fail_over

This is a virtual resolver designed to fail over between (real) resolvers.

Rules for result selection:

  1. The success result of the primary resolver will always be used before the timeout.

  2. The first success result either from the primary or the standby resolver will be used after the timeout.

  3. If no success result, the last error one will be used.

The following common keys are supported:

primary

required, type: string

Set the primary resolver to use.

standby

required, type: string

Set the standby resolver to use.

fallback_delay

optional, type:

Set the timeout for primary lookup.

default: 100ms

negative_ttl

optional, type: u32

Time-to-Live (TTL) for negative caching of failed DNS lookups.

default: 30

retry_empty_record

optional, type: bool

Set if we should do a fallback query if the first answer contains no IP address.

default: false

Added in version 1.7.13.