Regulate filesystem driver to max of 100 calls

It's easily possible for a flood of requests to trigger thousands of
concurrent file accesses on the storage driver. Each file I/O call creates
a new OS thread that is not reaped by the Golang runtime. By limiting it
to only 100 at a time we can effectively bound the number of OS threads
in use by the storage driver.

Docker-DCO-1.1-Signed-off-by: Josh Hawn <josh.hawn@docker.com> (github: jlhawn)

Signed-off-by: Tony Holdstock-Brown <tony@docker.com>
This commit is contained in:
Josh Hawn 2016-02-27 15:37:07 -08:00 committed by Tony Holdstock-Brown
parent 47d14555c0
commit e4dd3359cc
2 changed files with 153 additions and 3 deletions

View file

@ -0,0 +1,150 @@
package base
import (
"io"
"sync"
"github.com/docker/distribution/context"
storagedriver "github.com/docker/distribution/registry/storage/driver"
)
type regulator struct {
storagedriver.StorageDriver
sync.Cond
available uint
}
// NewRegulator wraps the given driver and is used to regulate concurrent calls
// to the given storage driver to a maximum of the given limit. This is useful
// for storage drivers that would otherwise create an unbounded number of OS
// threads if allowed to be called unregulated.
func NewRegulator(driver storagedriver.StorageDriver, limit uint) storagedriver.StorageDriver {
return &regulator{
StorageDriver: driver,
Cond: sync.Cond{
L: &sync.Mutex{},
},
available: limit,
}
}
func (r *regulator) condition() bool {
return r.available > 0
}
func (r *regulator) enter() {
r.L.Lock()
defer r.L.Unlock()
for !r.condition() {
r.Wait()
}
r.available--
}
func (r *regulator) exit() {
r.L.Lock()
defer r.Signal()
defer r.L.Unlock()
r.available++
}
// Name returns the human-readable "name" of the driver, useful in error
// messages and logging. By convention, this will just be the registration
// name, but drivers may provide other information here.
func (r *regulator) Name() string {
r.enter()
defer r.exit()
return r.StorageDriver.Name()
}
// GetContent retrieves the content stored at "path" as a []byte.
// This should primarily be used for small objects.
func (r *regulator) GetContent(ctx context.Context, path string) ([]byte, error) {
r.enter()
defer r.exit()
return r.StorageDriver.GetContent(ctx, path)
}
// PutContent stores the []byte content at a location designated by "path".
// This should primarily be used for small objects.
func (r *regulator) PutContent(ctx context.Context, path string, content []byte) error {
r.enter()
defer r.exit()
return r.StorageDriver.PutContent(ctx, path, content)
}
// ReadStream retrieves an io.ReadCloser for the content stored at "path"
// with a given byte offset.
// May be used to resume reading a stream by providing a nonzero offset.
func (r *regulator) ReadStream(ctx context.Context, path string, offset int64) (io.ReadCloser, error) {
r.enter()
defer r.exit()
return r.StorageDriver.ReadStream(ctx, path, offset)
}
// WriteStream stores the contents of the provided io.ReadCloser at a
// location designated by the given path.
// May be used to resume writing a stream by providing a nonzero offset.
// The offset must be no larger than the CurrentSize for this path.
func (r *regulator) WriteStream(ctx context.Context, path string, offset int64, reader io.Reader) (nn int64, err error) {
r.enter()
defer r.exit()
return r.StorageDriver.WriteStream(ctx, path, offset, reader)
}
// Stat retrieves the FileInfo for the given path, including the current
// size in bytes and the creation time.
func (r *regulator) Stat(ctx context.Context, path string) (storagedriver.FileInfo, error) {
r.enter()
defer r.exit()
return r.StorageDriver.Stat(ctx, path)
}
// List returns a list of the objects that are direct descendants of the
//given path.
func (r *regulator) List(ctx context.Context, path string) ([]string, error) {
r.enter()
defer r.exit()
return r.StorageDriver.List(ctx, path)
}
// Move moves an object stored at sourcePath to destPath, removing the
// original object.
// Note: This may be no more efficient than a copy followed by a delete for
// many implementations.
func (r *regulator) Move(ctx context.Context, sourcePath string, destPath string) error {
r.enter()
defer r.exit()
return r.StorageDriver.Move(ctx, sourcePath, destPath)
}
// Delete recursively deletes all objects stored at "path" and its subpaths.
func (r *regulator) Delete(ctx context.Context, path string) error {
r.enter()
defer r.exit()
return r.StorageDriver.Delete(ctx, path)
}
// URLFor returns a URL which may be used to retrieve the content stored at
// the given path, possibly using the given options.
// May return an ErrUnsupportedMethod in certain StorageDriver
// implementations.
func (r *regulator) URLFor(ctx context.Context, path string, options map[string]interface{}) (string, error) {
r.enter()
defer r.exit()
return r.StorageDriver.URLFor(ctx, path, options)
}

View file

@ -60,12 +60,12 @@ func FromParameters(parameters map[string]interface{}) *Driver {
// New constructs a new Driver with a given rootDirectory
func New(rootDirectory string) *Driver {
fsDriver := &driver{rootDirectory: rootDirectory}
return &Driver{
baseEmbed: baseEmbed{
Base: base.Base{
StorageDriver: &driver{
rootDirectory: rootDirectory,
},
StorageDriver: base.NewRegulator(fsDriver, 100),
},
},
}