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Edit HRMP opening info #5494

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78 changes: 45 additions & 33 deletions docs/build/build-hrmp-channels.md
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Expand Up @@ -7,40 +7,56 @@ keywords: [HRMP, parachain, statemint, proposal, asset hub, statemine]
slug: ../build-hrmp-channels
---

[HRMP](../learn/learn-xcm.md#xcmp-lite-hrmp) has the same interface and functionality as
[XCMP](../learn/learn-xcm.md#xcmp-cross-chain-message-passing) but is much more demanding on
resources since it passes all messages via the Relay Chain. When XCMP is implemented on Polkadot,
[HRMP](../learn/learn-xcm-transport.md#hrmp-xcmp-lite) has the same interface and functionality as
[XCMP](../learn/learn-xcm-transport.md#xcmp-cross-chain-message-passing) but is much more demanding
on resources since it passes all messages via the Relay Chain. When XCMP is implemented on Polkadot,
HRMP is planned to be deprecated and phased out in favor of it.

## Opening HRMP channel: parachain to parachain

To open a channel from one parachain to another that are not system chains on Polkadot, the
governance of each parachain needs to declare its intent to open a channel on the Relay Chain, and
To open a channel from one parachain to another, that is not a system chain on Polkadot, the
governance of each parachain needs to declare its intent to open a channel on the Relay Chain through a `Transact` XCM message with parachain origin, and
the second chain needs to accept and do the same.

In order to do this, the calls to be dispatched from both chains are:
To do this, the calls to be included in the `Transact` message from both chains are:

1. `hrmp > hrmpInitOpenChannel(recipient, proposedMaxCapacity, proposedMaxMessageSize)`: this call
initiates opening a channel from a parachain to a given recipient with given channel
initiates opening a channel from a parachain to a given recipient.

2. `hrmp > hrmpAcceptOpenChannel(sender)`: accepting the channel open request from the given sender.
2. `hrmp > hrmpAcceptOpenChannel(sender)`: this call is for accepting the channel open request from
the given sender.

Each parachain is to use its own governance process to execute this. The call will be executed on
the Relay Chain.
Each parachain is to use its governance process to execute this. The call will be executed on the
Relay Chain.
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@JuaniRios JuaniRios Jan 11, 2024 •
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If it is to be made only through governance, then why do we have the xcm instruction HrmpNewChannelOpenRequest sent by the relay as a notification?
At Polimec we are using this to do automatic channel opening, without going through governance.

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Although we had to modify the xcm-executor because it had that instruction left empty, so maybe that change can happen once the executor adds an implementation for those instructions 🤔


## Opening HRMP Channels with System Parachains

Opening an HRMP channel with a system parachain requires a referendum. Like all other governance
proposals, proposers should follow best practices like opening a discussion on
Opening an HRMP channel with a system parachain requires an
[OpenGov referendum](../learn/learn-guides-polkadot-opengov.md) using the
[General Admin Track](../learn/learn-polkadot-opengov-origins.md#general-admin). Like all other
governance proposals, proposers should follow best practices like opening a discussion on
[Polkassembly](https://polkadot.polkassembly.io/) or [Subsquare](https://polkadot.subsquare.io/) and
then submitting the proposal on-chain.

Before submitting the proposal, both the system parachain's and the parachain's sovereign accounts
(both [system accounts](../learn/learn-account-advanced.md#system-accounts)) must have the channel
deposit of 20 DOT plus the
[existential deposit](../learn/learn-accounts.md#existential-deposit-and-reaping). Opening HRMP
channels requires submitting a transaction; therefore, ensure you have some extra funds to cover
transaction fees.

:::info

After runtime 1,001,000, chains will not need any deposit for channels with system chains (and
should be fine without any balance in their accounts). There will be a `poke_deposit` function that
will refund any existing deposits.

:::

Proposals should generally be a `batch_all` call containing:

1. A `force_transfer` of the channel deposit from the Treasury to the System parachain's sovereign
account. Remember that a bi-direction channel is _two_ channels so will need double the amount.
1. A `force_open_hrmp_channel` from your chain to the system chain.
1. A `force_open_hrmp_channel` from the system chain to your chain.
2. A `force_open_hrmp_channel` from the system chain to your chain.

:::caution

Expand All @@ -52,9 +68,9 @@ than the old two-phase channel request/accept method.
## Publication on Polkassembly for discussion and feedback

The [discussions section of Polkassembly](https://polkadot.polkassembly.io/discussions) is the best
place to share the reasoning behind your proposal: make sure to log in with the proposer address (if
possible) before publishing yours, and if you can do this also make sure the address has an on-chain
identity.
place to share the reasoning behind your proposal: make sure to log in with the proposer’s address
(if possible) before publishing yours, and if you can do this, also make sure the address has an
on-chain identity.

### Example: Opening an HRMP Channel with the AssetHub

Expand All @@ -65,15 +81,11 @@ the community to review and ultimately vote on:
1. A request on what the proposal aims to do (opening an HRMP channel with the AssetHub);
2. The use cases this channel will support for your chain;
3. Technical details of the proposal, including proposal parameters and technical details of this
call (On Kusama, most proposals were designed as a batchAll calls):
call:

- A `forceTransfer` of 20 DOT from the Treasury to AssetHub sovereign account.
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- A `forceOpenhrmpchannel` from AssetHub (1,000) to ParaID.
- A `forceOpenhrmpChannel` from ParaID to AssetHub (1,000).

Please note that if governance decides to reduce the HRMP channel deposit on Polkadot to 0 DOT,
the first transaction should not be necessary (these guidelines will be updated accordingly).

4. The XCM message to the Asset Hub, which can be decoded on the network;
5. The call data to verify on
[Polkadot JS Apps Decode](https://polkadot.js.org/apps/?rpc=wss%3A%2F%2Frpc.polkadot.io#/extrinsics/decode)
Expand All @@ -84,27 +96,27 @@ the community to review and ultimately vote on:
the preimage hash needs to be submitted to and whitelisted by the
[Technical Fellowship](../learn/learn-polkadot-opengov.md#the-technical-fellowship).

Below is an example of how teams followed this process on Kusama, as a way to:
Below is an example of how teams followed this process on Kusama as a way to:

- Proposal to open HRMP channel between Bifrost and the Asset Hub: the motion can be found
[here](https://kusama.polkassembly.io/motion/418).

## Preimage submission on democracy tab (Polkadot JS Apps)
## Preimage submission on democracy tab (Polkadot-JS UI)

Once the community has given enough feedback (we expect these proposal to be non controversial)
please submit the image on the discussion post in the
Once the community has given enough feedback (we expect this proposal to be noncontroversial) please
submit the image on the discussion post in the
[Democracy](https://polkadot.js.org/apps/?rpc=wss%3A%2F%2Frpc.polkadot.io#/democracy) tab on
Polkadot JS Apps, by using the "Submit Preimage" button:

![submit preimage](../assets/democracy/submit-preimage.png)

On the pop up window, compose the preimage in the discussion post: making sure the proposal hash is
On the pop-up window, compose the preimage in the discussion post, making sure the proposal hash is
the same as in the post.

## Vote by the community

After the community voting period, there will be an enactment period. In general, on Kusama these
have been defined in shorter terms than the voting periods. Again, it is very important you
encourage the community to vote on this, highlighting the benefits for your chain, use cases enabled
with this submission, among other things. After the enactment period is over, both chains will
authorize the channel.
After the community voting period, there will be an enactment period. In general, these have been
defined in shorter terms than the voting periods on Kusama. Again, it would be best to encourage the
community to vote on this, highlighting the benefits for your chain use cases enabled with this
submission, among other things. After the enactment period is over, both chains will authorize the
channel.
7 changes: 4 additions & 3 deletions docs/build/build-parachains.md
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Expand Up @@ -325,9 +325,10 @@ available for this type of work.
### Rococo Testnet

[Rococo](https://github.com/paritytech/cumulus#rococo-crown) is a testnet built for testing
parachains. Rococo utilizes Cumulus and [HRMP](../learn/learn-xcm.md#xcmp-lite-hrmp) (Horizontal
Relay-routed Message Passing) in order to send transfers and messages between parachains and a Relay
Chain. Every message is sent to the Relay Chain, then from the Relay Chain to the desired parachain.
parachains. Rococo utilizes Cumulus and [HRMP](../learn/learn-xcm-transport.md#hrmp-xcmp-lite)
(Horizontal Relay-routed Message Passing) in order to send transfers and messages between parachains
and a Relay Chain. Every message is sent to the Relay Chain, then from the Relay Chain to the
desired parachain.

Rococo runs a few test system parachains:
[Rockmine](https://polkadot.js.org/apps/?rpc=wss%3A%2F%2Frococo-asset-hub-rpc.polkadot.io#/explorer),
Expand Down
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