Question: Is it possible to change the DNS resolution timeout in the configuration file?

[jburgoos]

Description

For our system, we are using the DNS resolver provided by APISIX. To do this, we configured the following in the configuration file:

apisix:
  node_listen:
    - ip: X.X.X.X
      port: 10080
  enable_ipv6: false
  dns_resolver:
    - "x.x.x.x"
    - "y.y.y.y"
  dns_resolver_valid: 30
  resolver_timeout: 1

With this configuration, we expected the DNS query timeout to be 1 second. However, it seems that regardless of the value we set, we still observe a DNS timeout of 2 seconds.

It appears that this setting configures the NGINX instance associated with the service, but the DNS resolution is performed earlier within APISIX itself.

While investigating the root cause, we found that the DNS resolution timeout seems to be hardcoded in the source code at the highlighted line (client.lua):

After testing by changing that value (from 2000 to 1000) and running systemctl reload apisix, we observed that the DNS resolution timeout then becomes 1 second, which is what we expected.

Is there any way to configure this timeout without modifying the source code? If not, is there any plan to make these values configurable in the future?

Environment

• APISIX version (run apisix version): 3.8.0
• Operating system (run uname -a): debian 11
• OpenResty / Nginx version (run openresty -V or nginx -V): openresty/1.21.4.2

[Baoyuantop]

APISIX employs two independent DNS resolution mechanisms with different timeout configurations that do not interfere with each other:

The Nginx-level resolver (controlled by the resolver_timeout configuration) is primarily responsible for scenarios where Nginx itself needs to resolve domain names. This mechanism only affects Nginx's native resolver directives, used for internal Nginx domain name resolution (e.g., when using proxy_pass to resolve a domain name to an upstream). The timeout is controlled by resolver_timeout.

The APISIX Lua-level DNS client (hardcoded 2000ms) is primarily responsible for all scenarios where APISIX needs to actively resolve domain names to IP addresses during request processing. The timeout is hardcoded in the code.

Could you describe your use case? Why is it necessary to modify this configuration?