vikings

Data synchronizer for service discovery and more

This package can be embedded in any nodejs app in order to share a key/value store with any other app that uses it as well.

The distributed KV store uses NATS IO node client in order to maintain data between KV clients.

Three operations are available: SET (alias PUT), GET and DEL.

For example:

 
let datasync = new DataSynchronizer(config);
 
datasync.put(key, value);
let myvalue = datasync.get(key);
datasync.del(key);
 

In order to get a live update of what happens in the KV store, you can use the following defined events (DataSynchronizer is an EventEmitter):

 
datasync.on('update', item => {
  console.log('data item update', item);
});
 
datasync.on('deleted', keys => {
  console.log('data items deleted', key);
});
 
datasync.on('node', nodeInfo => {
  console.log('node info', nodeInfo);
});
 
datasync.on('refreshed', dico => {
  console.log('full dico', dico);
});
 

Data values in the KV store has the following format:

 
{
  value: value,
  t: new Date().getTime()
}
 

This is due to the fact that we want to keep a track of timestamp info.

Services

(Micro-)Services can be declared as a class extension of Service class. Any method will be registered if not prefixed with '_' or similar name as EventEmitter methods.

Services declared this way will be available in the shared KV store.

Gateway (API gateway)

Any service declared in the KV store is made available every where on the network trough NATS IO pub/sub service. Instantiating Gateway class (or extending it), you can get a reference to available services. In order to call any of their methods, you need to do something like:

 
gateway.services.<service_name>.<method_name>(args).then( response => {
 
}).catch (err => {
 
});
 

If you are not sure that service is already available, you can use _waitForService function to wait until ready:

 
gateway._waitForService(serviceName[, timeout_ms]).then( () => {
 
}).catch(err => {
  console.log(err);
});