Nanomsg

This is a Haskell binding for the nanomsg library: http://nanomsg.org/.

There's support for blocking send and recv, a non-blocking receive, and for all the socket types and the functions you need to wire them up and tear them down again.

Most socket options are available through accessor and mutator functions. Sockets are typed, transports are not.

Socket type documentation is adapted or quoted verbatim from the nanomsg manual. Please refer to nanomsg.org for information on how to use the library.

Socket types

data Pair

Socket for communication with exactly one peer. Each party can send messages at any time. If the peer is not available or send buffer is full, subsequent calls to send will block until it’s possible to send the message.

Constructors

Pair

data Req

Used to implement a client application that sends requests and receives replies. The socket will resend requests automatically if there's no reply within a given time. The default timeout is 1 minute.

See also setRequestResendInterval.

Constructors

Req

data Rep

Used to implement a stateless worker that receives requests and sends replies.

Constructors

Rep

data Pub

This socket is used to distribute messages to multiple destinations. Can not receive.

Constructors

Pub

data Sub

Receives messages from the publisher. Only messages that the socket is subscribed to are received. When the socket is created there are no subscriptions and thus no messages will be received.

Send is not defined on this socket. The socket can be connected to at most one peer.

See also subscribe and unsubscribe.

Constructors

Sub

data Surveyor

Surveyor and respondent are used to broadcast a survey to multiple locations and gather the responses.

This socket is used to send the survey. The survey is delivered to all the connected respondents. Once the query is sent, the socket can be used to receive the responses.

When the survey deadline expires, receive will return ETIMEDOUT error.

See also setSurveyorDeadline

Constructors

Surveyor

data Respondent

Used to respond to a survey. Survey is received using receive function, response is sent using send function. This socket can be connected to at most one peer.

Constructors

Respondent

data Push

Push and Pull sockets fair queue messages from one processing step, load balancing them among instances of the next processing step.

This socket is used to send messages to a cluster of load-balanced nodes.

Receive operation is not implemented on this socket type.

Constructors

Push

data Pull

This socket is used to receive a message from a cluster of nodes.

Send operation is not implemented on this socket type.

Constructors

Pull

data Bus

Broadcasts messages from any node to all other nodes in the topology. The socket should never receives messages that it sent itself.

This pattern scales only to local level (within a single machine or within a single LAN). Trying to scale it further can result in overloading individual nodes with messages.

Constructors

Bus

Other types

data Socket a

Sockets are created by socket and connections are established with connect or bind.

Free sockets using close.

Instances

Eq a => Eq (Socket a)

Show a => Show (Socket a)

data Endpoint

Endpoint identifier. Created by connect or bind.

Close connections using shutdown.

Instances

Eq Endpoint

Show Endpoint

data NNException

Pretty much any error condition throws this exception.

Instances

Eq NNException

Show NNException

Typeable NNException

Exception NNException

Functions

socket :: Protocol a => a -> IO (Socket a)

Creates a socket. Connections are formed using bind or connect.

See also: close.

withSocket :: Protocol a => a -> (Socket a -> IO b) -> IO b

Creates a socket and runs your action with it.

E.g. collecting 10 messages:

 withSocket Sub $ \sub -> do
     _ <- connect sub "tcp://localhost:5560"
     subscribe sub (C.pack "")
     replicateM 10 (recv sub)

Ensures the socket is closed when your action is done.

bind :: Socket a -> String -> IO Endpoint

Binds the socket to a local interface.

See the nanomsg documentation for specifics on transports. Note that host names do not work for tcp. Some examples are:

 bind sock "tcp://*:5560"
 bind sock "tcp://eth0:5560"
 bind sock "tcp://127.0.0.1:5560"
 bind sock "inproc://test"
 bind sock "ipc:///tmp/test.ipc"

This function returns an Endpoint, which can be supplied to shutdown to remove a connection.

See also: connect, shutdown.

connect :: Socket a -> String -> IO Endpoint

Connects the socket to an endpoint.

e.g. :

 connect sock "tcp://localhost:5560"
 connect sock "inproc://test"

See also: bind, shutdown.

send :: (SendType a, Protocol a) => Socket a -> ByteString -> IO ()

Blocking function for sending a message

See also: recv, recv'.

recv :: (RecvType a, Protocol a) => Socket a -> IO ByteString

Blocking receive.

recv' :: (RecvType a, Protocol a) => Socket a -> IO (Maybe ByteString)

Nonblocking receive function.

subscribe :: (SubscriberType a, Protocol a) => Socket a -> ByteString -> IO ()

Subscribe to a given subject string.

unsubscribe :: (SubscriberType a, Protocol a) => Socket a -> ByteString -> IO ()

Unsubscribes from a subject.

shutdown :: Socket a -> Endpoint -> IO ()

Removes an endpoint from a socket.

See also: bind, connect.

close :: Socket a -> IO ()

Closes the socket. Any buffered inbound messages that were not yet received by the application will be discarded. The library will try to deliver any outstanding outbound messages for the time specified by NN_LINGER socket option. The call will block in the meantime.

term :: IO ()

Switches nanomsg into shutdown modus and interrupts any waiting function calls.

Socket option accessors and mutators

linger :: Socket a -> IO Int

Specifies how long should the socket try to send pending outbound messages after close has been called, in milliseconds.

Negative value means infinite linger. Default value is 1000 (1 second).

setLinger :: Socket a -> Int -> IO ()

Specifies how long should the socket try to send pending outbound messages after close has been called, in milliseconds.

Negative value means infinite linger. Default value is 1000 (1 second).

sndBuf :: Socket a -> IO Int

Size of the send buffer, in bytes. To prevent blocking for messages larger than the buffer, exactly one message may be buffered in addition to the data in the send buffer.

Default value is 128kB.

setSndBuf :: Socket a -> Int -> IO ()

Size of the send buffer, in bytes. To prevent blocking for messages larger than the buffer, exactly one message may be buffered in addition to the data in the send buffer.

Default value is 128kB.

rcvBuf :: Socket a -> IO Int

Size of the receive buffer, in bytes. To prevent blocking for messages larger than the buffer, exactly one message may be buffered in addition to the data in the receive buffer.

Default value is 128kB.

setRcvBuf :: Socket a -> Int -> IO ()

Size of the receive buffer, in bytes. To prevent blocking for messages larger than the buffer, exactly one message may be buffered in addition to the data in the receive buffer.

Default value is 128kB.

reconnectInterval :: Socket a -> IO Int

For connection-based transports such as TCP, this option specifies how long to wait, in milliseconds, when connection is broken before trying to re-establish it.

Note that actual reconnect interval may be randomised to some extent to prevent severe reconnection storms.

Default value is 100 (0.1 second).

setReconnectInterval :: Socket a -> Int -> IO ()

For connection-based transports such as TCP, this option specifies how long to wait, in milliseconds, when connection is broken before trying to re-establish it.

Note that actual reconnect interval may be randomised to some extent to prevent severe reconnection storms.

Default value is 100 (0.1 second).

reconnectIntervalMax :: Socket a -> IO Int

This option is to be used only in addition to NN_RECONNECT_IVL option. It specifies maximum reconnection interval. On each reconnect attempt, the previous interval is doubled until NN_RECONNECT_IVL_MAX is reached.

Value of zero means that no exponential backoff is performed and reconnect interval is based only on NN_RECONNECT_IVL. If NN_RECONNECT_IVL_MAX is less than NN_RECONNECT_IVL, it is ignored.

Default value is 0.

setReconnectIntervalMax :: Socket a -> Int -> IO ()

This option is to be used only in addition to NN_RECONNECT_IVL option. It specifies maximum reconnection interval. On each reconnect attempt, the previous interval is doubled until NN_RECONNECT_IVL_MAX is reached.

Value of zero means that no exponential backoff is performed and reconnect interval is based only on NN_RECONNECT_IVL. If NN_RECONNECT_IVL_MAX is less than NN_RECONNECT_IVL, it is ignored.

Default value is 0.

sndPrio :: Socket a -> IO Int

Sets outbound priority for endpoints subsequently added to the socket. This option has no effect on socket types that send messages to all the peers. However, if the socket type sends each message to a single peer (or a limited set of peers), peers with high priority take precedence over peers with low priority.

Highest priority is 1, lowest priority is 16. Default value is 8.

setSndPrio :: Socket a -> Int -> IO ()

Sets outbound priority for endpoints subsequently added to the socket. This option has no effect on socket types that send messages to all the peers. However, if the socket type sends each message to a single peer (or a limited set of peers), peers with high priority take precedence over peers with low priority.

Highest priority is 1, lowest priority is 16. Default value is 8.

ipv4Only :: Socket a -> IO Int

If set to 1, only IPv4 addresses are used. If set to 0, both IPv4 and IPv6 addresses are used.

Default value is 1.

setIpv4Only :: Socket a -> Int -> IO ()

If set to 1, only IPv4 addresses are used. If set to 0, both IPv4 and IPv6 addresses are used.

Default value is 1.

requestResendInterval :: ReqType a => Socket a -> IO Int

This option is defined on the full REQ socket. If reply is not received in specified amount of milliseconds, the request will be automatically resent.

Default value is 60000 (1 minute).

setRequestResendInterval :: ReqType a => Socket a -> Int -> IO ()

This option is defined on the full REQ socket. If reply is not received in specified amount of milliseconds, the request will be automatically resent.

Default value is 60000 (1 minute).

tcpNoDelay :: Socket a -> IO Int

This option, when set to 1, disables Nagle's algorithm.

Default value is 0.

setTcpNoDelay :: Socket a -> Int -> IO ()

This option, when set to 1, disables Nagle's algorithm.

Default value is 0.