A simple JS message hub
npm install centralize-js --save
Messages have the following form:
const message = {
logLevel: 10,
labels: {
app: 'my-app',
category: 'analytics',
metric: 'load-time'
},
timestamp: new Date(),
value: 10000 // in milliseconds
}A message sent by the hub will be dispatched to all receivers. To send a message, you can use the library provided logger or manually create and send a message.
You can use the utility function CreateMessage to create an empty message.
import {CreateMessage} from 'centralize-js';
const myAnalyticsMessage = CreateMessage(10, {type: 'analytics'});
myAnalyticsMessage.value = 'val';import Logger from 'centralize-js';
Logger.info('this is an info log');
Logger.debug('this is a debug log');Note: The logger contains the info(), debug(), warn()... methods because it is created using the DEFAULT_LOG_LEVELS.
You can use your own custom methods by creating a new logger with your own log levels:
import {Hub, LoggerClass} from 'centralize-js';
const myLogger = new LoggerClass(Hub, {foo: 10, bar: 20});
// myLogger.foo('my message');
// myLogger.bar('my other message');Or you can change the log levels using the setLogLevels() method.
import Logger from 'centralize-js';
Logger.setLogLevels({foo: 10, bar: 20});
// Logger.foo('my message');
// Logger.bar('my other message');import { Hub } from 'centralize-js';
// Create the message manually
const message = {
logLevel: 1000000,
labels: {},
timestamp: new Date(),
value: 'This is a very important message due to the high logLevel'
}
// alternatively use the CreateMessage function
// const message = CreateMessage(1000000);
// message.value = 'This is a very important message due to the high logLevel';
Hub.send(message);A receiver is any function that can receive a message.
To receive all messages, you can attach to the global stream:
import { Hub, Logger } from 'centralize-js';
const myReceiver = function(message) {
console.log(message.value);
};
Hub.messages.addReceiver(myReceiver);
Logger.info('this is an info log');
// console.log outputs 'this is an info log'Any configuration applied to the global stream will apply to all messages. There may be scenarios where you want to set log levels for certain messages and not at the global level.
To do this, you can use the matchAll() function to create a new substream that
receives all of the messages from the global stream. You can then apply the log
levels to the substream instead of the global stream.
const stream = Hub.messages.matchAll()
.setLogLevel(LOG_LEVELS.error).addReceiver(myreceiver);You can filter for specific messages by applying labels a message must match:
import { Hub, Logger } from 'centralize-js';
const myAppMessagesReceiver = function(message) {
console.log(message.value);
};
Hub.messages.matchLabels({app: 'my-app'}).addReceiver(myAppMessagesReceiver);
Logger.debug('my-app debug message', {app: 'my-app'});
Logger.debug('my-other-app message', {app: 'not-my-app'});
// console.log only prints 'my-app debug message'import { Hub, Logger } from 'centralize-js';
// Scenario: 3 environments (development, staging, production)
// receiver should only be triggered for staging and production
const stagingAndProductionReceiver = function(message) {
console.log(message.value);
};
Hub.messages
.matchConditions('env', 'IN', ['staging', 'production'])
.addReceiver(stagingAndProductionReceiver);
...
Logger.debug('my log in development', {env: 'development'});
Logger.debug('staging log', {env: 'staging'});
Logger.debug('production log', {env: 'production'});
// console.log only prints out 'staging log' and 'production log'matchConditions accepts the following operators:
- 'IN'
- 'NOT_IN'
- 'NOT'
Interceptors gives you the opportunity to change a message before it is passed down the stream.
An interceptor must either return a message, or null to stop the message from
propogating further.
const myInterceptor = (message) => {
message.value = 'bar';
return message;
};
const myReceiver = (message) => {
console.log(message.value);
};
Hub.messages.addInterceptor(myInterceptor);
Hub.messages.addReceiver(myReceiver);
Hub.messages.send({
value: 'foo';
});
// console.log outputs 'bar'const myInterceptor = (message) => {
// interceptor code
};
Hub.messages.removeInterceptor(myInterceptor);To set global log level for messages:
import { Hub, LOG_LEVELS } from 'centralize-js';
Hub.messages.setLogLevel(LOG_LEVELS.error);
// only messages that are 'errors' and higher will be dispatched.You can also set a loglevels for filtered messages:
import { Hub, LOG_LEVELS } from 'centralize-js';
const myAppReceiver = function(message) {
console.log(message.value);
};
const messages = Hub.messages.matchLabels({app: 'my-app'});
messages.setLogLevel(LOG_LEVELS.error);
messages.addReceiver(myAppReceiver);Note: that the global log level precedes everything, so setting a 'lower' log level for matched messages will have no effect if the global log level is 'higher'.
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