Backup servers in Nginx - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Nginx Backup Server Fallback Behavior

Given the following nginx upstream configuration, what will happen when the primary server is down?

Nginx

upstream backend {
    server primary.example.com max_fails=3 fail_timeout=30s;
    server backup.example.com backup;
}

server {
    location / {
        proxy_pass http://backend;
    }
}

A Requests will be sent to backup.example.com first, then primary.example.com if backup fails.

B Requests will be sent only to primary.example.com regardless of its status.

C Requests will be sent to backup.example.com only if primary.example.com fails 3 times within 30 seconds.

D Requests will be load balanced equally between primary.example.com and backup.example.com.

💡 Hint

Think about how the 'backup' keyword affects server selection in nginx upstream blocks.

The 'backup' server is used only when all non-backup servers are considered down. Here, primary.example.com is the main server and backup.example.com is used only after primary fails 3 times within 30 seconds.

❓ Configuration

intermediate

Configuring Multiple Backup Servers in Nginx

Which nginx upstream configuration correctly sets up one primary server and two backup servers?

A

upstream backend {
    server primary.example.com;
    server backup1.example.com backup;
    server backup2.example.com backup;
}

B

upstream backend {
    server primary.example.com;
    server backup1.example.com backup;
    server backup2.example.com;
}

C

upstream backend {
    server primary.example.com backup;
    server backup1.example.com;
    server backup2.example.com backup;
}

D

upstream backend {
    server primary.example.com;
    server backup1.example.com;
    server backup2.example.com backup;
}

💡 Hint

Backup servers must be marked with the 'backup' keyword to be used only when primary fails.

Only servers marked with 'backup' are used as backups. Option A correctly marks both backup1 and backup2 as backup servers.

❓ Troubleshoot

advanced

Troubleshooting Backup Server Not Used

You configured a backup server in nginx, but requests never go to it even when the primary server is down. What is the most likely cause?

A The backup server is not marked with the 'backup' keyword in the upstream block.

B The backup server is marked with 'backup' but has a higher weight than the primary server.

C The proxy_pass directive is missing in the server block.

D The primary server has 'max_fails' set too high, so nginx never marks it as down.

💡 Hint

Consider how nginx decides a server is down and when it switches to backup.

If 'max_fails' is set too high, nginx does not mark the primary server as down quickly, so it never switches to the backup server.

🔀 Workflow

advanced

Backup Server Failover Workflow

What is the correct sequence of events when nginx fails over from a primary to a backup server?

A 1,2,3,4

B 2,1,3,4

C 1,3,2,4

D 3,1,2,4

💡 Hint

Think about how nginx detects failure and switches servers step-by-step.

Nginx first detects failure (1), marks server down (2), switches to backup (3), and keeps checking primary (4).

✅ Best Practice

expert

Best Practice for Backup Server Health Checks

Which configuration snippet best ensures nginx properly detects backup server health before sending traffic to it?

A

upstream backend {
    server primary.example.com max_fails=3 fail_timeout=10s;
    server backup.example.com backup;
}

B

upstream backend {
    server primary.example.com max_fails=3 fail_timeout=10s;
    server backup.example.com backup max_fails=1 fail_timeout=5s;
}

C

upstream backend {
    server primary.example.com max_fails=3 fail_timeout=10s;
    server backup.example.com backup max_fails=10 fail_timeout=60s;
}

D

upstream backend {
    server primary.example.com max_fails=3 fail_timeout=10s;
    server backup.example.com max_fails=1 fail_timeout=5s;
}

💡 Hint

Backup servers should have health check parameters to avoid sending traffic to unhealthy backups.

Option B sets lower max_fails and fail_timeout for the backup server, allowing nginx to detect backup failures quickly before sending traffic.