[chenshi5012]

What type of PR is this?

• bug
• feature
• enhancement

What problem(s) does this PR solve?

Issue(s) number: #149

Description:

When a low-level JSON request fails, Connection can return an empty string. SessionPool::executeJsonWithParameter( ) then calls folly::parseJson() unconditionally. If parsing throws, the normal giveBack() path is skipped. Although the local Session may return its underlying connection to ConnectionPool during destruction, the Session wrapper is not returned to SessionPool::idleSessions_, permanently consuming a pool slot.

With a small pool, or after repeated failures, subsequent requests can fail with No idle session.

How do you solve it?

Return the acquired Session to SessionPool in the exception path before rethrowing the original exception. The normal success path continues to return the session as before.

This ensures that a failed JSON request or a JSON parsing exception does not permanently reduce the number of available session slots.

Special notes for your reviewer, ex. impact of this fix, design document, etc:

• Added the regression test SessionPoolTest.JsonParseFailureReturnsSessionToPool. It closes the underlying connection to deterministically produce an empty JSON response, verifies that parsing throws, and checks that the session slot remains available afterward.
• The focused regression test passed.
• The full session_pool_test CTest target passed.

Fixes #149

[CLAassistant]

All committers have signed the CLA.