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Cosmovisor

cosmovisor is a process manager for Cosmos SDK application binaries that automates application binary switch at chain upgrades. It polls the upgrade-info.json file that is created by the x/upgrade module at upgrade height, and then can automatically download the new binary, stop the current binary, switch from the old binary to the new one, and finally restart the node with the new binary.

Design​

Cosmovisor is designed to be used as a wrapper for a Cosmos SDK app:

  • it will pass arguments to the associated app (configured by DAEMON_NAME env variable). Running cosmovisor run arg1 arg2 .... will run app arg1 arg2 ...;
  • it will manage an app by restarting and upgrading if needed;
  • it is configured using environment variables, not positional arguments.

Note: If new versions of the application are not set up to run in-place store migrations, migrations will need to be run manually before restarting cosmovisor with the new binary. For this reason, we recommend applications adopt in-place store migrations.

tip

Only the latest version of cosmovisor is actively developed/maintained.

danger

Versions prior to v1.0.0 have a vulnerability that could lead to a DOS. Please upgrade to the latest version.

Contributing​

Cosmovisor is part of the Cosmos SDK monorepo, but it's a separate module with it's own release schedule.

Release branches have the following format release/cosmovisor/vA.B.x, where A and B are a number (e.g. release/cosmovisor/v1.3.x). Releases are tagged using the following format: cosmovisor/vA.B.C.

Setup​

Installation​

You can download Cosmovisor from the GitHub releases.

To install the latest version of cosmovisor, run the following command:

go install cosmossdk.io/tools/cosmovisor/cmd/cosmovisor@latest

To install a specific version, you can specify the version:

go install cosmossdk.io/tools/cosmovisor/cmd/cosmovisor@v1.5.0

Run cosmovisor version to check the cosmovisor version.

Alternatively, for building from source, simply run make cosmovisor. The binary will be located in tools/cosmovisor.

danger

Installing cosmovisor using go install will display the correct cosmovisor version. Building from source (make cosmovisor) or installing cosmovisor by other means won't display the correct version.

Command Line Arguments And Environment Variables​

The first argument passed to cosmovisor is the action for cosmovisor to take. Options are:

  • help, --help, or -h - Output cosmovisor help information and check your cosmovisor configuration.
  • run - Run the configured binary using the rest of the provided arguments.
  • version - Output the cosmovisor version and also run the binary with the version argument.
  • config - Display the current cosmovisor configuration, that means displaying the environment variables value that cosmovisor is using.
  • add-upgrade - Add an upgrade manually to cosmovisor. This command allow you to easily add the binary corresponding to an upgrade in cosmovisor.

All arguments passed to cosmovisor run will be passed to the application binary (as a subprocess). cosmovisor will return /dev/stdout and /dev/stderr of the subprocess as its own. For this reason, cosmovisor run cannot accept any command-line arguments other than those available to the application binary.

cosmovisor reads its configuration from environment variables, or its configuration file (use --cosmovisor-config <path>):

  • DAEMON_HOME is the location where the cosmovisor/ directory is kept that contains the genesis binary, the upgrade binaries, and any additional auxiliary files associated with each binary (e.g. $HOME/.gaiad, $HOME/.regend, $HOME/.simd, etc.).
  • DAEMON_NAME is the name of the binary itself (e.g. gaiad, regend, 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). By default, cosmovisor will not auto-download new binaries.
  • DAEMON_DOWNLOAD_MUST_HAVE_CHECKSUM (optional, default = false), if true cosmovisor will require that a checksum is provided in the upgrade plan for the binary to be downloaded. If false, cosmovisor will not require a checksum to be provided, but still check the checksum if one is provided.
  • DAEMON_RESTART_AFTER_UPGRADE (optional, default = true), if true, restarts the subprocess with the same command-line arguments and flags (but with the new binary) after a successful upgrade. Otherwise (false), cosmovisor stops running after an upgrade and requires the system administrator to manually restart it. Note restart is only after the upgrade and does not auto-restart the subprocess after an error occurs.
  • DAEMON_RESTART_DELAY (optional, default none), allow a node operator to define a delay between the node halt (for upgrade) and backup by the specified time. The value must be a duration (e.g. 1s).
  • DAEMON_SHUTDOWN_GRACE (optional, default none), if set, send interrupt to binary and wait the specified time to allow for cleanup/cache flush to disk before sending the kill signal. The value must be a duration (e.g. 1s).
  • DAEMON_POLL_INTERVAL (optional, default 300 milliseconds), is the interval length for polling the upgrade plan file. The value must be a duration (e.g. 1s).
  • DAEMON_DATA_BACKUP_DIR option to set a custom backup directory. If not set, DAEMON_HOME is used.
  • UNSAFE_SKIP_BACKUP (defaults to false), if set to true, upgrades directly without performing a backup. Otherwise (false, default) backs up the data before trying the upgrade. The default value of false is useful and recommended in case of failures and when a backup needed to rollback. We recommend using the default backup option UNSAFE_SKIP_BACKUP=false.
  • DAEMON_PREUPGRADE_MAX_RETRIES (defaults to 0). The maximum number of times to call pre-upgrade in the application after exit status of 31. After the maximum number of retries, Cosmovisor fails the upgrade.
  • COSMOVISOR_DISABLE_LOGS (defaults to false). If set to true, this will disable Cosmovisor logs (but not the underlying process) completely. This may be useful, for example, when a Cosmovisor subcommand you are executing returns a valid JSON you are then parsing, as logs added by Cosmovisor make this output not a valid JSON.
  • COSMOVISOR_COLOR_LOGS (defaults to true). If set to true, this will colorise Cosmovisor logs (but not the underlying process).
  • COSMOVISOR_TIMEFORMAT_LOGS (defaults to kitchen). If set to a value (layout|ansic|unixdate|rubydate|rfc822|rfc822z|rfc850|rfc1123|rfc1123z|rfc3339|rfc3339nano|kitchen), this will add timestamp prefix to Cosmovisor logs (but not the underlying process).
  • COSMOVISOR_CUSTOM_PREUPGRADE (defaults to ``). If set, this will run $DAEMON_HOME/cosmovisor/$COSMOVISOR_CUSTOM_PREUPGRADE prior to upgrade with the arguments [ upgrade.Name, upgrade.Height ]. Executes a custom script (separate and prior to the chain daemon pre-upgrade command)
  • COSMOVISOR_DISABLE_RECASE (defaults to false). If set to true, the upgrade directory will expected to match the upgrade plan name without any case changes

Folder Layout​

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

.
├── current -> genesis or upgrades/<name>
├── genesis
│   └── bin
│       └── $DAEMON_NAME
└── upgrades
│   └── <name>
│       ├── bin
│       │   └── $DAEMON_NAME
│       └── upgrade-info.json
└── preupgrade.sh (optional)

The cosmovisor/ directory includes a subdirectory for each version of the application (i.e. genesis or upgrades/<name>). Within each subdirectory is the application binary (i.e. bin/$DAEMON_NAME) and any additional auxiliary files associated with each binary. current is a symbolic link to the currently active directory (i.e. genesis or upgrades/<name>). The name variable in upgrades/<name> is the lowercased URI-encoded name of the upgrade as specified in the upgrade module plan. Note that the upgrade name path are normalized to be lowercased: for instance, MyUpgrade is normalized to myupgrade, and its path is upgrades/myupgrade.

Please note that $DAEMON_HOME/cosmovisor only stores the application binaries. The cosmovisor binary itself can be stored in any typical location (e.g. /usr/local/bin). The application will continue to store its data in the default data directory (e.g. $HOME/.simapp) or the data directory specified with the --home flag. $DAEMON_HOME is dependent of the data directory and must be set to the same directory as the data directory, you will end up with a configuration like the following:

.simapp
├── config
├── data
└── cosmovisor

Usage​

The system administrator is responsible for:

  • installing the cosmovisor binary
  • configuring the host's init system (e.g. systemd, launchd, etc.)
  • appropriately setting the environmental variables
  • creating the <DAEMON_HOME>/cosmovisor directory
  • creating the <DAEMON_HOME>/cosmovisor/genesis/bin folder
  • creating the <DAEMON_HOME>/cosmovisor/upgrades/<name>/bin folders
  • placing the different versions of the <DAEMON_NAME> executable in the appropriate bin folders.

cosmovisor will set the current link to point to genesis at first start (i.e. when no current link exists) and then handle switching binaries at the correct points in time so that the system administrator can prepare days in advance and relax at upgrade time.

In order to support downloadable binaries, a tarball for each upgrade binary will need to be packaged up and made available through a canonical URL. Additionally, a tarball that includes the genesis binary and all available upgrade binaries can be packaged up and made available so that all the necessary binaries required to sync a fullnode from start can be easily downloaded.

The DAEMON specific code and operations (e.g. cometBFT config, the application db, syncing blocks, etc.) all work as expected. The application binaries' directives such as command-line flags and environment variables also work as expected.

Initialization​

The cosmovisor init <path to executable> command creates the folder structure required for using cosmovisor.

It does the following:

  • creates the <DAEMON_HOME>/cosmovisor folder if it doesn't yet exist
  • creates the <DAEMON_HOME>/cosmovisor/genesis/bin folder if it doesn't yet exist
  • copies the provided executable file to <DAEMON_HOME>/cosmovisor/genesis/bin/<DAEMON_NAME>
  • creates the current link, pointing to the genesis folder

It uses the DAEMON_HOME and DAEMON_NAME environment variables for folder location and executable name.

The cosmovisor init command is specifically for initializing cosmovisor, and should not be confused with a chain's init command (e.g. cosmovisor run init).

Detecting Upgrades​

cosmovisor is polling the $DAEMON_HOME/data/upgrade-info.json file for new upgrade instructions. The file is created by the x/upgrade module in BeginBlocker when an upgrade is detected and the blockchain reaches the upgrade height. The following heuristic is applied to detect the upgrade:

  • When starting, cosmovisor doesn't know much about currently running upgrade, except the binary which is current/bin/. It tries to read the current/update-info.json file to get information about the current upgrade name.
  • If neither cosmovisor/current/upgrade-info.json nor data/upgrade-info.json exist, then cosmovisor will wait for data/upgrade-info.json file to trigger an upgrade.
  • If cosmovisor/current/upgrade-info.json doesn't exist but data/upgrade-info.json exists, then cosmovisor assumes that whatever is in data/upgrade-info.json is a valid upgrade request. In this case cosmovisor tries immediately to make an upgrade according to the name attribute in data/upgrade-info.json.
  • Otherwise, cosmovisor waits for changes in upgrade-info.json. As soon as a new upgrade name is recorded in the file, cosmovisor will trigger an upgrade mechanism.

When the upgrade mechanism is triggered, cosmovisor will:

  1. if DAEMON_ALLOW_DOWNLOAD_BINARIES is enabled, start by auto-downloading a new binary into cosmovisor/<name>/bin (where <name> is the upgrade-info.json:name attribute);
  2. update the current symbolic link to point to the new directory and save data/upgrade-info.json to cosmovisor/current/upgrade-info.json.

Adding Upgrade Binary​

cosmovisor has an add-upgrade command that allows to easily link a binary to an upgrade. It creates a new folder in cosmovisor/upgrades/<name> and copies the provided executable file to cosmovisor/upgrades/<name>/bin/<DAEMON_NAME>.

Using the --upgrade-height flag allows to specify at which height the binary should be switched, without going via a gorvernance proposal. This enables support for an emergency coordinated upgrades where the binary must be switched at a specific height, but there is no time to go through a governance proposal.

danger

--upgrade-height creates an upgrade-info.json file. This means if a chain upgrade via governance proposal is executed before the specified height with --upgrade-height, the governance proposal will overwrite the upgrade-info.json plan created by add-upgrade --upgrade-height <height>. Take this into consideration when using --upgrade-height.

Auto-Download​

Generally, cosmovisor requires that the system administrator place all relevant binaries on disk before the upgrade happens. However, for people who don't need such control and want an automated setup (maybe they are syncing a non-validating fullnode and want to do little maintenance), there is another option.

NOTE: we don't recommend using auto-download because it doesn't verify in advance if a binary is available. If there will be any issue with downloading a binary, the cosmovisor will stop and won't restart an App (which could lead to a chain halt).

If DAEMON_ALLOW_DOWNLOAD_BINARIES is set to true, and no local binary can be found when an upgrade is triggered, cosmovisor will attempt to download and install the binary itself based on the instructions in the info attribute in the data/upgrade-info.json file. The files is constructed by the x/upgrade module and contains data from the upgrade Plan object. The Plan has an info field that is expected to have one of the following two valid formats to specify a download:

  1. Store an os/architecture -> binary URI map in the upgrade plan info field as JSON under the "binaries" key. For example:

    {
      "binaries": {
        "linux/amd64":"https://example.com/gaia.zip?checksum=sha256:aec070645fe53ee3b3763059376134f058cc337247c978add178b6ccdfb0019f"
      }
    }

    You can include multiple binaries at once to ensure more than one environment will receive the correct binaries:

    {
      "binaries": {
        "linux/amd64":"https://example.com/gaia.zip?checksum=sha256:aec070645fe53ee3b3763059376134f058cc337247c978add178b6ccdfb0019f",
        "linux/arm64":"https://example.com/gaia.zip?checksum=sha256:aec070645fe53ee3b3763059376134f058cc337247c978add178b6ccdfb0019f",
        "darwin/amd64":"https://example.com/gaia.zip?checksum=sha256:aec070645fe53ee3b3763059376134f058cc337247c978add178b6ccdfb0019f"
        }
    }

    When submitting this as a proposal ensure there are no spaces. An example command using gaiad could look like:

    > gaiad tx upgrade software-upgrade Vega \
    --title Vega \
    --deposit 100uatom \
    --upgrade-height 7368420 \
    --upgrade-info '{"binaries":{"linux/amd64":"https://github.com/cosmos/gaia/releases/download/v6.0.0-rc1/gaiad-v6.0.0-rc1-linux-amd64","linux/arm64":"https://github.com/cosmos/gaia/releases/download/v6.0.0-rc1/gaiad-v6.0.0-rc1-linux-arm64","darwin/amd64":"https://github.com/cosmos/gaia/releases/download/v6.0.0-rc1/gaiad-v6.0.0-rc1-darwin-amd64"}}' \
    --summary "upgrade to Vega" \
    --gas 400000 \
    --from user \
    --chain-id test \
    --home test/val2 \
    --node tcp://localhost:36657 \
    --yes

  2. Store a link to a file that contains all information in the above format (e.g. if you want to specify lots of binaries, changelog info, etc. without filling up the blockchain). For example:

    https://example.com/testnet-1001-info.json?checksum=sha256:deaaa99fda9407c4dbe1d04bd49bab0cc3c1dd76fa392cd55a9425be074af01e

When cosmovisor is triggered to download the new binary, cosmovisor will parse the "binaries" field, download the new binary with go-getter, and unpack the new binary in the upgrades/<name> folder so that it can be run as if it was installed manually.

Note that for this mechanism to provide strong security guarantees, all URLs should include a SHA 256/512 checksum. This ensures that no false binary is run, even if someone hacks the server or hijacks the DNS. go-getter will always ensure the downloaded file matches the checksum if it is provided. go-getter will also handle unpacking archives into directories (in this case the download link should point to a zip file of all data in the bin directory).

To properly create a sha256 checksum on linux, you can use the sha256sum utility. For example:

sha256sum ./testdata/repo/zip_directory/autod.zip

The result will look something like the following: 29139e1381b8177aec909fab9a75d11381cab5adf7d3af0c05ff1c9c117743a7.

You can also use sha512sum if you would prefer to use longer hashes, or md5sum if you would prefer to use broken hashes. Whichever you choose, make sure to set the hash algorithm properly in the checksum argument to the URL.

Preparing for an Upgrade​

To prepare for an upgrade, use the prepare-upgrade command:

cosmovisor prepare-upgrade

This command performs the following actions:

  1. Retrieves upgrade information directly from the blockchain about the next scheduled upgrade.
  2. Downloads the new binary specified in the upgrade plan.
  3. Verifies the binary's checksum (if required by configuration).
  4. Places the new binary in the appropriate directory for Cosmovisor to use during the upgrade.

The prepare-upgrade command provides detailed logging throughout the process, including:

  • The name and height of the upcoming upgrade
  • The URL from which the new binary is being downloaded
  • Confirmation of successful download and verification
  • The path where the new binary has been placed

Example output:

INFO Preparing for upgrade name=v1.0.0 height=1000000
INFO Downloading upgrade binary url=https://example.com/binary/v1.0.0?checksum=sha256:339911508de5e20b573ce902c500ee670589073485216bee8b045e853f24bce8
INFO Upgrade preparation complete name=v1.0.0 height=1000000

Note: The current way of downloading manually and placing the binary at the right place would still work.

Example: SimApp Upgrade​

The following instructions provide a demonstration of cosmovisor using the simulation application (simapp) shipped with the Cosmos SDK's source code. The following commands are to be run from within the cosmos-sdk repository.

Chain Setup​

Let's create a new chain using the v0.47.4 version of simapp (the Cosmos SDK demo app):

git checkout v0.47.4
make build

Clean ~/.simapp (never do this in a production environment):

./build/simd tendermint unsafe-reset-all

Set up app config:

./build/simd config chain-id test
./build/simd config keyring-backend test
./build/simd config broadcast-mode sync

Initialize the node and overwrite any previous genesis file (never do this in a production environment):

./build/simd init test --chain-id test --overwrite

For the sake of this demonstration, amend voting_period in genesis.json to a reduced time of 20 seconds (20s):

cat <<< $(jq '.app_state.gov.params.voting_period = "20s"' $HOME/.simapp/config/genesis.json) > $HOME/.simapp/config/genesis.json

Create a validator, and setup genesis transaction:

./build/simd keys add validator
./build/simd genesis add-genesis-account validator 1000000000stake --keyring-backend test
./build/simd genesis gentx validator 1000000stake --chain-id test
./build/simd genesis collect-gentxs

Prepare Cosmovisor and Start the Chain​

Set the required environment variables:

export DAEMON_NAME=simd
export DAEMON_HOME=$HOME/.simapp

Set the optional environment variable to trigger an automatic app restart:

export DAEMON_RESTART_AFTER_UPGRADE=true

Initialize cosmovisor with the current binary:

cosmovisor init ./build/simd

Now you can run cosmovisor with simapp v0.47.4:

cosmovisor run start

Update App​

Update app to the latest version (e.g. v0.50.0).

note

Migration plans are defined using the x/upgrade module and described in In-Place Store Migrations. Migrations can perform any deterministic state change.

The migration plan to upgrade the simapp from v0.47 to v0.50 is defined in simapp/upgrade.go.

Build the new version simd binary:

make build

Add the new simd binary and the upgrade name:

danger

The migration name must match the one defined in the migration plan.

cosmovisor add-upgrade v047-to-v050 ./build/simd

Open a new terminal window and submit an upgrade proposal along with a deposit and a vote (these commands must be run within 20 seconds of each other):

./build/simd tx upgrade software-upgrade v047-to-v050 --title upgrade --summary upgrade --upgrade-height 200 --upgrade-info "{}" --no-validate --from validator --yes
./build/simd tx gov deposit 1 10000000stake --from validator --yes
./build/simd tx gov vote 1 yes --from validator --yes

The upgrade will occur automatically at height 200. Note: you may need to change the upgrade height in the snippet above if your test play takes more time.