at-container-registry/pkg/atproto/directory.go

package atproto

import (
	"context"
	"net"
	"net/http"
	"sync"
	"time"

	"github.com/bluesky-social/indigo/atproto/identity"
	"github.com/earthboundkid/versioninfo/v2"
)

var (
	// Shared identity directory instance (singleton)
	sharedDirectory identity.Directory
	directoryOnce   sync.Once
)

// GetDirectory returns a shared identity.Directory instance with a 24-hour cache TTL.
// This is based on indigo's DefaultDirectory() with event-driven cache invalidation.
//
// Cache entries are invalidated via Jetstream events (identity changes, account status)
// which allows for a longer TTL while maintaining freshness. The Purge() method is called
// when identity or account events are received, ensuring the cache reflects real-time changes.
//
// Using a shared instance ensures all identity lookups across the application
// use the same cache, which is more memory-efficient and provides better cache hit rates.
func GetDirectory() identity.Directory {
	directoryOnce.Do(func() {
		base := identity.BaseDirectory{
			PLCURL: identity.DefaultPLCURL,
			HTTPClient: http.Client{
				Timeout: time.Second * 10,
				Transport: &http.Transport{
					// would want this around 100ms for services doing lots of handle resolution. Impacts PLC connections as well, but not too bad.
					IdleConnTimeout: time.Millisecond * 1000,
					MaxIdleConns:    100,
				},
			},
			Resolver: net.Resolver{
				Dial: func(ctx context.Context, network, address string) (net.Conn, error) {
					d := net.Dialer{Timeout: time.Second * 3}
					return d.DialContext(ctx, network, address)
				},
			},
			TryAuthoritativeDNS: true,
			// primary Bluesky PDS instance only supports HTTP resolution method
			SkipDNSDomainSuffixes: []string{".bsky.social"},
			UserAgent:             "indigo-identity/" + versioninfo.Short(),
		}
		// Cache configuration:
		// - capacity: 250,000 entries
		// - hitTTL: 24 hours (event-driven invalidation via Jetstream provides freshness)
		// - errTTL: 2 minutes
		// - invalidHandleTTL: 5 minutes
		cached := identity.NewCacheDirectory(&base, 250_000, time.Hour*24, time.Minute*2, time.Minute*5)
		sharedDirectory = &cached
	})
	return sharedDirectory
}