github.com/cloudwego/kitex@v0.9.0/pkg/limiter/connection_limiter.go (about)

     1  /*
     2   * Copyright 2021 CloudWeGo Authors
     3   *
     4   * Licensed under the Apache License, Version 2.0 (the "License");
     5   * you may not use this file except in compliance with the License.
     6   * You may obtain a copy of the License at
     7   *
     8   *     http://www.apache.org/licenses/LICENSE-2.0
     9   *
    10   * Unless required by applicable law or agreed to in writing, software
    11   * distributed under the License is distributed on an "AS IS" BASIS,
    12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13   * See the License for the specific language governing permissions and
    14   * limitations under the License.
    15   */
    16  
    17  package limiter
    18  
    19  import (
    20  	"context"
    21  	"sync/atomic"
    22  )
    23  
    24  // connectionLimiter implements ConcurrencyLimiter.
    25  type connectionLimiter struct {
    26  	lim  int32
    27  	curr int32
    28  }
    29  
    30  // NewConnectionLimiter returns a new ConnectionLimiter with the given limit.
    31  func NewConnectionLimiter(lim int) ConcurrencyLimiter {
    32  	return &connectionLimiter{int32(lim), 0}
    33  }
    34  
    35  // Deprecated: Use NewConnectionLimiter instead.
    36  func NewConcurrencyLimiter(lim int) ConcurrencyLimiter {
    37  	return &connectionLimiter{int32(lim), 0}
    38  }
    39  
    40  // Acquire tries to increase the connection counter.
    41  // The return value indicates whether the operation is allowed under the connection limitation.
    42  // Acquired is executed in `OnActive` which is called when a new connection is accepted, so even if the limit is reached
    43  // the count is still need increase, but return false will lead the connection is closed then Release also be executed.
    44  func (ml *connectionLimiter) Acquire(ctx context.Context) bool {
    45  	limit := atomic.LoadInt32(&ml.lim)
    46  	x := atomic.AddInt32(&ml.curr, 1)
    47  	return x <= limit || limit <= 0
    48  }
    49  
    50  // Release decrease the connection counter.
    51  func (ml *connectionLimiter) Release(ctx context.Context) {
    52  	atomic.AddInt32(&ml.curr, -1)
    53  }
    54  
    55  // UpdateLimit updates the limit.
    56  func (ml *connectionLimiter) UpdateLimit(lim int) {
    57  	atomic.StoreInt32(&ml.lim, int32(lim))
    58  }
    59  
    60  // Status returns the current status.
    61  func (ml *connectionLimiter) Status(ctx context.Context) (limit, occupied int) {
    62  	limit = int(atomic.LoadInt32(&ml.lim))
    63  	occupied = int(atomic.LoadInt32(&ml.curr))
    64  	return
    65  }