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connchecker.go
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connchecker.go
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package connchecker
import (
"net"
"strings"
"sync"
"time"
"github.com/nbltrust/gocryptotrader/log"
)
// DefaultCheckInterval is a const that defines the amount of time between
// checking if the connection is lost
const (
DefaultCheckInterval = time.Second
ConnRe = "Internet connectivity re-established"
ConnLost = "Internet connectivity lost"
ConnFound = "Internet connectivity found"
ConnNotFound = "No internet connectivity"
)
// Default check lists
var (
DefaultDNSList = []string{"8.8.8.8", "8.8.4.4", "1.1.1.1", "1.0.0.1"}
DefaultDomainList = []string{"www.google.com", "www.cloudflare.com", "www.facebook.com"}
)
// New returns a new connection checker, if no values set it will default it out
func New(dnsList, domainList []string, checkInterval time.Duration) (*Checker, error) {
c := new(Checker)
if len(dnsList) == 0 {
c.DNSList = DefaultDNSList
} else {
c.DNSList = dnsList
}
if len(domainList) == 0 {
c.DomainList = DefaultDomainList
} else {
c.DomainList = domainList
}
if checkInterval == 0 {
c.CheckInterval = DefaultCheckInterval
} else {
c.CheckInterval = checkInterval
}
err := c.initialCheck()
if err != nil {
return nil, err
}
if c.connected {
log.Debugln(log.Global, ConnFound)
} else {
log.Warnln(log.Global, ConnNotFound)
}
c.shutdown = make(chan struct{}, 1)
var wg sync.WaitGroup
wg.Add(1)
go c.Monitor(&wg)
wg.Wait()
return c, nil
}
// Checker defines a struct to determine connectivity to the interwebs
type Checker struct {
DNSList []string
DomainList []string
CheckInterval time.Duration
shutdown chan struct{}
wg sync.WaitGroup
connected bool
sync.Mutex
}
// Shutdown cleanly shutsdown monitor routine
func (c *Checker) Shutdown() {
close(c.shutdown)
c.wg.Wait()
}
// Monitor determines internet connectivity via a DNS lookup
func (c *Checker) Monitor(wg *sync.WaitGroup) {
c.wg.Add(1)
tick := time.NewTicker(c.CheckInterval)
defer func() { tick.Stop(); c.wg.Done() }()
wg.Done()
for {
select {
case <-tick.C:
c.connectionTest()
case <-c.shutdown:
return
}
}
}
// initialCheck starts an initial connection check
func (c *Checker) initialCheck() error {
var connected bool
for i := range c.DNSList {
err := c.CheckDNS(c.DNSList[i])
if err != nil {
if strings.Contains(err.Error(), "unrecognized address") ||
strings.Contains(err.Error(), "invalid address") {
return err
}
continue
}
if !connected {
connected = true
}
}
for i := range c.DomainList {
err := c.CheckHost(c.DomainList[i])
if err != nil {
continue
}
if !connected {
connected = true
}
}
c.connected = connected
return nil
}
// ConnectionTest determines if a connection to the internet is available by
// iterating over a set list of dns ip and popular domains
func (c *Checker) connectionTest() {
for i := range c.DNSList {
err := c.CheckDNS(c.DNSList[i])
if err == nil {
c.Lock()
if !c.connected {
log.Debugln(log.Global, ConnRe)
c.connected = true
}
c.Unlock()
return
}
}
for i := range c.DomainList {
err := c.CheckHost(c.DomainList[i])
if err == nil {
c.Lock()
if !c.connected {
log.Debugln(log.Global, ConnRe)
c.connected = true
}
c.Unlock()
return
}
}
c.Lock()
if c.connected {
log.Warnln(log.Global, ConnLost)
c.connected = false
}
c.Unlock()
}
// CheckDNS checks current dns for connectivity
func (c *Checker) CheckDNS(dns string) error {
_, err := net.LookupAddr(dns)
return err
}
// CheckHost checks current host name for connectivity
func (c *Checker) CheckHost(host string) error {
_, err := net.LookupHost(host)
return err
}
// IsConnected returns if there is internet connectivity
func (c *Checker) IsConnected() bool {
c.Lock()
isConnected := c.connected
c.Unlock()
return isConnected
}