Interface DERPMapCache

tailcat.go:109–119

DERPMapCache is an option for [ConnInfo.Expand] and [FetchDERPMap] that caches fetched DERP maps. Without one, a process-wide in-memory cache is used; provide an implementation (like the tailcat CLI's on-disk one) to persist across processes. Implementations just store bytes; the freshness policy li

// (the ETag is opaque to us), and a stored map of any age is used as
// a fallback if the fetch fails or times out.
type DERPMapCache interface {
	// Get returns the previously stored DERP map response for url:
	// its raw JSON, the server's ETag (or ""), and when it was
	// stored. It returns ok == false if nothing usable is stored.
	Get(url string) (data []byte, etag string, storedAt time.Time, ok bool)

	// Put stores the DERP map response for url, replacing any prior
	// entry and marking it stored as of now. An empty etag means the
	// server sent none.
	Put(url string, data []byte, etag string) error
}

// derpMapCacheMaxAge is how old a cached DERP map may be and still be
// used without revalidating with the server.