mirror of
https://github.com/pezkuwichain/pezkuwi-subxt.git
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Gavin Wood
53de6871e0
* Stuff to help inspect the DMP activity * Fix teleport accounting * Fixes * Fixes * Fixes * Fixes
88 lines
4.1 KiB
Markdown
88 lines
4.1 KiB
Markdown
# UMP Module
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A module responsible for Upward Message Passing (UMP). See [Messaging Overview](../messaging.md) for more details.
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## Storage
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Storage related to UMP
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```rust
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/// The messages waiting to be handled by the relay-chain originating from a certain parachain.
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///
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/// Note that some upward messages might have been already processed by the inclusion logic. E.g.
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/// channel management messages.
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///
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/// The messages are processed in FIFO order.
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RelayDispatchQueues: map ParaId => Vec<UpwardMessage>;
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/// Size of the dispatch queues. Caches sizes of the queues in `RelayDispatchQueue`.
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///
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/// First item in the tuple is the count of messages and second
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/// is the total length (in bytes) of the message payloads.
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///
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/// Note that this is an auxilary mapping: it's possible to tell the byte size and the number of
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/// messages only looking at `RelayDispatchQueues`. This mapping is separate to avoid the cost of
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/// loading the whole message queue if only the total size and count are required.
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///
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/// Invariant:
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/// - The set of keys should exactly match the set of keys of `RelayDispatchQueues`.
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RelayDispatchQueueSize: map ParaId => (u32, u32); // (num_messages, total_bytes)
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/// The ordered list of `ParaId`s that have a `RelayDispatchQueue` entry.
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///
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/// Invariant:
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/// - The set of items from this vector should be exactly the set of the keys in
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/// `RelayDispatchQueues` and `RelayDispatchQueueSize`.
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NeedsDispatch: Vec<ParaId>;
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/// This is the para that gets dispatched first during the next upward dispatchable queue
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/// execution round.
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///
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/// Invariant:
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/// - If `Some(para)`, then `para` must be present in `NeedsDispatch`.
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NextDispatchRoundStartWith: Option<ParaId>;
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```
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## Initialization
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No initialization routine runs for this module.
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## Routines
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Candidate Acceptance Function:
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* `check_upward_messages(P: ParaId, Vec<UpwardMessage>`):
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1. Checks that there are at most `config.max_upward_message_num_per_candidate` messages.
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1. Checks that no message exceeds `config.max_upward_message_size`.
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1. Verify that `RelayDispatchQueueSize` for `P` has enough capacity for the messages
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Candidate Enactment:
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* `receive_upward_messages(P: ParaId, Vec<UpwardMessage>)`:
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1. Process each upward message `M` in order:
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1. Append the message to `RelayDispatchQueues` for `P`
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1. Increment the size and the count in `RelayDispatchQueueSize` for `P`.
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1. Ensure that `P` is present in `NeedsDispatch`.
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The following routine is meant to execute pending entries in upward message queues. This function doesn't fail, even if
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dispatching any of individual upward messages returns an error.
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`process_pending_upward_messages()`:
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1. Initialize a cumulative weight counter `T` to 0
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1. Iterate over items in `NeedsDispatch` cyclically, starting with `NextDispatchRoundStartWith`. If the item specified is `None` start from the beginning. For each `P` encountered:
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1. Dequeue the first upward message `D` from `RelayDispatchQueues` for `P`
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1. Decrement the size of the message from `RelayDispatchQueueSize` for `P`
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1. Delegate processing of the message to the runtime. The weight consumed is added to `T`.
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1. If `T >= config.ump_service_total_weight`, set `NextDispatchRoundStartWith` to `P` and finish processing.
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1. If `RelayDispatchQueues` for `P` became empty, remove `P` from `NeedsDispatch`.
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1. If `NeedsDispatch` became empty then finish processing and set `NextDispatchRoundStartWith` to `None`.
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> NOTE that in practice we would need to approach the weight calculation more thoroughly, i.e. incorporate all operations
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> that could take place on the course of handling these upward messages.
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## Session Change
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1. For each `P` in `outgoing_paras` (generated by `Paras::on_new_session`):
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1. Remove `RelayDispatchQueueSize` of `P`.
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1. Remove `RelayDispatchQueues` of `P`.
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1. Remove `P` if it exists in `NeedsDispatch`.
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1. If `P` is in `NextDispatchRoundStartWith`, then reset it to `None`
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- Note that if we don't remove the open/close requests since they are going to die out naturally at the end of the session.
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