github.com/KinWaiYuen/client-go/v2@v2.5.4/util/rate_limit.go (about)

     1  // Copyright 2021 TiKV Authors
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  // NOTE: The code in this file is based on code from the
    16  // TiDB project, licensed under the Apache License v 2.0
    17  //
    18  // https://github.com/pingcap/tidb/tree/cc5e161ac06827589c4966674597c137cc9e809c/store/tikv/util/rate_limit.go
    19  //
    20  
    21  // Copyright 2021 PingCAP, Inc.
    22  //
    23  // Licensed under the Apache License, Version 2.0 (the "License");
    24  // you may not use this file except in compliance with the License.
    25  // You may obtain a copy of the License at
    26  //
    27  //     http://www.apache.org/licenses/LICENSE-2.0
    28  //
    29  // Unless required by applicable law or agreed to in writing, software
    30  // distributed under the License is distributed on an "AS IS" BASIS,
    31  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    32  // See the License for the specific language governing permissions and
    33  // limitations under the License.
    34  
    35  package util
    36  
    37  // RateLimit wraps a fix sized channel to control concurrency.
    38  type RateLimit struct {
    39  	capacity int
    40  	token    chan struct{}
    41  }
    42  
    43  // NewRateLimit creates a limit controller with capacity n.
    44  func NewRateLimit(n int) *RateLimit {
    45  	return &RateLimit{
    46  		capacity: n,
    47  		token:    make(chan struct{}, n),
    48  	}
    49  }
    50  
    51  // GetToken acquires a token.
    52  func (r *RateLimit) GetToken(done <-chan struct{}) (exit bool) {
    53  	select {
    54  	case <-done:
    55  		return true
    56  	case r.token <- struct{}{}:
    57  		return false
    58  	}
    59  }
    60  
    61  // PutToken puts a token back.
    62  func (r *RateLimit) PutToken() {
    63  	select {
    64  	case <-r.token:
    65  	default:
    66  		panic("put a redundant token")
    67  	}
    68  }
    69  
    70  // GetCapacity returns the token capacity.
    71  func (r *RateLimit) GetCapacity() int {
    72  	return r.capacity
    73  }