go ipfs namesys

namesys

NameSystem interface

// Namesys represents a cohesive name publishing and resolving system.
//
// Publishing a name is the process of establishing a mapping, a key-value
// pair, according to naming rules and databases.
//
// Resolving a name is the process of looking up the value associated with the
// key (name).
type NameSystem interface {
	Resolver
	Publisher
}
           

namesys支援多種域名系統的解析，現支援ipns，dns和proquint。

// mpns (a multi-protocol NameSystem) implements generic IPFS naming.
//
// Uses several Resolvers:
// (a) IPFS routing naming: SFS-like PKI names.
// (b) dns domains: resolves using links in DNS TXT records
// (c) proquints: interprets string as the raw byte data.
//
// It can only publish to: (a) IPFS routing naming.
//
type mpns struct {
	dnsResolver, proquintResolver, ipnsResolver resolver
	ipnsPublisher                               Publisher

	staticMap map[string]path.Path
	cache     *lru.Cache
}
           

Publish

Publisher interface

// Publisher is an object capable of publishing particular names.
type Publisher interface {

	// Publish establishes a name-value mapping.
	// TODO make this not PrivKey specific.
	Publish(ctx context.Context, name ci.PrivKey, value path.Path) error

	// TODO: to be replaced by a more generic 'PublishWithValidity' type
	// call once the records spec is implemented
	PublishWithEOL(ctx context.Context, name ci.PrivKey, value path.Path, eol time.Time) error
}
           

IpnsPublisher

通過routing調用dht的put_value，将ipns記錄publish。

// IpnsPublisher is capable of publishing and resolving names to the IPFS
// routing system.
type IpnsPublisher struct {
	routing routing.ValueStore
	ds      ds.Datastore

	// Used to ensure we assign IPNS records *sequential* sequence numbers.
	mu sync.Mutex
}

func (p *IpnsPublisher) updateRecord(ctx context.Context, k ci.PrivKey, value path.Path, eol time.Time) (*pb.IpnsEntry, error) {
	id, err := peer.IDFromPrivateKey(k)
	if err != nil {
		return nil, err
	}

	p.mu.Lock()
	defer p.mu.Unlock()

	// get previous records sequence number
	rec, err := p.GetPublished(ctx, id, true)
	if err != nil {
		return nil, err
	}

	seqno := rec.GetSequence() // returns 0 if rec is nil
	if rec != nil && value != path.Path(rec.GetValue()) {
		// Don't bother incrementing the sequence number unless the
		// value changes.
		seqno++
	}

	// Create record
	entry, err := ipns.Create(k, []byte(value), seqno, eol)
	if err != nil {
		return nil, err
	}

	// Set the TTL
	// TODO: Make this less hacky.
	ttl, ok := checkCtxTTL(ctx)
	if ok {
		entry.Ttl = proto.Uint64(uint64(ttl.Nanoseconds()))
	}

	data, err := proto.Marshal(entry)
	if err != nil {
		return nil, err
	}

	// Put the new record.
	key := IpnsDsKey(id)
	if err := p.ds.Put(key, data); err != nil {
		return nil, err
	}
	if err := p.ds.Sync(key); err != nil {
		return nil, err
	}
	return entry, nil
}

// PublishWithEOL is a temporary stand in for the ipns records implementation
// see here for more details: https://github.com/ipfs/specs/tree/master/records
func (p *IpnsPublisher) PublishWithEOL(ctx context.Context, k ci.PrivKey, value path.Path, eol time.Time) error {
	record, err := p.updateRecord(ctx, k, value, eol)
	if err != nil {
		return err
	}

	return PutRecordToRouting(ctx, p.routing, k.GetPublic(), record)
}
           

Republish

每條ipns記錄的有效期預設為24h，預設每4h啟動1次Republish

// DefaultRebroadcastInterval is the default interval at which we rebroadcast IPNS records
var DefaultRebroadcastInterval = time.Hour * 4

// DefaultRecordLifetime is the default lifetime for IPNS records
const DefaultRecordLifetime = time.Hour * 24

type Republisher struct {
	ns   namesys.Publisher
	ds   ds.Datastore
	self ic.PrivKey
	ks   keystore.Keystore

	Interval time.Duration

	// how long records that are republished should be valid for
	RecordLifetime time.Duration
}

// NewRepublisher creates a new Republisher
func NewRepublisher(ns namesys.Publisher, ds ds.Datastore, self ic.PrivKey, ks keystore.Keystore) *Republisher {
	return &Republisher{
		ns:             ns,
		ds:             ds,
		self:           self,
		ks:             ks,
		Interval:       DefaultRebroadcastInterval,
		RecordLifetime: DefaultRecordLifetime,
	}
}

func (rp *Republisher) Run(proc goprocess.Process) {
	timer := time.NewTimer(InitialRebroadcastDelay)
	defer timer.Stop()
	if rp.Interval < InitialRebroadcastDelay {
		timer.Reset(rp.Interval)
	}

	for {
		select {
		case <-timer.C:
			timer.Reset(rp.Interval)
			err := rp.republishEntries(proc)
			if err != nil {
				log.Info("republisher failed to republish: ", err)
				if FailureRetryInterval < rp.Interval {
					timer.Reset(FailureRetryInterval)
				}
			}
		case <-proc.Closing():
			return
		}
	}
}
           

Resolve

Resolver interface

// Resolver is an object capable of resolving names.
type Resolver interface {

	// Resolve performs a recursive lookup, returning the dereferenced
	// path.  For example, if ipfs.io has a DNS TXT record pointing to
	//   /ipns/QmatmE9msSfkKxoffpHwNLNKgwZG8eT9Bud6YoPab52vpy
	// and there is a DHT IPNS entry for
	//   QmatmE9msSfkKxoffpHwNLNKgwZG8eT9Bud6YoPab52vpy
	//   -> /ipfs/Qmcqtw8FfrVSBaRmbWwHxt3AuySBhJLcvmFYi3Lbc4xnwj
	// then
	//   Resolve(ctx, "/ipns/ipfs.io")
	// will resolve both names, returning
	//   /ipfs/Qmcqtw8FfrVSBaRmbWwHxt3AuySBhJLcvmFYi3Lbc4xnwj
	//
	// There is a default depth-limit to avoid infinite recursion.  Most
	// users will be fine with this default limit, but if you need to
	// adjust the limit you can specify it as an option.
	Resolve(ctx context.Context, name string, options ...opts.ResolveOpt) (value path.Path, err error)

	// ResolveAsync performs recursive name lookup, like Resolve, but it returns
	// entries as they are discovered in the DHT. Each returned result is guaranteed
	// to be "better" (which usually means newer) than the previous one.
	ResolveAsync(ctx context.Context, name string, options ...opts.ResolveOpt) <-chan Result
}
           

IpnsResolver

通過routing調用dht的get_value，擷取到ipns記錄，再将其解析。

// IpnsResolver implements NSResolver for the main IPFS SFS-like naming
type IpnsResolver struct {
	routing routing.ValueStore
}