DnsOptions

class DnsOptions

A class configuring the host resolution functionality. Note that while we refer to DNS as the most common mechanism being used for brevity, settings apply to other means of resolving hostnames like hosts file resolution.

Hostnames can be resolved in two ways - either by using the system resolver (using getaddrinfo provided by system libraries), or by using a custom resolver which is tailored for the HTTP networking stack.

The built-in stack provides several advantages over using the global system resolver:

• It has been tailored to the needs of the HTTP networking stack, particularly speed and stability.
• getaddrinfo is a blocking call which requires dedicating worker threads and makes cancellation impossible (we need to abandon the thread until the call completes)
• The getaddrinfo interface gives no insight into the root cause of failures
• struct addrinfo provides no TTL (Time To Live) of the returned addresses. This restricts flexibility of handling caching (e.g. allowing the use of stale DNS records) and requires us to either rely on OS DNS caches, or be extremely conservative with the TTL.

Most configuration in this class is only applicable if the built-in DNS resolver is used.

Summary

Constants

static val DNS_OPTION_DISABLED: Int

Value: 2

static val DNS_OPTION_ENABLED: Int

Value: 1

static val DNS_OPTION_UNSPECIFIED: Int

Value: 0

Public methods

fun getPersistHostCache(): Int

fun getPersistHostCachePeriod(): Duration?

fun getPreestablishConnectionsToStaleDnsResults(): Int

fun getStaleDns(): Int

fun getStaleDnsOptions(): DnsOptions.StaleDnsOptions?

fun getUseHttpStackDnsResolver(): Int