Architecture

Actor

Tagion core's services are various actor's An actor is a task that is able to send and receive messages from other tasks. The actors have a hierarchical structure where the owner of an actor is called a supervisor and the actor owned by the supervisor is called a child.

When an actor fails the error is sent to the to the supervisor if the error is deemed unrecoverable the supervisor can decide to restart the supervision tree.

child stops when a supervisor sends a STOP signal to the child and the child sends an END when it stops if an error occurs in the child the error (Exception) should be sent to the supervisor.

Description of the services in a node

A node consist of the following services.

• tagionwave is the main task responsible all the service

• Main services
  • Supervisor manages all the other services
  • Input Validator This service handle the data-stream input to the network.
  • HiRPC Verifier service is responsible for receiving contracts, ensuring a valid data format of HiRPC requests and compliance with the HiRPC protocol before it is executed in the system.
  • Collector service is responsible for collecting input data for a Contract and ensuring the data is valid and signed before the contract is executed by the TVM.
  • TVM ("Tagion Virtual Machine") is responsible for executing the instructions in the contract ensuring the contracts are compliant with Consensus Rules producing outputs and sending new contracts to the Epoch Creator.
  • Transcript service is responsible for producing a Recorder ensuring correct inputs and output archives including no double input and output in the same Epoch and sending it to the DART.
  • Epoch Creator service is responsible for resolving the Hashgraph and producing a consensus ordered list of events, an Epoch.
  • DART service is responsible for executing data-base instruction and read/write to the physical file system.
  • DART Interface handles outside read requests to the dart
  • TRT "Transaction reverse table" stores a copy of the owner to bill relationship.
  • Replicator service is responsible for keeping record of the database instructions both to undo, replay and publish the instructions sequantially.
  • Node Interface service is responsible for handling and routing requests to and from the p2p node network.

• Support services
  • Logger takes care of handling the logger information for all the services.
  • Logger Subscription The logger subscript take care of handling remote logger and event logging.
  • Monitor Monitor interface to display the state of the HashGraph.

Connection types

By default all of these sockets are private, ie. they are linux abstract sockets and can only by accessed on the same machine. The socket address, and thereby the visibility can be changed in the tagionwave config file.

Input Validator	Dart Interface	Subscription	Node Interface
Write	Read-only	Pub	Half-duplex p2p wavefront communication
HiRPC methods	..	..	..
"submit"	"search"	"log"
	"dartCheckRead"
	"dartRead"
	"dartRim"
	"dartBullseye"
NNG Socket type	..	..	..
REPLY	REPLY	PUBLISH	???

Data Message flow

This graph show the primary data message flow in the node.

Tagion Service Hierarchy

This graph show the supervisor hierarchy of the services in the network.

The arrow indicates ownership is means of service-A points to service-B. Service-A has ownership of service-B.

This means that if Service-B fails service-A is responsible to handle and take-care of the action to restart or other action.