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pool.go
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pool.go
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package client
import (
"context"
"fmt"
"io"
"sync"
"time"
"github.com/go-kit/kit/log"
"github.com/go-kit/kit/log/level"
"github.com/prometheus/client_golang/prometheus"
"github.com/weaveworks/common/user"
"google.golang.org/grpc/health/grpc_health_v1"
"github.com/cortexproject/cortex/pkg/util"
util_log "github.com/cortexproject/cortex/pkg/util/log"
"github.com/cortexproject/cortex/pkg/util/services"
)
// PoolClient is the interface that should be implemented by a
// client managed by the pool.
type PoolClient interface {
grpc_health_v1.HealthClient
io.Closer
}
// PoolFactory defines the signature for a client factory.
type PoolFactory func(addr string) (PoolClient, error)
// PoolServiceDiscovery defines the signature of a function returning the list
// of known service endpoints. This function is used to remove stale clients from
// the pool (a stale client is a client connected to a service endpoint no more
// active).
type PoolServiceDiscovery func() ([]string, error)
// PoolConfig is config for creating a Pool.
type PoolConfig struct {
CheckInterval time.Duration
HealthCheckEnabled bool
HealthCheckTimeout time.Duration
}
// Pool holds a cache of grpc_health_v1 clients.
type Pool struct {
services.Service
cfg PoolConfig
discovery PoolServiceDiscovery
factory PoolFactory
logger log.Logger
clientName string
sync.RWMutex
clients map[string]PoolClient
clientsMetric prometheus.Gauge
}
// NewPool creates a new Pool.
func NewPool(clientName string, cfg PoolConfig, discovery PoolServiceDiscovery, factory PoolFactory, clientsMetric prometheus.Gauge, logger log.Logger) *Pool {
p := &Pool{
cfg: cfg,
discovery: discovery,
factory: factory,
logger: logger,
clientName: clientName,
clients: map[string]PoolClient{},
clientsMetric: clientsMetric,
}
p.Service = services.
NewTimerService(cfg.CheckInterval, nil, p.iteration, nil).
WithName(fmt.Sprintf("%s client pool", p.clientName))
return p
}
func (p *Pool) iteration(ctx context.Context) error {
p.removeStaleClients()
if p.cfg.HealthCheckEnabled {
p.cleanUnhealthy()
}
return nil
}
func (p *Pool) fromCache(addr string) (PoolClient, bool) {
p.RLock()
defer p.RUnlock()
client, ok := p.clients[addr]
return client, ok
}
// GetClientFor gets the client for the specified address. If it does not exist it will make a new client
// at that address
func (p *Pool) GetClientFor(addr string) (PoolClient, error) {
client, ok := p.fromCache(addr)
if ok {
return client, nil
}
p.Lock()
defer p.Unlock()
client, ok = p.clients[addr]
if ok {
return client, nil
}
client, err := p.factory(addr)
if err != nil {
return nil, err
}
p.clients[addr] = client
if p.clientsMetric != nil {
p.clientsMetric.Add(1)
}
return client, nil
}
// RemoveClientFor removes the client with the specified address
func (p *Pool) RemoveClientFor(addr string) {
p.Lock()
defer p.Unlock()
client, ok := p.clients[addr]
if ok {
delete(p.clients, addr)
if p.clientsMetric != nil {
p.clientsMetric.Add(-1)
}
// Close in the background since this operation may take awhile and we have a mutex
go func(addr string, closer PoolClient) {
if err := closer.Close(); err != nil {
level.Error(p.logger).Log("msg", fmt.Sprintf("error closing connection to %s", p.clientName), "addr", addr, "err", err)
}
}(addr, client)
}
}
// RegisteredAddresses returns all the service addresses for which there's an active client.
func (p *Pool) RegisteredAddresses() []string {
result := []string{}
p.RLock()
defer p.RUnlock()
for addr := range p.clients {
result = append(result, addr)
}
return result
}
// Count returns how many clients are in the cache
func (p *Pool) Count() int {
p.RLock()
defer p.RUnlock()
return len(p.clients)
}
func (p *Pool) removeStaleClients() {
// Only if service discovery has been configured.
if p.discovery == nil {
return
}
serviceAddrs, err := p.discovery()
if err != nil {
level.Error(util_log.Logger).Log("msg", "error removing stale clients", "err", err)
return
}
for _, addr := range p.RegisteredAddresses() {
if util.StringsContain(serviceAddrs, addr) {
continue
}
level.Info(util_log.Logger).Log("msg", "removing stale client", "addr", addr)
p.RemoveClientFor(addr)
}
}
// cleanUnhealthy loops through all servers and deletes any that fails a healthcheck.
func (p *Pool) cleanUnhealthy() {
for _, addr := range p.RegisteredAddresses() {
client, ok := p.fromCache(addr)
// not ok means someone removed a client between the start of this loop and now
if ok {
err := healthCheck(client, p.cfg.HealthCheckTimeout)
if err != nil {
level.Warn(util_log.Logger).Log("msg", fmt.Sprintf("removing %s failing healthcheck", p.clientName), "addr", addr, "reason", err)
p.RemoveClientFor(addr)
}
}
}
}
// healthCheck will check if the client is still healthy, returning an error if it is not
func healthCheck(client PoolClient, timeout time.Duration) error {
ctx, cancel := context.WithTimeout(context.Background(), timeout)
defer cancel()
ctx = user.InjectOrgID(ctx, "0")
resp, err := client.Check(ctx, &grpc_health_v1.HealthCheckRequest{})
if err != nil {
return err
}
if resp.Status != grpc_health_v1.HealthCheckResponse_SERVING {
return fmt.Errorf("failing healthcheck status: %s", resp.Status)
}
return nil
}