86 lines
1.8 KiB
Go
86 lines
1.8 KiB
Go
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package users
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import (
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"os/user"
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"sync"
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"time"
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"github.com/hashicorp/nomad/lib/lang"
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"oss.indeed.com/go/libtime"
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)
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const (
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cacheTTL = 1 * time.Hour
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failureTTL = 1 * time.Minute
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)
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type entry[T any] lang.Pair[T, time.Time]
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func (e *entry[T]) expired(now time.Time, ttl time.Duration) bool {
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return now.After(e.Second.Add(ttl))
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}
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type (
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userCache map[string]*entry[*user.User]
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userFailureCache map[string]*entry[error]
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)
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type lookupUserFunc func(string) (*user.User, error)
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type cache struct {
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clock libtime.Clock
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lookupUser lookupUserFunc
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lock sync.Mutex
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users userCache
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userFailures userFailureCache
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}
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func newCache() *cache {
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return &cache{
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clock: libtime.SystemClock(),
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lookupUser: internalLookupUser,
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users: make(userCache),
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userFailures: make(userFailureCache),
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}
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}
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func (c *cache) GetUser(username string) (*user.User, error) {
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c.lock.Lock()
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defer c.lock.Unlock()
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// record this moment as "now" for further cache operations
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now := c.clock.Now()
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// first check if the user is in the cache and the entry we have
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// is not yet expired
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usr, exists := c.users[username]
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if exists && !usr.expired(now, cacheTTL) {
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return usr.First, nil
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}
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// next check if there was a recent failure already, so we
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// avoid spamming the OS with dead user lookups
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failure, exists2 := c.userFailures[username]
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if exists2 {
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if !failure.expired(now, failureTTL) {
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return nil, failure.First
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}
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// may as well cleanup expired case
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delete(c.userFailures, username)
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}
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// need to perform an OS lookup
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u, err := c.lookupUser(username)
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// lookup was a failure, populate the failure cache
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if err != nil {
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c.userFailures[username] = &entry[error]{err, now}
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return nil, err
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}
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// lookup was a success, populate the user cache
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c.users[username] = &entry[*user.User]{u, now}
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return u, nil
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}
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