Physical security system having multiple server nodes

1. A method for interacting with a unattended display in a physical security system that comprises a plurality of server nodes, the method comprising:

(a) sending, from one of the server nodes (“second node”) communicative with the unattended display to another of the server nodes (“first node”) that is communicative with a client display, view state data indicative of a view displayed on the unattended display; and

wherein none of the server nodes is a centralized gateway server; and

wherein the first and second nodes and at least another of the plurality of server nodes comprise a server cluster, the first and second nodes comprise at least part of a group of server nodes in the cluster to which the second node can send the view state data in a totally ordered manner to all other server nodes in the group, and sending the view state data comprises the second node sending the data in a totally ordered manner to all the other server nodes in the group; and

(b) displaying, on the client display, at least a portion of the view displayed on the unattended display.

2. The method of claim 1 further comprising:

(a) sending, from the first node to the second node, a message to change the view of the unattended display; and

(b) updating the unattended display according to the message sent from the first node to the second node.

3. The method of claim 2 wherein, the first and second nodes comprise at least part of a group of server nodes in the cluster to which the first node can send the message to change the state of the unattended display in a totally ordered manner to all other server nodes in the group, and the first node sends the message to change the state of the unattended display in a totally ordered manner to all the other server nodes in the group.

4. The method of claim 1 further comprising sending from the second node to the first node a notification that the view of the unattended display is available to be controlled.

5. The method of claim 4 wherein sending the notification comprises disseminating the notification to all the server nodes in the server cluster using a gossip protocol that performs data exchanges between pairs of the server nodes in the cluster.

6. The method of claim 1 further comprising prior to sending the state of the unattended display to the client display, accessing, using the second node, a node identifier identifying the first node, wherein the first and second nodes comprise at least part of a server cluster and wherein the node identifier comprises at least part of cluster membership information identifying all and accessible by all server nodes in the server cluster.

7. The method of claim 6 wherein the cluster membership information comprises:

(a) a node identifier uniquely identifying each of the server nodes in the server cluster; and

(b) a cluster identifier uniquely identifying the server cluster to which the server nodes belong.

8. The method of claim 7 wherein each of the server nodes in the server cluster persistently stores its own version of the cluster membership information locally.

9. A physical security system, comprising:

(a) a client display;

(b) an unattended display; and

(c) a plurality of server nodes, wherein one of the server nodes (“first node”) is communicative with the client display and another of the server nodes (“second node”) is communicative with the unattended display,

wherein the second node is configured to send to the first node view state data indicative of a view displayed on the unattended display and the first node is configured to display, on the client display, at least a portion of the view displayed on the unattended display;

wherein none of the server nodes is a centralized gateway server; and

wherein the first and second nodes and at least another of the plurality of server nodes comprise a server cluster, the first and second nodes comprise at least part of a group of server nodes in the cluster to which the second node can send the view state data in a totally ordered manner to all other server nodes in the group, and wherein the second node is further configured to send the view state data in a totally ordered manner to all the other server nodes in the group.

10. A non-transitory computer readable medium having encoded thereon statements and instructions to cause a processor to perform a method for interacting with a unattended display in a physical security system that comprises a plurality of server nodes, the method comprising:

(a) sending, from one of the server nodes (“second node”) communicative with the unattended display to another of the server nodes (“first node”) that is communicative with a client display, view state data indicative of a view displayed on the unattended display;

wherein none of the server nodes is a centralized gateway server; and

wherein the first and second nodes and at least another of the plurality of server nodes comprise a server cluster, the first and second nodes comprise at least part of a group of server nodes in the cluster to which the second node can send the view state data in a totally ordered manner to all other server nodes in the group, and sending the view state data comprises the second node sending the data in a totally ordered manner to all the other server nodes in the group; and

(b) displaying, on the client display, at least a portion of the view displayed on the unattended display.

11. The system of claim 9 wherein:

(a) the first node is further configured to send to the second node a message to change the view of the unattended display; and

(b) the second node is further configured to update the unattended display according to the message sent from the first node to the second node.

12. The system of claim 11 wherein the first and second nodes comprise at least part of a group of server nodes in the cluster to which the first node can send the message to change the state of the unattended display in a totally ordered manner to all other server nodes in the group, and the first node is further configured to send the message to change the state of the unattended display in a totally ordered manner to all the other server nodes in the group.

13. The system of claim 9 wherein the second node is further configured to send to the first node a notification that the view of the unattended display is available to be controlled.

14. The system of claim 13 wherein sending the notification comprises disseminating the notification to all the server nodes in the server cluster using a gossip protocol that performs data exchanges between pairs of the server nodes in the cluster.

15. The system of claim 9 wherein the second node is further configured to, prior to sending the state of the unattended display to the client display, access, a node identifier identifying the first node, wherein the first and second nodes comprise at least part of a server cluster and wherein the node identifier comprises at least part of cluster membership information identifying all and accessible by all server nodes in the server cluster.

16. The system of claim 15 wherein the cluster membership information comprises:

(a) a node identifier uniquely identifying each of the server nodes in the server cluster; and

(b) a cluster identifier uniquely identifying the server cluster to which the server nodes belong.

17. The system of claim 16 wherein each of the server nodes in the server cluster persistently stores its own version of the cluster membership information locally.

18. The computer readable medium of claim 10 wherein the method further comprises:

(a) sending, from the first node to the second node, a message to change the view of the unattended display; and

(b) updating the unattended display according to the message sent from the first node to the second node, and

the first and second nodes comprise at least part of a group of server nodes in the cluster to which the first node can send the message to change the state of the unattended display in a totally ordered manner to all other server nodes in the group, and the first node sends the message to change the state of the unattended display in a totally ordered manner to all the other server nodes in the group.

19. The computer readable medium of claim 10 wherein the method further comprises sending from the second node to the first node a notification that the view of the unattended display is available to be controlled, and

wherein sending the notification comprises disseminating the notification to all the server nodes in the server cluster using a gossip protocol that performs data exchanges between pairs of the server nodes in the cluster.

20. The computer readable medium of claim 10 wherein the method further comprises prior to sending the state of the unattended display to the client display, accessing, using the second node, a node identifier identifying the first node, wherein the first and second nodes comprise at least part of a server cluster and wherein the node identifier comprises at least part of cluster membership information identifying all and accessible by all server nodes in the server cluster.

21. The computer readable medium of claim 20 wherein the cluster membership information comprises:

(a) a node identifier uniquely identifying each of the server nodes in the server cluster; and

(b) a cluster identifier uniquely identifying the server cluster to which the server nodes belong, and

wherein each of the server nodes in the server cluster persistently stores its own version of the cluster membership information locally.