High availability

Tessera supports deploying more than one instance sharing the same database.

By placing the instances behind a load balancer, downtime can be limited during maintenance operations, achieving high availability (HA).

Servers

Tessera exposes multiple interfaces for connectivity which can be configured in the serverConfigs in the configuration file. To enable high availability for the node, set each interface to use the load balancer's address for its serverAddress, and its own URL or IP for the bindingAddress, as shown in the following example.

Server configuration

"serverConfigs":[
    {
        "app": "ENCLAVE",
        // Defines us using a remote enclave, leave out if using built-in enclave
        "serverAddress": "http://localhost:9081",
        "communicationType": "REST"
    },
    {
        "app": "ThirdParty",
        "serverAddress": "http://LOAD_BALANCER_URL:9080",
        // Specify a bind to an internal IP while advertising an external IP using serverAddress.
        "bindingAddress": "http://OWN_URL:9080",
        "communicationType": "REST",
        ...
    },
    {
        "app": "Q2T",
        "serverAddress": "http://LOAD_BALANCER_URL:9101",
        // Specify a bind to an internal IP while advertising an external IP using serverAddress.
        "bindingAddress": "http://OWN_URL:9101",
        "communicationType" : "REST",
        ...
    },
    {
        "app": "P2P",
        "serverAddress": "http://LOAD_BALANCER_URL:9000",
        // Specify a bind to an internal IP while advertising an external IP using serverAddress.
        "bindingAddress": "http://OWN_URL:9000",
        "communicationType": "REST",
        ...
    }
],
...

Load balancer configuration

The load balancer must expose both client and node interfaces.

When configuring for high availability, configure the nodes in the Tessera cluster (Tessera A and Tessera B in the previous diagram) with the same set of keys and advertise the load balancer address.

events { }

http {
    upstream tessera_tp_9080 {
        server tessera_1:9080 max_fails=3 fail_timeout=5s;
        server tessera_2:9080 max_fails=3 fail_timeout=5s;
    }

    upstream tessera_q2t_9101 {
        server tessera_1:9101 max_fails=3 fail_timeout=5s;
        server tessera_2:9101 max_fails=3 fail_timeout=5s;
    }

    upstream tessera_p2p_9000 {
        server tessera_1:9000 max_fails=3 fail_timeout=5s;
        server tessera_2:9000 max_fails=3 fail_timeout=5s;
    }

    server {
        listen 9080;

        location / {
            proxy_pass http://tessera_tp_9080;
            health_check port=9000 uri=/upcheck;
        }
    }

    server {
        listen 9101;

        location / {
            proxy_pass http://tessera_q2t_9101;
            health_check port=9000 uri=/upcheck;
        }
    }

    server {
        listen 9000;

        location / {
            proxy_pass http://tessera_p2p_9000;
            health_check port=9000 uri=/upcheck;
        }
    }
}

The configuration defines two upstreams, tessera_tp_9080 and tessera_q2t_9101, both of which define health checks, max_fails=3 fail_timeout=5s.

The health checks help Nginx balance traffic among upstream servers.

Database

The last piece to configure in high availability is the database. Set the jdbc endpoint in the same configuration file. We strongly recommend using an SQL database also configured for HA independently. If using a cloud-based database, consider using AWS RDS, Azure Postgresql, or equivalent.