dnscache

Documentation

Overview

Package dnscache provides a thread-safe local single-flight DNS cache for LookupHost. The cache has a maximum size and a time-to-live (TTL) for each DNS entry. Duplicate LookupHost calls for the same host will wait for the first lookup to complete and return the same value.

Index

• type Cache
  • func New(resolver Resolver, size int, ttl time.Duration) *Cache
  • func (c *Cache) DialContext(ctx context.Context, network, address string) (net.Conn, error)
  • func (c *Cache) Len() int
  • func (c *Cache) LookupHost(ctx context.Context, host string) ([]string, error)
  • func (c *Cache) Remove(host string)
  • func (c *Cache) Reset()
• type Resolver

Types

type Cache

type Cache struct {
	// contains filtered or unexported fields
}

Cache represents the single-flight DNS cache.

func New

func New(resolver Resolver, size int, ttl time.Duration) *Cache

New creates a new single-flight DNS cache of the specified size and TTL. If the resolver parameter is nil, a default net.Resolver will be used. The size parameter determines the maximum number of DNS entries that can be cached (min = 1). If the size is less than or equal to zero, the cache will have a default size of 1. The ttl parameter specifies the time-to-live for each cached DNS entry.

func (*Cache) DialContext

func (c *Cache) DialContext(ctx context.Context, network, address string) (net.Conn, error)

DialContext dials the network and address specified by the parameters. It resolves the host from the address using the LookupHost method of the Resolver. It then attempts to establish a connection to each resolved IP address until a successful connection is made. If all connection attempts fail, it returns an error. The function returns the established net.Conn and any error encountered during the process. This function can replace the DialContext in http.Transport.

func (*Cache) Len

func (c *Cache) Len() int

Len returns the number of items in the cache.

func (*Cache) LookupHost

func (c *Cache) LookupHost(ctx context.Context, host string) ([]string, error)

LookupHost performs a DNS lookup for the given host. Duplicate lookup calls for the same host will wait for the first lookup to complete (single-flight). It also handles the case where the cache entry is removed or updated during the wait. The function returns the cached value if available; otherwise, it performs a new lookup. If the external lookup call is successful, it updates the cache with the newly obtained value.

func (*Cache) Remove

func (c *Cache) Remove(host string)

Remove removes the cache entry for the specified host.

func (*Cache) Reset

func (c *Cache) Reset()

Reset clears the whole cache.

type Resolver

type Resolver interface {
	LookupHost(ctx context.Context, host string) (addrs []string, err error)
}

Resolver is a net.Resolver interface for DNS lookups.