validation: make the “rolling forward” loop interruptible #33442

1. 
   l0rinc commented at 5:41 am on September 20, 2025: contributor

   Summary

   Restarting an unsuccessful reindex can result in replay of previously indexed blocks. This process can take many hours and is currently not interruptible.

   Reproducer:

   • start a normal ibd, stop after some progress
   • do a reindex, stop before it finishes
   • restart the node normally without specifying the reindex parameter It should start rolling the blocks forward.

   After this change you should be able to interrupt the process:

   02025-09-20T05:35:42Z Rolling forward 000000002f4f55aecfccc911076dc3f73ac0288c83dc1d79db0a026441031d40 (46245)
   12025-09-20T05:35:42Z Rolling forward 0000000017ffcf34c8eac010c529670ba6745ea59cf1edf7b820928e3b40acf6 (46246)
   2^C2025-09-20T05:35:42Z Rolling forward 000000002857934511131e0800ac1dcbe3ae7873b715a9528747f29ae090b0d4 (46247)
   32025-09-20T05:35:42Z [error] Unable to replay blocks. You will need to rebuild the database using -reindex-chainstate.
   4Error: Unable to replay blocks. You will need to rebuild the database using -reindex-chainstate.
   52025-09-20T05:35:42Z Shutdown in progress...
   62025-09-20T05:35:42Z scheduler thread exit
   72025-09-20T05:35:42Z Shutdown done
   

2. validation: make the "rolling forward" loop interruptible

   Reproducer:
   * start a normal ibd, stop after some progress
   * do a reindex, stop before it finishes
   * restart the node normally without specifying the reindex parameter
   It should start rolling the blocks forward.
   
   After this change you should be able to interrupt the process:
   ```
   2025-09-20T05:35:42Z Rolling forward 000000002f4f55aecfccc911076dc3f73ac0288c83dc1d79db0a026441031d40 (46245)
   2025-09-20T05:35:42Z Rolling forward 0000000017ffcf34c8eac010c529670ba6745ea59cf1edf7b820928e3b40acf6 (46246)
   ^C2025-09-20T05:35:42Z Rolling forward 000000002857934511131e0800ac1dcbe3ae7873b715a9528747f29ae090b0d4 (46247)
   2025-09-20T05:35:42Z [error] Unable to replay blocks. You will need to rebuild the database using -reindex-chainstate.
   Error: Unable to replay blocks. You will need to rebuild the database using -reindex-chainstate.
   2025-09-20T05:35:42Z Shutdown in progress...
   2025-09-20T05:35:42Z scheduler thread exit
   2025-09-20T05:35:42Z Shutdown done
   ```

   f74c8ea601
3. DrahtBot added the label Validation on Sep 20, 2025
4. 
   DrahtBot commented at 5:41 am on September 20, 2025: contributor

   The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

   Code Coverage & Benchmarks

   For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/33442.

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5. 
   mzumsande commented at 6:06 am on September 20, 2025: contributor

   I did this in #30155 a while back, but in a way such that any partial progress would be saved, and we continue with the next startup.

   In any case, now that we flush every hour it’s probably a less pressing issue.

6. 
   l0rinc commented at 6:09 am on September 20, 2025: contributor

   Closing in favor of https://github.com/bitcoin/bitcoin/pull/30155
7. l0rinc closed this on Sep 20, 2025

   ---

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