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tunnel/pump_buffers_test.go
| 1 | package main |
| 2 | |
| 3 | import ( |
| 4 | "net" |
| 5 | "sync/atomic" |
| 6 | "testing" |
| 7 | "time" |
| 8 | ) |
| 9 | |
| 10 | // An idle stream spends its life blocked in a read. The pump waits with a 4 KiB buffer and takes a 32 KiB one only for a read that filled the small one, giving it back when a |
| 11 | // read comes back short: an idle stream holds about 8 KiB of buffer, not 64 KiB (the chaos suite's memory-per-stream check). |
| 12 | func TestPump_AnIdleStreamHoldsNoBigBufferAndABulkTransferGetsOneAndGivesItBack(t *testing.T) { |
| 13 | e := newTestEnv(t, nil) |
| 14 | srcA, srcB := tcpPair(t) |
| 15 | dstA, dstB := tcpPair(t) |
| 16 | var ctr, total atomic.Int64 |
| 17 | done := make(chan error, 1) |
| 18 | go func() { done <- e.srv.pump("s1", "up", dstA, srcB, &ctr, &total, nil, nil) }() |
| 19 | drain := make(chan int, 1) |
| 20 | go func() { |
| 21 | n := 0 |
| 22 | buf := make([]byte, 1<<16) |
| 23 | for { |
| 24 | k, err := dstB.Read(buf) |
| 25 | n += k |
| 26 | if err != nil { |
| 27 | drain <- n |
| 28 | return |
| 29 | } |
| 30 | } |
| 31 | }() |
| 32 | time.Sleep(100 * time.Millisecond) |
| 33 | if got := e.srv.bigBuffersInUse.Load(); got != 0 { |
| 34 | t.Fatalf("an idle pump holds %d big buffers", got) |
| 35 | } |
| 36 | // a trickle never takes one |
| 37 | for i := 0; i < 5; i++ { |
| 38 | _, _ = srcA.Write([]byte("tiny")) |
| 39 | time.Sleep(20 * time.Millisecond) |
| 40 | } |
| 41 | if got := e.srv.bigBuffersInUse.Load(); got != 0 { |
| 42 | t.Fatalf("a trickle took %d big buffers", got) |
| 43 | } |
| 44 | // a bulk write fills the small buffer: the pump takes the big one for the following reads, and gives it back when a read comes back short |
| 45 | bulk := make([]byte, 1<<20) |
| 46 | var peak atomic.Int64 |
| 47 | stopPoll := make(chan struct{}) |
| 48 | go func() { |
| 49 | for { |
| 50 | select { |
| 51 | case <-stopPoll: |
| 52 | return |
| 53 | default: |
| 54 | if v := e.srv.bigBuffersInUse.Load(); v > peak.Load() { |
| 55 | peak.Store(v) |
| 56 | } |
| 57 | time.Sleep(100 * time.Microsecond) |
| 58 | } |
| 59 | } |
| 60 | }() |
| 61 | go func() { _, _ = srcA.Write(bulk) }() |
| 62 | eventually(t, "the bulk transfer went through", 5*time.Second, func() bool { return ctr.Load() >= int64(len(bulk)+20) }) |
| 63 | close(stopPoll) |
| 64 | if peak.Load() < 1 { |
| 65 | t.Fatalf("a bulk transfer never took a big buffer: its throughput would be that of 4 KiB reads") |
| 66 | } |
| 67 | _, _ = srcA.Write([]byte("short")) |
| 68 | eventually(t, "the big buffer went back to the pool after a short read", 3*time.Second, func() bool { return e.srv.bigBuffersInUse.Load() == 0 }) |
| 69 | _ = srcA.Close() |
| 70 | if err := <-done; err != nil { |
| 71 | t.Fatalf("a clean end of the source is not an error: %v", err) |
| 72 | } |
| 73 | _ = dstA.Close() |
| 74 | if n := <-drain; n != len(bulk)+20+5 { |
| 75 | t.Fatalf("the far side received %d bytes, want %d: the byte accounting changed", n, len(bulk)+25) |
| 76 | } |
| 77 | if got := e.srv.bigBuffersInUse.Load(); got != 0 { |
| 78 | t.Fatalf("%d big buffers leaked", got) |
| 79 | } |
| 80 | } |
| 81 | |
| 82 | func tcpPair(t *testing.T) (a, b net.Conn) { |
| 83 | t.Helper() |
| 84 | ln, err := net.Listen("tcp", "127.0.0.1:0") |
| 85 | if err != nil { |
| 86 | t.Fatal(err) |
| 87 | } |
| 88 | defer ln.Close() |
| 89 | acc := make(chan net.Conn, 1) |
| 90 | go func() { c, _ := ln.Accept(); acc <- c }() |
| 91 | a, err = net.Dial("tcp", ln.Addr().String()) |
| 92 | if err != nil { |
| 93 | t.Fatal(err) |
| 94 | } |
| 95 | b = <-acc |
| 96 | t.Cleanup(func() { _ = a.Close(); _ = b.Close() }) |
| 97 | return a, b |
| 98 | } |