ARCO-175: document callbacker microservice (#560)

CHANGELOG.md

@@ -4,6 +4,7 @@ All notable changes to this project will be documented in this file. The format
 
 ## Table of Contents
 - [Unreleased](#unreleased)
+- [1.3.0](#130---2024-08-21)
 - [1.2.0](#120---2024-08-13)
 - [1.1.91](#1191---2024-06-26)
 - [1.1.87](#1187---2024-06-10)
@@ -17,6 +18,11 @@ All notable changes to this project will be documented in this file. The format
 
 ## [Unreleased]
 
+## [1.3.0] - 2024-08-21
+
+### Changed
+- The functionality for callbacks has been moved from the `metamorph` microservice to the new `callbacker` microservice.
+
 ## [1.2.0] - 2024-08-13
 
 ### Added

doc/README.md

@@ -11,7 +11,7 @@ possible to connect to a large number of nodes without incurring large bandwidth
 
 The ARC design decouples the core functions of a transaction processor and encapsulates them as microservices with the ability to scale horizontally adaptively. Interaction between microservices is decoupled using asynchronous messaging where possible.
 
-ARC consists of 3 core microservices: [API](#API), [Metamorph](#Metamorph) and [BlockTx](#BlockTx), which are all described below.
+ARC consists of 4 core microservices: [API](#API), [Metamorph](#Metamorph), [Callbacker](#Callbacker) and [BlockTx](#BlockTx), which are all described below.
 
 All the microservices are designed to be horizontally scalable, and can be deployed on a single machine or on multiple machines. Each one has been programmed with a store interface. The default store is postgres, but any database that implements the store interface can be used.
 
@@ -84,9 +84,9 @@ When possible, the API is responsible for rejecting transactions that would be u
 
 Metamorph is a microservice that is responsible for processing transactions sent by the API to the Bitcoin network. It takes care of re-sending transactions if they are not acknowledged by the network within a certain time period (60 seconds by default).
 
-#### Callbacks
+### Callbacker
 
-Metamorph also can send callbacks to a specified URL. To register a callback, the client must add the `X-CallbackUrl` header to the request. The callbacker will then send a POST request to the URL specified in the header, with the transaction ID in the body.
+Callbacker is a microservice that sends callbacks to a specified URL. To register a callback, the client must add the `X-CallbackUrl` header to the request. The callbacker will then send a POST request to the URL specified in the header, with the transaction ID in the body.
 
 The following example shows the format of a callback body
 

doc/building_block_diagram.puml

@@ -1,4 +1,3 @@
-```plantuml
 @startuml
 digraph arc {
   rankdir=TB;
@@ -14,16 +13,15 @@ digraph arc {
 		color=black;
 
     api [shape=rectangle, label="API", style=filled, fillcolor=yellow]
-    api -> metamorph
-
     validation [shape=rectangle, label="validation"]
-    api -> validation
-
-    { rank=same; api; validation; }
-    { rank=same; metamorph; blocktx; }
+    empty [width=0 height=0 label="" margin="0.5,0" color="white"]  // to adjust nodes to the left
+
+    api -> {validation metamorph }
 
+    { rank=same; api; validation; empty; }
+    { rank=same; metamorph; blocktx; callbacker; }
 
-    metamorph -> blocktx [style="dashed", dir="both"]
+    metamorph -> {blocktx [style="dashed", dir="both"] callbacker}  
 
     subgraph cluster_mtm {
       label = "metamorph";
@@ -33,14 +31,18 @@ digraph arc {
       metamorph -> node_connection [style="dashed", arrowhead=none]
     }
 
-
     subgraph cluster_blocktx {
       label = "blocktx";
       blocktx_store [shape=cylinder, label="store", style=filled]
       blocktx [shape=rectangle, label="service", style=filled, fillcolor=yellow]
       blocktx -> blocktx_store
       blocktx -> node_connection [style="dashed", arrowhead=none]
     }
+
+    subgraph cluster_callbacker {
+      label = "callbacker";
+      callbacker [shape=rectangle, label="service", style=filled, fillcolor=yellow]
+    }
 	}
 
   subgraph cluster_nodes {