application server in the set of application servers associated with the VIP address; and
creates a record that associates the IP address with the client.
14. The non-transitory machine readable medium of claim 12 , the program further comprising sets of instructions for creating, in a persistence table of the home DNS cluster, an entry associating the VIP address with the client.
15. The non-transitory machine readable medium of claim 13 , wherein the DNS request is a first DNS request from the client, the domain name is a first domain name, the VIP address is a first VIP address, and the DNS response is a first DNS response, the program further comprising sets of instructions for:
at a second DNS cluster of the set of DNS clusters:
receiving, from the client, a second DNS request for a second domain name;
performing the hashing operation to produce the hash value from the identifier that identifies the client;
using the hash value to identify the home DNS cluster for the client; and
forwarding the second DNS request to the home DNS cluster, wherein the home DNS cluster supplies, to the client, a second DNS response that includes a second VIP address.
16. The non-transitory machine readable medium of claim 14 , wherein supplying the second DNS response comprises finding, based on the client identifier, the entry in the persistence table of the home DNS cluster.
17. The non-transitory machine readable medium of claim 15 , wherein finding the entry in the persistence table comprises applying a counting bloom filter and bloom collision hash to the identifier.
18. The non-transitory machine readable medium of claim 13 , wherein the home DNS cluster is a home DNS cluster to a plurality of clients, wherein the persistence table includes a persistence table entry for each client in the plurality of clients, the program further comprising sets of instructions for:
assigning a set of backup home DNS clusters to the home DNS cluster; and
backing up the persistence table of the home DNS cluster with each DNS cluster in the set of backup home DNS clusters.