@khaosdoctor/hermod
v1.1.5
Published
SDK for messaging
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Hermod
MQTT message client to, you know, send messages
Summary
Usage examples
Instalation:
npm i @khaosdoctor/hermod
Posting a message
const { MessageClient: Hermod } = require('@khaosdoctor/hermod')
const config = {
queueHostname: 'localhost'
}
const messenger = new Hermod(config)
messenger.postMessage('message', 'queueName') // Returns a promise
Listening to a queue
const { MessageClient: Hermod } = require('@khaosdoctor/hermod')
const config = {
queueHostname: 'localhost'
}
const messenger = new Hermod(config)
function handler (message) {
console.log(message.content.toString())
}
// Will call `handler` everytime a message arrives
messenger.listenToQueue('queueName', handler)
Switching queues
const { MessageClient: Hermod } = require('@khaosdoctor/hermod')
const config = {
queueHostname: 'localhost'
}
function handler (message) {
console.log(message.content.toString())
}
const messenger = new Hermod(config)
messenger.listenToQueue('queueName', handler)
messenger.changeQueue('anotherQueue').then((queueObject) => /* ... */)
Acking, Nacking and rejecting messages
Acking
const { MessageClient: Hermod } = require('@khaosdoctor/hermod')
const config = {
queueHostname: 'localhost'
}
const messenger = new Hermod(config)
function handler (message) {
console.log(message.content.toString())
messenger.ackMessage(message)
}
messenger.listenToQueue('queueName', handler)
Nacking
const { MessageClient: Hermod } = require('@khaosdoctor/hermod')
const config = {
queueHostname: 'localhost'
}
const messenger = new Hermod(config)
function handler (message) {
console.log(message.content.toString())
messenger.nackMessage(message)
}
messenger.listenToQueue('queueName', handler)
Rejecting
const { MessageClient: Hermod } = require('@khaosdoctor/hermod')
const config = {
queueHostname: 'localhost'
}
const messenger = new Hermod(config)
function handler (message) {
console.log(message.content.toString())
messenger.rejectMessage(message)
}
messenger.listenToQueue('queueName', handler)
Config object
Hermod takes a config object like the following:
{
queueHostname: string
queueName?: string
queueProtocol?: 'amqp' | 'amqps'
queuePort?: number
username?: string
password?: string
maxConnectionAttemps?: number
connectionRetryInterval?: number
durable?: boolean
noAck?: boolean
persistent?: boolean
}
- queueHostname (required): The broker hostname, without the protocol
- queueName: Default queue to be used when posting messages, if this is null you'll have to pass the name directly to the function, defaults to
undefined
- queueProtocol:
amqp
oramqps
depending on your implementation, defaults toamqp
- queuePort: Broker port, defaults to
5672
, which is rabbitMQ's default port - username: Username in case of authentication. If not, leave it blank
- password: Password in case of authentication. If not, leave it blank
- maxConnectionAttemps: Max connection attemps that will be made in case of error on first connection, defaults to
5
- connectionRetryInternal: The interval between connection attemps (in ms), this number will be multiplied by the number of attempts made in order to create a crescent interval, defaults to
1000
- durable: Defines if a queue should be durable, defaults to
true
- noAck: Defines if a consuming channel should auto acknowledge the messages it receives, defaults to
false
- persistent: Defines if a message will be persistently saved, defaults to
true
Channel, queue and message configurations such as
persistent
,durable
andnoAck
can be passed on directly to the function, if not the default config will have the claim
API
postMessage
postMessage (message: any, queueName?: string, persistent?: boolean): Promise<boolean>
Description: Posts message
to queueName
. If queueName
is null
or undefined
, the config.queueName
will be used
Parameters:
message
(required): Message content to be posted, it needs to be something which can be transformed into a Buffer (withBuffer.from
)queueName
: Optional queueName to override the queue from the default configuration (if any)persistent
: Setting it will override theconfig.persistent
value
Returns: Boolean value indicating succes of operation
listenToQueue
listenToQueue (queueName: string, handler: MessageHandler, noAck?: boolean, durable?: boolean): Promise<{ consumerTag: string }>
Description: Start consuming queueName
. Everytime a new message arrives, handler
will be called
Parameters:
queueName
(required): Queue name to be listened. This method does not read the defaultconfig.queueName
handler
(required): Function which will handle the message. Must have a signature like(message) => any
noAck
: This will overrideconfig.noAck
value for this specific consumerdurable
: This will overrideconfig.durable
value for this specific consumer
Returns: Promise with the new consumer tag
changeQueue
changeQueue (queueName: string, durable?: boolean): Promise<{ queue: string, messageCount: number, consumerCount: number }>
Description: Will assert a new queue on the channel
Parameters:
queueName
(required): Name of the queue to be asserteddurable
: Will overrideconfig.durable
value for this specific queue
Returns:
ackMessage
ackMessage (message: ConsumeMessage, allUpToThis: boolean = false): void
Description: Acknowledges a message
Parameters:
message
(required): The received message objectallUpToThis
: Will acknowledge all messages before the one being sent as well
nackMessage
nackMessage (message: ConsumeMessage, allUpToThis: boolean = false, requeue: boolean = true): void
Description: Nacks a message, requeuing it by default
Parameters:
message
(required): The received message objectallUpToThis
: Will not acknowledge all messages before the one being sent as wellrequeue
: Will also requeue the message
rejectMessage
rejectMessage (message: ConsumeMessage, requeue: boolean = false): void
Description: Rejects a message, not requeuing it by default
Parameters:
message
(required): The received message objectrequeue
: Will also requeue the message