upak_loader.go

package libkb

import (
	"errors"
	"fmt"
	"time"

	lru "github.com/hashicorp/golang-lru"
	"github.com/keybase/client/go/protocol/keybase1"
	"golang.org/x/net/context"
)

// UPAK Loader is a loader for UserPlusKeysV2AllIncarnations. It's a thin user object that is
// almost as good for many purposes, but can be safely copied and serialized.
type UPAKLoader interface {
	ClearMemory()
	Load(arg LoadUserArg) (ret *keybase1.UserPlusAllKeys, user *User, err error)
	LoadV2(arg LoadUserArg) (ret *keybase1.UserPlusKeysV2AllIncarnations, user *User, err error)
	CheckKIDForUID(ctx context.Context, uid keybase1.UID, kid keybase1.KID) (found bool, revokedAt *keybase1.KeybaseTime, deleted bool, err error)
	LoadUserPlusKeys(ctx context.Context, uid keybase1.UID, pollForKID keybase1.KID) (keybase1.UserPlusKeys, error)
	LoadKeyV2(ctx context.Context, uid keybase1.UID, kid keybase1.KID) (*keybase1.UserPlusKeysV2, *keybase1.PublicKeyV2NaCl, map[keybase1.Seqno]keybase1.LinkID, error)
	Invalidate(ctx context.Context, uid keybase1.UID)
	LoadDeviceKey(ctx context.Context, uid keybase1.UID, deviceID keybase1.DeviceID) (upak *keybase1.UserPlusAllKeys, deviceKey *keybase1.PublicKey, revoked *keybase1.RevokedKey, err error)
	LookupUsername(ctx context.Context, uid keybase1.UID) (NormalizedUsername, error)
	LookupUsernameUPAK(ctx context.Context, uid keybase1.UID) (NormalizedUsername, error)
	LookupUID(ctx context.Context, un NormalizedUsername) (keybase1.UID, error)
	LookupUsernameAndDevice(ctx context.Context, uid keybase1.UID, did keybase1.DeviceID) (username NormalizedUsername, deviceName string, deviceType string, err error)
	ListFollowedUIDs(uid keybase1.UID) ([]keybase1.UID, error)
	PutUserToCache(ctx context.Context, user *User) error
}

// CachedUPAKLoader is a UPAKLoader implementation that can cache results both
// in memory and on disk.
type CachedUPAKLoader struct {
	Contextified
	cache          *lru.Cache
	locktab        LockTable
	Freshness      time.Duration
	noCache        bool
	TestDeadlocker func()
}

// NewCachedUPAKLoader constructs a new CachedUPAKLoader
func NewCachedUPAKLoader(g *GlobalContext, f time.Duration) *CachedUPAKLoader {
	c, err := lru.New(g.Env.GetUPAKCacheSize())
	if err != nil {
		panic(fmt.Sprintf("could not create lru cache (size = %d)", g.Env.GetUPAKCacheSize()))
	}
	return &CachedUPAKLoader{
		Contextified: NewContextified(g),
		Freshness:    f,
		cache:        c,
		noCache:      false,
	}
}

// NewUncachedUPAKLoader creates a UPAK loader that doesn't do any caching.
// It uses the implementation of CachedUPAKLoader but disables all caching.
func NewUncachedUPAKLoader(g *GlobalContext) UPAKLoader {
	return &CachedUPAKLoader{
		Contextified: NewContextified(g),
		Freshness:    time.Duration(0),
		noCache:      true,
	}
}

func culDBKeyV1(uid keybase1.UID) DbKey {
	return DbKeyUID(DBUserPlusAllKeysV1, uid)
}

func culDBKeyVersioned(version int, uid keybase1.UID) DbKey {
	return DbKey{
		Typ: DBUserPlusKeysVersioned,
		Key: fmt.Sprintf("%d:%s", version, uid.String()),
	}
}

func culDBKeyV2(uid keybase1.UID) DbKey {
	return culDBKeyVersioned(2, uid)
}

func (u *CachedUPAKLoader) ClearMemory() {
	if u.noCache {
		return
	}
	u.purgeMemCache()
}

const UPK2MinorVersionCurrent = keybase1.UPK2MinorVersion_V5

func (u *CachedUPAKLoader) getCachedUPAK(ctx context.Context, uid keybase1.UID, info *CachedUserLoadInfo) (*keybase1.UserPlusKeysV2AllIncarnations, bool) {

	if u.Freshness == time.Duration(0) || u.noCache {
		u.G().VDL.CLogf(ctx, VLog0, "| cache miss since cache disabled")
		return nil, false
	}

	upak := u.getMemCache(ctx, uid)

	// Try loading from persistent storage if we missed memory cache.
	if upak != nil {
		// Note that below we check the minor version and then discard the cached object if it's
		// stale. But no need in memory, since we'll never have the old version in memory.
		u.G().VDL.CLogf(ctx, VLog0, "| hit memory cache")
		if info != nil {
			info.InCache = true
		}
	} else {
		var tmp keybase1.UserPlusKeysV2AllIncarnations
		found, err := u.G().LocalDb.GetInto(&tmp, culDBKeyV2(uid))
		if err != nil {
			u.G().Log.CWarningf(ctx, "trouble accessing UserPlusKeysV2AllIncarnations cache: %s", err)
		} else if !found {
			u.G().VDL.CLogf(ctx, VLog0, "| missed disk cache")
		} else if tmp.MinorVersion != UPK2MinorVersionCurrent {
			u.G().VDL.CLogf(ctx, VLog0, "| found old minor version %d, but wanted %d; will overwrite with fresh UPAK", tmp.MinorVersion, UPK2MinorVersionCurrent)
		} else {
			u.G().VDL.CLogf(ctx, VLog0, "| hit disk cache")
			upak = &tmp
			if info != nil {
				info.InDiskCache = true
			}
			// Insert disk object into memory.
			u.putMemCache(ctx, uid, tmp)
		}
	}

	if upak == nil {
		u.G().VDL.CLogf(ctx, VLog0, "| missed cache")
		return nil, true
	}
	diff := u.G().Clock().Now().Sub(keybase1.FromTime(upak.Uvv.CachedAt))
	fresh := (diff <= u.Freshness)
	if fresh {
		u.G().VDL.CLogf(ctx, VLog0, "| cache hit was fresh (cached %s ago)", diff)
	} else {
		u.G().VDL.CLogf(ctx, VLog0, "| cache hit was stale (by %s)", u.Freshness-diff)
	}
	return upak, fresh
}

type CachedUserLoadInfo struct {
	InCache      bool
	InDiskCache  bool
	TimedOut     bool
	StaleVersion bool
	LoadedLeaf   bool
	LoadedUser   bool
}

func (u *CachedUPAKLoader) Disable() {
	u.Freshness = time.Duration(0)
}

func culDebug(u keybase1.UID) string {
	return fmt.Sprintf("CachedUPAKLoader#Load(%s)", u)
}

func (u *CachedUPAKLoader) extractDeviceKey(upak keybase1.UserPlusAllKeys, deviceID keybase1.DeviceID) (deviceKey *keybase1.PublicKey, revoked *keybase1.RevokedKey, err error) {
	for i := range upak.Base.RevokedDeviceKeys {
		r := &upak.Base.RevokedDeviceKeys[i]
		pk := &r.Key
		if pk.DeviceID == deviceID {
			deviceKey = pk
			revoked = r
		}
	}
	for i := range upak.Base.DeviceKeys {
		pk := &upak.Base.DeviceKeys[i]
		if pk.DeviceID == deviceID {
			deviceKey = pk
			revoked = nil
		}
	}

	if deviceKey == nil {
		dkey := fmt.Sprintf("%s:%s", upak.Base.Uid, deviceID)
		return nil, nil, fmt.Errorf("device not found for %s", dkey)
	}

	return deviceKey, revoked, nil
}

func (u *CachedUPAKLoader) putUPAKToCache(ctx context.Context, obj *keybase1.UserPlusKeysV2AllIncarnations) error {

	if u.noCache {
		u.G().VDL.CLogf(ctx, VLog0, "| no cache enabled, so not putting UPAK")
		return nil
	}

	uid := obj.Current.Uid
	u.G().VDL.CLogf(ctx, VLog0, "| Caching UPAK for %s", uid)

	stale := false
	existing := u.getMemCache(ctx, uid)
	if existing != nil {
		if obj.IsOlderThan(*existing) {
			stale = true
		} else {
			u.putMemCache(ctx, uid, *obj)
		}
	} else {
		u.putMemCache(ctx, uid, *obj)
	}

	if stale {
		u.G().VDL.CLogf(ctx, VLog0, "| CachedUpakLoader#putUPAKToCache: Refusing to overwrite with stale object")
		return errors.New("stale object rejected")
	}

	err := u.G().LocalDb.PutObj(culDBKeyV2(uid), nil, *obj)
	if err != nil {
		u.G().Log.CWarningf(ctx, "Error in writing UPAK for %s: %s", uid, err)
	}
	u.deleteV1UPAK(uid)
	return err
}

func (u *CachedUPAKLoader) PutUserToCache(ctx context.Context, user *User) error {

	lock := u.locktab.AcquireOnName(ctx, u.G(), user.GetUID().String())
	defer lock.Release(ctx)
	upak, err := user.ExportToUPKV2AllIncarnations()
	if err != nil {
		return err
	}
	upak.Uvv.CachedAt = keybase1.ToTime(u.G().Clock().Now())
	err = u.putUPAKToCache(ctx, upak)
	return err
}

// loadWithInfo loads a user from the CachedUPAKLoader object. The 'info'
// object contains information about how the request was handled, but otherwise,
// this method behaves like (and implements) the public CachedUPAKLoader#Load
// method below. If `accessor` is nil, then a deep copy of the UPAK is returned.
// In some cases, that deep copy can be expensive, so as for users who have lots of
// followees. So if you provide accessor, the UPAK won't be deep-copied, but you'll
// be able to access it from inside the accessor with exclusion.
func (u *CachedUPAKLoader) loadWithInfo(arg LoadUserArg, info *CachedUserLoadInfo, accessor func(k *keybase1.UserPlusKeysV2AllIncarnations) error, shouldReturnFullUser bool) (ret *keybase1.UserPlusKeysV2AllIncarnations, user *User, err error) {

	// Shorthand
	g := u.G()

	// Add a LU= tax to this context, for all subsequent debugging
	ctx := arg.WithLogTag()

	defer g.CVTrace(ctx, VLog0, culDebug(arg.uid), func() error { return err })()

	if arg.uid.IsNil() {
		if len(arg.name) == 0 {
			return nil, nil, errors.New("need a UID or username to load UPAK from loader")
		}
		// Modifies the load arg, setting a UID
		arg.uid, err = u.LookupUID(ctx, NewNormalizedUsername(arg.name))
		if err != nil {
			return nil, nil, err
		}
	}

	lock := u.locktab.AcquireOnName(ctx, g, arg.uid.String())

	defer func() {
		lock.Release(ctx)

		if !shouldReturnFullUser {
			user = nil
		}
		if user != nil && err == nil {
			// Update the full-self cacher after the lock is released, to avoid
			// any circular locking.
			if fs := u.G().GetFullSelfer(); fs != nil && arg.self {
				fs.Update(ctx, user)
			}
		}
	}()

	returnUPAK := func(upak *keybase1.UserPlusKeysV2AllIncarnations, needCopy bool) (*keybase1.UserPlusKeysV2AllIncarnations, *User, error) {
		if accessor != nil {
			err := accessor(upak)
			if err != nil {
				return nil, nil, err
			}
			return nil, user, err
		}
		if needCopy {
			tmp := upak.DeepCopy()
			upak = &tmp
		}
		return upak, user, nil
	}

	var upak *keybase1.UserPlusKeysV2AllIncarnations
	var fresh bool

	if !arg.forceReload {
		upak, fresh = u.getCachedUPAK(ctx, arg.uid, info)
	}
	if arg.forcePoll {
		g.VDL.CLogf(ctx, VLog0, "%s: force-poll required us to repoll (fresh=%v)", culDebug(arg.uid), fresh)
		fresh = false
	}

	if upak != nil {
		g.VDL.CLogf(ctx, VLog0, "%s: cache-hit; fresh=%v", culDebug(arg.uid), fresh)
		if fresh || arg.staleOK {
			return returnUPAK(upak, true)
		}
		if info != nil {
			info.TimedOut = true
		}

		var sigHints *SigHints
		var leaf *MerkleUserLeaf

		sigHints, leaf, err = lookupSigHintsAndMerkleLeaf(ctx, u.G(), arg.uid, true)
		if err != nil {
			return nil, nil, err
		}

		if info != nil {
			info.LoadedLeaf = true
		}

		if leaf.eldest == "" {
			g.VDL.CLogf(ctx, VLog0, "%s: cache-hit; but user is nuked, evicting", culDebug(arg.uid))

			// Our cached user turned out to be in reset state (without
			// current sigchain), remove from cache, and then fall
			// through. LoadUser shall return an error, which we will
			// return to the caller.
			u.removeMemCache(ctx, arg.uid)

			err := u.G().LocalDb.Delete(culDBKeyV2(arg.uid))
			if err != nil {
				u.G().Log.Warning("Failed to remove %s from disk cache: %s", arg.uid, err)
			}
			u.deleteV1UPAK(arg.uid)
		} else if leaf.public != nil && leaf.public.Seqno == keybase1.Seqno(upak.Uvv.SigChain) {
			g.VDL.CLogf(ctx, VLog0, "%s: cache-hit; fresh after poll", culDebug(arg.uid))

			upak.Uvv.CachedAt = keybase1.ToTime(g.Clock().Now())
			// This is only necessary to update the levelDB representation,
			// since the previous line updates the in-memory cache satisfactorially.
			if err := u.putUPAKToCache(ctx, upak); err != nil {
				u.G().Log.CDebugf(ctx, "continuing past error in putUPAKToCache: %s", err)
			}

			return returnUPAK(upak, true)
		}

		if info != nil {
			info.StaleVersion = true
		}
		arg.sigHints = sigHints
		arg.merkleLeaf = leaf
	} else if arg.cachedOnly {
		return nil, nil, UserNotFoundError{UID: arg.uid, Msg: "no cached user found"}
	}

	g.VDL.CLogf(ctx, VLog0, "%s: LoadUser", culDebug(arg.uid))
	user, err = LoadUser(arg)
	if info != nil {
		info.LoadedUser = true
	}

	if user != nil {
		// The `err` value might be non-nil above! Don't overwrite it.
		var exportErr error
		ret, exportErr = user.ExportToUPKV2AllIncarnations()
		if exportErr != nil {
			return nil, nil, exportErr
		}
		ret.Uvv.CachedAt = keybase1.ToTime(g.Clock().Now())
	}

	// In some cases, it's OK to have a user object and an error. This comes up in
	// Identify2 when identifying users who don't have a sigchain. Note that we'll never
	// hit the cache in this case (for now...)
	if err != nil {
		return ret, user, err
	}

	if user == nil {
		return nil, nil, UserNotFoundError{UID: arg.uid, Msg: "LoadUser failed"}
	}

	if err := u.putUPAKToCache(ctx, ret); err != nil {
		u.G().Log.CDebugf(ctx, "continuing past error in putUPAKToCache: %s", err)
	}

	if u.TestDeadlocker != nil {
		u.TestDeadlocker()
	}

	return returnUPAK(ret, false)
}

// Load a UserPlusKeysV2AllIncarnations from the local cache, falls back to
// LoadUser, and cache the user. Can only perform lookups by UID. Will return a
// non-nil UserPlusKeysV2AllIncarnations, or a non-nil error, but never both
// non-nil, nor never both nil. If we had to do a full LoadUser as part of the
// request, it's returned too. Convert to UserPlusAllKeys on the way out, for
// backwards compatibility.
func (u *CachedUPAKLoader) Load(arg LoadUserArg) (*keybase1.UserPlusAllKeys, *User, error) {
	ret, user, err := u.loadWithInfo(arg, nil, nil, true)

	// NOTE -- it's OK to return an error and a user, since certain code paths
	// want both (see note in loadWithInfo).
	var converted *keybase1.UserPlusAllKeys
	if ret != nil {
		tmp := keybase1.UPAKFromUPKV2AI(*ret)
		converted = &tmp
	}

	return converted, user, err
}

// Load a UserPlusKeysV2AllIncarnations from the local cache, falls back to
// LoadUser, and cache the user. Can only perform lookups by UID. Will return a
// non-nil UserPlusKeysV2AllIncarnations, or a non-nil error, but never both
// non-nil, nor never both nil. If we had to do a full LoadUser as part of the
// request, it's returned too.
func (u *CachedUPAKLoader) LoadV2(arg LoadUserArg) (*keybase1.UserPlusKeysV2AllIncarnations, *User, error) {
	return u.loadWithInfo(arg, nil, nil, true)
}

func (u *CachedUPAKLoader) CheckKIDForUID(ctx context.Context, uid keybase1.UID, kid keybase1.KID) (found bool, revokedAt *keybase1.KeybaseTime, deleted bool, err error) {

	var info CachedUserLoadInfo
	larg := NewLoadUserByUIDArg(ctx, u.G(), uid).WithPublicKeyOptional()
	upak, _, err := u.loadWithInfo(larg, &info, nil, false)

	if err != nil {
		return false, nil, false, err
	}
	found, revokedAt, deleted = CheckKID(upak, kid)
	if found || info.LoadedLeaf || info.LoadedUser {
		return found, revokedAt, deleted, nil
	}
	larg = larg.WithForceReload()
	upak, _, err = u.loadWithInfo(larg, nil, nil, false)
	if err != nil {
		return false, nil, false, err
	}
	found, revokedAt, deleted = CheckKID(upak, kid)
	return found, revokedAt, deleted, nil
}

func (u *CachedUPAKLoader) LoadUserPlusKeys(ctx context.Context, uid keybase1.UID, pollForKID keybase1.KID) (keybase1.UserPlusKeys, error) {
	var up keybase1.UserPlusKeys
	if uid.IsNil() {
		return up, NoUIDError{}
	}

	arg := NewLoadUserArg(u.G()).WithUID(uid).WithPublicKeyOptional().WithNetContext(ctx)
	forcePollValues := []bool{false, true}

	for _, fp := range forcePollValues {

		arg = arg.WithForcePoll(fp)

		upak, _, err := u.Load(arg)
		if err != nil {
			return up, err
		}
		if upak == nil {
			return up, fmt.Errorf("Nil user, nil error from LoadUser")
		}
		up = upak.Base
		if pollForKID.IsNil() || up.FindKID(pollForKID) != nil {
			break
		}

	}
	return up, nil
}

// LoadKeyV2 looks through all incarnations for the user and returns the incarnation with the given
// KID, as well as the Key data associated with that KID. It picks the latest such
// incarnation if there are multiple.
func (u *CachedUPAKLoader) LoadKeyV2(ctx context.Context, uid keybase1.UID, kid keybase1.KID) (ret *keybase1.UserPlusKeysV2, key *keybase1.PublicKeyV2NaCl, linkMap map[keybase1.Seqno]keybase1.LinkID, err error) {
	defer u.G().CVTrace(ctx, VLog0, fmt.Sprintf("LoadKeyV2 uid:%s,kid:%s", uid, kid), func() error { return err })()
	if uid.IsNil() {
		return nil, nil, nil, NoUIDError{}
	}

	argBase := NewLoadUserArg(u.G()).WithUID(uid).WithPublicKeyOptional().WithNetContext(ctx)

	// Make the retry mechanism increasingly aggresive. See CORE-8851.
	// It should be that a ForcePoll is good enough, but in some rare cases,
	// people have cached values for previous pre-reset user incarnations that
	// were incorrect. So clobber over that if it comes to it.
	attempts := []LoadUserArg{
		argBase,
		argBase.WithForcePoll(true),
		argBase.WithForceReload(),
	}

	for _, arg := range attempts {

		u.G().VDL.CLogf(ctx, VLog0, "| reloading with arg: %s", arg.String())

		upak, _, err := u.LoadV2(arg)
		if err != nil {
			return nil, nil, nil, err
		}
		if upak == nil {
			return nil, nil, nil, fmt.Errorf("Nil user, nil error from LoadUser")
		}

		linkMap = upak.SeqnoLinkIDs
		ret, key = upak.FindKID(kid)
		if key != nil {
			u.G().VDL.CLogf(ctx, VLog0, "- found kid in UPAK: %v", ret.Uid)
			return ret, key, linkMap, nil
		}
		ret = nil
	}

	return nil, nil, nil, NotFoundError{Msg: "Not found: User"}
}

func (u *CachedUPAKLoader) Invalidate(ctx context.Context, uid keybase1.UID) {

	u.G().VDL.CLogf(ctx, VLog0, "| CachedUPAKLoader#Invalidate(%s)", uid)

	if u.noCache {
		return
	}

	lock := u.locktab.AcquireOnName(ctx, u.G(), uid.String())
	defer lock.Release(ctx)

	u.removeMemCache(ctx, uid)

	err := u.G().LocalDb.Delete(culDBKeyV2(uid))
	if err != nil {
		u.G().Log.CWarningf(ctx, "Failed to remove %s from disk cache: %s", uid, err)
	}
	u.deleteV1UPAK(uid)
}

// Load the PublicKey for a user's device from the local cache, falling back to LoadUser, and cache the user.
// If the user exists but the device doesn't, will force a load in case the device is very new.
func (u *CachedUPAKLoader) LoadDeviceKey(ctx context.Context, uid keybase1.UID, deviceID keybase1.DeviceID) (upakv1 *keybase1.UserPlusAllKeys, deviceKey *keybase1.PublicKey, revoked *keybase1.RevokedKey, err error) {
	var info CachedUserLoadInfo
	larg := NewLoadUserByUIDArg(ctx, u.G(), uid)
	upakV2, _, err := u.loadWithInfo(larg, &info, nil, false)
	if err != nil {
		return nil, nil, nil, err
	}
	upakV1 := keybase1.UPAKFromUPKV2AI(*upakV2)

	deviceKey, revoked, err = u.extractDeviceKey(upakV1, deviceID)
	if err == nil {
		// Early success, return
		return &upakV1, deviceKey, revoked, err
	}

	// Try again with a forced load in case the device is very new.
	larg = larg.WithForcePoll(true)
	upakV2, _, err = u.loadWithInfo(larg, nil, nil, false)
	if err != nil {
		return nil, nil, nil, err
	}
	upakV1 = keybase1.UPAKFromUPKV2AI(*upakV2)

	deviceKey, revoked, err = u.extractDeviceKey(upakV1, deviceID)
	return &upakV1, deviceKey, revoked, err
}

// LookupUsername uses the UIDMapper to find a username for uid.
func (u *CachedUPAKLoader) LookupUsername(ctx context.Context, uid keybase1.UID) (NormalizedUsername, error) {
	var empty NormalizedUsername
	uids := []keybase1.UID{uid}
	namePkgs, err := u.G().UIDMapper.MapUIDsToUsernamePackages(ctx, u.G(), uids, 0, 0, false)
	if err != nil {
		return empty, err
	}
	if len(namePkgs) == 0 {
		return empty, UserNotFoundError{UID: uid, Msg: "in CachedUPAKLoader"}
	}

	if u.TestDeadlocker != nil {
		u.TestDeadlocker()
	}

	return namePkgs[0].NormalizedUsername, nil
}

// LookupUsernameUPAK uses the upak loader to find a username for uid.
func (u *CachedUPAKLoader) LookupUsernameUPAK(ctx context.Context, uid keybase1.UID) (NormalizedUsername, error) {
	var info CachedUserLoadInfo
	arg := NewLoadUserByUIDArg(ctx, u.G(), uid).WithStaleOK(true).WithPublicKeyOptional()
	var ret NormalizedUsername
	_, _, err := u.loadWithInfo(arg, &info, func(upak *keybase1.UserPlusKeysV2AllIncarnations) error {
		if upak == nil {
			return UserNotFoundError{UID: uid, Msg: "in CachedUPAKLoader"}
		}
		ret = NewNormalizedUsername(upak.Current.Username)
		return nil
	}, false)
	return ret, err
}

// LookupUID is a verified map of username -> UID. IT calls into the resolver, which gives un untrusted
// UID, but verifies with the UPAK loader that the mapping UID -> username is correct.
func (u *CachedUPAKLoader) LookupUID(ctx context.Context, un NormalizedUsername) (keybase1.UID, error) {
	rres := u.G().Resolver.Resolve(un.String())
	if err := rres.GetError(); err != nil {
		return keybase1.UID(""), err
	}
	un2, err := u.LookupUsername(ctx, rres.GetUID())
	if err != nil {
		return keybase1.UID(""), err
	}
	if !un.Eq(un2) {
		u.G().Log.CWarningf(ctx, "Unexpected mismatched usernames (uid=%s): %s != %s", rres.GetUID(), un.String(), un2.String())
		return keybase1.UID(""), NewBadUsernameError(un.String())
	}
	return rres.GetUID(), nil
}

func (u *CachedUPAKLoader) lookupUsernameAndDeviceWithInfo(ctx context.Context, uid keybase1.UID, did keybase1.DeviceID, info *CachedUserLoadInfo) (username NormalizedUsername, deviceName string, deviceType string, err error) {
	arg := NewLoadUserByUIDArg(ctx, u.G(), uid)

	// First iteration through, say it's OK to load a stale user. Note that the
	// mappings of UID to Username and DeviceID to DeviceName are immutable, so this
	// data can never be stale. However, our user might be out of date and lack the
	// mappings, so the second time through, we request a fresh object.
	staleOK := []bool{true, false}
	for _, b := range staleOK {
		arg = arg.WithStaleOK(b)
		found := false
		u.loadWithInfo(arg, info, func(upak *keybase1.UserPlusKeysV2AllIncarnations) error {
			if upak == nil {
				return nil
			}
			if pk := upak.FindDevice(did); pk != nil {
				username = NewNormalizedUsername(upak.Current.Username)
				deviceName = pk.DeviceDescription
				deviceType = pk.DeviceType
				found = true
			}
			return nil
		}, false)
		if found {
			return username, deviceName, deviceType, nil
		}
	}
	if err == nil {
		err = NotFoundError{fmt.Sprintf("UID/Device pair %s/%s not found", uid, did)}
	}
	return NormalizedUsername(""), "", "", err
}

func (u *CachedUPAKLoader) LookupUsernameAndDevice(ctx context.Context, uid keybase1.UID, did keybase1.DeviceID) (username NormalizedUsername, deviceName string, deviceType string, err error) {
	return u.lookupUsernameAndDeviceWithInfo(ctx, uid, did, nil)
}

func (u *CachedUPAKLoader) ListFollowedUIDs(uid keybase1.UID) ([]keybase1.UID, error) {
	arg := NewLoadUserByUIDArg(nil, u.G(), uid)
	upak, _, err := u.Load(arg)
	if err != nil {
		return nil, err
	}
	var ret []keybase1.UID
	for _, t := range upak.RemoteTracks {
		ret = append(ret, t.Uid)
	}
	return ret, nil
}

// v1 UPAKs are all legacy and need to be gradually cleaned from cache.
func (u *CachedUPAKLoader) deleteV1UPAK(uid keybase1.UID) {
	err := u.G().LocalDb.Delete(culDBKeyV1(uid))
	if err != nil {
		u.G().Log.Warning("Failed to remove %s v1 object from disk cache: %s", uid, err)
	}
}

func (u *CachedUPAKLoader) getMemCache(ctx context.Context, uid keybase1.UID) *keybase1.UserPlusKeysV2AllIncarnations {
	val, ok := u.cache.Get(uid)
	if !ok {
		return nil
	}

	upak, ok := val.(keybase1.UserPlusKeysV2AllIncarnations)
	if !ok {
		u.G().Log.CWarningf(ctx, "invalid type in upak cache: %T", val)
		return nil
	}

	return &upak
}

func (u *CachedUPAKLoader) putMemCache(ctx context.Context, uid keybase1.UID, upak keybase1.UserPlusKeysV2AllIncarnations) {
	u.cache.Add(uid, upak)
}

func (u *CachedUPAKLoader) removeMemCache(ctx context.Context, uid keybase1.UID) {
	u.cache.Remove(uid)
}

func (u *CachedUPAKLoader) purgeMemCache() {
	u.cache.Purge()
}