Fix IPC JSON-RPC concurrent request handling using streaming parser

[MqllR]

Description

Fixes issue where concurrent JSON-RPC requests sent to the IPC socket fail with parse errors when they arrive in the same buffer as concatenated JSON objects.

Problem

When multiple requests arrive simultaneously at the IPC socket, they can be concatenated in a single buffer:

{"id":1,"method":"eth_blockNumber"}{"id":2,"method":"eth_chainId"}

The current implementation tries to parse this as either a single JsonObject or JsonArray, which fails because concatenated JSON objects are neither.

Solution

Replaced manual JSON parsing with Jackson's streaming parser (JsonParser), which can naturally handle multiple JSON objects in a stream - similar to Go's json.Decoder used in go-ethereum.

Key changes:

• Added JsonRpcParserHandler.ipcJsonParser() using Jackson's streaming API
• Simplified JsonRpcIpcService.java from ~300 to ~170 lines
• Added test for concatenated requests: concatenatedJsonRequestsShouldBeHandledIndependently()

Benefits

• ✅ Handles concurrent requests (concatenated JSON)
• ✅ Maintains backward compatibility (single requests & batch arrays)
• ✅ Simpler code using standard Jackson library
• ✅ Parity with go-ethereum's IPC implementation
• ✅ All existing tests pass + new test for concurrent requests

Testing

All 6 IPC tests pass:

✅ successfulExecution()
✅ successfulBatchExecution()
✅ validJsonButNotRpcShouldReturnInvalidRequest()
✅ nonJsonRequestShouldReturnParseError()
✅ concatenatedJsonRequestsShouldBeHandledIndependently() ← NEW
✅ shouldDeleteSocketFileOnStop()

Files Changed

1. JsonRpcParserHandler.java - Added streaming JSON parser
2. JsonRpcIpcService.java - Simplified to use streaming parser
3. JsonRpcIpcServiceTest.java - Added concurrent request test

Related

This addresses the root cause discovered during investigation of why concurrent IPC requests fail while sequential requests succeed. Fixes #9495

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[jflo]

see performance notes, and CI is not currently passing. Once addressed, this is good to go!

[jflo]

JsonFactory and ObjectMappers are pretty heavyweight, these will get re-created on every ipc connection. Suggest making it a static member of the class or some other means of reuse. It is thread safe.

[MqllR]

Moved them as static members of the class 👍