Skip to main content

Cosmos Hub 2 Upgrade

The following document describes the necessary steps involved that full-node operators must take in order to upgrade from cosmoshub-2 to cosmoshub-3. The Tendermint team will post an official updated genesis file, but it is recommended that validators execute the following instructions in order to verify the resulting genesis file.

There is a strong social consensus around proposal Cosmos Hub 3 Upgrade Proposal E on cosmoshub-2. This indicates that the upgrade procedure should be performed on December 11, 2019 at or around 14:27 UTC on block 2,902,000.


Many changes have occurred to the Cosmos SDK and the Gaia application since the latest major upgrade (cosmoshub-2). These changes notably consist of many new features, protocol changes, and application structural changes that favor developer ergonomics and application development.

First and foremost, the Cosmos SDK and the Gaia application have been split into separate repositories. This allows for both the Cosmos SDK and Gaia to evolve naturally and independently. Thus, any future releases of Gaia going forward, including this one, will be built and tagged from this repository not the Cosmos SDK.

Since the Cosmos SDK and Gaia have now been split into separate repositories, their versioning will also naturally diverge. In an attempt to decrease community confusion and strive for semantic versioning, the Cosmos SDK will continue on its current versioning path (i.e. v0.36.x ) and the Gaia application will become v2.0.x.

Gaia application v2.0.3 is what full node operators will upgrade to and run in this next major upgrade.

Major Updates

There are many notable features and changes in the upcoming release of the SDK. Many of these are discussed at a high level in July's Cosmos development update found here.

Some of the biggest changes to take note on when upgrading as a developer or client are the following:

  • Tagging/Events: The entire system of what we used to call tags has been replaced by a more robust and flexible system called events. Any client that depended on querying or subscribing to tags should take note on the new format as old queries will not work and must be updated. More in depth docs on the events system can be found here. In addition, each module documents its own events in the specs (e.g. slashing).
  • Height Queries: Both the CLI and REST clients now (re-)enable height queries via the --height and ?height arguments respectively. An important note to keep in mind are that height queries against pruning nodes will return errors when a pruned height is queried against. When no height is provided, the latest height will be used by default keeping current behavior intact. In addition, many REST responses now wrap the query results in a new structure {"height": ..., "result": ...}. That is, the height is now returned to the client for which the resource was queried at.


As a validator performing the upgrade procedure on your consensus nodes carries a heightened risk of double-signing and being slashed. The most important piece of this procedure is verifying your software version and genesis file hash before starting your validator and signing.

The riskiest thing a validator can do is discover that they made a mistake and repeat the upgrade procedure again during the network startup. If you discover a mistake in the process, the best thing to do is wait for the network to start before correcting it. If the network is halted and you have started with a different genesis file than the expected one, seek advice from a Tendermint developer before resetting your validator.


Prior to exporting cosmoshub-2 state, validators are encouraged to take a full data snapshot at the export height before proceeding. Snapshotting depends heavily on infrastructure, but generally this can be done by backing up the .gaia directories.

It is critically important to back-up the .gaia/data/priv_validator_state.json file after stopping your gaiad process. This file is updated every block as your validator participates in a consensus rounds. It is a critical file needed to prevent double-signing, in case the upgrade fails and the previous chain needs to be restarted.

In the event that the upgrade does not succeed, validators and operators must downgrade back to v0.34.6+ of the Cosmos SDK and restore to their latest snapshot before restarting their nodes.

Upgrade Procedure

Note: It is assumed you are currently operating a full-node running v0.34.6+ of the Cosmos SDK.

  • The version/commit hash of Gaia v2.0.3: 2f6783e298f25ff4e12cb84549777053ab88749a
  • The upgrade height as agreed upon by governance: 2,902,000
  • You may obtain the canonical UTC timestamp of the exported block by any of the following methods:
    • Block explorer
    • Through manually querying an RPC node (e.g. /block?height=2902000)
    • Through manually querying a Gaia REST client (e.g. /blocks/2902000)
  1. Verify you are currently running the correct version (v0.34.6+) of the Cosmos SDK:

    $ gaiad version --long
    cosmos-sdk: 0.34.6
    git commit: 80234baf91a15dd9a7df8dca38677b66b8d148c1
    vendor hash: f60176672270c09455c01e9d880079ba36130df4f5cd89df58b6701f50b13aad
    build tags: netgo ledger
    go version go1.12.2 linux/amd64
  2. Export existing state from cosmoshub-2:

    NOTE: It is recommended for validators and operators to take a full data snapshot at the export height before proceeding in case the upgrade does not go as planned or if not enough voting power comes online in a sufficient and agreed upon amount of time. In such a case, the chain will fallback to continue operating cosmoshub-2. See Recovery for details on how to proceed.

    Before exporting state via the following command, the gaiad binary must be stopped!

    gaiad export --for-zero-height --height=2902000 > cosmoshub_2_genesis_export.json
  3. Verify the SHA256 of the (sorted) exported genesis file:

    $ jq -S -c -M '' cosmoshub_2_genesis_export.json | shasum -a 256
    [PLACEHOLDER] cosmoshub_2_genesis_export.json
  4. At this point you now have a valid exported genesis state! All further steps now require v2.0.3 of Gaia.

    NOTE: Go 1.13+ is required!

    git clone && cd gaia && git checkout v2.0.3; make install
  5. Verify you are currently running the correct version (v2.0.3) of the Gaia:

    $ gaiad version --long
    name: gaia
    server_name: gaiad
    client_name: gaiacli
    version: 2.0.3
    commit: 2f6783e298f25ff4e12cb84549777053ab88749a
    build_tags: netgo,ledger
    go: go version go1.13.3 darwin/amd64
  6. Migrate exported state from the current v0.34.6+ version to the new v2.0.3 version:

    gaiad migrate v0.36 cosmoshub_2_genesis_export.json --chain-id=cosmoshub-3 --genesis-time=[PLACEHOLDER]> genesis.json

    NOTE: The migrate command takes an input genesis state and migrates it to a targeted version. Both v0.36 and v0.37 are compatible as far as state structure is concerned.

    Genesis time should be computed relative to the blocktime of 2,902,000. The genesis time shall be the blocktime of 2,902,000 + 60 minutes with the subseconds truncated.

    An example shell command(tested on OS X Mojave) to compute this values is:

    curl\?height\=2902000 | jq -r '.result["block_meta"]["header"]["time"]'|xargs -0 date -v +60M  -j  -f "%Y-%m-%dT%H:%M:%S" +"%Y-%m-%dT%H:%M:%SZ"
  7. Now we must update all parameters that have been agreed upon through governance. There is only a single parameter, max_validators, that we're upgrading based on proposal 10

    cat genesis.json | jq '.app_state["staking"]["params"]["max_validators"]=125' > tmp_genesis.json && mv tmp_genesis.json genesis.json
  8. Verify the SHA256 of the final genesis JSON:

    $ jq -S -c -M '' genesis.json | shasum -a 256
    [PLACEHOLDER] genesis.json
  9. Reset state:

    NOTE: Be sure you have a complete backed up state of your node before proceeding with this step. See Recovery for details on how to proceed.

    gaiad unsafe-reset-all
  10. Move the new genesis.json to your .gaia/config/ directory

  11. Replace the db_backend on .gaia/config/config.toml to:

    db_backend = "goleveldb"
  12. Note, if you have any application configuration in gaiad.toml, that file has now been renamed to app.toml:

    mv .gaia/config/gaiad.toml .gaia/config/app.toml

Notes for Service Providers

  1. The transition from cosmoshub-2 to cosmoshub-3 contains an unusual amount of API breakage. After this upgrade will maintain the CosmosSDK API stability guarantee to avoid breaking APIs for at least 6 months and hopefully long.
  2. Anyone running signing infrastructure(wallets and exchanges) should be conscious that the type: field on StdTx will have changed from "type":"auth/StdTx","value":... to "type":"cosmos-sdk/StdTx","value":...
  3. As mentioned in the notes and SDK CHANGELOG, many queries to cosmos cli are wrapped with height fields now.
  4. We highly recommend standing up a testnet with the gaia-2.0 release or joining the gaia-13006 testnet. More info for joining the testnet can be found in the riot validator room.
  5. We expect that developers with iOS or Android based apps may have to notify their users of downtime and ship an upgrade for cosmoshub-3 compatibility unless they have some kind of switch they can throw for the new tx formats. Server side applications should experience briefer service interruptions and be able to just spin up new nodes and migrate to the new apis.