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Validator Identity Transition Demo

This document demonstrates how to transition a staked validator from one machine to another without a restart. Using this technique, a validator software update can be accomplished with virtually no downtime.

This method is less sophisticated than the etcd failover setup in that it does not require you to setup an etcd cluster, and you must manage relocating the tower file.

For an Ansible version of this guide, please refer to https://github.com/backbone-link/solana-identity-transition

Setup

The demo is run locally on your machine.

Install Solana 1.9.7 or greater

See https://docs.solana.com/cli/install-solana-cli-tools

Start a test validator to simulate the overall Solana cluster

A test validator instance is used to simulate the overall Solana cluster. In a production environment you would be connecting to Mainnet Beta instead.

The --slots-per-epoch 750 argument is also provided to decrease the epoch durations from ~3 days to ~5 minutes for quicker testing:

$ solana-test-validator --reset --slots-per-epoch 750 --limit-ledger-size 500000000

Start it in a separate terminal and wait until the reported "Finalized Slot" is 100 before continuing

Setup the validator identity, vote account and stake

Establish your validator identity and vote account for the test environment

$ solana-keygen new -s --no-bip39-passphrase -o staked-identity.json
$ solana-keygen new -s --no-bip39-passphrase -o authorized-withdrawer.json
$ solana-keygen new -s --no-bip39-passphrase -o vote-account.json
$ solana -ul --keypair staked-identity.json airdrop 42
$ solana -ul create-vote-account vote-account.json staked-identity.json authorized-withdrawer.json

then delegate stake to it. Delegating 200,000 SOL will be ~16% of the stake in the test validator setup, which is enough to be added to the test-validator leader schedule:

$ solana-keygen new -s --no-bip39-passphrase -o stake-account.json
$ solana -ul create-stake-account stake-account.json 200000
$ solana -ul delegate-stake stake-account.json vote-account.json --force

Setup the primary and secondary validator identities

Create two unstaked identity keypairs for the primary and secondary validator machines:

$ solana-keygen new -s --no-bip39-passphrase -o primary-unstaked-identity.json
$ solana-keygen new -s --no-bip39-passphrase -o secondary-unstaked-identity.json

Then create symlinks for both so that the primary validator starts using the staked identity and the secondary validator starts unstaked:

$ ln -sf staked-identity.json primary-identity.json
$ ln -sf secondary-unstaked-identity.json secondary-identity.json

Start the primary and secondary validators

Primary

$ solana-validator --entrypoint 127.0.0.1:1024 \
    --identity primary-identity.json \
    --vote-account vote-account.json \
    --authorized-voter staked-identity.json \
    --ledger primary-ledger --allow-private-addr --rpc-port 9999

Once started, from another terminal confirm that the validator is well by running the monitor:

$ solana-validator -l primary-ledger monitor

Secondary

This validator instance represents the secondary validator. In a production environment you'd run the secondary validator on a different physical machine:

$ solana-validator --entrypoint 127.0.0.1:1024 \
    --identity secondary-identity.json \
    --vote-account vote-account.json \
    --authorized-voter staked-identity.json \
    --ledger secondary-ledger --allow-private-addr --rpc-port 19999

Once started, from another terminal confirm that the validator is well by running the monitor:

$ solana-validator -l secondary-ledger monitor

Check the list of validators

Run

$ solana -ul validators

and you should see two validators. The test-validator representing the overall cluster and your primary validator.

The secondary validator is not shown in the output because it is not actively voting.

Transition Steps

The situation at the start of the transition is:

  • The primary validator is using the staked-identity.json identity account and actively voting with vote-account.json
  • The secondary validator is using the secondary-unstaked-identity.json identity account and not actively voting

The situation at the end of the transition will be:

  • The primary validator will be using the primary-unstaked-identity.json identity account and not actively voting
  • The secondary validator will be using the staked-identity.json identity account and actively voting with vote-account.json

In production you will likely want to automate all the following steps.

Step 1. Wait for a restart window

It's undesirable to transition between machines when the validator is about to produce blocks, as that will likely result in skipped blocks. Two minutes of idle time should be plenty:

$ solana-validator -l primary-ledger wait-for-restart-window --min-idle-time 2 --skip-new-snapshot-check

Step 2. Move your primary validator to the unstaked identity

Direct the primary validator to stop using the staked identity

$ solana-validator -l primary-ledger set-identity primary-unstaked-identity.json

Rewrite the identity symlink, so that if the primary validator restarts it will not revert back to using the staked identity

$ ln -sf primary-unstaked-identity.json primary-identity.json

Important! Your primary validator is now not voting and the following steps must be performed as quickly as possible to avoid delinquency.

Step 3. Transfer your tower file from primary to secondary validator

In this demo environment, a simple mv command is sufficient to transfer the tower file:

$ mv primary-ledger/tower-{,1_9-}$(solana-keygen pubkey staked-identity.json).bin secondary-ledger/

In a production environment, scp and rm can be used to transfer the tower file from the primary to secondary machine.

Transferring the tower file is essential to ensure that when your secondary validator resumes voting it will respect any voting lockouts that your primary validator was under at the time. Skipping this step may result in being slashed in the future.

Step 4. Move your secondary validator to the staked identity

Direct the secondary validator to start using the staked identity. The --require-tower flag is used to ensure that the tower file is actually present

$ solana-validator -l secondary-ledger set-identity --require-tower staked-identity.json

Rewrite the identity symlink, so that if the secondary validator restarts it will resume using the staked identity

$ ln -sf staked-identity.json secondary-identity.json

Done!

The secondary validator is now voting. Running solana -ul validators to confirm and at this point halting the primary validator will not cause delinquency.

Upgrade your primary validator, restart it, and then perform the steps in opposite direction to transition voting and block production back to your primary machine