621164bc84
After iterating on the GRPC API, the changes required for the actual implementation are now included in the content store. The begin change is the move to a single, atomic `Ingester.Writer` method for locking content ingestion on a key. From this, comes several new interface definitions. The main benefit here is the clarification between `Status` and `Info` that came out of the GPRC API. `Status` tells the status of a write, whereas `Info` is for querying metadata about various blobs. Signed-off-by: Stephen J Day <stephen.day@docker.com>
57 lines
1.1 KiB
Go
57 lines
1.1 KiB
Go
package content
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import (
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"sync"
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"github.com/nightlyone/lockfile"
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"github.com/pkg/errors"
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)
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// In addition to providing inter-process locks for content ingest, we also
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// define a global in process lock to prevent two goroutines writing to the
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// same file.
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//
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// This is pretty unsophisticated for now. In the future, we'd probably like to
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// have more information about who is holding which locks, as well as better
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// error reporting.
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var (
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errLocked = errors.New("key is locked")
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// locks lets us lock in process, as well as output of process.
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locks = map[lockfile.Lockfile]struct{}{}
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locksMu sync.Mutex
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)
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func tryLock(lock lockfile.Lockfile) error {
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locksMu.Lock()
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defer locksMu.Unlock()
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if _, ok := locks[lock]; ok {
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return errLocked
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}
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if err := lock.TryLock(); err != nil {
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if errors.Cause(err) == lockfile.ErrBusy {
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return errLocked
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}
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return errors.Wrapf(err, "lock.TryLock() encountered an error")
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}
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locks[lock] = struct{}{}
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return nil
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}
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func unlock(lock lockfile.Lockfile) error {
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locksMu.Lock()
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defer locksMu.Unlock()
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if _, ok := locks[lock]; !ok {
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return nil
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}
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delete(locks, lock)
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return lock.Unlock()
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}
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