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Implementer's Guide: Router fixes (#1727)

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* Guide: Reindent the router module with 4 spaces

The guide used to use 2 spaces for indentation. The problem with that is `mdbook` doesn't recognize them as a proper indentation and thus doesn't render indent properly.

A couple of things are not indented here because they will be changed in the following commits

* Guide: a bunch of fixes
This commit is contained in:
Sergei Shulepov
2020-09-16 17:52:42 +02:00
committed by GitHub
parent b9d36c70e8
commit 5d4ddeee7a
5 changed files with 88 additions and 82 deletions
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polkadot/roadmap/implementers-guide/src/runtime/inclusioninherent.md
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@@ -22,5 +22,5 @@ Included: Option<()>,
1. Invoke `Scheduler::schedule(freed)`
1. Invoke the `Inclusion::process_candidates` routine with the parameters `(backed_candidates, Scheduler::scheduled(), Scheduler::group_validators)`.
1. Call `Scheduler::occupied` using the return value of the `Inclusion::process_candidates` call above, first sorting the list of assigned core indices.
1. Call the `Router::process_upward_dispatchables` routine to execute all messages in upward dispatch queues.
1. Call the `Router::process_pending_upward_dispatchables` routine to execute all messages in upward dispatch queues.
1. If all of the above succeeds, set `Included` to `Some(())`.
polkadot/roadmap/implementers-guide/src/runtime/router.md
+84 -77
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@@ -4,23 +4,30 @@ The Router module is responsible for all messaging mechanisms supported between
## Storage
Storage layout:
General storage entries
```rust
/// Paras that are to be cleaned up at the end of the session.
/// The entries are sorted ascending by the para id.
OutgoingParas: Vec<ParaId>;
```
### Upward Message Passing (UMP)
```rust
/// Dispatchable objects ready to be dispatched onto the relay chain. The messages are processed in FIFO order.
/// This is subject to `max_upward_queue_count` and
/// `watermark_queue_size` from `HostConfiguration`.
RelayDispatchQueues: map ParaId => Vec<RawDispatchable>;
RelayDispatchQueues: map ParaId => Vec<(ParachainDispatchOrigin, RawDispatchable)>;
/// Size of the dispatch queues. Caches sizes of the queues in `RelayDispatchQueue`.
/// First item in the tuple is the count of messages and second
/// is the total length (in bytes) of the message payloads.
///
/// Note that this is an auxilary mapping: it's possible to tell the byte size and the number of
/// messages only looking at `RelayDispatchQueues`. This mapping is separate to avoid the cost of
/// loading the whole message queue if only the total size and count are required.
RelayDispatchQueueSize: map ParaId => (u32, u32);
/// The ordered list of `ParaId`s that have a `RelayDispatchQueue` entry.
NeedsDispatch: Vec<ParaId>;
/// This is the para that gets will get dispatched first during the next upward dispatchable queue
/// This is the para that will get dispatched first during the next upward dispatchable queue
/// execution round.
NextDispatchRoundStartWith: Option<ParaId>;
```
@@ -36,7 +43,7 @@ DownwardMessageQueues: map ParaId => Vec<InboundDownwardMessage>;
///
/// Each link in this chain has a form:
/// `(prev_head, B, H(M))`, where
/// - `prev_head`: is the previous head hash.
/// - `prev_head`: is the previous head hash or zero if none.
/// - `B`: is the relay-chain block number in which a message was appended.
/// - `H(M)`: is the hash of the message being appended.
DownwardMessageQueueHeads: map ParaId => Option<Hash>;
@@ -180,62 +187,62 @@ Candidate Acceptance Function:
1. Check that `HrmpChannels` for `ch` exists.
1. Check that `ch` is not in the `HrmpCloseChannelRequests` set.
* `check_processed_downward_messages(P: ParaId, processed_downward_messages)`:
1. Checks that `DownwardMessageQueues` for `P` is at least `processed_downward_messages` long.
1. Checks that `processed_downward_messages` is at least 1 if `DownwardMessageQueues` for `P` is not empty.
1. Checks that `DownwardMessageQueues` for `P` is at least `processed_downward_messages` long.
1. Checks that `processed_downward_messages` is at least 1 if `DownwardMessageQueues` for `P` is not empty.
* `check_hrmp_watermark(P: ParaId, new_hrmp_watermark)`:
1. `new_hrmp_watermark` should be strictly greater than the value of `HrmpWatermarks` for `P` (if any).
1. `new_hrmp_watermark` must not be greater than the context's block number.
1. `new_hrmp_watermark` should be either
1. equal to the context's block number
1. or in `HrmpChannelDigests` for `P` an entry with the block number should exist
1. `new_hrmp_watermark` should be strictly greater than the value of `HrmpWatermarks` for `P` (if any).
1. `new_hrmp_watermark` must not be greater than the context's block number.
1. `new_hrmp_watermark` should be either
1. equal to the context's block number
1. or in `HrmpChannelDigests` for `P` an entry with the block number should exist
* `verify_outbound_hrmp(sender: ParaId, Vec<OutboundHrmpMessage>)`:
1. For each horizontal message `M` with the channel `C` identified by `(sender, M.recipient)` check:
1. exists
1. `M`'s payload size doesn't exceed a preconfigured limit `C.limit_message_size`
1. `M`'s payload size summed with the `C.used_bytes` doesn't exceed a preconfigured limit `C.limit_used_bytes`.
1. `C.used_places + 1` doesn't exceed a preconfigured limit `C.limit_used_places`.
1. For each horizontal message `M` with the channel `C` identified by `(sender, M.recipient)` check:
1. exists
1. `M`'s payload size doesn't exceed a preconfigured limit `C.limit_message_size`
1. `M`'s payload size summed with the `C.used_bytes` doesn't exceed a preconfigured limit `C.limit_used_bytes`.
1. `C.used_places + 1` doesn't exceed a preconfigured limit `C.limit_used_places`.
Candidate Enactment:
* `queue_outbound_hrmp(sender: ParaId, Vec<OutboundHrmpMessage>)`:
1. For each horizontal message `HM` with the channel `C` identified by `(sender, HM.recipient)`:
1. Append `HM` into `HrmpChannelContents` that corresponds to `C` with `sent_at` equals to the current block number.
1. Locate or create an entry in ``HrmpChannelDigests`` for `HM.recipient` and append `sender` into the entry's list.
1. Increment `C.used_places`
1. Increment `C.used_bytes` by `HM`'s payload size
1. Append a new link to the MQC and save the new head in `C.mqc_head`. Note that the current block number as of enactment is used for the link.
1. For each horizontal message `HM` with the channel `C` identified by `(sender, HM.recipient)`:
1. Append `HM` into `HrmpChannelContents` that corresponds to `C` with `sent_at` equals to the current block number.
1. Locate or create an entry in `HrmpChannelDigests` for `HM.recipient` and append `sender` into the entry's list.
1. Increment `C.used_places`
1. Increment `C.used_bytes` by `HM`'s payload size
1. Append a new link to the MQC and save the new head in `C.mqc_head`. Note that the current block number as of enactment is used for the link.
* `prune_hrmp(recipient, new_hrmp_watermark)`:
1. From ``HrmpChannelDigests`` for `recipient` remove all entries up to an entry with block number equal to `new_hrmp_watermark`.
1. From the removed digests construct a set of paras that sent new messages within the interval between the old and new watermarks.
1. For each channel `C` identified by `(sender, recipient)` for each `sender` coming from the set, prune messages up to the `new_hrmp_watermark`.
1. For each pruned message `M` from channel `C`:
1. Decrement `C.used_places`
1. Decrement `C.used_bytes` by `M`'s payload size.
1. Set `HrmpWatermarks` for `P` to be equal to `new_hrmp_watermark`
1. From `HrmpChannelDigests` for `recipient` remove all entries up to an entry with block number equal to `new_hrmp_watermark`.
1. From the removed digests construct a set of paras that sent new messages within the interval between the old and new watermarks.
1. For each channel `C` identified by `(sender, recipient)` for each `sender` coming from the set, prune messages up to the `new_hrmp_watermark`.
1. For each pruned message `M` from channel `C`:
1. Decrement `C.used_places`
1. Decrement `C.used_bytes` by `M`'s payload size.
1. Set `HrmpWatermarks` for `P` to be equal to `new_hrmp_watermark`
* `prune_dmq(P: ParaId, processed_downward_messages)`:
1. Remove the first `processed_downward_messages` from the `DownwardMessageQueues` of `P`.
1. Remove the first `processed_downward_messages` from the `DownwardMessageQueues` of `P`.
* `enact_upward_messages(P: ParaId, Vec<UpwardMessage>)`:
1. Process all upward messages in order depending on their kinds:
1. If the message kind is `Dispatchable`:
1. Append the message to `RelayDispatchQueues` for `P`
1. Increment the size and the count in `RelayDispatchQueueSize` for `P`.
1. Ensure that `P` is present in `NeedsDispatch`.
1. If the message kind is `HrmpInitOpenChannel(recipient, max_places, max_message_size)`:
1. Increase `HrmpOpenChannelRequestCount` by 1 for `P`.
1. Append `(P, recipient)` to `HrmpOpenChannelRequestsList`.
1. Add a new entry to `HrmpOpenChannelRequests` for `(sender, recipient)`
1. Set `sender_deposit` to `config.hrmp_sender_deposit`
1. Set `limit_used_places` to `max_places`
1. Set `limit_message_size` to `max_message_size`
1. Set `limit_used_bytes` to `config.hrmp_channel_max_size`
1. Reserve the deposit for the `P` according to `config.hrmp_sender_deposit`
1. If the message kind is `HrmpAcceptOpenChannel(sender)`:
1. Reserve the deposit for the `P` according to `config.hrmp_recipient_deposit`
1. For the request in `HrmpOpenChannelRequests` identified by `(sender, P)`, set `confirmed` flag to `true`.
1. Increase `HrmpAcceptedChannelRequestCount` by 1 for `P`.
1. If the message kind is `HrmpCloseChannel(ch)`:
1. If not already there, insert a new entry `Some(())` to `HrmpCloseChannelRequests` for `ch`
and append `ch` to `HrmpCloseChannelRequestsList`.
1. Process all upward messages in order depending on their kinds:
1. If the message kind is `Dispatchable`:
1. Append the message to `RelayDispatchQueues` for `P`
1. Increment the size and the count in `RelayDispatchQueueSize` for `P`.
1. Ensure that `P` is present in `NeedsDispatch`.
1. If the message kind is `HrmpInitOpenChannel(recipient, max_places, max_message_size)`:
1. Increase `HrmpOpenChannelRequestCount` by 1 for `P`.
1. Append `(P, recipient)` to `HrmpOpenChannelRequestsList`.
1. Add a new entry to `HrmpOpenChannelRequests` for `(sender, recipient)`
1. Set `sender_deposit` to `config.hrmp_sender_deposit`
1. Set `limit_used_places` to `max_places`
1. Set `limit_message_size` to `max_message_size`
1. Set `limit_used_bytes` to `config.hrmp_channel_max_size`
1. Reserve the deposit for the `P` according to `config.hrmp_sender_deposit`
1. If the message kind is `HrmpAcceptOpenChannel(sender)`:
1. Reserve the deposit for the `P` according to `config.hrmp_recipient_deposit`
1. For the request in `HrmpOpenChannelRequests` identified by `(sender, P)`, set `confirmed` flag to `true`.
1. Increase `HrmpAcceptedChannelRequestCount` by 1 for `P`.
1. If the message kind is `HrmpCloseChannel(ch)`:
1. If not already there, insert a new entry `Some(())` to `HrmpCloseChannelRequests` for `ch`
and append `ch` to `HrmpCloseChannelRequestsList`.
The following routine is intended to be called in the same time when `Paras::schedule_para_cleanup` is called.
@@ -245,19 +252,19 @@ The following routine is intended to be called in the same time when `Paras::sch
The following routine is meant to execute pending entries in upward dispatchable queues. This function doesn't fail, even if
any of dispatchables return an error.
`process_upward_dispatchables()`:
1. Initialize a cumulative weight counter `T` to 0
1. Iterate over items in `NeedsDispatch` cyclically, starting with `NextDispatchRoundStartWith`. If the item specified is `None` start from the beginning. For each `P` encountered:
1. Dequeue `D` the first dispatchable `D` from `RelayDispatchQueues` for `P`
1. Decrement the size of the message from `RelayDispatchQueueSize` for `P`
1. Decode `D` into a dispatchable. Otherwise, if succeeded:
1. If `weight_of(D) > config.dispatchable_upward_message_critical_weight` then skip the dispatchable. Otherwise:
1. Execute `D` and add the actual amount of weight consumed to `T`.
1. If `weight_of(D) + T > config.preferred_dispatchable_upward_messages_step_weight`, set `NextDispatchRoundStartWith` to `P` and finish processing.
> NOTE that in practice we would need to approach the weight calculation more thoroughly, i.e. incorporate all operations
> that could take place on the course of handling these dispatchables.
1. If `RelayDispatchQueues` for `P` became empty, remove `P` from `NeedsDispatch`.
1. If `NeedsDispatch` became empty then finish processing and set `NextDispatchRoundStartWith` to `None`.
`process_pending_upward_dispatchables()`:
1. Initialize a cumulative weight counter `T` to 0
1. Iterate over items in `NeedsDispatch` cyclically, starting with `NextDispatchRoundStartWith`. If the item specified is `None` start from the beginning. For each `P` encountered:
1. Dequeue `D` the first dispatchable `D` from `RelayDispatchQueues` for `P`
1. Decrement the size of the message from `RelayDispatchQueueSize` for `P`
1. Decode `D` into a dispatchable. Otherwise, if succeeded:
1. If `weight_of(D) > config.dispatchable_upward_message_critical_weight` then skip the dispatchable. Otherwise:
1. Execute `D` and add the actual amount of weight consumed to `T`.
1. If `weight_of(D) + T > config.preferred_dispatchable_upward_messages_step_weight`, set `NextDispatchRoundStartWith` to `P` and finish processing.
> NOTE that in practice we would need to approach the weight calculation more thoroughly, i.e. incorporate all operations
> that could take place on the course of handling these dispatchables.
1. If `RelayDispatchQueues` for `P` became empty, remove `P` from `NeedsDispatch`.
1. If `NeedsDispatch` became empty then finish processing and set `NextDispatchRoundStartWith` to `None`.
Utility routines.
@@ -270,17 +277,17 @@ Utility routines.
## Session Change
1. Drain `OutgoingParas`. For each `P` happened to be in the list:
1. Remove all inbound channels of `P`, i.e. `(_, P)`,
1. Remove all outbound channels of `P`, i.e. `(P, _)`,
1. Remove all `DownwardMessageQueues` of `P`.
1. Remove `DownwardMessageQueueHeads` for `P`.
1. Remove `RelayDispatchQueueSize` of `P`.
1. Remove `RelayDispatchQueues` of `P`.
1. Remove `HrmpOpenChannelRequestCount` for `P`
1. Remove `HrmpAcceptedChannelRequestCount` for `P`.
1. Remove `P` if it exists in `NeedsDispatch`.
1. If `P` is in `NextDispatchRoundStartWith`, then reset it to `None`
- 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.
1. Remove all inbound channels of `P`, i.e. `(_, P)`,
1. Remove all outbound channels of `P`, i.e. `(P, _)`,
1. Remove all `DownwardMessageQueues` of `P`.
1. Remove `DownwardMessageQueueHeads` for `P`.
1. Remove `RelayDispatchQueueSize` of `P`.
1. Remove `RelayDispatchQueues` of `P`.
1. Remove `HrmpOpenChannelRequestCount` for `P`
1. Remove `HrmpAcceptedChannelRequestCount` for `P`.
1. Remove `P` if it exists in `NeedsDispatch`.
1. If `P` is in `NextDispatchRoundStartWith`, then reset it to `None`
- 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.
1. For each channel designator `D` in `HrmpOpenChannelRequestsList` we query the request `R` from `HrmpOpenChannelRequests`:
1. if `R.confirmed = false`:
1. increment `R.age` by 1.
polkadot/roadmap/implementers-guide/src/types/candidate.md
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@@ -129,7 +129,7 @@ struct PersistedValidationData {
///
/// The DMQ MQC head will be used by the validation function to authorize the downward messages
/// passed by the collator.
dmq_mqc_head: Hash,
dmq_mqc_head: Option<Hash>,
/// The list of MQC heads for the inbound channels paired with the sender para ids. This
/// vector is sorted ascending by the para id and doesn't contain multiple entries with the same
/// sender.
polkadot/roadmap/implementers-guide/src/types/messages.md
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@@ -7,7 +7,7 @@ although with smaller scalability potential.
## HrmpChannelId
A type that uniquely identifies a HRMP channel. A HRMP channel is established between two paras.
A type that uniquely identifies an HRMP channel. An HRMP channel is established between two paras.
In text, we use the notation `(A, B)` to specify a channel between A and B. The channels are
unidirectional, meaning that `(A, B)` and `(B, A)` refer to different channels. The convention is
that we use the first item tuple for the sender and the second for the recipient. Only one channel
polkadot/roadmap/implementers-guide/src/types/runtime.md
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@@ -45,8 +45,7 @@ struct HostConfiguration {
///
/// NOTE that this is a soft limit and could be exceeded.
pub preferred_dispatchable_upward_messages_step_weight: u32,
/// Any dispatchable upward message that requests more than the critical amount is rejected
/// with `DispatchResult::CriticalWeightExceeded`.
/// Any dispatchable upward message that requests more than the critical amount is rejected.
///
/// The parameter value is picked up so that no dispatchable can make the block weight exceed
/// the total budget. I.e. that the sum of `preferred_dispatchable_upward_messages_step_weight`