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x/upgrade

Abstract

x/upgrade is an implementation of a Cosmos SDK module that facilitates smoothly upgrading a live Cosmos chain to a new (breaking) software version. It accomplishes this by providing a BeginBlocker hook that prevents the blockchain state machine from proceeding once a pre-defined upgrade block height has been reached.

The module does not prescribe anything regarding how governance decides to do an upgrade, but just the mechanism for coordinating the upgrade safely. Without software support for upgrades, upgrading a live chain is risky because all of the validators need to pause their state machines at exactly the same point in the process. If this is not done correctly, there can be state inconsistencies which are hard to recover from.

Concepts

Plan

The x/upgrade module defines a Plan type in which a live upgrade is scheduled to occur. A Plan can be scheduled at a specific block height. A Plan is created once a (frozen) release candidate along with an appropriate upgrade Handler (see below) is agreed upon, where the Name of a Plan corresponds to a specific Handler. Typically, a Plan is created through a governance proposal process, where if voted upon and passed, will be scheduled. The Info of a Plan may contain various metadata about the upgrade, typically application specific upgrade info to be included on-chain such as a git commit that validators could automatically upgrade to.

Sidecar Process

If an operator running the application binary also runs a sidecar process to assist in the automatic download and upgrade of a binary, the Info allows this process to be seamless. This tool is Cosmovisor.

type Plan struct {
Name string
Height int64
Info string
}

Handler

The x/upgrade module facilitates upgrading from major version X to major version Y. To accomplish this, node operators must first upgrade their current binary to a new binary that has a corresponding Handler for the new version Y. It is assumed that this version has fully been tested and approved by the community at large. This Handler defines what state migrations need to occur before the new binary Y can successfully run the chain. Naturally, this Handler is application specific and not defined on a per-module basis. Registering a Handler is done via Keeper#SetUpgradeHandler in the application.

type UpgradeHandler func(Context, Plan, VersionMap) (VersionMap, error)

During each EndBlock execution, the x/upgrade module checks if there exists a Plan that should execute (is scheduled at that height). If so, the corresponding Handler is executed. If the Plan is expected to execute but no Handler is registered or if the binary was upgraded too early, the node will gracefully panic and exit.

StoreLoader

The x/upgrade module also facilitates store migrations as part of the upgrade. The StoreLoader sets the migrations that need to occur before the new binary can successfully run the chain. This StoreLoader is also application specific and not defined on a per-module basis. Registering this StoreLoader is done via app#SetStoreLoader in the application.

func UpgradeStoreLoader (upgradeHeight int64, storeUpgrades *store.StoreUpgrades) baseapp.StoreLoader

If there's a planned upgrade and the upgrade height is reached, the old binary writes Plan to the disk before panicking.

This information is critical to ensure the StoreUpgrades happens smoothly at correct height and expected upgrade. It eliminiates the chances for the new binary to execute StoreUpgrades multiple times everytime on restart. Also if there are multiple upgrades planned on same height, the Name will ensure these StoreUpgrades takes place only in planned upgrade handler.

Proposal

Typically, a Plan is proposed and submitted through governance via a proposal containing a MsgSoftwareUpgrade message. This proposal prescribes to the standard governance process. If the proposal passes, the Plan, which targets a specific Handler, is persisted and scheduled. The upgrade can be delayed or hastened by updating the Plan.Height in a new proposal.

proto/cosmos/upgrade/v1beta1/tx.proto
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Cancelling Upgrade Proposals

Upgrade proposals can be cancelled. There exists a gov-enabled MsgCancelUpgrade message type, which can be embedded in a proposal, voted on and, if passed, will remove the scheduled upgrade Plan. Of course this requires that the upgrade was known to be a bad idea well before the upgrade itself, to allow time for a vote.

proto/cosmos/upgrade/v1beta1/tx.proto
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If such a possibility is desired, the upgrade height is to be 2 * (VotingPeriod + DepositPeriod) + (SafetyDelta) from the beginning of the upgrade proposal. The SafetyDelta is the time available from the success of an upgrade proposal and the realization it was a bad idea (due to external social consensus).

A MsgCancelUpgrade proposal can also be made while the original MsgSoftwareUpgrade proposal is still being voted upon, as long as the VotingPeriod ends after the MsgSoftwareUpgrade proposal.

State

The internal state of the x/upgrade module is relatively minimal and simple. The state contains the currently active upgrade Plan (if one exists) by key 0x0 and if a Plan is marked as "done" by key 0x1. The state contains the consensus versions of all app modules in the application. The versions are stored as big endian uint64, and can be accessed with prefix 0x2 appended by the corresponding module name of type string. The state maintains a Protocol Version which can be accessed by key 0x3.

  • Plan: 0x0 -> Plan
  • Done: 0x1 | byte(plan name) -> BigEndian(Block Height)
  • ConsensusVersion: 0x2 | byte(module name) -> BigEndian(Module Consensus Version)
  • ProtocolVersion: 0x3 -> BigEndian(Protocol Version)

The x/upgrade module contains no genesis state.

Events

The x/upgrade does not emit any events by itself. Any and all proposal related events are emitted through the x/gov module.

Client

CLI

A user can query and interact with the upgrade module using the CLI.

Query

The query commands allow users to query upgrade state.

simd query upgrade --help
applied

The applied command allows users to query the block header for height at which a completed upgrade was applied.

simd query upgrade applied [upgrade-name] [flags]

If upgrade-name was previously executed on the chain, this returns the header for the block at which it was applied. This helps a client determine which binary was valid over a given range of blocks, as well as more context to understand past migrations.

Example:

simd query upgrade applied "test-upgrade"

Example Output:

"block_id": {
"hash": "A769136351786B9034A5F196DC53F7E50FCEB53B48FA0786E1BFC45A0BB646B5",
"parts": {
"total": 1,
"hash": "B13CBD23011C7480E6F11BE4594EE316548648E6A666B3575409F8F16EC6939E"
}
},
"block_size": "7213",
"header": {
"version": {
"block": "11"
},
"chain_id": "testnet-2",
"height": "455200",
"time": "2021-04-10T04:37:57.085493838Z",
"last_block_id": {
"hash": "0E8AD9309C2DC411DF98217AF59E044A0E1CCEAE7C0338417A70338DF50F4783",
"parts": {
"total": 1,
"hash": "8FE572A48CD10BC2CBB02653CA04CA247A0F6830FF19DC972F64D339A355E77D"
}
},
"last_commit_hash": "DE890239416A19E6164C2076B837CC1D7F7822FC214F305616725F11D2533140",
"data_hash": "E3B0C44298FC1C149AFBF4C8996FB92427AE41E4649B934CA495991B7852B855",
"validators_hash": "A31047ADE54AE9072EE2A12FF260A8990BA4C39F903EAF5636B50D58DBA72582",
"next_validators_hash": "A31047ADE54AE9072EE2A12FF260A8990BA4C39F903EAF5636B50D58DBA72582",
"consensus_hash": "048091BC7DDC283F77BFBF91D73C44DA58C3DF8A9CBC867405D8B7F3DAADA22F",
"app_hash": "28ECC486AFC332BA6CC976706DBDE87E7D32441375E3F10FD084CD4BAF0DA021",
"last_results_hash": "E3B0C44298FC1C149AFBF4C8996FB92427AE41E4649B934CA495991B7852B855",
"evidence_hash": "E3B0C44298FC1C149AFBF4C8996FB92427AE41E4649B934CA495991B7852B855",
"proposer_address": "2ABC4854B1A1C5AA8403C4EA853A81ACA901CC76"
},
"num_txs": "0"
}
module versions

The module_versions command gets a list of module names and their respective consensus versions.

Following the command with a specific module name will return only that module's information.

simd query upgrade module_versions [optional module_name] [flags]

Example:

simd query upgrade module_versions

Example Output:

module_versions:
- name: auth
version: "2"
- name: authz
version: "1"
- name: bank
version: "2"
- name: capability
version: "1"
- name: crisis
version: "1"
- name: distribution
version: "2"
- name: evidence
version: "1"
- name: feegrant
version: "1"
- name: genutil
version: "1"
- name: gov
version: "2"
- name: ibc
version: "2"
- name: mint
version: "1"
- name: params
version: "1"
- name: slashing
version: "2"
- name: staking
version: "2"
- name: transfer
version: "1"
- name: upgrade
version: "1"
- name: vesting
version: "1"

Example:

regen query upgrade module_versions ibc

Example Output:

module_versions:
- name: ibc
version: "2"
plan

The plan command gets the currently scheduled upgrade plan, if one exists.

regen query upgrade plan [flags]

Example:

simd query upgrade plan

Example Output:

height: "130"
info: ""
name: test-upgrade
time: "0001-01-01T00:00:00Z"
upgraded_client_state: null

REST

A user can query the upgrade module using REST endpoints.

Applied Plan

AppliedPlan queries a previously applied upgrade plan by its name.

/cosmos/upgrade/v1beta1/applied_plan/{name}

Example:

curl -X GET "http://localhost:1317/cosmos/upgrade/v1beta1/applied_plan/v2.0-upgrade" -H "accept: application/json"

Example Output:

{
"height": "30"
}

Current Plan

CurrentPlan queries the current upgrade plan.

/cosmos/upgrade/v1beta1/current_plan

Example:

curl -X GET "http://localhost:1317/cosmos/upgrade/v1beta1/current_plan" -H "accept: application/json"

Example Output:

{
"plan": "v2.1-upgrade"
}

Module versions

ModuleVersions queries the list of module versions from state.

/cosmos/upgrade/v1beta1/module_versions

Example:

curl -X GET "http://localhost:1317/cosmos/upgrade/v1beta1/module_versions" -H "accept: application/json"

Example Output:

{
"module_versions": [
{
"name": "auth",
"version": "2"
},
{
"name": "authz",
"version": "1"
},
{
"name": "bank",
"version": "2"
},
{
"name": "capability",
"version": "1"
},
{
"name": "crisis",
"version": "1"
},
{
"name": "distribution",
"version": "2"
},
{
"name": "evidence",
"version": "1"
},
{
"name": "feegrant",
"version": "1"
},
{
"name": "genutil",
"version": "1"
},
{
"name": "gov",
"version": "2"
},
{
"name": "ibc",
"version": "2"
},
{
"name": "mint",
"version": "1"
},
{
"name": "params",
"version": "1"
},
{
"name": "slashing",
"version": "2"
},
{
"name": "staking",
"version": "2"
},
{
"name": "transfer",
"version": "1"
},
{
"name": "upgrade",
"version": "1"
},
{
"name": "vesting",
"version": "1"
}
]
}

gRPC

A user can query the upgrade module using gRPC endpoints.

Applied Plan

AppliedPlan queries a previously applied upgrade plan by its name.

cosmos.upgrade.v1beta1.Query/AppliedPlan

Example:

grpcurl -plaintext \
-d '{"name":"v2.0-upgrade"}' \
localhost:9090 \
cosmos.upgrade.v1beta1.Query/AppliedPlan

Example Output:

{
"height": "30"
}

Current Plan

CurrentPlan queries the current upgrade plan.

cosmos.upgrade.v1beta1.Query/CurrentPlan

Example:

grpcurl -plaintext localhost:9090 cosmos.slashing.v1beta1.Query/CurrentPlan

Example Output:

{
"plan": "v2.1-upgrade"
}

Module versions

ModuleVersions queries the list of module versions from state.

cosmos.upgrade.v1beta1.Query/ModuleVersions

Example:

grpcurl -plaintext localhost:9090 cosmos.slashing.v1beta1.Query/ModuleVersions

Example Output:

{
"module_versions": [
{
"name": "auth",
"version": "2"
},
{
"name": "authz",
"version": "1"
},
{
"name": "bank",
"version": "2"
},
{
"name": "capability",
"version": "1"
},
{
"name": "crisis",
"version": "1"
},
{
"name": "distribution",
"version": "2"
},
{
"name": "evidence",
"version": "1"
},
{
"name": "feegrant",
"version": "1"
},
{
"name": "genutil",
"version": "1"
},
{
"name": "gov",
"version": "2"
},
{
"name": "ibc",
"version": "2"
},
{
"name": "mint",
"version": "1"
},
{
"name": "params",
"version": "1"
},
{
"name": "slashing",
"version": "2"
},
{
"name": "staking",
"version": "2"
},
{
"name": "transfer",
"version": "1"
},
{
"name": "upgrade",
"version": "1"
},
{
"name": "vesting",
"version": "1"
}
]
}

Resources

A list of (external) resources to learn more about the x/upgrade module.