coredns/middleware/erratic

erratic

erratic is a middleware useful for testing client behavior. It returns a static response to all queries, but the responses can be delayed by a random amount of time or dropped all together, i.e. no answer at all.

The erratic middleware will respond to every A or AAAA query. For any other type it will return a SERVFAIL response. The reply for A will return 192.0.2.53 (see RFC 5737), for AAAA it returns 2001:DB8::53 (see RFC 3849).

Syntax

erratic {
    drop [AMOUNT]
    delay [AMOUNT [DURATION]]
}

• drop: drop 1 per AMOUNT of the queries, the default is 2.
• delay: delay 1 per AMOUNT of queries for DURATION, the default for AMOUNT is 2 and the default for DURATION is 100ms.

Examples

.:53 {
    erratic {
        drop 3
    }
}

Or even shorter if the defaults suits you. Note this only drops queries, it does not delay them.

. {
    erratic
}

Delay 1 in 3 queries for 50ms, but also drop 1 in 2.

. {
    erratic {
        delay 3 50ms
    }
}

To stop dropping you'll need to explicitally set that to 0:

. {
    erratic {
        delay 3 50ms
        drop 0
    }
}