ZIO Tutorial: Nodes
Table of Contents
ZIO provides zio.Node to provide simpler construction and management
of zio.Port objects (writeup and tutorial) and to more easily
participate in peering (writeup and tutorial)
1 When to use a node
A node is a distinct entity as seen on the network. This means a single application may create multiple nodes and each will be seen as a distinct and independent peer on the network. A node may have zero or more ports and each port may bind and/or connect to zero or more addresses. How to choose between these levels of multiplicity depends on the need of the application. Typically, each well defined program or possibly component will have a single node.
2 Create a node
A node must be created with a nick name, an optional origin number and an optional host name (or IP address). This last is used if a default binds on a port is later requested.
node = zio.Node("mynode", 42, '130.199.22.40')
3 Making ports
The main thing a node provides is a simplified port construction.
pi = node.port("input", zmq.SUB)
po = node.port("output", zmq.PUB)
See port tutorial for how to now connect and/or bind a port to addresses.
4 Going online
When a node goes online it brings its ports online in a careful order so that ZIO peering can be used to resolve abstract connection addresses. The application can also include additional headers that will be advertised to the network.
node.online(greeting = 'Hello World') peer = zio.Peer("other") peer.drain() print (peer.peers) # { UUID('b9d9476e-eb96-4ab2-98a2-9733c0ae013e'): # PeerInfo(uuid=UUID('b9d9476e-eb96-4ab2-98a2-9733c0ae013e'), # nick='mynode', # headers={'greeting': 'Hello World', # 'zio.port.input.socket': 'SUB', # 'zio.port.output.socket': 'PUB'})}
5 Going offline
When a node is taken offline, all its ports are taken offline. This undoes any connections and binds. It also deletes the underlying peer held by the node so the node will "disappear" from the Zyre network.
A node must be explicitly taken offline or deleted by the application or it may hang on shutdown.