@r2d2bzh/broker-autobot
v0.0.2
Published
self-configuring robotic lifeform to manage centrally the configuration of all Moleculer brokers
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:source-highlighter: highlightjs ifdef::env-github[] :status: :outfilesuffix: .adoc :caution-caption: :fire: :important-caption: :exclamation: :note-caption: :paperclip: :tip-caption: :bulb: :warning-caption: :warning: endif::[]
:wikipedia-autobot: https://en.wikipedia.org/wiki/Autobot :lodash-merge: https://lodash.com/docs/#merge :moleculer: https://moleculer.services/ :moleculer-doc: {moleculer}/docs/0.14 :moleculer-action: {moleculer-doc}/actions.html :moleculer-broker: {moleculer-doc}/broker.html :moleculer-event: {moleculer-doc}/events.html :moleculer-service: {moleculer-doc}/services.html
= The broker autobot
The {wikipedia-autobot}[Autobots] are benevolent, sentient, self-configuring robotic lifeforms from the planet Cybertron. This particular autobot is designed to ease the configuration updates of {moleculer}[Moleculer] services {moleculer-broker}[brokers].
== Typical use case
You manage multiple {moleculer-service}[Moleculer services] and you want to easily update the configuration of the brokers hosting the service instances at once. For instance, you have common settings for timeouts or log levels for all these brokers.
On start, broker-autobot
will:
. get these common settings through a configurable {moleculer-action}[Moleculer action] (a temporary broker is used)
. parse these settings through a customizable parser (broker-autobot
setting)
. create a new broker with these settings and create your services with this broker instance
. start the broker
Additionally broker-autobot
can subscribe to a customizable event (broker-autobot
setting) through its own service in order to be aware of a configuration change.
While receiving this event it will:
. decide whether this event applies to its configuration through a customizable predicate (broker-autobot
setting)
. retrieve the new common settings and parse them
. TODO: decide for a restart order between the broker instances impacted by the modification and wait for one's turn
. stop the current broker instance
. create a new broker with these settings and create your services with this broker instance
. start the broker
. TODO: tell other brokers that we are finished with the update
[WARNING]
Some broker configuration settings must not be retrieved/updated by the broker-autobot
, this is by design.
Namely:
namespace
transporter
serializer
Basically all settings related to the communication between brokers cannot be changed dynamically. This due to the fact that these settings are needed by the temporary broker used to retrieve the common settings.
== Usage
Get the broker-autobot
module:
[source,bash]
npm install @r2d2bzh/broker-autobot
In your main module:
.Base usage
.index.js [source,javascript]
const brokerAutobot = require('@r2d2bzh/broker-autobot');
const schema1Factory = () => { // return your service schema 1 here }; const schema2Factory = () => { // return your service schema 2 here };
const autobot = brokerAutobot({ initialSettings: { // initial broker settings, typically settings related to the communication between brokers transporter: process.env.TRANSPORTER }, schemaFactories: [schema1Factory, schema2Factory], });
autobot.start();
NOTE: Here there is neither an action nor an event to manage the broker configuration, the broker will start with an empty configuration.
== Retrieving the common broker configuration
To register an action to retrieve the common broker configuration:
.Retrieving the common broker settings
.index.js [source,javascript]
const autobot = brokerAutobot({ settingsRetrievalAction: { serviceName: 'configuration-holder-service', actionName: 'get-broker-config', params: { // action parameters }, parser: (retrieveActionResult) => { // parse retrieveActionResult and return the broker configuration object }, }, });
NOTE: If no parser is provided, the retrieveActionResult
is directly used as the broker configuration object.
== Overloading the common configuration
If some specific settings need to be applied to this particular broker instance, the common configuration can be overloaded:
.Broker settings settingsOverload
.index.js [source,javascript]
const autobot = brokerAutobot({ settingsRetrievalAction: { // ... }, settingsOverload: { logLevel: { '**': 'warn' }, }, });
NOTE: {lodash-merge}[Lodash merge] is used to merge settingsOverload
over the common broker settings.
== Broker configuration update event
In order for the broker-autobot
to be aware of a broker configuration update, a {moleculer-event}[Moleculer event] can be used to trigger its restart.
name:: The name of the moleculer update event name to listen for (mandatory).
throttling:: Minimum time to wait until taking into account any new update event (optional, default: () => true
).
predicate:: Decides whether or not the update event will trigger a broker restart (optional, default: 30e3
milliseconds).
[NOTE]
The throttling parameter is also used to create an update window size. This is to avoid all autobots to restart at the same time which would disrupt services resilience.