sui-indexer-alt-framework: rename fetch to checkpoint

[evan-wall-mysten]

Description

This PR renames fetch to checkpoint in anticipation of future PRs that will add additional methods like chain_id and latest_checkpoint_number.

Test plan

No functional changes.

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Release notes

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• Protocol:
• Nodes (Validators and Full nodes):
• gRPC:
• JSON-RPC:
• GraphQL:
• CLI:
• Rust SDK:
• Indexing Framework: Renamed IngestionClientTrait::fetch to IngestionClientTrait::checkpoint.

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Project	Deployment	Actions	Updated (UTC)
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[amnn]

@evan-wall-mysten, please can you explain what those other functions would be used for, why they belong on IngestionClient, and how they would be implemented on our existing ingestion clients? It's not clear to me that they would be easy to implement on the object-store-based ingestion clients.

[evan-wall-mysten]

@evan-wall-mysten, please can you explain what those other functions would be used for, why they belong on IngestionClient, and how they would be implemented on our existing ingestion clients? It's not clear to me that they would be easy to implement on the object-store-based ingestion clients.

I looked through the StoreIngestionClient API and think the 2 functions can be implemented like this, but I haven't actually tested them out:

• fetch_chain_id() to store and compare chain_id to make sure it does not change
  • object-store impl
    1. StoreIngestionClient::checkpoint(0).summary.content_digest
  • rpc-client impl
    1. Client::ledger_client().get_service_info().chain_id()
• fetch_latest_checkpoint_number() to seed a starting checkpoint to index backwards from
  • object-store impl:
    1. StoreIngestionClient::end_of_epoch_checkpoints.pop() to get last checkpoint of the most recently ended epoch
    2. exponential binary search to find a range between an existing and missing checkpoint (self.store.head to check if file exists)
    3. binary search to find largest existing checkpoint in that range (self.store.head to check if file exists)
  • rpc-client impl
    1. Client::ledger_client().get_service_info().checkpoint_height()

[amnn]

Got it, thanks for clarifying -- the chain_id part makes sense to me, the latest_checkpoint_number part I have more questions for but overall that makes sense for this PR.

Also let's just drop fetch_ from all these names -- it's kind of an empty word for a client trait, which is fine when there's only one function on the trait, but if you have multiple, and they all start with fetch_ then you might as well get rid of it.