hdwallet-provider never being garbage collected

[Sveagruva]

Issue

hdwallet-provider not being garbage collected

Steps to Reproduce

create hdwallet-provider track weak reference stop engine

const HDWalletProvider = require("@truffle/hdwallet-provider");

let provider = new HDWalletProvider({
    privateKeys: [privateKey],
    providerOrUrl: process.env.RPC_URL,
});

const  weakRef = new WeakRef(provider);
new Promise(async (resolve, reject) => {
    while(true) {
        await new Promise(resolve => setTimeout(resolve, 1000));
        const providerReferenced = weakRef.deref();

        if(providerReferenced === undefined) {
            console.log("provider garbage collected");
            resolve();
        } else {
            console.log("provider not garbage collected");
        }
    }
});

provider.engine.stop();
provider = null;

Environment

• Operating System: Linux
• Truffle version -
• @truffle/hdwallet-provider: 2.1.0,
• node version 18.11.0
• npm version 8.19.2

[davidmurdoch]

Interesting. I was able to reproduce this, and even tried enclosing the provider in its own scope just in case the while loop was keep a reference to it some how, but still wasn't seeing the GC happen.

How did you stumble on this issue?

[Sveagruva]

I was creating new provider for every operation on backend with user provided pk. every instance was continuing making web3 requests

[davidmurdoch]

I think I've figured out what is going on. During the lifecycle of a truffle command, like migrate ortest, atruffle-config.jsfile may be loaded several times. Each config instance may have its ownHDWalletProvider, but all set with the same accounts. BecauseHDWalletProvider` tracks the current nonce of each account, if different instances of a provider is used during the life of the command they won't track nonces accurately. To work around this, a nonce tracker singleton object is created and shared among any and all HDWalletProviders. The tracker holds on to a reference to the provider, and since it can never be garbage collected, neither can the providers it references.

You can work around this workaround by setting shareNonce to false (new HDWalletProvider({shareNonce: false})). Which should work fine for you.

The workaround for nonce tracking was the wrong solution and a should be reverted. A proper fix that does not involve a global shared singleton should be implemented.

[cliffoo]

Closing for issue maintenance. Thanks @Sveagruva for bringing this up. If the shareNonce fix suggested by David doesn't work for you feel free to re-open! Thanks.

[davidmurdoch]

@cliffoo this is still an issue I think Truffle should fix the root cause of.