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hearbeatconn: convert dead integration test into Go test (#842)
fixes https://github.com/zrepl/zrepl/issues/417
This commit is contained in:
Christian Schwarz
GitHub
parent
dc05cd00f2
commit
f1608aba15
@ -0,0 +1,104 @@
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package heartbeatconn_test
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import (
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"net"
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"sync"
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"sync/atomic"
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"testing"
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"time"
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"github.com/stretchr/testify/require"
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"github.com/zrepl/zrepl/internal/rpc/dataconn/heartbeatconn"
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"github.com/zrepl/zrepl/internal/util/socketpair"
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)
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// Test behavior of heartbeatconn when the client is dead.
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//
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// Test strategy is to have a proxy between two heartbeatconn.Conn instances,
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// set up working heartbeatconn instances on both sides, then stop the proxy.
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func TestHeartbeatconnDeadClient(t *testing.T) {
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var wg sync.WaitGroup
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defer wg.Wait()
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a, b, err := socketpair.SocketPair()
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require.NoError(t, err)
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c, d, err := socketpair.SocketPair()
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require.NoError(t, err)
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var stopProxy atomic.Bool
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proxy := func(src, dst *net.UnixConn, done chan struct{}) {
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defer wg.Done()
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defer close(done)
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defer t.Log("proxy exiting")
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buf := make([]byte, 1024)
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for stopProxy.Load() == false {
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n, err := src.Read(buf)
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require.NoError(t, err)
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t.Logf("proxy read %d bytes", n)
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for i := 0; i < n; {
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nwritten, err := dst.Write(buf[i:n])
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require.NoError(t, err)
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i += nwritten
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}
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}
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}
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wg.Add(1)
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proxyBC := make(chan struct{})
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go proxy(b, c, proxyBC)
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wg.Add(1)
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proxyCB := make(chan struct{})
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go proxy(c, b, proxyCB)
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const heartbeatInterval = 100 * time.Millisecond
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const heartbeatTimeout = 10 * heartbeatInterval
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aHc := heartbeatconn.Wrap(a, heartbeatInterval, heartbeatTimeout)
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defer aHc.Shutdown()
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dHc := heartbeatconn.Wrap(d, heartbeatInterval, heartbeatTimeout)
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defer dHc.Shutdown()
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// follow API requirements to always ReadFrame
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aOut := make(chan net.Error, 1)
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dOut := make(chan net.Error, 1)
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readFrame := func(conn *heartbeatconn.Conn, out chan net.Error) {
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defer wg.Done()
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_, err := conn.ReadFrame()
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require.Error(t, err, "%T %s\n\n%#v", err, err, err)
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netErr, ok := err.(net.Error)
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require.True(t, ok)
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out <- netErr
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}
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wg.Add(1)
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go readFrame(aHc, aOut)
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wg.Add(1)
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go readFrame(dHc, dOut)
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time.Sleep(30 * heartbeatInterval)
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t.Logf("stop proxy")
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stopProxy.Store(true)
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<-proxyBC
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<-proxyCB
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// heartbeatconn should fail ReadFrame within heartbeatTimeout + scheduler delay
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const slop = 10 * time.Millisecond
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waitStart := time.Now()
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var aErr net.Error = nil
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var dErr net.Error = nil
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for aErr == nil || dErr == nil {
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select {
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case aErr = <-aOut:
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t.Logf("aErr: %s", aErr)
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case dErr = <-dOut:
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t.Logf("dErr: %s", dErr)
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}
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}
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waitTime := time.Since(waitStart)
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// assert timeline unblock of ReadFrame()
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require.True(t, waitTime > heartbeatTimeout-slop, "waitTime=%s", waitTime)
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require.True(t, waitTime < heartbeatTimeout+slop, "waitTime=%s", waitTime)
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// assert the error is Timeout(), so zrepl replication driver makes a new attempt
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require.True(t, aErr.Timeout())
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require.True(t, dErr.Timeout())
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}
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@ -1,140 +0,0 @@
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// This integration test exercises the behavior of heartbeatconn
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// where the server is slow at handling the data received over the connection.
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// Note that the server is still sending heartbeats to the client, it's just the
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// data handling (usually I/O in case of zrepl endpoint.Receiver) that is slow.
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//
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// In commit 082335df5d85e1b0b9faa35ff182c71886142d3e and earlier, heartbeatconn would fail
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// this benchmark with a writev I/O timeout (here the ss(8) output at the time of failure)
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//
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// ESTAB 33369 0 127.0.0.1:12345 127.0.0.1:57282 users:(("heartbeatconn_i",pid=25953,fd=5))
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// cubic wscale:7,7 rto:203 rtt:2.992/5.849 ato:162 mss:32768 pmtu:65535 rcvmss:32741 advmss:65483 cwnd:10 bytes_sent:48 bytes_acked:48 bytes_received:195401 segs_out:44 segs_in:57 data_segs_out:6 data_segs_in:34 send 876.1Mbps lastsnd:125 lastrcv:9390 lastack:125 pacing_rate 1752.0Mbps delivery_rate 6393.8Mbps delivered:7 app_limited busy:42ms rcv_rtt:1 rcv_space:65483 rcv_ssthresh:65483 minrtt:0.029
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// --
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// ESTAB 0 3956805 127.0.0.1:57282 127.0.0.1:12345 users:(("heartbeatconn_i",pid=26100,fd=3))
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// cubic wscale:7,7 rto:211 backoff:5 rtt:10.38/16.937 ato:40 mss:32768 pmtu:65535 rcvmss:536 advmss:65483 cwnd:10 bytes_sent:195401 bytes_acked:195402 bytes_received:48 segs_out:57 segs_in:45 data_segs_out:34 data_segs_in:6 send 252.5Mbps lastsnd:9390 lastrcv:125 lastack:125 pacing_rate 505.1Mbps delivery_rate 1971.0Mbps delivered:35 busy:30127ms rwnd_limited:30086ms(99.9%) rcv_space:65495 rcv_ssthresh:65495 notsent:3956805 minrtt:0.007
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// panic: writev tcp 127.0.0.1:57282->127.0.0.1:12345: i/o timeout
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//
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// The assumed reason for those writev timeouts is the following:
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// - Sporadic server stalls (sever data handling, usually I/O) cause TCP exponential backoff on the client for client->server
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// - Go runtime unblocks after the deadline expires, resultin gin writev I/O timeout
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// - That is, even though the client observed heartbeats from the server
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// -> TCP doesn't assume symmetric connection behavior, but our implementation does.
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//
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// The fix contained in the commit this message was committed with resets the deadline whenever
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// a heartbeat is received from the server.
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//
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// How to run this integration test:
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//
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// Terminal 1:
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// $ ZREPL_RPC_DATACONN_HEARTBEATCONN_DEBUG=1 go run heartbeatconn_integration_variablereceiverate.go -mode server -addr 127.0.0.1:12345
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// rpc/dataconn/heartbeatconn: send heartbeat
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// rpc/dataconn/heartbeatconn: send heartbeat
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// ...
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//
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// Terminal 2:
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// $ ZREPL_RPC_DATACONN_HEARTBEATCONN_DEBUG=1 go run heartbeatconn_integration_variablereceiverate.go -mode client -addr 127.0.0.1:12345
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// rpc/dataconn/heartbeatconn: received heartbeat, resetting write timeout
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// rpc/dataconn/heartbeatconn: renew frameconn write timeout returned errT=<nil> err=%!s(<nil>)
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// rpc/dataconn/heartbeatconn: send heartbeat
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// rpc/dataconn/heartbeatconn: received heartbeat, resetting write timeout
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// rpc/dataconn/heartbeatconn: renew frameconn write timeout returned errT=<nil> err=%!s(<nil>)
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// rpc/dataconn/heartbeatconn: received heartbeat, resetting write timeout
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// ...
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package main
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import (
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"bytes"
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"flag"
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"fmt"
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"io"
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"log"
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"math/rand"
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"net"
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"os"
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"os/exec"
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"path"
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"time"
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"github.com/zrepl/zrepl/internal/util/devnoop"
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"github.com/zrepl/zrepl/internal/rpc/dataconn/heartbeatconn"
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)
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func orDie(err error) {
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if err != nil {
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grepfield := path.Base(os.Args[0])[:10]
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fmt.Fprintf(os.Stderr, "grepping for %s\n", grepfield)
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sh := fmt.Sprintf("ss -ntpi | grep -A1 %s", grepfield)
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cmd := exec.Command("bash", "-c", sh)
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o, _ := cmd.CombinedOutput()
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buf := bytes.NewBuffer(o)
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_, _ = io.Copy(os.Stderr, buf)
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panic(err)
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}
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}
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var mode string
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var addr string
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func main() {
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flag.StringVar(&mode, "mode", "", "server|client")
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flag.StringVar(&addr, "addr", "INVALID", "")
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flag.Parse()
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modemap := map[string]func(){
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"server": server,
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"client": client,
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}
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modemap[mode]()
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}
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func server() {
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ln, err := net.Listen("tcp", addr)
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orDie(err)
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l := ln.(*net.TCPListener)
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for {
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c, err := l.AcceptTCP()
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if err != nil {
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log.Printf("accept err: %s", err)
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continue
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}
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hc := heartbeatconn.Wrap(c, 5*time.Second, 10*time.Second)
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for {
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f, err := hc.ReadFrame()
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orDie(err)
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// _, err = buf.Write(f.Buffer.Bytes())
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// orDie(err)
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sleep := time.Duration(rand.NormFloat64()*500) * time.Millisecond
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time.Sleep(sleep)
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f.Buffer.Free()
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}
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}
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}
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func client() {
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c, err := net.Dial("tcp", addr)
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orDie(err)
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hc := heartbeatconn.Wrap(c.(*net.TCPConn), 5*time.Second, 10*time.Second)
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// follow API requirements to always ReadFrame
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go func() {
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for {
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f, err := hc.ReadFrame()
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orDie(err)
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f.Buffer.Free()
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}
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}()
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dn := devnoop.Get()
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var buf [1 << 10]byte
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for {
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n, err := dn.Read(buf[:])
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orDie(err)
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err = hc.WriteFrame(buf[:n], 23)
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orDie(err)
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}
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}
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