Setting up high availability

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Scenario

Several servers on which the Connection Service (CS) is running can be connected to form a so-called cluster using the Active Directory component Domain Name System (DNS). This means that only one IP address is required for communication with the participating CS servers.

 

If one of the CS servers involved fails, the client computers (or the ThinPrint Hub) automatically connect to one of the remaining CS servers and the printing server – in the example scenario, the central print server – also sends its print jobs to one of the remaining CS servers. Only the print jobs currently being processed at the time of the failure will be lost.

Preparing the CS servers

  • The CS servers – here the nodes – are located in a specific subnet (with static IP addresses). MCast via UDP is used. For this, each node must be configured as follows:
    • The parameter MCastNodeInterface specifies the IP address of the network interface used for communication.
    • The parameter MCastNodeIfBits specifies the number of least significant bits of the network address. For example, to specify the (IPv4) Class-C network 192.168.1.11/24 (IP address + subnet mask), MCastNodeInterface=192.168.1.11 and MCastNodeIfBits=8. However, a Class-C network would be unnecessarily large. The subnet should be as small as possible to avoid unnecessary traffic. The best way to do this is if the IP addresses of the CS servers are as close together as possible.

A practicable example would therefore be:
MCastNodeInterface=192.168.1.11 and MCastNodeIfBits=3, that is, a subnet with 8 IP addresses (from 192.168.1.8 to 192.168.1.15).

Proceed as follows:

  • Open the configuration console of the Connection Service (Start→ ThinPrint Connection Service→ Connection Service Configuration)
  • Change the TCP port for server connections to the Connection Service from 4000 to 4002 (see screenshot).

  • Open the Windows Registry.
  • Navigate there to hkey_local_machine\software\thinprint\tpconnect.

  • Add the following values here:
Value Type Dates
MCastNodeIfBits REG_DWORD 3
(or a value that includes all IP addresses of the CS servers)
MCastNodeInterface REG_SZ <CS server’s IP adress>
MCastNodePort REG_DWORD 4013
ReplicatorNodePort REG_DWORD 4012
ServerNodePort REG_DWORD 4014

The result is shown in the following screenshot.

  • Restart the Windows service ThinPrint Connection Service – e. g. using Restart Service in the configuration console (see above).

Setup in DNS (using Windows as an example)

  • Add an entry in the DNS for each IP address of the CS servers.
    Always use the same name, e. g. CS-Cluster:

  • Reduce the value for TTL to e. g. 30 seconds. To do this, select View→ Advanced in the DNS configuration and then open the properties of the relevant DNS entries. The smaller the TTL, the more often a new address is obtained.

  • If you place the Connection Service in a DMZ, you should also create an alias name to connect the external and internal addresses.

Preparing the ThinPrint Engines

  • Add a Connection Service Port in the ThinPrint Port Manager. Enter the address of the Connection Service as the address of the cluster, i. e. CS-Cluster. The TCP port must match the Connection Service set up for Server, here 4002.

Setup on one of the CS servers

The setting made here is automatically synchronized with all other CS Servers.

  • In the configuration console add all client IDs (client-id) and authentication keys (auth-key) of the ThinPrint Clients, here e. g. 66 and 666.

Alternatively, you can also do this on the command line with:

tpconnect -add <client-id>:<auth-key>

Preparing the ThinPrint Clients

  • On the workstations (or ThinPrint Hubs) you also specify the cluster address of the Connection Service in the ThinPrint Client, here CS-Cluster, the above mentioned TCP port (here 4001) as well as the values Client ID (here 66) and Authentication key (here 666) configured in the Connection Service.
    This is also possible by remote configuration.

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