import (
"errors"
"net/http"
+ "sort"
"sync"
- "sync/atomic"
"time"
"git.arvados.org/arvados.git/sdk/go/arvados"
"git.arvados.org/arvados.git/sdk/go/arvadosclient"
"git.arvados.org/arvados.git/sdk/go/keepclient"
- lru "github.com/hashicorp/golang-lru"
"github.com/prometheus/client_golang/prometheus"
"github.com/sirupsen/logrus"
)
logger logrus.FieldLogger
registry *prometheus.Registry
metrics cacheMetrics
- sessions *lru.TwoQueueCache
+ sessions map[string]*cachedSession
setupOnce sync.Once
+ mtx sync.Mutex
chPruneSessions chan struct{}
}
}
type cachedSession struct {
+ cache *cache
expire time.Time
- fs atomic.Value
client *arvados.Client
arvadosclient *arvadosclient.ArvadosClient
keepclient *keepclient.KeepClient
- user atomic.Value
+
+ // Each session uses a system of three mutexes (plus the
+ // cache-wide mutex) to enable the following semantics:
+ //
+ // - There are never multiple sessions in use for a given
+ // token.
+ //
+ // - If the cached in-memory filesystems/user records are
+ // older than the configured cache TTL when a request starts,
+ // the request will use new ones.
+ //
+ // - Unused sessions are garbage-collected.
+ //
+ // In particular, when it is necessary to reset a session's
+ // filesystem/user record (to save memory or respect the
+ // configured cache TTL), any operations that are already
+ // using the existing filesystem/user record are allowed to
+ // finish before the new filesystem is constructed.
+ //
+ // The locks must be acquired in the following order:
+ // cache.mtx, session.mtx, session.refresh, session.inuse.
+
+ // mtx is RLocked while session is not safe to evict from
+ // cache -- i.e., a checkout() has decided to use it, and its
+ // caller is not finished with it. When locking or rlocking
+ // this mtx, the cache mtx MUST already be held.
+ //
+ // This mutex enables pruneSessions to detect when it is safe
+ // to completely remove the session entry from the cache.
+ mtx sync.RWMutex
+ // refresh must be locked in order to read or write the
+ // fs/user/userLoaded/lastuse fields. This mutex enables
+ // GetSession and pruneSessions to remove/replace fs and user
+ // values safely.
+ refresh sync.Mutex
+ // inuse must be RLocked while the session is in use by a
+ // caller. This mutex enables pruneSessions() to wait for all
+ // existing usage to finish by calling inuse.Lock().
+ inuse sync.RWMutex
+
+ fs arvados.CustomFileSystem
+ user arvados.User
+ userLoaded bool
+ lastuse time.Time
+}
+
+func (sess *cachedSession) Release() {
+ sess.inuse.RUnlock()
+ sess.mtx.RUnlock()
+ select {
+ case sess.cache.chPruneSessions <- struct{}{}:
+ default:
+ }
}
func (c *cache) setup() {
var err error
- c.sessions, err = lru.New2Q(c.cluster.Collections.WebDAVCache.MaxSessions)
+ c.sessions = map[string]*cachedSession{}
if err != nil {
panic(err)
}
}
func (c *cache) updateGauges() {
- c.metrics.collectionBytes.Set(float64(c.collectionBytes()))
- c.metrics.sessionEntries.Set(float64(c.sessions.Len()))
+ n, size := c.sessionsSize()
+ c.metrics.collectionBytes.Set(float64(size))
+ c.metrics.sessionEntries.Set(float64(n))
}
var selectPDH = map[string]interface{}{
"select": []string{"portable_data_hash"},
}
-// ResetSession unloads any potentially stale state. Should be called
-// after write operations, so subsequent reads don't return stale
-// data.
-func (c *cache) ResetSession(token string) {
- c.setupOnce.Do(c.setup)
- c.sessions.Remove(token)
-}
-
-// Get a long-lived CustomFileSystem suitable for doing a read operation
-// with the given token.
-func (c *cache) GetSession(token string) (arvados.CustomFileSystem, *cachedSession, *arvados.User, error) {
+func (c *cache) checkout(token string) (*cachedSession, error) {
c.setupOnce.Do(c.setup)
- now := time.Now()
- ent, _ := c.sessions.Get(token)
- sess, _ := ent.(*cachedSession)
- expired := false
+ c.mtx.Lock()
+ defer c.mtx.Unlock()
+ sess := c.sessions[token]
if sess == nil {
- c.metrics.sessionMisses.Inc()
- sess = &cachedSession{
- expire: now.Add(c.cluster.Collections.WebDAVCache.TTL.Duration()),
- }
- var err error
- sess.client, err = arvados.NewClientFromConfig(c.cluster)
+ client, err := arvados.NewClientFromConfig(c.cluster)
if err != nil {
- return nil, nil, nil, err
+ return nil, err
}
- sess.client.AuthToken = token
- sess.arvadosclient, err = arvadosclient.New(sess.client)
+ client.AuthToken = token
+ client.Timeout = time.Minute
+ client.Logger = c.logger
+ // A non-empty origin header tells controller to
+ // prioritize our traffic as interactive, which is
+ // true most of the time.
+ origin := c.cluster.Services.WebDAVDownload.ExternalURL
+ client.SendHeader = http.Header{"Origin": {origin.Scheme + "://" + origin.Host}}
+ arvadosclient, err := arvadosclient.New(client)
if err != nil {
- return nil, nil, nil, err
+ return nil, err
}
- sess.keepclient = keepclient.New(sess.arvadosclient)
- c.sessions.Add(token, sess)
- } else if sess.expire.Before(now) {
- c.metrics.sessionMisses.Inc()
- expired = true
- } else {
- c.metrics.sessionHits.Inc()
- }
- select {
- case c.chPruneSessions <- struct{}{}:
- default:
+ kc := keepclient.New(arvadosclient)
+ kc.DiskCacheSize = c.cluster.Collections.WebDAVCache.DiskCacheSize
+ sess = &cachedSession{
+ cache: c,
+ client: client,
+ arvadosclient: arvadosclient,
+ keepclient: kc,
+ }
+ c.sessions[token] = sess
}
+ sess.mtx.RLock()
+ return sess, nil
+}
- fs, _ := sess.fs.Load().(arvados.CustomFileSystem)
- if fs == nil || expired {
- fs = sess.client.SiteFileSystem(sess.keepclient)
- fs.ForwardSlashNameSubstitution(c.cluster.Collections.ForwardSlashNameSubstitution)
- sess.fs.Store(fs)
+// Get a long-lived CustomFileSystem suitable for doing a read or
+// write operation with the given token.
+//
+// If the returned error is nil, the caller must call Release() on the
+// returned session when finished using it.
+func (c *cache) GetSession(token string) (arvados.CustomFileSystem, *cachedSession, *arvados.User, error) {
+ sess, err := c.checkout(token)
+ if err != nil {
+ return nil, nil, nil, err
}
+ sess.refresh.Lock()
+ defer sess.refresh.Unlock()
+ now := time.Now()
+ sess.lastuse = now
+ refresh := sess.expire.Before(now)
+ if sess.fs == nil || !sess.userLoaded || refresh {
+ // Wait for all active users to finish (otherwise they
+ // might make changes to an old fs after we start
+ // using the new fs).
+ sess.inuse.Lock()
+ if !sess.userLoaded || refresh {
+ err := sess.client.RequestAndDecode(&sess.user, "GET", "arvados/v1/users/current", nil, nil)
+ if he := errorWithHTTPStatus(nil); errors.As(err, &he) && he.HTTPStatus() == http.StatusForbidden {
+ // token is OK, but "get user id" api is out
+ // of scope -- use existing/expired info if
+ // any, or leave empty for unknown user
+ } else if err != nil {
+ sess.inuse.Unlock()
+ sess.mtx.RUnlock()
+ return nil, nil, nil, err
+ }
+ sess.userLoaded = true
+ }
- user, _ := sess.user.Load().(*arvados.User)
- if user == nil || expired {
- user = new(arvados.User)
- err := sess.client.RequestAndDecode(user, "GET", "/arvados/v1/users/current", nil, nil)
- if he := errorWithHTTPStatus(nil); errors.As(err, &he) && he.HTTPStatus() == http.StatusForbidden {
- // token is OK, but "get user id" api is out
- // of scope -- return nil, signifying unknown
- // user
- } else if err != nil {
- return nil, nil, nil, err
+ if sess.fs == nil || refresh {
+ sess.fs = sess.client.SiteFileSystem(sess.keepclient)
+ sess.fs.ForwardSlashNameSubstitution(c.cluster.Collections.ForwardSlashNameSubstitution)
+ sess.expire = now.Add(c.cluster.Collections.WebDAVCache.TTL.Duration())
+ c.metrics.sessionMisses.Inc()
+ } else {
+ c.metrics.sessionHits.Inc()
}
- sess.user.Store(user)
+ sess.inuse.Unlock()
+ } else {
+ c.metrics.sessionHits.Inc()
}
+ sess.inuse.RLock()
+ return sess.fs, sess, &sess.user, nil
+}
- return fs, sess, user, nil
+type sessionSnapshot struct {
+ token string
+ sess *cachedSession
+ lastuse time.Time
+ fs arvados.CustomFileSystem
+ size int64
+ prune bool
}
-// Remove all expired session cache entries, then remove more entries
-// until approximate remaining size <= maxsize/2
+// Remove all expired idle session cache entries, and remove in-memory
+// filesystems until approximate remaining size <= maxsize
func (c *cache) pruneSessions() {
now := time.Now()
- keys := c.sessions.Keys()
- sizes := make([]int64, len(keys))
+ c.mtx.Lock()
+ snaps := make([]sessionSnapshot, 0, len(c.sessions))
+ for token, sess := range c.sessions {
+ snaps = append(snaps, sessionSnapshot{
+ token: token,
+ sess: sess,
+ })
+ }
+ c.mtx.Unlock()
+
+ // Load lastuse/fs/expire data from sessions. Note we do this
+ // after unlocking c.mtx because sess.refresh.Lock sometimes
+ // waits for another goroutine to finish "[re]fetch user
+ // record".
+ for i := range snaps {
+ snaps[i].sess.refresh.Lock()
+ snaps[i].lastuse = snaps[i].sess.lastuse
+ snaps[i].fs = snaps[i].sess.fs
+ snaps[i].prune = snaps[i].sess.expire.Before(now)
+ snaps[i].sess.refresh.Unlock()
+ }
+
+ // Sort sessions with oldest first.
+ sort.Slice(snaps, func(i, j int) bool {
+ return snaps[i].lastuse.Before(snaps[j].lastuse)
+ })
+
+ // Add up size of sessions that aren't already marked for
+ // pruning based on expire time.
var size int64
- for i, token := range keys {
- ent, ok := c.sessions.Peek(token)
- if !ok {
- continue
+ for i, snap := range snaps {
+ if !snap.prune && snap.fs != nil {
+ size := snap.fs.MemorySize()
+ snaps[i].size = size
+ size += size
+ }
+ }
+ // Mark more sessions for deletion until reaching desired
+ // memory size limit, starting with the oldest entries.
+ for i, snap := range snaps {
+ if size <= int64(c.cluster.Collections.WebDAVCache.MaxCollectionBytes) {
+ break
}
- s := ent.(*cachedSession)
- if s.expire.Before(now) {
- c.sessions.Remove(token)
+ if snap.prune {
continue
}
- if fs, ok := s.fs.Load().(arvados.CustomFileSystem); ok {
- sizes[i] = fs.MemorySize()
- size += sizes[i]
+ snaps[i].prune = true
+ size -= snap.size
+ }
+
+ // Mark more sessions for deletion until reaching desired
+ // session count limit.
+ mustprune := len(snaps) - c.cluster.Collections.WebDAVCache.MaxSessions
+ for i := range snaps {
+ if snaps[i].prune {
+ mustprune--
}
}
- // Remove tokens until reaching size limit, starting with the
- // least frequently used entries (which Keys() returns last).
- for i := len(keys) - 1; i >= 0 && size > c.cluster.Collections.WebDAVCache.MaxCollectionBytes; i-- {
- if sizes[i] > 0 {
- c.sessions.Remove(keys[i])
- size -= sizes[i]
+ for i := range snaps {
+ if mustprune < 1 {
+ break
+ } else if !snaps[i].prune {
+ snaps[i].prune = true
+ mustprune--
}
}
-}
-// collectionBytes returns the approximate combined memory size of the
-// collection cache and session filesystem cache.
-func (c *cache) collectionBytes() uint64 {
- var size uint64
- for _, token := range c.sessions.Keys() {
- ent, ok := c.sessions.Peek(token)
- if !ok {
+ c.mtx.Lock()
+ defer c.mtx.Unlock()
+ for _, snap := range snaps {
+ if !snap.prune {
continue
}
- if fs, ok := ent.(*cachedSession).fs.Load().(arvados.CustomFileSystem); ok {
- size += uint64(fs.MemorySize())
+ sess := snap.sess
+ if sess.mtx.TryLock() {
+ delete(c.sessions, snap.token)
+ continue
+ }
+ // We can't remove a session that's been checked out
+ // -- that would allow another session to be created
+ // for the same token using a different in-memory
+ // filesystem. Instead, we wait for active requests to
+ // finish and then "unload" it. After this, either the
+ // next GetSession will reload fs/user, or a
+ // subsequent pruneSessions will remove the session.
+ go func() {
+ // Ensure nobody is mid-GetSession() (note we
+ // already know nobody is mid-checkout()
+ // because we have c.mtx locked)
+ sess.refresh.Lock()
+ defer sess.refresh.Unlock()
+ // Wait for current usage to finish (i.e.,
+ // anyone who has decided to use the current
+ // values of sess.fs and sess.user, and hasn't
+ // called Release() yet)
+ sess.inuse.Lock()
+ defer sess.inuse.Unlock()
+ // Release memory
+ sess.fs = nil
+ // Next GetSession will make a new fs
+ }()
+ }
+}
+
+// sessionsSize returns the number and approximate total memory size
+// of all cached sessions.
+func (c *cache) sessionsSize() (n int, size int64) {
+ c.mtx.Lock()
+ n = len(c.sessions)
+ sessions := make([]*cachedSession, 0, n)
+ for _, sess := range c.sessions {
+ sessions = append(sessions, sess)
+ }
+ c.mtx.Unlock()
+ for _, sess := range sessions {
+ sess.refresh.Lock()
+ fs := sess.fs
+ sess.refresh.Unlock()
+ if fs != nil {
+ size += fs.MemorySize()
}
}
- return size
+ return
}
projects / arvados.git / blobdiff