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| 1 | +package monitorapi |
| 2 | + |
| 3 | +import ( |
| 4 | + "context" |
| 5 | + "errors" |
| 6 | + "fmt" |
| 7 | + "log/slog" |
| 8 | + "net" |
| 9 | + "os" |
| 10 | + "sync" |
| 11 | + "time" |
| 12 | + |
| 13 | + "github.com/arduino/router/msgpackrouter" |
| 14 | + "github.com/arduino/router/msgpackrpc" |
| 15 | +) |
| 16 | + |
| 17 | +var lock sync.RWMutex |
| 18 | +var socket net.Conn |
| 19 | +var monitorConnectionLost sync.Cond = *sync.NewCond(&lock) |
| 20 | + |
| 21 | +// Register the Monitor API methods |
| 22 | +func Register(router *msgpackrouter.Router, addr string) error { |
| 23 | + listener, err := net.Listen("tcp", addr) |
| 24 | + if err != nil { |
| 25 | + return fmt.Errorf("failed to start listener: %w", err) |
| 26 | + } |
| 27 | + go connectionHandler(listener) |
| 28 | + _ = router.RegisterMethod("mon/connected", connected) |
| 29 | + _ = router.RegisterMethod("mon/read", read) |
| 30 | + _ = router.RegisterMethod("mon/write", write) |
| 31 | + _ = router.RegisterMethod("mon/reset", reset) |
| 32 | + return nil |
| 33 | +} |
| 34 | + |
| 35 | +func connectionHandler(listener net.Listener) { |
| 36 | + for { |
| 37 | + conn, err := listener.Accept() |
| 38 | + if err != nil { |
| 39 | + slog.Error("Failed to accept monitor connection", "error", err) |
| 40 | + return |
| 41 | + } |
| 42 | + |
| 43 | + slog.Info("Accepted monitor connection", "from", conn.RemoteAddr()) |
| 44 | + lock.Lock() |
| 45 | + socket = conn |
| 46 | + lock.Unlock() |
| 47 | + |
| 48 | + lock.Lock() |
| 49 | + for socket != nil { |
| 50 | + monitorConnectionLost.Wait() |
| 51 | + } |
| 52 | + lock.Unlock() |
| 53 | + } |
| 54 | +} |
| 55 | + |
| 56 | +func connected(ctx context.Context, rpc *msgpackrpc.Connection, params []any) (_result any, _err any) { |
| 57 | + if len(params) != 0 { |
| 58 | + return nil, []any{1, "Invalid number of parameters, expected no parameters"} |
| 59 | + } |
| 60 | + |
| 61 | + lock.RLock() |
| 62 | + connected := socket != nil |
| 63 | + lock.RUnlock() |
| 64 | + |
| 65 | + return connected, nil |
| 66 | +} |
| 67 | + |
| 68 | +func read(ctx context.Context, rpc *msgpackrpc.Connection, params []any) (_result any, _err any) { |
| 69 | + if len(params) != 1 { |
| 70 | + return nil, []any{1, "Invalid number of parameters, expected max bytes to read"} |
| 71 | + } |
| 72 | + maxBytes, ok := msgpackrpc.ToUint(params[0]) |
| 73 | + if !ok { |
| 74 | + return nil, []any{1, "Invalid parameter type, expected positive int for max bytes to read"} |
| 75 | + } |
| 76 | + |
| 77 | + lock.RLock() |
| 78 | + conn := socket |
| 79 | + lock.RUnlock() |
| 80 | + |
| 81 | + // No active connection, return empty slice |
| 82 | + if conn == nil { |
| 83 | + return []byte{}, nil |
| 84 | + } |
| 85 | + |
| 86 | + buffer := make([]byte, maxBytes) |
| 87 | + // It seems that the only way to make a non-blocking read is to set a read deadline. |
| 88 | + // BTW setting the read deadline to time.Now() will always returns an empty (zero bytes) |
| 89 | + // read, so we set it to a very short duration in the future. |
| 90 | + if err := conn.SetReadDeadline(time.Now().Add(time.Millisecond)); err != nil { |
| 91 | + return nil, []any{3, "Failed to set read timeout: " + err.Error()} |
| 92 | + } |
| 93 | + n, err := conn.Read(buffer) |
| 94 | + if errors.Is(err, os.ErrDeadlineExceeded) { |
| 95 | + // timeout |
| 96 | + } else if err != nil { |
| 97 | + // If we get an error other than timeout, we assume the connection is lost. |
| 98 | + slog.Error("Monitor connection lost, closing connection", "error", err) |
| 99 | + close() |
| 100 | + return nil, []any{3, "Failed to read from connection: " + err.Error()} |
| 101 | + } |
| 102 | + |
| 103 | + return buffer[:n], nil |
| 104 | +} |
| 105 | + |
| 106 | +func write(ctx context.Context, rpc *msgpackrpc.Connection, params []any) (_result any, _err any) { |
| 107 | + if len(params) != 1 { |
| 108 | + return nil, []any{1, "Invalid number of parameters, expected data to write"} |
| 109 | + } |
| 110 | + data, ok := params[0].([]byte) |
| 111 | + if !ok { |
| 112 | + if dataStr, ok := params[0].(string); ok { |
| 113 | + data = []byte(dataStr) |
| 114 | + } else { |
| 115 | + // If data is not []byte or string, return an error |
| 116 | + return nil, []any{1, "Invalid parameter type, expected []byte or string for data to write"} |
| 117 | + } |
| 118 | + } |
| 119 | + |
| 120 | + lock.RLock() |
| 121 | + conn := socket |
| 122 | + lock.RUnlock() |
| 123 | + |
| 124 | + if conn == nil { // No active connection, drop the data |
| 125 | + return len(data), nil |
| 126 | + } |
| 127 | + |
| 128 | + n, err := conn.Write(data) |
| 129 | + if err != nil { |
| 130 | + // If we get an error, we assume the connection is lost. |
| 131 | + slog.Error("Monitor connection lost, closing connection", "error", err) |
| 132 | + close() |
| 133 | + |
| 134 | + return nil, []any{3, "Failed to write to connection: " + err.Error()} |
| 135 | + } |
| 136 | + |
| 137 | + return n, nil |
| 138 | +} |
| 139 | + |
| 140 | +func reset(ctx context.Context, rpc *msgpackrpc.Connection, params []any) (_result any, _err any) { |
| 141 | + if len(params) != 0 { |
| 142 | + return nil, []any{1, "Invalid number of parameters, expected no parameters"} |
| 143 | + } |
| 144 | + close() |
| 145 | + slog.Info("Monitor connection reset") |
| 146 | + return true, nil |
| 147 | +} |
| 148 | + |
| 149 | +func close() { |
| 150 | + lock.Lock() |
| 151 | + if socket != nil { |
| 152 | + _ = socket.Close() |
| 153 | + } |
| 154 | + socket = nil |
| 155 | + monitorConnectionLost.Broadcast() |
| 156 | + lock.Unlock() |
| 157 | +} |
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