Configure the channel pool to open a new channel when all of the currently open channels reach 100 subscriptions each

[steveluscher]

Summary

When you make ‘too many’ subscriptions over a single channel/connection/socket, RPC providers will throw errors. The idea behind this PR is to set the default subscriptions-per-channel low enough so as to avoid running afoul of even the most restrictive provider's limit.

This was determined experimentally by hitting various nodes with this script.

• Triton Public Mainnet (api.mainnet-beta.solana.com): 100
• Helius: ~1450
• QuickNode: ~4500

The ground truth is this:

1. Some nodes have definite limits set, like the public Triton mainnet node.
2. Some nodes don't have limits set, but unceremoniously close the connection roughly around the same number of subscriptions.

The right thing to do here would be for providers not to kill the channels, but rather to respond to the suscription request with a JSON-RPC response, of the form:

{
  "error": {
    "code": ???,
    "message": "OK, that's enough subscriptions for now.",
  },
  "id": 123,
  "jsonrpc": "2.0"
}

If everyone did that, and we all decided on an error code in the range -32000 to -32099, as demanded by what the JSON-RPC spec says about errors, then the channel pool could catch that error to know when a new channel needed to be added to the pool. Because they don't, we have to participate in this tragedy of the commons, and hardcode the limit to 100 so that people using the public endpoint will not get caught off-guard by the limit.

Note

There might actually be two kinds of errors: ‘I can't give you this subscription over this channel, open a new one’ and ‘I can't give you this subscription over any channel, please stop opening subscriptions.’

cc/ @linuskendall, @WilfredAlmeida, @vovkman

[changeset-bot]

⚠️ No Changeset found

Latest commit: b02fb40

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[steveluscher]

• Configure the channel pool to open a new channel when all of the currently open channels reach 100 subscriptions each #3380 👈
• master

This stack of pull requests is managed by Graphite. Learn more about stacking.

Join @steveluscher and the rest of your teammates on Graphite

[lorisleiva]

Makes sense. Thanks for the detailed explanation of this limit. Looking forward to seeing these consistent error codes in the future. 🙏

[github-actions]

Because there has been no activity on this PR for 14 days since it was merged, it has been automatically locked. Please open a new issue if it requires a follow up.