mirror of
https://github.com/ChronosX88/go-gun.git
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133 lines
4.1 KiB
Go
133 lines
4.1 KiB
Go
package gun
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import (
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"context"
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"errors"
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"fmt"
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"sync"
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"time"
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)
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// ErrStorageNotFound is returned by Storage.Get and sometimes Storage.Put when
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// the field doesn't exist.
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var ErrStorageNotFound = errors.New("Not found")
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// Storage is the interface that storage adapters must implement.
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type Storage interface {
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// Get obtains the value (which can be nil) and state from storage for the
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// given field. If the field does not exist, this errors with
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// ErrStorageNotFound.
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Get(ctx context.Context, parentSoul, field string) (Value, State, error)
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// Put sets the value (which can be nil) and state in storage for the given
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// field if the conflict resolution says it should (see ConflictResolve). It
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// also returns the conflict resolution. If onlyIfExists is true and the
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// field does not exist, this errors with ErrStorageNotFound. Otherwise, if
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// the resulting resolution is an immediate update, it is done. If the
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// resulting resolution is deferred for the future, it is scheduled for then
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// but is not even attempted if context is completed or storage is closed.
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Put(ctx context.Context, parentSoul, field string, val Value, state State, onlyIfExists bool) (ConflictResolution, error)
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// Close closes this storage and disallows future gets or puts.
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Close() error
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}
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type storageInMem struct {
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values map[parentSoulAndField]*valueWithState
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valueLock sync.RWMutex
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closed bool // Do not mutate outside of valueLock
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purgeCancelFn context.CancelFunc
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}
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type parentSoulAndField struct{ parentSoul, field string }
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type valueWithState struct {
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val Value
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state State
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}
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// NewStorageInMem creates an in-memory storage that automatically purges
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// values that are older than the given oldestAllowed. If oldestAllowed is 0,
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// it keeps all values forever.
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func NewStorageInMem(oldestAllowed time.Duration) Storage {
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s := &storageInMem{values: map[parentSoulAndField]*valueWithState{}}
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// Start the purger
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if oldestAllowed > 0 {
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var ctx context.Context
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ctx, s.purgeCancelFn = context.WithCancel(context.Background())
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go func() {
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tick := time.NewTicker(5 * time.Second)
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defer tick.Stop()
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for {
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select {
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case <-ctx.Done():
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return
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case t := <-tick.C:
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oldestStateAllowed := StateFromTime(t.Add(-oldestAllowed))
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s.valueLock.Lock()
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s.valueLock.Unlock()
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for k, v := range s.values {
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if v.state < oldestStateAllowed {
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delete(s.values, k)
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}
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}
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}
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}
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}()
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}
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return s
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}
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func (s *storageInMem) Get(ctx context.Context, parentSoul, field string) (Value, State, error) {
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s.valueLock.RLock()
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defer s.valueLock.RUnlock()
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if s.closed {
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return nil, 0, fmt.Errorf("Storage closed")
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} else if vs := s.values[parentSoulAndField{parentSoul, field}]; vs == nil {
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return nil, 0, ErrStorageNotFound
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} else {
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return vs.val, vs.state, nil
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}
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}
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func (s *storageInMem) Put(
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ctx context.Context, parentSoul, field string, val Value, state State, onlyIfExists bool,
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) (confRes ConflictResolution, err error) {
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s.valueLock.Lock()
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defer s.valueLock.Unlock()
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key, newVs := parentSoulAndField{parentSoul, field}, &valueWithState{val, state}
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sysState := StateNow()
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if s.closed {
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return 0, fmt.Errorf("Storage closed")
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} else if existingVs := s.values[key]; existingVs == nil && onlyIfExists {
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return 0, ErrStorageNotFound
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} else if existingVs == nil {
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confRes = ConflictResolutionNeverSeenUpdate
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} else {
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confRes = ConflictResolve(existingVs.val, existingVs.state, val, state, sysState)
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}
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if confRes == ConflictResolutionTooFutureDeferred {
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// Schedule for 100ms past when it's deferred to
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time.AfterFunc(time.Duration(state-sysState)*time.Millisecond+100, func() {
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s.valueLock.RLock()
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closed := s.closed
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s.valueLock.RUnlock()
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// TODO: what to do w/ error?
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if !closed && ctx.Err() == nil {
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s.Put(ctx, parentSoul, field, val, state, onlyIfExists)
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}
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})
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} else if confRes.IsImmediateUpdate() {
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s.values[key] = newVs
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}
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return
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}
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func (s *storageInMem) Close() error {
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if s.purgeCancelFn != nil {
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s.purgeCancelFn()
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}
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s.valueLock.Lock()
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defer s.valueLock.Unlock()
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s.closed = true
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return nil
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}
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