coopernurse
Is it possible to have a callback when the minimum number of connections is created?
Pretty cool module, I must say. I am using it for a project of mine and I couldn't find out whether it's really possible or not. Can the pool call a custom callback when the minimum number of connections are created?
Example: I am using the following piece of code to create the pool. Would it be possible to have a callback executed when the minimum number of connections (in this case, 3) is created?
var pool = gp.Pool({
name : 'connection_pool',
validate : function(client) {
console.log('INFO- Validate called:' + (!client.hadError && client.readyState === 'connected'));
return (!client.hadError && client.readyState === 'connected');
},
destroy : function(client) {
// if the client is already closed don't call end
if (!client.hadError && client.readyState !== 'closed') {
client.end();
}
},
max : 25,
min : 3,
idleTimeoutMillis : 30000,
log : false,
refreshIdle : true,
create : function(callback) {
options.autoReconnect = true;
var client = hdb.createClient(options);
client.hadError = false;
client.once('error', function onerror(err) {
console.error('Client error:', err);
client.hadError = true;
});
client.connect(function(err) {
if (err) {
return console.error("Error:" + err);
}
});
callback(null, client);
}
});
Currently it's not possible at the moment although in theory it could be added. Whats your use case for it?
@sandfox : I am building a service on Cloud Foundry PaaS, which initializes the pool with the minimum number of connections. The service is an HTTP component, which uses the pool for connection resource handling. I want to make it certain that unless the minimum connections have been created, HTTP calls must be blocked (or a maintenance error is returned). Without a callback, I am currently not finding a way to do this.
Sounds like a good reason. At the moment the only ways to achieve that (that I can think of) without library changes is to poll the pool and check pool.getPoolSize() to see how "full" it is. It's not exactly a clean solution though and has plenty of room for being needlessly slow.
Alternatively (and I think this is the better option) you could add some code inside your create function that did something like incrementing a counter for you and once that counter crossed a threshold (the min pool size), you could then do some other action (e.g call a callback to allow your http server to start accepting connections).
Otherwise it's going to mean adding some event emitters / callbacks to the pool for events like "resource created" etc, but I'm not sure I'm going to have time to do that in the near future.
@sandfox: The counter-increment code inside the 'create' function is how I am doing this now. Probably a good way to achieve this but a callback would certainly be smoother.
4 years later, it seems like this issue could be relatively easily solved by adding a custom Event for this? The library is EventEmitter-enabled right now and an an .emit near the minimum regulating code seems like all it would take?
