Crate pallet_xcm_bridge_router

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Expand description

A pallet that can be used as an alternative in the XCM router configuration — see the SendXcm implementation for details.

§Features

This pallet offers several optional features to customize functionality:

§Message Size Fee

An optional fee based on T::FeeAsset and T::ByteFee. If T::FeeAsset is not specified, this fee is not calculated.

§Dynamic Fees and Congestion

This pallet supports storing the congestion status of bridge outbound queues. The fee increases exponentially if the queue between this chain and a sibling or child bridge hub becomes congested. All other bridge hub queues provide backpressure mechanisms, so if any of these queues are congested, it will eventually lead to increased queuing on this chain.

There are two methods for storing congestion status:

  1. A dedicated extrinsic update_bridge_status, which relies on T::UpdateBridgeStatusOrigin. This allows the message exporter to send, for example, an XCM Transact.
  2. An implementation of bp_xcm_bridge::LocalXcmChannelManager.

§Usage

This pallet provides several implementations, such as ViaLocalBridgeExporter and ViaRemoteBridgeExporter, which can expose or access these features.

This router can be used in two main scenarios, depending on where the router and message exporter (e.g., pallet_xcm_bridge_hub or another pallet with an ExportXcm implementation) are deployed:

§On the Same Chain as the Message Exporter

In this setup, the router directly calls an ExportXcm implementation. In this case, ViaLocalBridgeExporter can be used as a wrapper with T::MessageExporter.

§On a Different Chain than the Message Exporter

In this setup, we need to provide a SendXcm implementation for T::MessageExporter, which sends ExportMessage. For example, SovereignPaidRemoteExporter can be used with ViaRemoteBridgeExporter.

Note on Terminology: When we refer to the bridge hub, we mean the chain that has the pallet-bridge-messages with an ExportXcm implementation deployed, such as pallet-xcm-bridge. Depending on the deployment setup, T::MessageExporter can be configured accordingly — see T::MessageExporter for additional documentation.

Re-exports§

Modules§

  • impls
    Various implementations supporting easier configuration of the pallet.
  • pallet
    The pallet module in each FRAME pallet hosts the most important items needed to construct this pallet.
  • weights
    Autogenerated weights for pallet_xcm_bridge_hub_router

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