New parachain runtime skeleton

Cargo.toml

@@ -29,6 +29,7 @@ members = [
 	"network/test",
 	"primitives",
 	"runtime/common",
+	"runtime/parachains",
 	"runtime/polkadot",
 	"runtime/kusama",
 	"runtime/westend",

roadmap/implementors-guide/guide.md

@@ -472,12 +472,27 @@ It's also responsible for managing parachain validation code upgrades as well as
 
 Utility structs:
 ```rust
+// the two key times necessary to track for every code replacement.
+pub struct ReplacementTimes {
+	/// The relay-chain block number that the code upgrade was expected to be activated.
+	/// This is when the code change occurs from the para's perspective - after the
+	/// first parablock included with a relay-parent with number >= this value.
+	expected_at: BlockNumber,
+	/// The relay-chain block number at which the parablock activating the code upgrade was
+	/// actually included. This means considered included and available, so this is the time at which
+	/// that parablock enters the acceptance period in this fork of the relay-chain.
+	activated_at: BlockNumber,
+}
+
 /// Metadata used to track previous parachain validation code that we keep in
 /// the state.
 pub struct ParaPastCodeMeta {
-	// Block numbers where the code was replaced. These can be used as indices
+	// Block numbers where the code was expected to be replaced and where the code
+	// was actually replaced, respectively. The first is used to do accurate lookups
+	// of historic code in historic contexts, whereas the second is used to do
+	// pruning on an accurate timeframe. These can be used as indices
 	// into the `PastCode` map along with the `ParaId` to fetch the code itself.
-	upgrade_times: Vec<BlockNumber>,
+	upgrade_times: Vec<ReplacementTimes>,
 	// This tracks the highest pruned code-replacement, if any.
 	last_pruned: Option<BlockNumber>,
 }
@@ -513,7 +528,11 @@ PastCode: map (ParaId, BlockNumber) => Option<ValidationCode>;
 /// but we also keep their code on-chain for the same amount of time as outdated code
 /// to keep it available for secondary checkers.
 PastCodeMeta: map ParaId => ParaPastCodeMeta;
-/// Which paras have past code that needs pruning and the relay-chain block in which context the code was replaced.
+/// Which paras have past code that needs pruning and the relay-chain block at which the code was replaced.
+/// Note that this is the actual height of the included block, not the expected height at which the
+/// code upgrade would be applied, although they may be equal.
+/// This is to ensure the entire acceptance period is covered, not an offset acceptance period starting
+/// from the time at which the parachain perceives a code upgrade as having occurred.
 /// Multiple entries for a single para are permitted. Ordered ascending by block number.
 PastCodePruning: Vec<(ParaId, BlockNumber)>;
 /// The block number at which the planned code change is expected for a para.
@@ -547,7 +566,7 @@ OutgoingParas: Vec<ParaId>;
 * `schedule_para_cleanup(ParaId)`: schedule a para to be cleaned up at the next session.
 * `schedule_code_upgrade(ParaId, ValidationCode, expected_at: BlockNumber)`: Schedule a future code upgrade of the given parachain, to be applied after inclusion of a block of the same parachain executed in the context of a relay-chain block with number >= `expected_at`.
 * `note_new_head(ParaId, HeadData, BlockNumber)`: note that a para has progressed to a new head, where the new head was executed in the context of a relay-chain block with given number. This will apply pending code upgrades based on the block number provided.
-* `validation_code_at(ParaId, at: BlockNumber, assume_intermediate: Option<BlockNumber>)`: Fetches the validation code to be used when validating a block in the context of the given relay-chain height. A second block number parameter may be used to tell the lookup to proceed as if an intermediate parablock has been included at the given relay-chain height. This may return past, current, or (with certain choices of `assume_intermediate`) future code. `assume_intermediate`, if provided, must be before `at`. If `at` is too old or the `ParaId` does not reference any live para, this may return `None`.
+* `validation_code_at(ParaId, at: BlockNumber, assume_intermediate: Option<BlockNumber>)`: Fetches the validation code to be used when validating a block in the context of the given relay-chain height. A second block number parameter may be used to tell the lookup to proceed as if an intermediate parablock has been included at the given relay-chain height. This may return past, current, or (with certain choices of `assume_intermediate`) future code. `assume_intermediate`, if provided, must be before `at`. If `at` is not within `config.acceptance_period` of the current block number, this will return `None`.
 
 #### Finalization
 
@@ -767,6 +786,7 @@ All failed checks should lead to an unrecoverable error making the block invalid
     1. Return a list of freed cores consisting of the cores where candidates have become available.
   * `process_candidates(BackedCandidates, scheduled: Vec<CoreAssignment>)`:
     1. check that each candidate corresponds to a scheduled core and that they are ordered in ascending order by `ParaId`.
+    1. Ensure that any code upgrade scheduled by the candidate does not happen within `config.validation_upgrade_frequency` of the currently scheduled upgrade, if any, comparing against the value of `Paras::FutureCodeUpgrades` for the given para ID.
     1. check the backing of the candidate using the signatures and the bitfields.
     1. create an entry in the `PendingAvailability` map for each backed candidate with a blank `availability_votes` bitfield.
     1. Return a `Vec<CoreIndex>` of all scheduled cores of the list of passed assignments that a backed candidate was successfully included for.

runtime/parachains/Cargo.toml

@@ -0,0 +1,84 @@
+[package]
+name = "polkadot-runtime-parachains"
+version = "0.8.0"
+authors = ["Parity Technologies <[email protected]>"]
+edition = "2018"
+
+[dependencies]
+bitvec = { version = "0.17.4", default-features = false, features = ["alloc"] }
+codec = { package = "parity-scale-codec", version = "1.3.0", default-features = false, features = ["derive"] }
+log = { version = "0.3.9", optional = true }
+rustc-hex = { version = "2.0.1", default-features = false }
+serde = { version = "1.0.102", default-features = false }
+serde_derive = { version = "1.0.102", optional = true }
+
+sp-api = { git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
+inherents = { package = "sp-inherents", git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
+sp-std = { package = "sp-std", git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
+sp-io = { git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
+sp-runtime = { git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
+sp-session = { git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
+sp-staking = { git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
+sp-core = { git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
+
+authorship = { package = "pallet-authorship", git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
+balances = { package = "pallet-balances", git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
+session = { package = "pallet-session", git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
+frame-support = { git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
+staking = { package = "pallet-staking", git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
+system = { package = "frame-system", git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
+timestamp = { package = "pallet-timestamp", git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
+vesting = { package = "pallet-vesting", git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
+offences = { package = "pallet-offences", git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
+frame-benchmarking = { git = "https://github.com/paritytech/substrate", branch = "master", default-features = false, optional = true }
+
+primitives = { package = "polkadot-primitives", path = "../../primitives", default-features = false }
+libsecp256k1 = { version = "0.3.2", default-features = false, optional = true }
+
+[dev-dependencies]
+hex-literal = "0.2.1"
+keyring = { package = "sp-keyring", git = "https://github.com/paritytech/substrate", branch = "master" }
+sp-trie = { git = "https://github.com/paritytech/substrate", branch = "master" }
+babe = { package = "pallet-babe", git = "https://github.com/paritytech/substrate", branch = "master" }
+sp-application-crypto = { git = "https://github.com/paritytech/substrate", branch = "master" }
+randomness-collective-flip = { package = "pallet-randomness-collective-flip", git = "https://github.com/paritytech/substrate", branch = "master" }
+pallet-staking-reward-curve = { git = "https://github.com/paritytech/substrate", branch = "master" }
+treasury = { package = "pallet-treasury", git = "https://github.com/paritytech/substrate", branch = "master" }
+trie-db = "0.20.0"
+serde_json = "1.0.41"
+libsecp256k1 = "0.3.2"
+
+[features]
+default = ["std"]
+no_std = []
+std = [
+	"bitvec/std",
+	"codec/std",
+	"log",
+	"rustc-hex/std",
+	"serde_derive",
+	"serde/std",
+	"primitives/std",
+	"inherents/std",
+	"sp-core/std",
+	"sp-api/std",
+	"sp-std/std",
+	"sp-io/std",
+	"frame-support/std",
+	"authorship/std",
+	"balances/std",
+	"sp-runtime/std",
+	"sp-session/std",
+	"sp-staking/std",
+	"session/std",
+	"staking/std",
+	"system/std",
+	"timestamp/std",
+	"vesting/std",
+]
+runtime-benchmarks = [
+	"libsecp256k1/hmac",
+	"frame-benchmarking",
+	"frame-support/runtime-benchmarks",
+	"system/runtime-benchmarks",
+]