|
| 1 | +package client |
| 2 | + |
| 3 | +import ( |
| 4 | + "bytes" |
| 5 | + "encoding/binary" |
| 6 | + "fmt" |
| 7 | + "io" |
| 8 | + "net" |
| 9 | + "time" |
| 10 | +) |
| 11 | + |
| 12 | +type LockingCenter interface { |
| 13 | + Lock(key string) |
| 14 | + Unlock(key string) |
| 15 | + Wait(key string) |
| 16 | + Reset(key string) |
| 17 | +} |
| 18 | + |
| 19 | +type lockingCenter struct { |
| 20 | + address *net.TCPAddr |
| 21 | +} |
| 22 | + |
| 23 | +func NewLockingCenter(address string) (LockingCenter, error) { |
| 24 | + addr, err := net.ResolveTCPAddr("tcp", address) |
| 25 | + if err != nil { |
| 26 | + return nil, err |
| 27 | + } |
| 28 | + |
| 29 | + lc := &lockingCenter{ |
| 30 | + address: addr, |
| 31 | + } |
| 32 | + if err := lc.ping(); err != nil { |
| 33 | + return nil, err |
| 34 | + } |
| 35 | + return lc, nil |
| 36 | +} |
| 37 | + |
| 38 | +func (l *lockingCenter) connect() (*net.TCPConn, error) { |
| 39 | + conn, err := net.DialTCP("tcp", nil, l.address) |
| 40 | + if err != nil { |
| 41 | + return nil, err |
| 42 | + } |
| 43 | + return conn, nil |
| 44 | +} |
| 45 | + |
| 46 | +func (l *lockingCenter) ping() error { |
| 47 | + conn, err := l.connect() |
| 48 | + if err != nil { |
| 49 | + return err |
| 50 | + } |
| 51 | + return conn.Close() |
| 52 | +} |
| 53 | + |
| 54 | +func (l *lockingCenter) preparePackage(key string, action byte) ([]byte, error) { |
| 55 | + if len(key) == 0 || len(key) > 128 { |
| 56 | + return nil, fmt.Errorf("key can not be empty or more than 128 characters") |
| 57 | + } |
| 58 | + |
| 59 | + data := make([]byte, 0) |
| 60 | + buffer := bytes.NewBuffer(data) |
| 61 | + |
| 62 | + keySize := int8(len(key)) |
| 63 | + if err := binary.Write(buffer, binary.LittleEndian, keySize); err != nil { |
| 64 | + return nil, err |
| 65 | + } |
| 66 | + |
| 67 | + if err := binary.Write(buffer, binary.LittleEndian, []byte(key)); err != nil { |
| 68 | + return nil, err |
| 69 | + } |
| 70 | + |
| 71 | + if err := binary.Write(buffer, binary.LittleEndian, action); err != nil { |
| 72 | + return nil, err |
| 73 | + } |
| 74 | + |
| 75 | + return buffer.Bytes(), nil |
| 76 | +} |
| 77 | + |
| 78 | +func (l *lockingCenter) result(conn *net.TCPConn) bool { |
| 79 | + r := make([]byte, 1) |
| 80 | + |
| 81 | + if _, err := io.ReadAtLeast(conn, r, len(r)); err != nil { |
| 82 | + return false |
| 83 | + } |
| 84 | + |
| 85 | + return string(r) == "+" |
| 86 | +} |
| 87 | + |
| 88 | +func (l *lockingCenter) Lock(key string) { |
| 89 | + query := func() bool { |
| 90 | + conn, err := l.connect() |
| 91 | + if err != nil { |
| 92 | + fmt.Printf("ERROR: connection failure: %s\n", err) |
| 93 | + return false |
| 94 | + } |
| 95 | + defer conn.Close() |
| 96 | + |
| 97 | + if err := l.query(conn, key, 1); err != nil { |
| 98 | + fmt.Printf("ERROR: locking error: %s\n", err) |
| 99 | + return false |
| 100 | + } |
| 101 | + |
| 102 | + return true |
| 103 | + } |
| 104 | + |
| 105 | + for !query() { |
| 106 | + time.Sleep(time.Second) |
| 107 | + } |
| 108 | +} |
| 109 | + |
| 110 | +func (l *lockingCenter) Unlock(key string) { |
| 111 | + query := func() bool { |
| 112 | + conn, err := l.connect() |
| 113 | + if err != nil { |
| 114 | + fmt.Printf("ERROR: connection failure: %s\n", err) |
| 115 | + return false |
| 116 | + } |
| 117 | + defer conn.Close() |
| 118 | + |
| 119 | + if err := l.query(conn, key, 2); err != nil { |
| 120 | + fmt.Printf("ERROR: unlocking error: %s\n", err) |
| 121 | + return false |
| 122 | + } |
| 123 | + |
| 124 | + return true |
| 125 | + } |
| 126 | + |
| 127 | + for !query() { |
| 128 | + time.Sleep(time.Second) |
| 129 | + } |
| 130 | +} |
| 131 | + |
| 132 | +func (l *lockingCenter) Wait(key string) { |
| 133 | + l.Lock(key) |
| 134 | + defer l.Unlock(key) |
| 135 | +} |
| 136 | + |
| 137 | +func (l *lockingCenter) Reset(key string) { |
| 138 | + query := func() bool { |
| 139 | + conn, err := l.connect() |
| 140 | + if err != nil { |
| 141 | + fmt.Printf("ERROR: connection failure: %s\n", err) |
| 142 | + return false |
| 143 | + } |
| 144 | + defer conn.Close() |
| 145 | + |
| 146 | + if err := l.query(conn, key, 3); err != nil { |
| 147 | + fmt.Printf("ERROR: reseting error: %s\n", err) |
| 148 | + return false |
| 149 | + } |
| 150 | + |
| 151 | + return true |
| 152 | + } |
| 153 | + |
| 154 | + for !query() { |
| 155 | + time.Sleep(time.Second) |
| 156 | + } |
| 157 | +} |
| 158 | + |
| 159 | +func (l *lockingCenter) query(conn *net.TCPConn, key string, action byte) error { |
| 160 | + payload, err := l.preparePackage(key, action) |
| 161 | + if err != nil { |
| 162 | + return err |
| 163 | + } |
| 164 | + |
| 165 | + if _, err := conn.Write(payload); err != nil { |
| 166 | + return err |
| 167 | + } |
| 168 | + |
| 169 | + if !l.result(conn) { |
| 170 | + return fmt.Errorf("remote server execution error") |
| 171 | + } |
| 172 | + |
| 173 | + return nil |
| 174 | +} |
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