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[release-v2.0] main: Use backported mixing updates. #3431

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merged 11 commits into from
Aug 28, 2024

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@davecgh davecgh commented Aug 28, 2024

This updates the 2.0 release branch to use the latest version of the mixing module which includes updates to improve session formation and increase performance.

In particular, the following updated module version is used:

- github.com/decred/dcrd/[email protected]

Note that it also cherry picks all of the commits included in updates to the mixing module to ensure they are also included in the release branch even though it is not strictly necessary since go.mod has been updated to require the new release and thus will pull in the new code. However, from past experience, not having code backported to modules available in the release branch too leads to headaches for devs building from source in their local workspace with overrides such as those in go.work.

The mixing-related parts of the following PRs are included:

jholdstock and others added 11 commits August 28, 2024 12:05
Immediately appending to a slice initialized with a non-zero length will
lead to a slice which is twice as large as intended, with the initial
half of the entries being left at their zero value.

This is fixed by initializing the slice with **capacity** instead of
length.
The submit queue channel was not actually increasing any performance.
(*peer).submit() would synchronously wait for all error results, and the call
to (*Wallet).SubmitMixMessage was already synchronized by the mixpool mutex.

Furthermore, this also fixes a deadlock that was observed after a mixing
wallet with the RPC syncer mode reconnected to a restarted dcrd.  Pair request
messages were being submitted onto the channel with the client mutex held in
(*Client).Dicemix.  However, handleSubmitQueue had already exited and the
client had not yet been restarted after dcrd reconnect, and was unable to be
started due to the locked mutex.
The client mutex was being held during the initial publishing of pair request
messages to prevent a situation where a submit errored but the peer was still
associated with the client, or the message was submitted to mixpool and sent
to other peers but our local peer had not yet been associated to the client at
the time an epoch tick occurred.  This should not be a situation we will
encounter anymore, since the PR submissions are spaced out intentionally to
avoid sending them close to the epoch.
…ions

The alternate session forming only incrementally removes PRs from the
currently considered PR set.  Even if a PR by a responsive peer is known, if
it was removed due to not passing the majority checks earlier, it will never
be used by our peers during this epoch.  With that in mind, we should only use
the most recent KEs with the lowest referenced PR counts when trying to form
an alternate session, as the additional PRs from earlier KEs will never be
reconsidered by that KE's identity.
This updates the 2.0 release branch to use the latest version of the
mixing module which includes updates to improve session formation and
increase performance.

In particular, the following updated module version is used:

- github.com/decred/dcrd/[email protected]
@davecgh davecgh added this to the 2.0.4 milestone Aug 28, 2024
@davecgh davecgh merged commit 9b28257 into decred:release-v2.0 Aug 28, 2024
2 checks passed
@davecgh davecgh deleted the rel20_mixing_backports branch August 28, 2024 18:43
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3 participants