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tcpchecker.go
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tcpchecker.go
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package checkup
import (
"crypto/tls"
"crypto/x509"
"errors"
"fmt"
"io/ioutil"
"net"
"time"
)
// TCPChecker implements a Checker for TCP endpoints.
type TCPChecker struct {
// Name is the name of the endpoint.
Name string `json:"endpoint_name"`
// URL is the URL of the endpoint.
URL string `json:"endpoint_url"`
// TLSEnabled controls whether to enable TLS or not.
// If set, TLS is enabled.
TLSEnabled bool `json:"tls,omitempty"`
// TLSSkipVerify controls whether to skip server TLS
// certificat validation or not.
TLSSkipVerify bool `json:"tls_skip_verify,omitempty"`
// TLSCAFile is the Certificate Authority used
// to validate the server TLS certificate.
TLSCAFile string `json:"tls_ca_file,omitempty"`
// Timeout is the maximum time to wait for a
// TCP connection to be established.
Timeout time.Duration `json:"timeout,omitempty"`
// ThresholdRTT is the maximum round trip time to
// allow for a healthy endpoint. If non-zero and a
// request takes longer than ThresholdRTT, the
// endpoint will be considered unhealthy. Note that
// this duration includes any in-between network
// latency.
ThresholdRTT time.Duration `json:"threshold_rtt,omitempty"`
// Attempts is how many requests the client will
// make to the endpoint in a single check.
Attempts int `json:"attempts,omitempty"`
// Retries is how many retry requests.
Retries int `json:"retries,omitempty"`
// RetrySpacing spaces out each retry in a check
// by this duration to avoid hitting a remote too
// quickly in succession. By default, no waiting
// occurs between retries.
RetrySpacing time.Duration `json:"retry_spacing,omitempty"`
}
// Check performs checks using c according to its configuration.
// An error is only returned if there is a configuration error.
func (c TCPChecker) Check() (Result, error) {
if c.Attempts < 1 {
c.Attempts = 1
}
if c.Retries < 1 {
c.Retries = 0
}
result := Result{Title: c.Name, Endpoint: c.URL, Timestamp: Timestamp()}
result.Times = c.doChecks()
return c.conclude(result), nil
}
// doChecks executes and returns each attempt.
func (c TCPChecker) doChecks() Attempts {
timeout := c.Timeout
if timeout == 0 {
timeout = 1 * time.Second
}
checks := make(Attempts, c.Attempts)
for i := 0; i < c.Attempts; i++ {
start := time.Now()
err := c.doCheck(timeout)
if err != nil {
// retries
if c.Retries > 0 {
err = c.doRetries(timeout)
if err != nil {
checks[i].Error = err.Error()
} else {
checks[i].RTT = time.Since(start)
}
} else {
checks[i].Error = err.Error()
}
} else {
checks[i].RTT = time.Since(start)
}
}
return checks
}
// doRetries executes retries and returns last error.
func (c TCPChecker) doRetries(timeout time.Duration) error {
j := 1
for {
if c.RetrySpacing > 0 {
time.Sleep(c.RetrySpacing)
}
err := c.doCheck(timeout)
if j >= c.Retries || err == nil {
return err
}
j++
}
}
func (c TCPChecker) doCheck(timeout time.Duration) error {
var err error
var conn net.Conn
if c.TLSEnabled {
// Dialer with timeout
dialer := &net.Dialer{
Timeout: timeout,
}
// TLS config based on configuration
var tlsConfig tls.Config
tlsConfig.InsecureSkipVerify = c.TLSSkipVerify
if c.TLSCAFile != "" {
rootPEM, err := ioutil.ReadFile(c.TLSCAFile)
if err != nil || rootPEM == nil {
err = errors.New("failed to read root certificate")
}
pool := x509.NewCertPool()
ok := pool.AppendCertsFromPEM([]byte(rootPEM))
if !ok {
err = errors.New("failed to parse root certificate")
}
tlsConfig.RootCAs = pool
}
if conn, err = tls.DialWithDialer(dialer, "tcp", c.URL, &tlsConfig); err == nil {
conn.Close()
}
} else {
if conn, err = net.DialTimeout("tcp", c.URL, c.Timeout); err == nil {
conn.Close()
}
}
return err
}
// conclude takes the data in result from the attempts and
// computes remaining values needed to fill out the result.
// It detects degraded (high-latency) responses and makes
// the conclusion about the result's status.
func (c TCPChecker) conclude(result Result) Result {
result.ThresholdRTT = c.ThresholdRTT
// Check errors (down)
for i := range result.Times {
if result.Times[i].Error != "" {
result.Down = true
return result
}
}
// Check round trip time (degraded)
if c.ThresholdRTT > 0 {
stats := result.ComputeStats()
if stats.Median > c.ThresholdRTT {
result.Notice = fmt.Sprintf("median round trip time exceeded threshold (%s)", c.ThresholdRTT)
result.Degraded = true
return result
}
}
result.Healthy = true
return result
}