## Basic example showcasing a migration using the MBM framework
This PR has been built on top of
https://github.com/paritytech/polkadot-sdk/pull/1781 and adds two new
example crates to the `examples` pallet
### Changes Made:
Added the `pallet-example-mbm` crate: This crate provides a minimal
example of a pallet that uses MBM. It showcases a storage migration
where values are migrated from a `u32` to a `u64`.
---------
Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: Liam Aharon <liam.aharon@hotmail.com>
closes#1324
#### Problem
Currently, it is possible to accidentally use inner unversioned
migration instead of `VersionedMigration` since both implement
`OnRuntimeUpgrade`.
#### Solution
With this change, we make it clear that value of `Inner` is not intended
to be used directly. It is achieved by bounding `Inner` to new trait
`UncheckedOnRuntimeUpgrade`, which has the same interface (except
`unchecked_` prefix) as `OnRuntimeUpgrade`.
#### `try-runtime` functions
Since developers can implement `try-runtime` for `Inner` value in
`VersionedMigration` and have custom logic for it, I added the same
`try-runtime` functions to `UncheckedOnRuntimeUpgrade`. I looked for a
ways to not duplicate functions, but couldn't find anything that doesn't
significantly change the codebase. So I would appreciate If you have any
suggestions to improve this
cc @liamaharon @xlc
polkadot address: 16FqwPZ8GRC5U5D4Fu7W33nA55ZXzXGWHwmbnE1eT6pxuqcT
---------
Co-authored-by: Liam Aharon <liam.aharon@hotmail.com>
This MR is the merge of
https://github.com/paritytech/substrate/pull/14414 and
https://github.com/paritytech/substrate/pull/14275. It implements
[RFC#13](https://github.com/polkadot-fellows/RFCs/pull/13), closes
https://github.com/paritytech/polkadot-sdk/issues/198.
-----
This Merge request introduces three major topicals:
1. Multi-Block-Migrations
1. New pallet `poll` hook for periodic service work
1. Replacement hooks for `on_initialize` and `on_finalize` in cases
where `poll` cannot be used
and some more general changes to FRAME.
The changes for each topical span over multiple crates. They are listed
in topical order below.
# 1.) Multi-Block-Migrations
Multi-Block-Migrations are facilitated by creating `pallet_migrations`
and configuring `System::Config::MultiBlockMigrator` to point to it.
Executive picks this up and triggers one step of the migrations pallet
per block.
The chain is in lockdown mode for as long as an MBM is ongoing.
Executive does this by polling `MultiBlockMigrator::ongoing` and not
allowing any transaction in a block, if true.
A MBM is defined through trait `SteppedMigration`. A condensed version
looks like this:
```rust
/// A migration that can proceed in multiple steps.
pub trait SteppedMigration {
type Cursor: FullCodec + MaxEncodedLen;
type Identifier: FullCodec + MaxEncodedLen;
fn id() -> Self::Identifier;
fn max_steps() -> Option<u32>;
fn step(
cursor: Option<Self::Cursor>,
meter: &mut WeightMeter,
) -> Result<Option<Self::Cursor>, SteppedMigrationError>;
}
```
`pallet_migrations` can be configured with an aggregated tuple of these
migrations. It then starts to migrate them one-by-one on the next
runtime upgrade.
Two things are important here:
- 1. Doing another runtime upgrade while MBMs are ongoing is not a good
idea and can lead to messed up state.
- 2. **Pallet Migrations MUST BE CONFIGURED IN `System::Config`,
otherwise it is not used.**
The pallet supports an `UpgradeStatusHandler` that can be used to notify
external logic of upgrade start/finish (for example to pause XCM
dispatch).
Error recovery is very limited in the case that a migration errors or
times out (exceeds its `max_steps`). Currently the runtime dev can
decide in `FailedMigrationHandler::failed` how to handle this. One
follow-up would be to pair this with the `SafeMode` pallet and enact
safe mode when an upgrade fails, to allow governance to rescue the
chain. This is currently not possible, since governance is not
`Mandatory`.
## Runtime API
- `Core`: `initialize_block` now returns `ExtrinsicInclusionMode` to
inform the Block Author whether they can push transactions.
### Integration
Add it to your runtime implementation of `Core` and `BlockBuilder`:
```patch
diff --git a/runtime/src/lib.rs b/runtime/src/lib.rs
@@ impl_runtime_apis! {
impl sp_block_builder::Core<Block> for Runtime {
- fn initialize_block(header: &<Block as BlockT>::Header) {
+ fn initialize_block(header: &<Block as BlockT>::Header) -> RuntimeExecutiveMode {
Executive::initialize_block(header)
}
...
}
```
# 2.) `poll` hook
A new pallet hook is introduced: `poll`. `Poll` is intended to replace
mostly all usage of `on_initialize`.
The reason for this is that any code that can be called from
`on_initialize` cannot be migrated through an MBM. Currently there is no
way to statically check this; the implication is to use `on_initialize`
as rarely as possible.
Failing to do so can result in broken storage invariants.
The implementation of the poll hook depends on the `Runtime API` changes
that are explained above.
# 3.) Hard-Deadline callbacks
Three new callbacks are introduced and configured on `System::Config`:
`PreInherents`, `PostInherents` and `PostTransactions`.
These hooks are meant as replacement for `on_initialize` and
`on_finalize` in cases where the code that runs cannot be moved to
`poll`.
The reason for this is to make the usage of HD-code (hard deadline) more
explicit - again to prevent broken invariants by MBMs.
# 4.) FRAME (general changes)
## `frame_system` pallet
A new memorize storage item `InherentsApplied` is added. It is used by
executive to track whether inherents have already been applied.
Executive and can then execute the MBMs directly between inherents and
transactions.
The `Config` gets five new items:
- `SingleBlockMigrations` this is the new way of configuring migrations
that run in a single block. Previously they were defined as last generic
argument of `Executive`. This shift is brings all central configuration
about migrations closer into view of the developer (migrations that are
configured in `Executive` will still work for now but is deprecated).
- `MultiBlockMigrator` this can be configured to an engine that drives
MBMs. One example would be the `pallet_migrations`. Note that this is
only the engine; the exact MBMs are injected into the engine.
- `PreInherents` a callback that executes after `on_initialize` but
before inherents.
- `PostInherents` a callback that executes after all inherents ran
(including MBMs and `poll`).
- `PostTransactions` in symmetry to `PreInherents`, this one is called
before `on_finalize` but after all transactions.
A sane default is to set all of these to `()`. Example diff suitable for
any chain:
```patch
@@ impl frame_system::Config for Test {
type MaxConsumers = ConstU32<16>;
+ type SingleBlockMigrations = ();
+ type MultiBlockMigrator = ();
+ type PreInherents = ();
+ type PostInherents = ();
+ type PostTransactions = ();
}
```
An overview of how the block execution now looks like is here. The same
graph is also in the rust doc.
<details><summary>Block Execution Flow</summary>
<p>
</p>
</details>
## Inherent Order
Moved to https://github.com/paritytech/polkadot-sdk/pull/2154
---------------
## TODO
- [ ] Check that `try-runtime` still works
- [ ] Ensure backwards compatibility with old Runtime APIs
- [x] Consume weight correctly
- [x] Cleanup
---------
Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: Liam Aharon <liam.aharon@hotmail.com>
Co-authored-by: Juan Girini <juangirini@gmail.com>
Co-authored-by: command-bot <>
Co-authored-by: Francisco Aguirre <franciscoaguirreperez@gmail.com>
Co-authored-by: Gavin Wood <gavin@parity.io>
Co-authored-by: Bastian Köcher <git@kchr.de>
Original PR https://github.com/paritytech/substrate/pull/14641
---
Closes https://github.com/paritytech/polkadot-sdk/issues/109
### Problem
Quoting from the above issue:
> When adding a pallet to chain after genesis we currently don't set the
StorageVersion. So, when calling on_chain_storage_version it returns 0
while the pallet is maybe already at storage version 9 when it was added
to the chain. This could lead to issues when running migrations.
### Solution
- Create a new trait `BeforeAllRuntimeMigrations` with a single method
`fn before_all_runtime_migrations() -> Weight` trait with a noop default
implementation
- Modify `Executive` to call
`BeforeAllRuntimeMigrations::before_all_runtime_migrations` for all
pallets before running any other hooks
- Implement `BeforeAllRuntimeMigrations` in the pallet proc macro to
initialize the on-chain version to the current pallet version if the
pallet has no storage set (indicating it has been recently added to the
runtime and needs to have its version initialised).
### Other changes in this PR
- Abstracted repeated boilerplate to access the `pallet_name` in the
pallet expand proc macro.
### FAQ
#### Why create a new hook instead of adding this logic to the pallet
`pre_upgrade`?
`Executive` currently runs `COnRuntimeUpgrade` (custom migrations)
before `AllPalletsWithSystem` migrations. We need versions to be
initialized before the `COnRuntimeUpgrade` migrations are run, because
`COnRuntimeUpgrade` migrations may use the on-chain version for critical
logic. e.g. `VersionedRuntimeUpgrade` uses it to decide whether or not
to execute.
We cannot reorder `COnRuntimeUpgrade` and `AllPalletsWithSystem` so
`AllPalletsWithSystem` runs first, because `AllPalletsWithSystem` have
some logic in their `post_upgrade` hooks to verify that the on-chain
version and current pallet version match. A common use case of
`COnRuntimeUpgrade` migrations is to perform a migration which will
result in the versions matching, so if they were reordered these
`post_upgrade` checks would fail.
#### Why init the on-chain version for pallets without a current storage
version?
We must init the on-chain version for pallets even if they don't have a
defined storage version so if there is a future version bump, the
on-chain version is not automatically set to that new version without a
proper migration.
e.g. bad scenario:
1. A pallet with no 'current version' is added to the runtime
2. Later, the pallet is upgraded with the 'current version' getting set
to 1 and a migration is added to Executive Migrations to migrate the
storage from 0 to 1
a. Runtime upgrade occurs
b. `before_all` hook initializes the on-chain version to 1
c. `on_runtime_upgrade` of the migration executes, and sees the on-chain
version is already 1 therefore think storage is already migrated and
does not execute the storage migration
Now, on-chain version is 1 but storage is still at version 0.
By always initializing the on-chain version when the pallet is added to
the runtime we avoid that scenario.
---------
Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>
Co-authored-by: Bastian Köcher <git@kchr.de>
Closes https://github.com/paritytech/polkadot-sdk/issues/1916
Changes:
- Trivially wrap the migration into a version migration to enforce
idempotency.
- Opinionated logging nits
@liamaharon maybe we can add a check to the `try-runtime-cli` that
migrations are idempotent? It should be possible to check that the
storage root is identical after executing a second time (and that it
does not panic like it did here 😆).
---------
Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: Liam Aharon <liam.aharon@hotmail.com>
Co-authored-by: Francisco Aguirre <franciscoaguirreperez@gmail.com>
`VersionedMigration` has become somewhat widely used for handling
version bumps in migrations the last few months.
It is currently behind the `experimental` feature flag, requiring every
pallet that writes a new migration with version bumps to set up the
`experimental` flag in their own Cargo.tomls, and also for every runtime
using these pallets to explicitly enable the `experimental` flag for
each pallet.
This is becoming quite verbose, and I can only see the number of pallets
requiring the experimental flag increasing for no other reason than
using what has become a commonly used feature.
Additionally, I'm writing migration docs and would like to avoid
stepping through how to use the `experimental` feature to get
`VersionedMigration` working.
Since the feature has been used in production for some time now without
any reported issues, is becoming commonly used and ready to advertise in
docs, I feel this is a good time to make it non-experimental.
* Improve handling of unset `StorageVersion`
When a user is forgetting to set the storage version in a pallet and calls
`current_storage_version` to compare it against the `on_chain_storage_version` it will now fail to
compile the code. Before the pallet macro just returned `StorageVersion::default()` for
`current_storage_version` leading to potential issues with migrations. Besides that it also checks
in `post_upgrade` that the pallet storage version was upgraded and thus, no migration was missed.
* Use correct `Cargo.lock`
* Fixes
* Fix test
* Update frame/support/test/tests/pallet.rs
* Ensure we don't set a storage version when the pallet is missing the attribute
* Fix merge conflict
* Update frame/support/procedural/src/pallet/expand/hooks.rs
Co-authored-by: Roman Useinov <roman.useinov@gmail.com>
* Update frame/support/procedural/src/pallet/expand/hooks.rs
Co-authored-by: Roman Useinov <roman.useinov@gmail.com>
* Fix compilation
* Do not run everything with `try-runtime`
* Fix test
* Apply suggestions from code review
Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
* Fix `no-metadata-docs`
---------
Co-authored-by: Roman Useinov <roman.useinov@gmail.com>
Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: parity-processbot <>
* Change copyright year to 2023 from 2022
* Fix incorrect update of copyright year
* Remove years from copy right header
* Fix remaining files
* Fix typo in a header and remove update-copyright.sh
* update api
* update
* remove unused
* remove `one` api
* fix unused
* fmt
* add saturating accrue
* remove `Weight::new()`
* use some macros
* div makes no sense
* Update weight_v2.rs
* missed some
* more patch
* fixes
* more fixes
* more fix
* more fix
* Update frame/support/src/weights/weight_v2.rs
* not needed
* fix weight file
* Move `PalletVersion` away from the crate version
Before this pr, `PalletVersion` was referring to the crate version that
hosted the pallet. This pr introduces a custom `package.metadata.frame`
section in the `Cargo.toml` that can contain a `pallet-version` key
value pair. While the value is expected to be a valid u16. If this
key/value pair isn't given, the version is set to 1.
It also changes the `PalletVersion` declaration. We now only have one
`u16` that represents the version. Not a major/minor/patch version. As
the old `PalletVersion` was starting with the `u16` major, decoding the
old values will work.
* Overhaul the entire implementation
- Drop PalletVersion
- Introduce StorageVersion
- StorageVersion needs to be set in the crate and set for the macros
- Added migration
* Fix migrations
* Review feedback
* Remove unneeded dep
* remove pub consts
* Brings back logging and implements `GetStorageVersion`
* Return weight from migration
* Fmt and remove unused import
* Update frame/support/src/dispatch.rs
Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>
* Update frame/support/src/traits/metadata.rs
Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>
Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>
Juan Girini