| 1 | package dbreads |
| 2 | |
| 3 | import ( |
| 4 | "context" |
| 5 | "errors" |
| 6 | "testing" |
| 7 | "time" |
| 8 | ) |
| 9 | |
| 10 | type unitsSeam struct { |
| 11 | n int |
| 12 | err error |
| 13 | } |
| 14 | |
| 15 | func (u *unitsSeam) count(context.Context) (int, error) { return u.n, u.err } |
| 16 | |
| 17 | func gib(n uint64) uint64 { return n << 30 } |
| 18 | |
| 19 | func TestAdmissionTwoReadsThenBusy(t *testing.T) { |
| 20 | t.Parallel() |
| 21 | u := &unitsSeam{} |
| 22 | a := newAdmission(u.count, func() (uint64, uint64, error) { return gib(100), gib(200), nil }) |
| 23 | ctx := context.Background() |
| 24 | for _, id := range []string{"r1", "r2"} { |
| 25 | if err := a.admitRead(ctx, id); err != nil { |
| 26 | t.Fatalf("%s: %v", id, err) |
| 27 | } |
| 28 | } |
| 29 | if err := a.admitRead(ctx, "r3"); !errors.Is(err, errBusy) { |
| 30 | t.Fatalf("a third read: %v", err) |
| 31 | } |
| 32 | // The probe still has its connection (spec §7.1, codex 9). |
| 33 | if !a.opened() || !a.opened() || !a.admitProbe(ctx) || !a.opened() { |
| 34 | t.Fatal("two reads and a probe do not fit three connections") |
| 35 | } |
| 36 | if a.opened() { |
| 37 | t.Fatal("a fourth connection was allowed") |
| 38 | } |
| 39 | } |
| 40 | |
| 41 | // T12, unit half: free space that fits one read admits one. |
| 42 | func TestAdmissionDiskFitsOneOfTwo(t *testing.T) { |
| 43 | t.Parallel() |
| 44 | a := newAdmission((&unitsSeam{}).count, func() (uint64, uint64, error) { return gib(12), gib(20), nil }) |
| 45 | ctx := context.Background() |
| 46 | if err := a.admitRead(ctx, "r1"); err != nil { |
| 47 | t.Fatal(err) |
| 48 | } |
| 49 | if err := a.admitRead(ctx, "r2"); !errors.Is(err, errNoRoom) { |
| 50 | t.Fatalf("a second read on a box with room for one: %v", err) |
| 51 | } |
| 52 | if err := a.grow("r1", int64(gib(8))); !errors.Is(err, errNoRoom) { |
| 53 | t.Fatalf("growing past the floor and 10%%: %v", err) |
| 54 | } |
| 55 | if err := a.grow("r1", int64(gib(6))); err != nil { |
| 56 | t.Fatalf("growing within room: %v", err) |
| 57 | } |
| 58 | } |
| 59 | |
| 60 | // An orphan (a unit this agent is not running) blocks every admission until |
| 61 | // it is gone, and no size is guessed for it (spec §5.7, codex 8). |
| 62 | func TestAdmissionRefusesBesideAnOrphan(t *testing.T) { |
| 63 | t.Parallel() |
| 64 | u := &unitsSeam{n: 1} |
| 65 | a := newAdmission(u.count, func() (uint64, uint64, error) { return gib(100), gib(200), nil }) |
| 66 | ctx := context.Background() |
| 67 | if err := a.admitRead(ctx, "r1"); !errors.Is(err, errOrphans) { |
| 68 | t.Fatalf("beside an orphan: %v", err) |
| 69 | } |
| 70 | if a.admitProbe(ctx) { |
| 71 | t.Fatal("a probe beside an orphan") |
| 72 | } |
| 73 | u.n = 0 |
| 74 | if err := a.admitRead(ctx, "r1"); err != nil { |
| 75 | t.Fatalf("once the orphan is gone: %v", err) |
| 76 | } |
| 77 | } |
| 78 | |
| 79 | // A finished read's reservation is held until no db-read unit is left, since |
| 80 | // systemd removes the scratch only at unit stop. |
| 81 | func TestAdmissionHoldsAReservationUntilItsUnitIsGone(t *testing.T) { |
| 82 | t.Parallel() |
| 83 | u := &unitsSeam{} |
| 84 | // 12 GiB free of 20: r1 grown to 6 leaves room for r2's floor only once |
| 85 | // r1's reservation is released. |
| 86 | a := newAdmission(u.count, func() (uint64, uint64, error) { return gib(12), gib(20), nil }) |
| 87 | ctx := context.Background() |
| 88 | if err := a.admitRead(ctx, "r1"); err != nil { |
| 89 | t.Fatal(err) |
| 90 | } |
| 91 | a.opened() |
| 92 | if err := a.grow("r1", int64(gib(6))); err != nil { |
| 93 | t.Fatal(err) |
| 94 | } |
| 95 | u.n = 1 |
| 96 | a.closed() |
| 97 | a.finish("r1") |
| 98 | // The unit is still deactivating: one unit, no connection. Refused. |
| 99 | if err := a.admitRead(ctx, "r2"); !errors.Is(err, errOrphans) { |
| 100 | t.Fatalf("while the unit deactivates: %v", err) |
| 101 | } |
| 102 | u.n = 0 |
| 103 | if err := a.admitRead(ctx, "r2"); err != nil { |
| 104 | t.Fatalf("after the unit is gone the reservation is free: %v", err) |
| 105 | } |
| 106 | } |
| 107 | |
| 108 | // Review Focus 5: a unit listing that fails admits nothing and skips the |
| 109 | // probe rather than guessing. |
| 110 | func TestAdmissionFailsClosedWhenUnitsCannotBeListed(t *testing.T) { |
| 111 | t.Parallel() |
| 112 | u := &unitsSeam{err: errors.New("systemctl: not found")} |
| 113 | a := newAdmission(u.count, func() (uint64, uint64, error) { return gib(100), gib(200), nil }) |
| 114 | if err := a.admitRead(context.Background(), "r1"); err == nil { |
| 115 | t.Fatal("admitted with no unit listing") |
| 116 | } |
| 117 | if a.admitProbe(context.Background()) { |
| 118 | t.Fatal("probed with no unit listing") |
| 119 | } |
| 120 | } |
| 121 | |
| 122 | // A read admitted and then lost in the election started no worker: its |
| 123 | // floor goes at once, even while another read's unit is running. |
| 124 | func TestAdmissionAbandonFreesAtOnce(t *testing.T) { |
| 125 | t.Parallel() |
| 126 | u := &unitsSeam{} |
| 127 | // 17 GiB of 20: room for two floors (17-10 = 7), not three. |
| 128 | a := newAdmission(u.count, func() (uint64, uint64, error) { return gib(17), gib(20), nil }) |
| 129 | ctx := context.Background() |
| 130 | if err := a.admitRead(ctx, "running"); err != nil { |
| 131 | t.Fatal(err) |
| 132 | } |
| 133 | a.opened() |
| 134 | u.n = 1 // its worker unit is up, so finished reservations stay held |
| 135 | if err := a.admitRead(ctx, "lost"); err != nil { |
| 136 | t.Fatal(err) |
| 137 | } |
| 138 | a.abandon("lost") // it lost the election; no worker started |
| 139 | if err := a.admitRead(ctx, "next"); err != nil { |
| 140 | t.Fatalf("the lost read's floor is still held: %v", err) |
| 141 | } |
| 142 | } |
| 143 | |
| 144 | // Plan review finding 10: a retried read keeps its first attempt's |
| 145 | // reservation while that worker's unit is still stopping, and settle waits |
| 146 | // for the unit. Mutation: retry leaves held[id] in place instead of moving |
| 147 | // it to a retired key; the grow below then fits and this test is red. |
| 148 | func TestAdmissionRetryHoldsTheOldReservation(t *testing.T) { |
| 149 | t.Parallel() |
| 150 | u := &unitsSeam{} |
| 151 | a := newAdmission(u.count, func() (uint64, uint64, error) { return gib(12), gib(20), nil }) |
| 152 | ctx := context.Background() |
| 153 | if err := a.admitRead(ctx, "r1"); err != nil { |
| 154 | t.Fatal(err) |
| 155 | } |
| 156 | if err := a.grow("r1", int64(gib(6))); err != nil { |
| 157 | t.Fatal(err) |
| 158 | } |
| 159 | u.n = 1 // the first worker's connection is closed; its unit is stopping |
| 160 | a.retry("r1", 1) |
| 161 | if err := a.grow("r1", int64(gib(5))); !errors.Is(err, errNoRoom) { |
| 162 | t.Fatalf("the stopping worker's scratch was not held: %v", err) |
| 163 | } |
| 164 | short, cancel := context.WithTimeout(ctx, 100*time.Millisecond) |
| 165 | defer cancel() |
| 166 | if err := a.settle(short, 10*time.Millisecond); !errors.Is(err, context.DeadlineExceeded) { |
| 167 | t.Fatalf("settle returned beside a live unit: %v", err) |
| 168 | } |
| 169 | u.n = 0 |
| 170 | if err := a.settle(ctx, 10*time.Millisecond); err != nil { |
| 171 | t.Fatal(err) |
| 172 | } |
| 173 | if err := a.grow("r1", int64(gib(5))); err != nil { |
| 174 | t.Fatalf("after the unit stopped: %v", err) |
| 175 | } |
| 176 | } |
| 177 | |
| 178 | func TestAdmissionFailsClosedWhenTheDiskCannotBeRead(t *testing.T) { |
| 179 | t.Parallel() |
| 180 | a := newAdmission((&unitsSeam{}).count, func() (uint64, uint64, error) { return 0, 0, errors.New("statfs") }) |
| 181 | if err := a.admitRead(context.Background(), "r1"); !errors.Is(err, errNoRoom) { |
| 182 | t.Fatalf("admitted with no disk reading: %v", err) |
| 183 | } |
| 184 | } |
| 185 | |
amadan