github.com/mailgun/holster/v4@v4.20.0/grpcconn/idpool.go (about)

     1  package grpcconn
     2  
     3  import (
     4  	"strconv"
     5  	"sync"
     6  )
     7  
     8  // IDPool maintains a pool of ID values that can be released and reused.
     9  // This is handy to keep cardinality low as gRPC connections are periodically
    10  // released and reconnected and require an id.
    11  // This solves the problem of infinitely incrementing ids used in Prometheus
    12  // metric labels causing infinite growth of historical metric values.
    13  type IDPool struct {
    14  	pool      map[ID]bool
    15  	allocated int
    16  	allocMu   sync.RWMutex
    17  }
    18  
    19  type ID int
    20  
    21  func NewIDPool() *IDPool {
    22  	return &IDPool{
    23  		pool: make(map[ID]bool),
    24  	}
    25  }
    26  
    27  func (i *IDPool) Allocate() ID {
    28  	i.allocMu.Lock()
    29  	defer i.allocMu.Unlock()
    30  
    31  	for id, allocFlag := range i.pool {
    32  		if allocFlag {
    33  			continue
    34  		}
    35  
    36  		i.allocated++
    37  		i.pool[id] = true
    38  		return id
    39  	}
    40  
    41  	// Dynamically expand pool.
    42  	newID := ID(len(i.pool) + 1)
    43  	i.pool[newID] = true
    44  	return newID
    45  }
    46  
    47  func (i *IDPool) Release(id ID) {
    48  	i.allocMu.Lock()
    49  	defer i.allocMu.Unlock()
    50  
    51  	if allocFlag, ok := i.pool[id]; !ok || !allocFlag {
    52  		return
    53  	}
    54  
    55  	i.allocated--
    56  	i.pool[id] = false
    57  }
    58  
    59  func (id ID) String() string {
    60  	return strconv.Itoa(int(id))
    61  }