Created
January 24, 2018 04:44
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Reproducer for stale tcp sessions
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| package main | |
| // Build and run as root since this code uses iptables to emulate a network outage. | |
| // Make sure rules in iptables are cleared: | |
| // sudo iptables -D INPUT -j DROP -p tcp --destination-port 2379; sudo iptables -D INPUT -j DROP -p tcp --source-port 2379 | |
| import ( | |
| "context" | |
| "log" | |
| "os/exec" | |
| "time" | |
| "github.com/coreos/etcd/clientv3" | |
| ) | |
| func main() { | |
| cli, err := clientv3.New(clientv3.Config{ | |
| Endpoints: []string{"localhost:2379"}, | |
| DialTimeout: 5 * time.Second, | |
| }) | |
| if err != nil { | |
| panic(err) | |
| } | |
| defer cli.Close() | |
| go func() { | |
| for { | |
| log.Println("++ Putting") | |
| ctx, _ := context.WithTimeout(context.Background(), time.Second) | |
| _, err := cli.Put(ctx, "/test", "somedata") | |
| if err != nil { | |
| log.Printf("Put error: %s\n", err) | |
| } | |
| time.Sleep(time.Second * 2) | |
| } | |
| }() | |
| go func() { | |
| log.Println("Starting watch") | |
| watchCh := cli.Watch(context.Background(), "/test") | |
| for ev := range watchCh { | |
| if ev.Err() != nil { | |
| log.Printf("Watch error: %s\n", ev.Err()) | |
| continue | |
| } | |
| log.Printf("++ Watch: %+v", ev.Events) | |
| } | |
| }() | |
| cmd := exec.Command("bash", "-c", "netstat -nap | grep ':2379'") | |
| out, err := cmd.Output() | |
| if err != nil { | |
| log.Panicf("netstat failed", err) | |
| } | |
| log.Printf("netstat: %s\n", out) | |
| log.Println("Start dropping packets in 5 seconds") | |
| time.Sleep(time.Second * 5) | |
| log.Println("Dropping packets") | |
| cmd = exec.Command("bash", "-c", "iptables -A INPUT -j DROP -p tcp --destination-port 2379; iptables -A INPUT -j DROP -p tcp --source-port 2379") | |
| err = cmd.Run() | |
| if err != nil { | |
| log.Panicf("iptables failed", err) | |
| } | |
| cmd = exec.Command("bash", "-c", "netstat -nap | grep ':2379'") | |
| out, err = cmd.Output() | |
| if err != nil { | |
| log.Panicf("netstat failed", err) | |
| } | |
| log.Printf("netstat: %s\n", out) | |
| log.Println("Waiting for 10 seconds") | |
| time.Sleep(time.Second * 10) | |
| log.Println("Restoring connectivity") | |
| cmd = exec.Command("bash", "-c", "iptables -D INPUT -j DROP -p tcp --destination-port 2379; iptables -D INPUT -j DROP -p tcp --source-port 2379") | |
| err = cmd.Run() | |
| if err != nil { | |
| log.Panicf("iptables failed", err) | |
| } | |
| cmd = exec.Command("bash", "-c", "netstat -nap | grep ':2379'") | |
| out, err = cmd.Output() | |
| if err != nil { | |
| log.Panicf("netstat failed", err) | |
| } | |
| log.Printf("netstat: %s\n", out) | |
| log.Println("Waiting for 10 seconds") | |
| time.Sleep(time.Second * 10) | |
| cmd = exec.Command("bash", "-c", "netstat -nap | grep ':2379'") | |
| out, err = cmd.Output() | |
| if err != nil { | |
| log.Panicf("netstat failed", err) | |
| } | |
| log.Printf("netstat: %s\n", out) | |
| } |
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The output would look like (etcd binary is renamed to
etcddin this example):