Subgraph Composition: Option to force rpc to fetch block ptrs

[incrypto32]

Composable subgraphs need to fetch block ptrs to handle reorgs, when its not in the cache graph-node uses firehose endpoint to fetch the block using a SingleBlockRequest but this is currently slower than RPC.
This PR

• Adds an option to force using RPC to fetch block ptrs when an RPC endpoint is available
• Parralize fetching blocks when using firehose
• Added some refactoring in FirehoseEndpoints code

[Copilot]

Pull Request Overview

This PR introduces an option to force the use of RPC for fetching block pointers in composable subgraphs, parallelizes block fetching when using Firehose, and includes refactoring in the Firehose endpoints and environment configuration.

• Adds a configuration flag for RPC-based block pointer fetching.
• Refactors Firehose endpoint functions to improve error handling and introduce retry logic.
• Parallelizes block fetching using futures’ buffered streams and updates environment variable mappings.

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
node/src/chain.rs	Passes the additional eth_adapters parameter to support RPC option.
graph/src/firehose/endpoints.rs	Refactors block fetching functions with retry logic and error context.
graph/src/env/mod.rs	Introduces a new environment variable for Firehose block batch size.
chain/ethereum/src/env.rs	Adds a flag to force the use of RPC for block pointer fetching.
chain/ethereum/src/chain.rs	Introduces RPC fallback logic based on the new force flag and refactors block loading.

Comments suppressed due to low confidence (3)

graph/src/firehose/endpoints.rs:456

• [nitpick] Consider adding a brief comment explaining why multiple clones of 'endpoint' and 'logger' are needed in the retry closure; this will help clarify that the clones are intentional due to async lifetime requirements.

let endpoint = self.cheap_clone();

chain/ethereum/src/chain.rs:945

• [nitpick] The variable name 'eth_adapters' in the RPC branch might be misleading since it represents an adapter used specifically for RPC requests; consider renaming it to 'rpc_adapters' or a similar name for better clarity.

ChainClient::Rpc(eth_adapters) => {

chain/ethereum/src/env.rs:201

• Double-check that setting the default for GRAPH_ETHEREUM_FORCE_RPC_FOR_BLOCK_PTRS to true is intended, as it forces RPC usage even when Firehose might be available.

force_rpc_for_block_ptrs: EnvVarBoolean,

[mangas]

Check comment, the rpc feature is on by default right now