Add more information about http2 connection

[polRk]

Is your feature request related to a problem? Please describe.

CONTEXT

Within the YDB SDK, client-side load balancing is used. We send a single request to any database node, and it returns an array of available endpoints. Our task is to maintain connections to these endpoints as needed: close connections that we no longer need to use, create new connections to those that are missing, balance requests across these connections, and have the ability to send a request to a specific connection.

PROBLEM

Currently, it's not very clear how to properly close a connection (graceful shutdown), how to obtain the status of a connection, and how to receive notifications when a connection has been closed.

ONLY FOR HTTP2

Describe the solution you'd like

Extends Transport with EventEmitter, emit information about transport status changes, add current status of connection.

Additional context
https://ydb.tech/docs/en/recipes/ydb-sdk/balancing
https://blog.ydb.tech/client-side-balancing-in-ydb-89677b34fd5b

[srikrsna-buf]

For H/2 you can use the nodeOptions transport option to override createConnection callback to get a handle on the connection and inspect the status. If you want greater control over the connections you can use the sessionManager option to provide a NodeHttp2ClientSessionManager type to manage the connection.

connect-es/packages/connect-node/src/node-transport-options.ts

Lines 39 to 53 in ba861a3

	export type NodeHttp2TransportOptions = {
	/**
	* A manager for the HTTP/2 connection of the transport.
	*
	* Providing this option makes nodeOptions as well as the HTTP/2 session
	* options (pingIntervalMs et cetera) ineffective.
	*/
	sessionManager?: NodeHttp2ClientSessionManager;
	/**
	* Options passed to the connect() call of the Node.js built-in
	* http2 module.
	*/
	nodeOptions?: http2.ClientSessionOptions | http2.SecureClientSessionOptions;
	} & Http2SessionOptions;

[polRk]

Is connect-es provides default NodeHttp2ClientSessionManager ?

[timostamm]

Yes, see the export Http2SessionManager.

[polRk]

How to gracefully shutdown htt2 connection (for example, server send me information do not use this endpoint) ? Maybe will be good implement disposable in transport?

I need HTTP2 connection management tools to help me balance my clients. I open 20 connections at once and keep them updated if the server sends me information about new endpoints or if any of the endpoints become unavailable. I need to be able to safely close the connection and create new ones.

For now, I can only createTransport, but I don't know how to gracefully shutdown them.

[polRk]

It may be that the endpoint is available now, and after 5 minutes it is unavailable, and then it is available again. I need to effectively manage the current connections, understand in advance that the connection should not be used due to an error or loss of connection.

[srikrsna-buf]

It may be that the endpoint is available now, and after 5 minutes it is unavailable, and then it is available again.

The default session manager manages the connections according to HTTP/2 semantics (like goaway) and has settings to tweak ping/idle timeouts. You can look at the source code here. If the existing options don't cover your use case you can tweak it to do as you need.

[polRk]

@srikrsna-buf I have a clear belief that Transport needs graceful shutdown (for example, Symbol.disposable), what do you think?