[PULL] Update RPC server to use asynchronous IO

[jordanlewis]

As per http://bitcointalk.org/index.php?topic=6599.0.

This patch set updates bitcoin's RPC server to use boost::asio's async_read, _write, etc instead of their non-asynchronous versions.

The server still exists as a single separate thread, but the async calls should greatly improve performance under high load. The next step in robustifying the RPC server is to create a pool of threads for the RPC server, each of which handle a number of asynchronously reading and writing connections.


Pull request here: https://github.com/bitcoin/bitcoin/pull/214

[Gavin Andresen]

... but the async calls should greatly improve performance under high load.

Have you done any benchmarking to see if that is true?

[jrmithdobbs]

... but the async calls should greatly improve performance under high load.

Have you done any benchmarking to see if that is true?

I haven't done benchmarking per-se but it's very easy to test if you have access to miners that can do ~4-5Ghash/s.

Without patch: "Problems communicating with RPC server" (or equiv depending on miner) at least once every 5 seconds.
With patch: One every now and then due to network hiccups.

Further proof: luke-jr has a similar (though VERY hacky) patch he uses or bitcoind falls over for Eligius, his is a threaded implementation that would need quite a bit of cleanup though.

I'm pretty sure, whether publicly stated or not, this is the case for all of the >10Ghash/s pools.

[Luke-Jr]

Further proof: luke-jr has a similar (though VERY hacky) patch he uses or bitcoind falls over for Eligius, his is a threaded implementation that would need quite a bit of cleanup though.

Sorry, but my patch probably doesn't help your case. Some corrections:

• It's not really that hacky, I just never bothered to make it work with SSL.
• It doesn't help failover in any way.
• It requires each RPC command to enable threading-- currently I have only enabled it for getwork.
• Eligius only needs/uses it for calling RPC command from inside the coinbaser (which blocks getwork).

[jordanlewis]

Gavin - what kind of evidence do you need in order to take this patch into consideration? I haven't had the resources to perform proper load testing on it, but jrmithdobbs provides encouraging anecdotal data that suggests that the patch does indeed improve performance significantly.

The original implementation was synchronous and blocking: it allowed only one connection to be processed at once. My patch improves this behavior by rewriting the connection handling code to use asynchronous IO - enabling many connections to be processed at once. It should be clear why this improves performance.

[Gavin Andresen]

Sounds like this is good for pool operators that have high 'getwork' loads-- have any high-volume merchants sites or e-wallet sites tried it?

I've got a long list of things to do when I get back from vacation week after next, or I'd volunteer to run it on the Faucet to help stress test it.

[dbitcoin]

Any news here?
I already use this patch in my pool more than week and see nice performance boost with rpc.
This code should be verified(probably improved) and merged with master upstream.

[xf2_org]

Any news here?
I already use this patch in my pool more than week and see nice performance boost with rpc.
This code should be verified(probably improved) and merged with master upstream.

It's already a pull request.  Right now there is a logjam of pull requests, simply because we're trying to get out some critical bug fixes, and this is not strictly a bug fix.