web3.js Connection http agent hanging tests and cli utilities

[kklas]

Problem

In the Connection class the AgentManager is used in order to pool http connections to the rpc server. Since the keepAlive option is used, the agent will hang until destroy() is called. To go around this there is a timeout which will destroy the agent 5 seconds after the last request.

But this still hangs the node process for 5 seconds which is an issue for CLI utilities and tests which use Connection. For example, it causes the following message when running jest tests (which I'm sure many have encoutered due to this):

Jest did not exit one second after the test run has completed.

This usually means that there are asynchronous operations that weren't stopped in your tests. Consider running Jest with `--detectOpenHandles` to troubleshoot this issue.

Proposed Solution

Either / or:

1. add ability to pass a custom agent to be used via an option in the Connection constructor
2. add a connection.close() method which will call agent.destroy() to clean up the connection gracefully

cc @steveluscher @jstarry

[steveluscher]

Love it. Thanks for pointing this out.

[rabbygit]

Is there any update about this issue?

[steveluscher]

Hey! No update, no. Still worth doing though! We just have to do it thoughtfully. I haven't sat down to really think about whether making the Agent an explicit input is the right thing to do (breaking change) or whether to add a destructor (not effective unless people use it).

[DavidPesta]

Thanks for working on this. Looking forward to this being resolved. 👍

[steveluscher]

K, I wasn't comfortable creating a whole bunch of new API surface area, so what I ended up doing was to:

1. Let you override or disable the default agent via config on Connection
2. Automatically disable the default agent when process.env.NODE_ENV is test, which should cover you in Jest.

#29125.