feat: Enable zstd response compression for RPC providers

[dylankilkenny]

Summary

Providers such as QuickNode can compress RPC responses with zstd, but the relayer never asked for it. Large responses arrived uncompressed and slowly enough to hit request timeouts. The worst case is Stellar getTransaction, whose Soroban XDR payloads can reach hundreds of kilobytes.

This change enables zstd response negotiation across the relayer's RPC clients. Enabling reqwest's zstd feature makes every reqwest client send Accept-Encoding: zstd and decompress responses transparently. Cargo feature unification extends this to the EVM and Solana clients, which use the same reqwest crate. Stellar getTransaction needed more than the feature flag. The stellar-rpc-client crate sits on a jsonrpsee transport that cannot decompress responses, so this call now goes through the provider's existing raw reqwest JSON-RPC path instead. The remaining stellar-rpc-client calls stay uncompressed and would need the same migration if they ever show up in timeout logs.

Reviewers should focus on the retry changes in the raw path. It previously treated non-2xx responses as JSON decode errors, and it mapped JSON-RPC error objects only after the retry loop finished. As a result, rate limits and transient server errors were never retried and never triggered failover. Both cases are now classified inside the retried operation. A side effect is that get_transaction errors change shape. They surface as typed ProviderError variants instead of jsonrpsee message strings, so log queries that match the old wording will stop matching for this call.

Testing Process

New unit tests cover:

• End-to-end zstd negotiation and decompression, against a mockito server that returns pre-compressed bodies.
• A 429 response is classified as rate limiting and retried.
• A retriable JSON-RPC error (code -32005) is retried, and a non-retriable one (code -32601) fails fast without retrying.

Formatting, the CI clippy gate, and the provider and Stellar domain test suites all pass locally.

Checklist

• Add a reference to related issues in the PR description.
• Add unit tests if applicable.

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Walkthrough

Enables the zstd feature for reqwest and adds a zstd dev-dependency. Documents and tests shared client zstd handling. Reworks Stellar provider's raw JSON-RPC path with centralized HTTP/JSON-RPC error mapping, migrates get_transaction and raw_request_dyn to the raw path, and adds retry/zstd tests.

Changes

Zstd decompression and Stellar raw JSON-RPC path

Layer / File(s)	Summary
Enable reqwest zstd feature Cargo.toml	Adds zstd feature to reqwest and a zstd = "0.13" dev-dependency for compressing test fixtures.
Shared RPC client zstd documentation and test src/services/provider/mod.rs	Documents that shared clients advertise Accept-Encoding: zstd and decompress responses; adds a mock-server test verifying this end-to-end.
Raw JSON-RPC request/error handling helpers src/services/provider/stellar/mod.rs	Adds HTTP status checking in retry_raw_request, a new raw_json_rpc_request helper, and json_rpc_error_to_provider_error mapping.
get_transaction and raw_request_dyn migration src/services/provider/stellar/mod.rs	Switches get_transaction and raw_request_dyn to use the new raw JSON-RPC path instead of the jsonrpsee client; updates error assertions.
Zstd and retry classification tests src/services/provider/stellar/mod.rs	Adds tests for zstd-compressed responses, HTTP 429 retry classification, and retriable/non-retriable JSON-RPC error codes.

Estimated code review effort: 3 (Moderate) | ~25 minutes

Sequence Diagram(s)

sequenceDiagram
    participant Client as StellarProvider
    participant Http as reqwest Client
    participant Server as RPC Server

    Client->>Http: raw_json_rpc_request(method, params)
    Http->>Server: POST request (Accept-Encoding: zstd)
    Server-->>Http: zstd-compressed JSON-RPC response
    Http-->>Client: decompressed JSON body

    alt HTTP error status
        Client->>Client: error_for_status_ref -> ProviderError
    else JSON-RPC "error" field present
        Client->>Client: json_rpc_error_to_provider_error(code)
        Client->>Client: retry_raw_request (if retriable)
    else success
        Client->>Client: extract "result" field
    end

Loading

Poem

A hop, a skip, past bytes compressed,
Zstd whispers "Accept" with zest!
Errors mapped with codes so neat,
Retries dance to their own beat.
🐰 Through JSON-RPC fields I dig,
No more jsonrpsee, just my rig!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly summarizes the main change: enabling zstd compression for RPC providers.
Description check	✅ Passed	The description matches the template with Summary, Testing Process, and Checklist sections, and includes relevant implementation and test details.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/quicknode-zstd-compression

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[codecov]

Codecov Report

❌ Patch coverage is 94.57014% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.59%. Comparing base (b035c5a) to head (9ca9ec9).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
src/services/provider/stellar/mod.rs	94.57%	12 Missing ⚠️

Additional details and impacted files

Flag	Coverage Δ
ai	0.00% <0.00%> (ø)
dev	89.59% <94.57%> (+0.04%)	⬆️
properties	0.01% <0.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

@@            Coverage Diff             @@
##             main     #821      +/-   ##
==========================================
+ Coverage   89.54%   89.59%   +0.04%     
==========================================
  Files         303      303              
  Lines      128773   129442     +669     
==========================================
+ Hits       115314   115972     +658     
- Misses      13459    13470      +11     

Files with missing lines	Coverage Δ
src/services/provider/mod.rs	93.63% <ø> (ø)
src/services/provider/stellar/mod.rs	91.31% <94.57%> (+1.04%)	⬆️

... and 5 files with indirect coverage changes

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[tirumerla]

Couple nits, otherwise lgtm. Thanks

[Copilot]

Pull request overview

This PR enables zstd response compression negotiation for RPC calls made via reqwest, reducing payload sizes and mitigating timeout risk for large RPC responses (notably Stellar getTransaction with large Soroban XDR).

Changes:

• Enable reqwest’s zstd feature so relayer HTTP clients advertise zstd support and transparently decompress zstd responses.
• Re-route Stellar getTransaction through the existing raw reqwest JSON-RPC path (since the jsonrpsee transport cannot decompress), and improve retry classification by mapping HTTP status errors and JSON-RPC error objects inside the retried operation.
• Add unit tests validating zstd negotiation/decompression and retry behavior for HTTP 429 and JSON-RPC error codes.

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated no comments.

File	Description
src/services/provider/stellar/mod.rs	Moves get_transaction to the raw reqwest JSON-RPC path and fixes retry classification for HTTP status + JSON-RPC errors; adds targeted tests.
src/services/provider/mod.rs	Documents zstd behavior for the shared reqwest client builder and adds a decompression test.
Cargo.toml	Enables reqwest zstd feature and adds zstd as a dev-dependency for tests.
Cargo.lock	Updates lockfile to include zstd-related dependencies.

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