L7 Load Balancing with the MapR Data Access Gateway

You can use nginx for L7 load balancing of clients that use the MapR Data Access Gateway. This topic describes how to install, configure, and run nginx, and how to set your client connection string to connect to the load balancing service.

Determine the server where you want to run the load balancing service. The server must be reachable by the clients using the Data Access Gateway. It also must be able to connect to the Data Access Gateway.

Install the nginx service on the server you have identified:
CentOS
```
sudo yum install nginx
```
Ubuntu
```
sudo apt install nginx
```
SUSE
```
sudo zypper install nginx
```
Configure the nginx service by setting the following parameters in the configuration file at /etc/nginx/nginx.conf:
1. In the http section, create an upstream block with one server entry for each Data Access Gateway server:
```
upstream <upstream_name> {
    server <DAG_server_host1>:<DAG_server_port1>;
    server <DAG_server_host2>:<DAG_server_port2>;
    ...
    server <DAG_server_hostN>:<DAG_server_portN>
    }
```
2. Create (or modify) the server block, depending on whether your MapR cluster is secure or nonsecure:
  Secure MapR Cluster
  For a secure cluster, you must specify the following SSL parameters:
  
  Listen port and protocol
  
  Path to the SSL certificate
  
  Path to the SSL key
  
  Path to the file containing the SSL password
  
  server { listen 80 ssl http2; listen [::]:80; ssl_certificate <path_to_certificate>; ssl_certificate_key <path_to_key>; ssl_password_file <path_to_password_file>; access_log logs/access.log main; location / { grpc_pass grpcs://<upstream_name>; } }
  Nonsecure MapR Cluster
  server { listen 80 http2; listen [::]:80; access_log logs/access.log main; location / { grpc_pass grpc://<upstream_name>; } }
  The <upstream_name> is the parameter you specified in Step 2a.
Restart the nginx service:
```
sudo service nginx restart 
```

Setting Your Client Connection String

Assume you have the following nginx configuration settings and you have installed nginx on node1.cluster.com:

Secure MapR Cluster

user mapr;
worker_processes 1;
error_log /var/log/nginx/error.log warn;
pid /var/run/nginx.pid;
events {
    worker_connections  1024;
}
http {
    log_format  main  '$remote_addr - $remote_user [$time_local] "$request"'
                      '$status $body_bytes_sent "$http_referer"'
                      '"$http_user_agent"';
    upstream servers {
        server node1.cluster.com:5678;
        server node2.cluster.com:5678;
    }
    server {
        listen 80 ssl http2;
        listen [::]:80;

        ssl_certificate /opt/mapr/conf/ssl_keystore.pem;
        ssl_certificate_key /opt/mapr/conf/ssl_keystore.pem;
        ssl_password_file /root/passwd;

        access_log logs/access.log main;

        location / {
            grpc_pass grpcs://servers;
        }
    }
}

You can use the following client connection string with this sample configuration:

node1.cluster.com:80?auth=basic;user=mapr;password=mapr;ssl=true;sslCA=/opt/mapr/conf/ssl_truststore.pem;sslTargetNameOverride=node1.cluster.com

Nonsecure MapR Cluster

user mapr;
worker_processes 1;
error_log /var/log/nginx/error.log warn;
pid /var/run/nginx.pid;
events {
    worker_connections  1024;
}
http {
    log_format  main  '$remote_addr - $remote_user [$time_local] "$request"'
                      '$status $body_bytes_sent "$http_referer"'
                      '"$http_user_agent"';
    upstream servers {
        server node1.cluster.com:5678;
        server node2.cluster.com:5678;
    }
    server {
        listen 80 http2;
        listen [::]:80;

        access_log logs/access.log main;

        location / {
            grpc_pass grpc://servers;
        }
    }
}

You can use the following client connection string with this sample configuration:

node1.cluster.com:80?auth=basic;user=mapr;password=mapr;ssl=false