Use bitcoin core's txospenderindex to find spending transactions

[sstone]

Eclair now requires that bitcoin core's txospenderindex (added in version 31.0) is available and synced, and will fail to start if it is not.

Our Watcher will use the txospenderindex` to find spending transactions instead of scanning blocks (which was both expensive and limited as we would only scan a small number of blocks into the past).

Deployment note:

You must enable the new index on bitcoin core with txospenderindex=1 and wait until it is synchronised before you start eclair. Syncing the index from scratch will take a few hours, during which bitcoin core is usable (indexes are independent) but make be slower to respond.
You can also copy the index from another node (that is running the same version), just copy the entire .bitcoin/indexes/txospenderindex directory.

The index requires an additional 88Gb as of block 944339.

[pm47]

As discussed offline, imo we should make txospenderindex a hard requirement (just like txindex) and drop the block scanning implementation altogether. This was just really a hacky workaround. Simplification FTW!

[sstone]

As discussed offline, imo we should make txospenderindex a hard requirement (just like txindex) and drop the block scanning implementation altogether. This was just really a hacky workaround. Simplification FTW!

done in cd31b14. Eclair won't start if the index is not enabled and synced.

[t-bast]

We should make sure that we only merge this PR once we're using a version of bitcoind that includes bitcoin/bitcoin#35531, since it vastly improves the index.

[fanquake]

a version of bitcoind that includes bitcoin/bitcoin#35531

The first release that will contain that change will be 32.0 (bitcoin/bitcoin#35122).

[t-bast]

Thanks @fanquake 🙏

[hodlinator]

32.0 will also contain this fix: bitcoin/bitcoin#35889

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Codecov Report

❌ Patch coverage is 92.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.64%. Comparing base (d769db0) to head (19e21c3).
⚠️ Report is 17 commits behind head on master.

Files with missing lines	Patch %	Lines
.../acinq/eclair/blockchain/bitcoind/ZmqWatcher.scala	80.00%	2 Missing ⚠️
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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3279      +/-   ##
==========================================
- Coverage   88.64%   88.64%   -0.01%     
==========================================
  Files         222      223       +1     
  Lines       21910    22107     +197     
  Branches      867      889      +22     
==========================================
+ Hits        19423    19597     +174     
- Misses       2487     2510      +23     

Files with missing lines	Coverage Δ
...ir-core/src/main/scala/fr/acinq/eclair/Setup.scala	72.10% <100.00%> (+0.75%)	⬆️
...ala/fr/acinq/eclair/blockchain/OnChainWallet.scala	100.00% <ø> (ø)
...ir/blockchain/bitcoind/rpc/BitcoinCoreClient.scala	89.79% <100.00%> (+0.21%)	⬆️
...inq/eclair/channel/fund/InteractiveTxBuilder.scala	91.83% <100.00%> (-0.65%)	⬇️
...cinq/eclair/channel/publish/MempoolTxMonitor.scala	87.20% <100.00%> (ø)
...ir/channel/publish/ReplaceableTxPrePublisher.scala	71.15% <100.00%> (ø)
.../acinq/eclair/blockchain/bitcoind/ZmqWatcher.scala	82.50% <80.00%> (-1.43%)	⬇️

... and 6 files with indirect coverage changes

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