Test for jack

[divagant-martian]

Issue Addressed

This is a test that reproduces #4331

I doubt it's meant to be merged at all, but per request of @jmcph4, a playground for him to solve this

The test goes like this:

• epochs are of 8 slots
• chain's oldest block at the beginning is slot 28
• chain needs to backfill to slot 17
• the test finishes when backfill reports a Completed outcome (never does)

To run the test

• first cd beacon_node/network/src/sync
• cargo test jacks_hack

These are the logs it produces

running 1 test
Jul 04 03:05:19.540 DEBG Connection established, connection: Listener, peer_id: 1AfaK87Fe2RMZ5yxJVBfpZshXNLtBz1mhWG1DL3ZZCFyQh
Jul 04 03:05:19.540 DEBG Resuming backfill sync, processing_target: 3, awaiting_batches: 0, start_epoch: 3
Jul 04 03:05:19.540 TRCE Sending backfill BlocksByRange Request, peer: 1AfaK87Fe2RMZ5yxJVBfpZshXNLtBz1mhWG1DL3ZZCFyQh, count: 16, method: BlocksByRange
Jul 04 03:05:19.541 DEBG Requesting batch, start_slot: 25, end_slot: 40, downloaded: 0, processed: 0, processed_no_penalty: 0, state: Downloading(1AfaK87Fe2RMZ5yxJVBfpZshXNLtBz1mhWG1DL3ZZCFyQh, 0 blocks, 1), epoch: 3
Jul 04 03:05:19.541 INFO initial state, state: Syncing { completed: 0, remaining: 7 }
Jul 04 03:05:19.541 INFO got: request blocks
Jul 04 03:05:19.548 DEBG Completed batch received, awaiting_batches: 0, blocks: 2, epoch: 3
Jul 04 03:05:19.548 TRCE Sending backfill BlocksByRange Request, peer: 1AfaK87Fe2RMZ5yxJVBfpZshXNLtBz1mhWG1DL3ZZCFyQh, count: 16, method: BlocksByRange
Jul 04 03:05:19.549 DEBG Requesting batch, start_slot: 9, end_slot: 24, downloaded: 0, processed: 0, processed_no_penalty: 0, state: Downloading(1AfaK87Fe2RMZ5yxJVBfpZshXNLtBz1mhWG1DL3ZZCFyQh, 0 blocks, 2), epoch: 1
Jul 04 03:05:19.549 INFO got: process blocks
Jul 04 03:05:19.549 INFO Backfill moved the chain to 25
Jul 04 03:05:19.549 DEBG Backfill batch processed, client: Unknown, peer: 1AfaK87Fe2RMZ5yxJVBfpZshXNLtBz1mhWG1DL3ZZCFyQh, batch_epoch: 3, start_slot: 25, end_slot: 40, downloaded: 0, processed: 0, processed_no_penalty: 0, state: Processing(1AfaK87Fe2RMZ5yxJ
VBfpZshXNLtBz1mhWG1DL3ZZCFyQh), result: Success { was_non_empty: true }
Jul 04 03:05:19.550 INFO got: request blocks
Jul 04 03:05:19.557 DEBG Completed batch received, awaiting_batches: 0, blocks: 2, epoch: 1
Jul 04 03:05:19.557 TRCE Sending backfill BlocksByRange Request, peer: 1AfaK87Fe2RMZ5yxJVBfpZshXNLtBz1mhWG1DL3ZZCFyQh, count: 16, method: BlocksByRange
Jul 04 03:05:19.558 DEBG Requesting batch, start_slot: 1, end_slot: 16, downloaded: 0, processed: 0, processed_no_penalty: 0, state: Downloading(1AfaK87Fe2RMZ5yxJVBfpZshXNLtBz1mhWG1DL3ZZCFyQh, 0 blocks, 3), epoch: 0
Jul 04 03:05:19.558 INFO got: request blocks
Jul 04 03:05:19.564 DEBG Completed batch received, awaiting_batches: 0, blocks: 2, epoch: 0

thread 'sync::backfill_sync::tests::jacks_hack' has overflowed its stack

it needs to go to slot 17 but goes all the way to slot 1 why?
hint: solving this needs to update two lines of code

If you need help ping @AgeManning or me

[jmcph4]

Closed by #4465 (thanks @divagant-martian!)