chore: docs: nv-skeleton documentation

documentation/misc/Building_a_network_skeleton.md

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+# Network Upgrade Skeleton in Lotus
+
+This guide will walk you through the process of creating a skeleton for a network upgrade in Lotus. The process involves making changes in multiple repositories in the following order:
+
+1. [`ref-fvm`](#ref-fvm-checklist)
+2. [`filecoin-ffi`](#filecoin-ffi-checklist)
+3. [`go-state-types`](#go-state-types-checklist)
+4. [`lotus`](#lotus-checklist)
+
+Each repository has its own set of steps that need to be followed. This guide will provide detailed instructions for each repository.
+
+## Setup
+
+1. Clone the [ref-fvm](https://github.com/filecoin-project/ref-fvm.git) repository.
+
+2. Clone the [filecoin-ffi](https://github.com/filecoin-project/filecoin-ffi.git) repository.
+
+3. Clone the [go-state-types](https://github.com/filecoin-project/go-state-types) repository.
+
+4. In your Lotus repository, add `replace github.com/filecoin-project/go-state-types => ../go-state-types` to the very end of your Lotus `go.mod` file.
+    - This ensures that your local clone copy of `go-state-types` is used. Any changes you make there will be reflected in your Lotus project.
+
+## Ref-FVM Checklist
+
+1. Add support for the new network version in Ref-FVM:
+
+    - In `fvm/Cargo.toml` add `nvXX-dev` as a feature flag in the [features]-section.
+    - In `fvm/src/gas/price_list.rs`, extend the `price_list_by_network_version` function to support the new network version with the `nvXX-dev` feature flag.
+    - In fvm/src/machine/default.rs, locate the new function within your machine context. You'll find a SUPPORTED_VERSIONS constant that sets the range of supported network versions. Update this range to include the new network version. Do this by replacing the existing feature flag nvXX-dev and NetworkVersion::VXX with the new ones corresponding to your new network version.
+    - In `shared/src/version/mod.rs`, in the `NetworkVersion` implementation, you will find a series of constants representing different network versions. To add a new network version, you need to declare a new constant: `pub const (VXX+1): Self = Self(XX+1);` 
+
+You can take a look at [this Ref-FVM PR as a reference](https://github.com/filecoin-project/ref-fvm/pull/1929), which added the skeleton for network version 22.
+
+## Filecoin-FFI Checklist
+
+1. Update the `TryFrom<u32>` implementation for `EngineVersion` in `rust/src/fvm/engine.rs`
+    - Add the new network version number (XX+1) to the existing match arm for the network version.
+
+2. Patch the FVM-dependency (fvm3) in `rust/cargo.toml` to use the custom branch of the FVM created in the [Ref-FVM Checklist](#ref-fvm-checklist))
+    -  Add `features = ["your-ref-fvm-branch"]` to tell Cargo to use you Ref-FVM branch.
+
+You can take a look at this [Filecoin-FFI PR as a reference](https://github.com/filecoin-project/filecoin-ffi/pull/438), which added the skeleton for network version 22.
+
+## Go-State-Types Checklist
+
+1. Follow the [go-state-types actor version checklist](https://github.com/filecoin-project/go-state-types/blob/master/actors_version_checklist.md):
+
+    - Copy `go-state-types/builtin/vX` to `go-state-types/builtin/v(X+1)`.
+    - Change all references from vX to v(X+1) in the new files.
+    - Add new network version to `network/version.go`.
+    - Add new actors version to `actors/version.go`.
+        - Add `Version(XX+1) Version = XX+1` as a constant.
+        - In `func VersionForNetwork` add `case network.Version(XX+1): return Version(XX+1), nil`.
+    - Add the new version to the gen step of the makefile.
+        - Add `$(GO_BIN) run ./builtin/v(XX+1)/gen/gen.go`.
+
+You can take a look at this [Go-State-Types PR as a reference](https://github.com/filecoin-project/go-state-types/pull/232), which added the skeleton for network version 22.
+
+## Lotus Checklist
+
+1. Import new actors:
+
+    - Create a mock actor-bundle for the new network version.
+    - In `/build/actors` run `./pack.sh vXX+1 vXX.0.0` where XX is the current actor bundle version.
+
+2. Define upgrade heights in `build/params_`:
+
+    - Update the following files:
+        - `params_2k.go`
+            - Set previous `UpgradeXxxxxHeight = abi.ChainEpoch(-xx-1)`
+            - Add `var UpgradeXxxxxHeight = abi.ChainEpoch(200)`
+            - Add `UpgradeXxxxxHeight = getUpgradeHeight("LOTUS_XXXXX_HEIGHT", UpgradeXXXXHeight)`
+            - Set `const GenesisNetworkVersion = network.VersionXX` where XX is the network version you are upgrading from.
+        - `params_butterfly.go`
+            - set previous upgrade to `var UpgradeXxxxxHeigh = abi.ChainEpoch(-xx-1)`
+            - Add comment with ?????? signaling that the new upgrade date is unkown
+            - Add `const UpgradeXxxxxHeight = 999999999999999`
+        - `params_calibnet.go`
+            - Add comment with `??????` signaling that the new upgrade date is unkown
+            - Add `const UpgradeXxxxxHeight = 999999999999999`
+        - `params_interop.go`
+            - set previous upgrade to `var UpgradeXxxxxHeigh = abi.ChainEpoch(-xx-1)`
+            - Add `const UpgradeXxxxxHeight = 50`
+        - `params_mainnet.go`
+            - Set previous upgrade to `const UpgradeXxxxxHeight = XX`
+            - Add comment with ???? signaling that the new upgrade date is unkown
+            - Add `var UpgradeXxxxxxHeight = abi.ChainEpoch(9999999999)`
+            - Change the `LOTUS_DISABLE_XXXX` env variable to the new network name
+        - `params_testground.go`
+            - Add `UpgradeXxxxxHeight     abi.ChainEpoch = (-xx-1)`
+
+3. Generate adapters:
+
+    - Update `gen/inlinegen-data.json`.
+        - Add `XX+1` to "actorVersions" and set "latestActorsVersion" to `XX+1`.
+        - Add `XX+1` to "networkVersions" and set "latestNetworkVersion" to `XX+1`.
+
+    - Run `make actors-gen`. This generates the `/chain/actors/builtin/*` code, `/chain/actors/policy/policy.go` code, `/chain/actors/version.go`, and `/itest/kit/ensemble_opts_nv.go`.
+
+4. Update `chain/consensus/filcns/upgrades.go`.
+    - Import `nv(XX+1) "github.com/filecoin-project/go-state-types/builtin/v(XX+1)/migration`.
+    - Add Schedule. [^1]
+    - Add Migration. [^2]
+
+5. Add actorstype to the NewActorRegistry in `/chain/consensus/computestate.go`.
+    - Add `inv.Register(actorstypes.Version(XX+1), vm.ActorsVersionPredicate(actorstypes.Version(XX+1)), builtin.MakeRegistry(actorstypes.Version(XX+1))`.
+
+6. Add upgrade field to `api/types.go/ForkUpgradeParams`.
+    - Add `UpgradeXxxxxHeight      abi.ChainEpoch` to `ForkUpgradeParams` struct.
+
+7. Add upgrade to `node/impl/full/state.go`.
+    - Add `UpgradeXxxxxHeight:      build.UpgradeXxxxxHeight,`.
+
+8. Add network version to `chain/state/statetree.go`.
+    - Add `network.VersionXX+1` to `VersionForNetwork` function.
+
+9. Run `make gen`.
+
+10. Run `make docsgen-cli`.
+
+And you're done! This should create a network upgrade skeleton that you are able to run locally with your local go-state-types clones, and a mock Actors-bundle. This will allow you to:
+
+- Have a local developer network that starts at the current network version.
+- Be able to see the Actor CIDs/Actor version for the mock v12-bundle through `lotus state actor-cids --network-version XX+1`
+- Have a successful pre-migration.
+- Complete Migration at upgrade epoch, but fail immidiately after the upgrade.
+
+You can take a look at this [Lotus PR as a reference](https://github.com/filecoin-project/lotus/pull/11432), which added the skeleton for network version 22.
+
+// TODO: Create a video-tutorial going through all the steps
+
+[^1]: Here is an example of how you can add a schedule:
+
+    ```go
+    {
+        Height:    build.UpgradeXxxxHeight,
+        Network:   network.Version(XX+1),
+        Migration: UpgradeActorsV(XX+1),
+        PreMigrations: []stmgr.PreMigration{{
+            PreMigration:    PreUpgradeActors(VXX+1),
+            StartWithin:     120,
+            DontStartWithin: 15,
+            StopWithin:      10,
+        }},
+        Expensive: true,
+    },
+    ```
+
+    This schedule should be added to the `DefaultUpgradeSchedule` function, specifically within the `updates` array.
+
+[^2]: Here is an example of how you can add a migration:
+
+    ```go
+    func PreUpgradeActorsV(XX+1)(ctx context.Context, sm *stmgr.StateManager, cache stmgr.MigrationCache, root cid.Cid, epoch abi.ChainEpoch, ts *types.TipSet) error {
+        // Use half the CPUs for pre-migration, but leave at least 3.
+        workerCount := MigrationMaxWorkerCount
+        if workerCount <= 4 {
+            workerCount = 1
+        } else {
+            workerCount /= 2
+        }
+
+        lbts, lbRoot, err := stmgr.GetLookbackTipSetForRound(ctx, sm, ts, epoch)
+        if err != nil {
+            return xerrors.Errorf("error getting lookback ts for premigration: %w", err)
+        }
+
+        config := migration.Config{
+            MaxWorkers:        uint(workerCount),
+            ProgressLogPeriod: time.Minute * 5,
+        }
+
+        _, err = upgradeActorsV(XX+1)Common(ctx, sm, cache, lbRoot, epoch, lbts, config)
+        return err
+    }
+
+    func UpgradeActorsV(XX+1)(ctx context.Context, sm *stmgr.StateManager, cache stmgr.MigrationCache, cb stmgr.ExecMonitor,
+        root cid.Cid, epoch abi.ChainEpoch, ts *types.TipSet) (cid.Cid, error) {
+        // Use all the CPUs except 2.
+        workerCount := MigrationMaxWorkerCount - 3
+        if workerCount <= 0 {
+            workerCount = 1
+        }
+        config := migration.Config{
+            MaxWorkers:        uint(workerCount),
+            JobQueueSize:      1000,
+            ResultQueueSize:   100,
+            ProgressLogPeriod: 10 * time.Second,
+        }
+        newRoot, err := upgradeActorsV(XX+1)Common(ctx, sm, cache, root, epoch, ts, config)
+        if err != nil {
+            return cid.Undef, xerrors.Errorf("migrating actors v11 state: %w", err)
+        }
+        return newRoot, nil
+    }
+
+    func upgradeActorsV(XX+1)Common(
+        ctx context.Context, sm *stmgr.StateManager, cache stmgr.MigrationCache,
+        root cid.Cid, epoch abi.ChainEpoch, ts *types.TipSet,
+        config migration.Config,
+    ) (cid.Cid, error) {
+        writeStore := blockstore.NewAutobatch(ctx, sm.ChainStore().StateBlockstore(), units.GiB/4)
+        adtStore := store.ActorStore(ctx, writeStore)
+        // ensure that the manifest is loaded in the blockstore
+        if err := bundle.LoadBundles(ctx, writeStore, actorstypes.Version(XX+1)); err != nil {
+            return cid.Undef, xerrors.Errorf("failed to load manifest bundle: %w", err)
+        }
+
+        // Load the state root.
+        var stateRoot types.StateRoot
+        if err := adtStore.Get(ctx, root, &stateRoot); err != nil {
+            return cid.Undef, xerrors.Errorf("failed to decode state root: %w", err)
+        }
+
+        if stateRoot.Version != types.StateTreeVersion5 {
+            return cid.Undef, xerrors.Errorf(
+                "expected state root version 5 for actors v(XX+1) upgrade, got %d",
+                stateRoot.Version,
+            )
+        }
+
+        manifest, ok := actors.GetManifest(actorstypes.Version(XX+1))
+        if !ok {
+            return cid.Undef, xerrors.Errorf("no manifest CID for v(XX+1) upgrade")
+        }
+
+        // Perform the migration
+        newHamtRoot, err := nv(XX+1).MigrateStateTree(ctx, adtStore, manifest, stateRoot.Actors, epoch, config,
+            migrationLogger{}, cache)
+        if err != nil {
+            return cid.Undef, xerrors.Errorf("upgrading to actors v11: %w", err)
+        }
+
+        // Persist the result.
+        newRoot, err := adtStore.Put(ctx, &types.StateRoot{
+            Version: types.StateTreeVersion5,
+            Actors:  newHamtRoot,
+            Info:    stateRoot.Info,
+        })
+        if err != nil {
+            return cid.Undef, xerrors.Errorf("failed to persist new state root: %w", err)
+        }
+
+        // Persists the new tree and shuts down the flush worker
+        if err := writeStore.Flush(ctx); err != nil {
+            return cid.Undef, xerrors.Errorf("writeStore flush failed: %w", err)
+        }
+
+        if err := writeStore.Shutdown(ctx); err != nil {
+            return cid.Undef, xerrors.Errorf("writeStore shutdown failed: %w", err)
+        }
+
+        return newRoot, nil
+    }
+    ```