First building blocks for Sharding API: ShardIndex and TransportIdentity #970
Conversation
Refactor `RoleResolvingTransport` to make the use of it nicer
Codecov ReportAttention: Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## main #970 +/- ##
==========================================
+ Coverage 89.29% 89.43% +0.14%
==========================================
Files 162 163 +1
Lines 21844 21897 +53
==========================================
+ Hits 19505 19584 +79
+ Misses 2339 2313 -26 ☔ View full report in Codecov by Sentry. |
| type Item = Vec<u8>; | ||
|
|
||
| fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> { | ||
| self.project().0.poll_next(cx) |
There was a problem hiding this comment.
What is project() and where is it coming from? Is it defined in Stream?
| pub struct ChannelId { | ||
| pub role: Role, | ||
| pub struct ChannelId<I: transport::Identity> { | ||
| pub peer: I, |
There was a problem hiding this comment.
This name: peer confuses me. Why did you change this from role? What does it mean here? And can you add a comment?
There was a problem hiding this comment.
the reason I had to rename it is that this struct is now used to communicate between shards too and there is no notion of helper role for such communications. ChannelId<ShardIndex> would have role: ShardIndex field which looks even more confusing, hence a neutral peer that can be anything that wants to communicate with this instance
| "Current shard index '{this}' >= '{max}' (total number of shards)" | ||
| ); | ||
|
|
||
| max.iter().filter(move |&v| v != this) |
There was a problem hiding this comment.
What does that move syntax do here?
There was a problem hiding this comment.
it moves this to the closure, so Rust compiler can see that filter closure cannot outlive it. We return an iterator and filter closure is part of it, so Rust wants to know that this closure does not borrow from local context
See #969 for overall approach.
This change introduces two fundamental concepts for horizontal scaling -
ShardIndexandTransportidentity.The former will be used the same way as
HelperIdentityis used nowadays - unique identifier of a peer we are communicating with. Having in mind 200B events, we may need more than 65k shards, thus 4 byte identifier usage.TransportIdentityis a generalization for peer identifiers used at transport layer. Two fundamental structs implement it:HelperIdentityandShardIndexto allow communication via MPC and shard channels.Roleis used at the Gateway/Context layer for communication purposes andRoleResolvingTransportis a convenient abstraction, so it also implementsTransportIdentity.Transporttrait became generic overTransportIdentity- I tested it in my private branch where I have a complete implementation, so this approach works.I also did a bit of a refactoring and made
RoleResolvingTransportto implement theTransporttrait because it can now.