cosmos-sdk/cosmovisor

Cosmosvisor Quick Start

cosmovisor is a small process manager around Cosmos SDK binaries that monitors the governance module via stdout to see if there's a chain upgrade proposal coming in. If it see a proposal that gets approved it can be run manually or automatically to download the new code, stop the node, run the migration script, replace the node binary, and start with the new genesis file.

Installation

Run:

go get github.com/cosmos/cosmos-sdk/cosmovisor/cmd/cosmovisor

Command Line Arguments And Environment Variables

All arguments passed to the cosmovisor program will be passed to the current daemon binary (as a subprocess). It will return /dev/stdout and /dev/stderr of the subprocess as its own. Because of that, it cannot accept any command line arguments, nor print anything to output (unless it terminates unexpectedly before executing a binary).

cosmovisor reads its configuration from environment variables:

• DAEMON_HOME is the location where upgrade binaries should be kept (e.g. $HOME/.gaiad or $HOME/.xrnd).
• DAEMON_NAME is the name of the binary itself (eg. xrnd, gaiad, simd, etc).
• DAEMON_ALLOW_DOWNLOAD_BINARIES (optional) if set to true will enable auto-downloading of new binaries (for security reasons, this is intended for full nodes rather than validators).
• DAEMON_RESTART_AFTER_UPGRADE (optional) if set to true it will restart the sub-process with the same command line arguments and flags (but new binary) after a successful upgrade. By default, cosmovisor dies afterwards and allows the supervisor to restart it if needed. Note that this will not auto-restart the child if there was an error.

Data Folder Layout

$DAEMON_HOME/cosmovisor is expected to belong completely to cosmovisor and subprocesses that are controlled by it. The folder content is organised as follows:

.
├── current -> genesis or upgrades/<name>
├── genesis
│   └── bin
│       └── $DAEMON_NAME
└── upgrades
    └── <name>
        └── bin
            └── $DAEMON_NAME

Each version of the Cosmos SDK application is stored under either genesis or upgrades/<name>, which holds bin/$DAEMON_NAME along with any other needed files such as auxiliary client programs or libraries. current is a symbolic link to the currently active folder (so current/bin/$DAEMON_NAME is the currently active binary).

Note: the name variable in upgrades/<name> holds the URI-encoded name of the upgrade as specified in the upgrade module plan.

Please note that $DAEMON_HOME/cosmovisor just stores the binaries and associated program code. The cosmovisor binary can be stored in any typical location (eg /usr/local/bin). The actual blockchain program will store it's data under their default data directory (e.g. $HOME/.gaiad) which is independent of the $DAEMON_HOME. You can choose to set $DAEMON_HOME to the actual binary's home directory and then end up with a configuation like the following, but this is left as a choice to the system admininstrator for best directory layout:

.gaiad
├── config
├── data
└── cosmovisor

Usage

The system administrator admin is responsible for:

• installing the cosmovisor binary and configure the host's init system (e.g. systemd, launchd, etc) along with the environmental variables appropriately;
• installing the genesis folder manually;
• installing the upgrades/<name> folders manually.

cosmovisor will set the current link to point to genesis at first start (when no current link exists) and handles binaries switch overs at the correct points in time, so that the system administrator can prepare days in advance and relax at upgrade time.

Note that blockchain applications that wish to support upgrades may package up a genesis cosmovisor tarball with this information, just as they prepare the genesis binary tarball. In fact, they may offer a tarball will all upgrades up to current point for easy download for those who wish to sync a fullnode from start.

The DAEMON specific code and operations (e.g. tendermint config, the application db, syncing blocks, etc) are performed as normal. Application binaries' directives such as command-line flags and environment variables work normally.

Example: simd

The following instructions provide a demonstration of cosmovisor's integration with the simd application shipped along the Cosmos SDK's source code.

First compile simd:

cd cosmos-sdk/
make build

Create a new key and setup the simd node:

rm -rf $HOME/.simapp
./build/simd keys --keyring-backend=test add validator
./build/simd init testing --chain-id test
./build/simd add-genesis-account --keyring-backend=test $(./build/simd keys --keyring-backend=test show validator -a) 1000000000stake,1000000000validatortoken
./build/simd gentx --keyring-backend test --chain-id test validator 100000stake
./build/simd collect-gentxs

Set the required environment variables:

export DAEMON_NAME=simd         # binary name
export DAEMON_HOME=$HOME/.simapp  # daemon's home directory

Create the cosmovisor’s genesis folders and deploy the binary:

mkdir -p $DAEMON_HOME/cosmovisor/genesis/bin
cp ./build/simd $DAEMON_HOME/cosmovisor/genesis/bin

For the sake of this demonstration, we would amend voting_params.voting_period in .simapp/config/genesis.json to a reduced time ~5 minutes (300s) and eventually launch cosmosvisor:

cosmovisor start

Submit a software upgrade proposal:

./build/simd tx gov submit-proposal software-upgrade test1 --title "upgrade-demo" --description "upgrade"  --from validator --upgrade-height 100 --deposit 10000000stake --chain-id test --keyring-backend test -y

Query the proposal to ensure it was correctly broadcast and added to a block:

./build/simd query gov proposal 1

Submit a Yes vote for the upgrade proposal:

./build/simd tx gov vote 1 yes --from validator --keyring-backend test --chain-id test -y

For the sake of this demonstration, we will hardcode a modification in simapp to simulate a code change. In simapp/app.go, find the line containing the upgrade Keeper initialisation, it should look like app.UpgradeKeeper = upgradekeeper.NewKeeper(skipUpgradeHeights, keys[upgradetypes.StoreKey], appCodec, homePath). After that line, add the following snippet:

app.UpgradeKeeper.SetUpgradeHandler("test1", func(ctx sdk.Context, plan upgradetypes.Plan) {
   	// Add some coins to a random account
   	addr, err := sdk.AccAddressFromBech32("cosmos18cgkqduwuh253twzmhedesw3l7v3fm37sppt58")
   	if err != nil {
   		panic(err)
   	}
   	err = app.BankKeeper.AddCoins(ctx, addr, sdk.Coins{sdk.Coin{Denom: "stake", Amount: sdk.NewInt(345600000)}})
   	if err != nil {
   		panic(err)
   	}
   })

Now recompile a new binary and place it in $DAEMON_HOME/cosmosvisor/upgrades/test1/bin:

make build
cp ./build/simd $DAEMON_HOME/cosmovisor/upgrades/test1/bin

The upgrade will occur automatically at height 100.