spock_apply: bound per-message memory; add 022 regression guard

[ibrarahmad]

Run the exception-log body in ApplyOperationContext and reset that context once per dispatched message in replication_handler so JSON and tuple allocations no longer accumulate in TopTransactionContext for the outer apply transaction. 022 samples worker RSS via ps during use_try_block and asserts growth is bounded.

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR fixes a memory-context leak in the apply worker by scoping exception-handling allocations to ApplyOperationContext and centralizing per-operation cleanup. A new TAP regression test validates the fix by triggering a multi-row transaction, detecting the apply worker mid-apply, and asserting that RSS growth stays below a configured threshold.

Changes

Apply Worker Memory Context Leak Fix

Layer / File(s)	Summary
Apply worker memory context isolation src/spock_apply.c	log_insert_exception() now switches into ApplyOperationContext before building/updating exception-log entries and restores context on exit. replication_handler() adds centralized MemoryContextReset(ApplyOperationContext) after error-context stack handling to clean up per-message allocations in one place.
Regression test cluster setup and warm-up tests/tap/t/022_apply_mem_context.pl	TAP test imports modules, documents the per-row context leak scenario, configures environment-driven sizing/timeouts, spins up a 2-node cluster with replicated table and unique indexes, and performs a warm-up insert to confirm replication.
Leak detection and RSS assertion tests/tap/t/022_apply_mem_context.pl	Test runs a large single-transaction INSERT, disables subscription mid-apply to interrupt the commit state, re-enables subscription, detects active apply worker via pg_stat_activity, samples process RSS over time, and asserts growth stays below configured threshold in a SKIP-guarded block.
Memory context diagnostics and test completion tests/tap/t/022_apply_mem_context.pl, tests/tap/schedule	Test invokes pg_log_backend_memory_contexts(), parses server log to extract "used" bytes for three named memory contexts, prints consolidated diagnostic report with RSS and context metrics, tears down cluster, finishes TAP run, and test is added to PR schedule.

Poem

A rabbit hops through memory's maze,
Where contexts leak in apply's haze—
Now scoped so tight, so clean, so bound,
With metrics sampled, truth we've found:
The leak is fixed, no more it grows! 🐰

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely summarizes the main change: bounding per-message memory in spock_apply and adding a regression test guard.
Description check	✅ Passed	The description directly relates to the changeset, explaining the memory context improvements and the new regression test that validates the fix.
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.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch MEM_CONSUM_6

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[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

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🟢 Metrics 0 duplication

Metric	Results
Duplication	0

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@tests/tap/t/022_apply_mem_context.pl`:
- Line 40: Remove the unused variable $THRESHOLD: delete the declaration "my
$THRESHOLD = $ENV{SPOCK_LEAK_THRESHOLD} // 5_000_000;" and update or remove the
stale comment referencing "5 MB" so the test reflects that the RSS growth limit
is actually controlled by $RSS_GROWTH (the active variable used later in the
test); ensure no remaining references to $THRESHOLD remain and that the comment
accurately describes $RSS_GROWTH's default.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: c664da9f-d2cb-49d5-aeb7-ad19af24defc

📥 Commits

Reviewing files that changed from the base of the PR and between 922ea93 and 23b1e08.

📒 Files selected for processing (3)

• src/spock_apply.c
• tests/tap/schedule
• tests/tap/t/022_apply_mem_context.pl