github.com/m3db/m3@v1.5.0/src/dbnode/storage/limits/permits/fixed_permits.go (about)

     1  // Copyright (c) 2021 Uber Technologies, Inc.
     2  //
     3  // Permission is hereby granted, free of charge, to any person obtaining a copy
     4  // of this software and associated documentation files (the "Software"), to deal
     5  // in the Software without restriction, including without limitation the rights
     6  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
     7  // copies of the Software, and to permit persons to whom the Software is
     8  // furnished to do so, subject to the following conditions:
     9  //
    10  // The above copyright notice and this permission notice shall be included in
    11  // all copies or substantial portions of the Software.
    12  //
    13  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    14  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    15  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    16  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    17  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    18  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    19  // THE SOFTWARE.
    20  
    21  package permits
    22  
    23  import (
    24  	"go.uber.org/zap"
    25  
    26  	"github.com/m3db/m3/src/x/context"
    27  	"github.com/m3db/m3/src/x/instrument"
    28  )
    29  
    30  type fixedPermits struct {
    31  	permits chan Permit
    32  	iOpts   instrument.Options
    33  }
    34  
    35  type fixedPermitsManager struct {
    36  	fp fixedPermits
    37  }
    38  
    39  var (
    40  	_ Permits = &fixedPermits{}
    41  	_ Manager = &fixedPermitsManager{}
    42  )
    43  
    44  // NewFixedPermitsManager returns a permits manager that uses a fixed size of permits.
    45  func NewFixedPermitsManager(size int, quotaPerPermit int64, iOpts instrument.Options) Manager {
    46  	fp := fixedPermits{permits: make(chan Permit, size), iOpts: iOpts}
    47  	for i := 0; i < size; i++ {
    48  		fp.permits <- NewPermit(quotaPerPermit, iOpts)
    49  	}
    50  	return &fixedPermitsManager{fp: fp}
    51  }
    52  
    53  func (f *fixedPermitsManager) NewPermits(_ context.Context) (Permits, error) {
    54  	return &f.fp, nil
    55  }
    56  
    57  func (f *fixedPermits) Acquire(ctx context.Context) (AcquireResult, error) {
    58  	// don't acquire a permit if ctx is already done.
    59  	select {
    60  	case <-ctx.GoContext().Done():
    61  		return AcquireResult{}, ctx.GoContext().Err()
    62  	default:
    63  	}
    64  
    65  	select {
    66  	case <-ctx.GoContext().Done():
    67  		return AcquireResult{}, ctx.GoContext().Err()
    68  	case p := <-f.permits:
    69  		p.PreAcquire()
    70  		return AcquireResult{
    71  			Permit: p,
    72  		}, nil
    73  	}
    74  }
    75  
    76  func (f *fixedPermits) TryAcquire(ctx context.Context) (Permit, error) {
    77  	// don't acquire a permit if ctx is already done.
    78  	select {
    79  	case <-ctx.GoContext().Done():
    80  		return nil, ctx.GoContext().Err()
    81  	default:
    82  	}
    83  
    84  	select {
    85  	case p := <-f.permits:
    86  		p.PreAcquire()
    87  		return p, nil
    88  	default:
    89  		return nil, nil
    90  	}
    91  }
    92  
    93  func (f *fixedPermits) Release(permit Permit) {
    94  	permit.PostRelease()
    95  
    96  	select {
    97  	case f.permits <- permit:
    98  	default:
    99  		instrument.EmitAndLogInvariantViolation(f.iOpts, func(l *zap.Logger) {
   100  			l.Error("more permits released than acquired")
   101  		})
   102  	}
   103  }
   104  
   105  func (f *fixedPermits) Close() {
   106  }