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checks.go
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checks.go
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// Copyright 2017 by the contributors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package healthcheck
import (
"context"
"database/sql"
"fmt"
"net"
"net/http"
"runtime"
"time"
)
// TCPDialCheck returns a Check that checks TCP connectivity to the provided
// endpoint.
func TCPDialCheck(addr string, timeout time.Duration) Check {
return func() error {
conn, err := net.DialTimeout("tcp", addr, timeout)
if err != nil {
return err
}
return conn.Close()
}
}
// HTTPGetCheck returns a Check that performs an HTTP GET request against the
// specified URL. The check fails if the response times out or returns a non-200
// status code.
func HTTPGetCheck(url string, timeout time.Duration) Check {
client := http.Client{
Timeout: timeout,
// never follow redirects
CheckRedirect: func(*http.Request, []*http.Request) error {
return http.ErrUseLastResponse
},
}
return func() error {
resp, err := client.Get(url)
if err != nil {
return err
}
resp.Body.Close()
if resp.StatusCode != 200 {
return fmt.Errorf("returned status %d", resp.StatusCode)
}
return nil
}
}
// DatabasePingCheck returns a Check that validates connectivity to a
// database/sql.DB using Ping().
func DatabasePingCheck(database *sql.DB, timeout time.Duration) Check {
return func() error {
ctx, cancel := context.WithTimeout(context.Background(), timeout)
defer cancel()
if database == nil {
return fmt.Errorf("database is nil")
}
return database.PingContext(ctx)
}
}
// DNSResolveCheck returns a Check that makes sure the provided host can resolve
// to at least one IP address within the specified timeout.
func DNSResolveCheck(host string, timeout time.Duration) Check {
resolver := net.Resolver{}
return func() error {
ctx, cancel := context.WithTimeout(context.Background(), timeout)
defer cancel()
addrs, err := resolver.LookupHost(ctx, host)
if err != nil {
return err
}
if len(addrs) < 1 {
return fmt.Errorf("could not resolve host")
}
return nil
}
}
// GoroutineCountCheck returns a Check that fails if too many goroutines are
// running (which could indicate a resource leak).
func GoroutineCountCheck(threshold int) Check {
return func() error {
count := runtime.NumGoroutine()
if count > threshold {
return fmt.Errorf("too many goroutines (%d > %d)", count, threshold)
}
return nil
}
}