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casper-node-launcher

A binary which runs and upgrades the casper-node of the Casper network.

Usage

The casper-node-launcher takes no arguments other than the standard --help and --version.

On startup, the launcher either tries to read its previously cached state from disk, or assumes a fresh start. On a fresh start, the launcher searches for the lowest installed version of casper-node and starts running it in validator mode.

After every run of the casper-node binary in validator mode, the launcher does the following based upon the exit code returned by casper-node:

  • If 0 (success), searches for the immediate next installed version of casper-node and runs it in migrate-data mode
  • If 102 (downgrade), searches for the immediate previous installed version of casper-node and runs it in validator mode
  • Any other value causes the launcher to exit with an error

After every run of the casper-node binary in migrate-data mode, the launcher does the following based upon the exit code returned by casper-node:

  • If 0 (success), runs the same version of casper-node in validator mode
  • If 102 (downgrade), searches for the immediate previous installed version of casper-node and runs it in validator mode
  • Any other value causes the launcher to exit with an error

If the launcher cannot find an appropriate version at any stage of upgrading or downgrading, it exits with an error.

The default path for the casper-node's config file is /etc/casper/1_0_0/config.toml where the folder 1_0_0 indicates the semver version of the node software.

The default path for the launcher's cached state file is /etc/casper/casper-node-launcher-state.toml.

For testing purposes, the common folder /etc/casper can be overridden by setting the environment variable CASPER_CONFIG_DIR to a different folder.

The default path for the casper-node binary is /var/lib/casper/bin/1_0_0/casper-node where the folder 1_0_0 likewise indicates the version. The default path for the casper-node-launcher binary is /var/lib/casper/bin/casper-node-launcher.

For testing purposes, the common folder /var/lib/casper/bin can be overridden by setting the environment variable CASPER_BIN_DIR to a different folder.