Paolo/txpool metrics

[paologalligit]

Description

This updates txpool metrics so txpool_current_tx_count represents the current pool contents by source, type, and status, instead of mixing add/remove deltas with synthetic sources like washed or n/a.

Txs now track their source explicitly — local, remote, or fill — and their status (executable / non_executable) is reflected on the gauge label.

Wash removals decrement the current-count gauge using the removed tx's real labels and also increment a separate txpool_washed_tx_count{source,type} counter.

TxObject.executable is now atomic.Bool so the metric helper can read it safely from concurrent Remove and wash paths.

The internal wash() return surface is collapsed to a single removed int; the per-type breakdown now lives only on the counter.

NOTE — Backward-incompatible changes

Dashboards / alerts:

• txpool_current_tx_count gains a new status label (executable | non_executable). Existing grafana queries that sums or groups the gauge must use sum without(status) to reproduce the old totals; otherwise series will double-count or appear as separate rows.
• source="washed" and source="n/a" are no longer emitted on txpool_current_tx_count. Any panel or alert filtering on those values will go silent. The per-source/per-type wash rate now lives on the new txpool_washed_tx_count{source,type} counter — switch wash dashboards to rate(txpool_washed_tx_count[...]).
• Filled (sync-replayed) txs now report source="fill" instead of source="remote".

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• New and existing E2E tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have not added any vulnerable dependencies to my code

[codecov-commenter]

Codecov Report

❌ Patch coverage is 92.72727% with 4 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
txpool/tx_pool.go	90.90%	4 Missing ⚠️

📢 Thoughts on this report? Let us know!

[libotony]

My understading is executable does not have a race condition as it is well managed in the pool, it's fine for the metrics handler to have a snapshot of this value, no need to mark it atomic.

[paologalligit]

There's a tiny chance of a race condition in:

• wash(): while running Executable() it writes o.payer = &payer and o.cost = prepaid.
• if packer packed that tx, then it calls Remove(): it calls RemoveByHash, which reads txObj.Payer() and txObj.Cost() under the map lock, but the TxObject fields aren't covered by that lock.

It looks a very rare case, but probably it should be addressed. I can revert the atomic bool and introduce this fix in a follow-up PR, if you prefere