diff options
Diffstat (limited to 'vendor/github.com/hashicorp/go-plugin/mux_broker.go')
-rw-r--r-- | vendor/github.com/hashicorp/go-plugin/mux_broker.go | 204 |
1 files changed, 204 insertions, 0 deletions
diff --git a/vendor/github.com/hashicorp/go-plugin/mux_broker.go b/vendor/github.com/hashicorp/go-plugin/mux_broker.go new file mode 100644 index 000000000..01c45ad7c --- /dev/null +++ b/vendor/github.com/hashicorp/go-plugin/mux_broker.go @@ -0,0 +1,204 @@ +package plugin + +import ( + "encoding/binary" + "fmt" + "log" + "net" + "sync" + "sync/atomic" + "time" + + "github.com/hashicorp/yamux" +) + +// MuxBroker is responsible for brokering multiplexed connections by unique ID. +// +// It is used by plugins to multiplex multiple RPC connections and data +// streams on top of a single connection between the plugin process and the +// host process. +// +// This allows a plugin to request a channel with a specific ID to connect to +// or accept a connection from, and the broker handles the details of +// holding these channels open while they're being negotiated. +// +// The Plugin interface has access to these for both Server and Client. +// The broker can be used by either (optionally) to reserve and connect to +// new multiplexed streams. This is useful for complex args and return values, +// or anything else you might need a data stream for. +type MuxBroker struct { + nextId uint32 + session *yamux.Session + streams map[uint32]*muxBrokerPending + + sync.Mutex +} + +type muxBrokerPending struct { + ch chan net.Conn + doneCh chan struct{} +} + +func newMuxBroker(s *yamux.Session) *MuxBroker { + return &MuxBroker{ + session: s, + streams: make(map[uint32]*muxBrokerPending), + } +} + +// Accept accepts a connection by ID. +// +// This should not be called multiple times with the same ID at one time. +func (m *MuxBroker) Accept(id uint32) (net.Conn, error) { + var c net.Conn + p := m.getStream(id) + select { + case c = <-p.ch: + close(p.doneCh) + case <-time.After(5 * time.Second): + m.Lock() + defer m.Unlock() + delete(m.streams, id) + + return nil, fmt.Errorf("timeout waiting for accept") + } + + // Ack our connection + if err := binary.Write(c, binary.LittleEndian, id); err != nil { + c.Close() + return nil, err + } + + return c, nil +} + +// AcceptAndServe is used to accept a specific stream ID and immediately +// serve an RPC server on that stream ID. This is used to easily serve +// complex arguments. +// +// The served interface is always registered to the "Plugin" name. +func (m *MuxBroker) AcceptAndServe(id uint32, v interface{}) { + conn, err := m.Accept(id) + if err != nil { + log.Printf("[ERR] plugin: plugin acceptAndServe error: %s", err) + return + } + + serve(conn, "Plugin", v) +} + +// Close closes the connection and all sub-connections. +func (m *MuxBroker) Close() error { + return m.session.Close() +} + +// Dial opens a connection by ID. +func (m *MuxBroker) Dial(id uint32) (net.Conn, error) { + // Open the stream + stream, err := m.session.OpenStream() + if err != nil { + return nil, err + } + + // Write the stream ID onto the wire. + if err := binary.Write(stream, binary.LittleEndian, id); err != nil { + stream.Close() + return nil, err + } + + // Read the ack that we connected. Then we're off! + var ack uint32 + if err := binary.Read(stream, binary.LittleEndian, &ack); err != nil { + stream.Close() + return nil, err + } + if ack != id { + stream.Close() + return nil, fmt.Errorf("bad ack: %d (expected %d)", ack, id) + } + + return stream, nil +} + +// NextId returns a unique ID to use next. +// +// It is possible for very long-running plugin hosts to wrap this value, +// though it would require a very large amount of RPC calls. In practice +// we've never seen it happen. +func (m *MuxBroker) NextId() uint32 { + return atomic.AddUint32(&m.nextId, 1) +} + +// Run starts the brokering and should be executed in a goroutine, since it +// blocks forever, or until the session closes. +// +// Uses of MuxBroker never need to call this. It is called internally by +// the plugin host/client. +func (m *MuxBroker) Run() { + for { + stream, err := m.session.AcceptStream() + if err != nil { + // Once we receive an error, just exit + break + } + + // Read the stream ID from the stream + var id uint32 + if err := binary.Read(stream, binary.LittleEndian, &id); err != nil { + stream.Close() + continue + } + + // Initialize the waiter + p := m.getStream(id) + select { + case p.ch <- stream: + default: + } + + // Wait for a timeout + go m.timeoutWait(id, p) + } +} + +func (m *MuxBroker) getStream(id uint32) *muxBrokerPending { + m.Lock() + defer m.Unlock() + + p, ok := m.streams[id] + if ok { + return p + } + + m.streams[id] = &muxBrokerPending{ + ch: make(chan net.Conn, 1), + doneCh: make(chan struct{}), + } + return m.streams[id] +} + +func (m *MuxBroker) timeoutWait(id uint32, p *muxBrokerPending) { + // Wait for the stream to either be picked up and connected, or + // for a timeout. + timeout := false + select { + case <-p.doneCh: + case <-time.After(5 * time.Second): + timeout = true + } + + m.Lock() + defer m.Unlock() + + // Delete the stream so no one else can grab it + delete(m.streams, id) + + // If we timed out, then check if we have a channel in the buffer, + // and if so, close it. + if timeout { + select { + case s := <-p.ch: + s.Close() + } + } +} |