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05-PubsubForValidators.md

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The x/pubsub Module for Validators

Before Sommelier v7, the Steward Registry was used to record the CA and server endpoint of all steward processes. This database was then used by Strategy Providers (SPs) to send requests to each steward instance.

The Steward Registry has been deprecated in favor of a (mostly) generalized pubslisher/subscriber registry Cosmos SDK module, x/pubsub.

For more information on x/pubsub itself, please refer to the protocol documentation

Registering Steward as a Subscriber

A Subscriber is an entity representing the identity of your steward instance. It contains your Sommelier delegate (orchestrator) address, server Certificate Authority, and the Steward server endpoint to which Strategy Providers (publishers) will send requests.

Prerequisites

  • The latest sommelier binary release
  • Key, CA, and self-signed certificate generated using the steps in the previous doc.
  • Your delegate (orchestrator) Sommelier address registered on the gravity module
  • A domain and port that will or already points to your steward server
  • Firewall configured to allow requests to the former

Steps

A subscriber can be created using the following CLI command

sommelier tx pubsub add-subscriber <subscriber_address> [<ca_cert_file>] [<push_url>]

Where subscriber_address is your delegate (orchestrator) address, and push_url is your steward server endpoint including domain and port. The transaction must be signed by your delegate key.

For example:

sommelier tx pubsub add-subscriber somm15yudhpkj8ztxrq29nr69qt79c9gmzrq5qtaqh0 server_ca.crt steward.example.com:5734

Note that even though the CA file and push URL args are "optional" in the command, they are required in order to facilitate Cellar calls from strategists.

To update an existing subscriber, such as to replace an expired CA cert or change domains, simply run the same command for your delegate address with the new CA file and/or push URL.

If a subscriber needs to be altogether replaced, such as if a change in keys occurs, the old subscriber can be removed using the counterpart to the previous command:

sommelier tx pubsub remove-subscriber <subscriber_address>

Once again, the signer of the transaction must match the subscriber_address argument.

Overriding Default Subscriptions

For convenience, default subscriptions exist in x/pubsub that map Cellar IDs to their agreed upon "default" publisher. Steward will load these subscriptions into its Publisher Trust Cache automatically once configured. It is possible that Sommelier participants may choose to delegate managing authority to a different publisher for a particular Cellar. This can be accomplished by creating a SubscriberIntent, whereby a validator registers their intent to receive requests for the target Cellar from an alternative publisher. Steward will override any default subscriptions in its cache with the respective subscriber intents registered by the owning validator.

To create a subscriber intent use the following command:

sommelier tx pubsub add-subscriber-intent <subscription_id> <subscriber_address> <publisher_domain>

Where subscription ID is the concatenated Chain ID and checksum contract address of the Cellar with a colon (:) inbetween.

For example, in order to subscribe to an alternative publisher for a Cellar 0x97e6e0a40a3d02f12d1cec30ebfbae04e37c119e on Arbitrum (chain ID 42161):

sommelier tx pubsub add-subscriber-intent 42161:0x97e6e0a40a3d02f12d1cec30ebfbae04e37c119e somm15yudhpkj8ztxrq29nr69qt79c9gmzrq5qtaqh0 alternative-strategist.example.com

Steward will now ignore function calls from the default publisher for the Arbitrum cellar at the provided contract address, and instead only process calls from the registered Publisher who owns the domain "alternative-strategist.example.com".

Note that subscriber intents can only be added for permitted publishers. The domain provided must belong to a publisher that has been added on chain via a governance proposal.

See the protocol docs for more details on the different entities in x/pubsub.

Blocking a Publisher

In certain cases such as if a publisher's keys are compromised or the publisher has become malicious it is desirable to "block" requests from the publisher's domain. Simply add the publisher's registered domain to Steward's publisher domain block list