Merge bitcoin/bitcoin#21726: Improve Indices on pruned nodes via prune blockers

71c3f0356c01521a95c64fba1e7375aea6286bb0 move-only: Rename index + pruning functional test (Fabian Jahr)
de08932efa953e9a237cbf879460488ad8947411 test: Update test for indices on pruned nodes (Fabian Jahr)
825d19839bf71245306d4c8edde040e5941caa46 Index: Allow coinstatsindex with pruning enabled (Fabian Jahr)
f08c9fb0c6a799e3cb75ca5f763a746471625beb Index: Use prune locks for blockfilterindex (Fabian Jahr)
2561823531c25e1510c107eb41de944b00444ce0 blockstorage: Add prune locks to BlockManager (Fabian Jahr)
231fc7b035481f748159968353c1cab81354e843 refactor: Introduce GetFirstStoredBlock helper function (Fabian Jahr)

Pull request description:

  # Motivation
  The main motivation of this change and only behavior change noticeable by user is to allow running `coinstatsindex` on pruned nodes as has been requested [here for example](https://twitter.com/benthecarman/status/1388170854140452870?s=20).

  # Background
  `coinstatsindex` on pruned nodes can be enabled in a much simpler than it is done here but it comes with downside. The ability to run `blockfilterindex`on pruned nodes was added in #15946 but it also added the `blockfilterindex` as a dependency to `validation` and it introduced two new circular dependencies. Enabling `coinstatsindex` on pruned nodes in a similar way would add it as a dependency as well and introduce another circular dependency.

  Instead, this PR introduces a `m_prune_blockers` map to `BlockManager` as a flexible approach to block pruning. Entities like `blockfilterindex`, for example, can add a key and a height to block pruning over that height. These entities need to update that value to allow more pruning when they are ready.

  # Alternative approach
  Upon completing the first draft of this PR I found #19463 as an alternative that follows the same but follows a very different approach. I am listing the main differences here as I see them:
  - Usage of globals
  - Blocks pruning with a start and a stop height
  - Can persist blockers across restarts
  - Blockers can be set/unset via RPCs

  Personally, I don't think any of these are necessary to be added here but if the general approach or specific features are more appealing to reviewers I am happy to change to a solution based on that PR or port over specific parts of it here.

ACKs for top commit:
  mzumsande:
    Code review ACK 71c3f0356c01521a95c64fba1e7375aea6286bb0
  ryanofsky:
    Code review ACK 71c3f0356c01521a95c64fba1e7375aea6286bb0. Changes since last review: just tweaking comments and asserts, and rebasing
  w0xlt:
    tACK https://github.com/bitcoin/bitcoin/pull/21726/commits/71c3f0356c01521a95c64fba1e7375aea6286bb0 on signet.

Tree-SHA512: de7efda08b44aa31013fbebc47a02cd2de32db170b570f9643e1f013fee0e8e7ca3068952d1acc6e5e74a70910735c5f263437981ad73df841ad945b52d36b71

1 files changed, 1 insertions, 3 deletions

diff --git a/src/init.cpp b/src/init.cpp
index 69f9452ec7..cccb088eec 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -421,7 +421,7 @@ void SetupServerArgs(ArgsManager& argsman)
         -GetNumCores(), MAX_SCRIPTCHECK_THREADS, DEFAULT_SCRIPTCHECK_THREADS), ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
     argsman.AddArg("-persistmempool", strprintf("Whether to save the mempool on shutdown and load on restart (default: %u)", DEFAULT_PERSIST_MEMPOOL), ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
     argsman.AddArg("-pid=<file>", strprintf("Specify pid file. Relative paths will be prefixed by a net-specific datadir location. (default: %s)", BITCOIN_PID_FILENAME), ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
-    argsman.AddArg("-prune=<n>", strprintf("Reduce storage requirements by enabling pruning (deleting) of old blocks. This allows the pruneblockchain RPC to be called to delete specific blocks, and enables automatic pruning of old blocks if a target size in MiB is provided. This mode is incompatible with -txindex and -coinstatsindex. "
+    argsman.AddArg("-prune=<n>", strprintf("Reduce storage requirements by enabling pruning (deleting) of old blocks. This allows the pruneblockchain RPC to be called to delete specific blocks and enables automatic pruning of old blocks if a target size in MiB is provided. This mode is incompatible with -txindex. "
             "Warning: Reverting this setting requires re-downloading the entire blockchain. "
             "(default: 0 = disable pruning blocks, 1 = allow manual pruning via RPC, >=%u = automatically prune block files to stay under the specified target size in MiB)", MIN_DISK_SPACE_FOR_BLOCK_FILES / 1024 / 1024), ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
     argsman.AddArg("-reindex", "Rebuild chain state and block index from the blk*.dat files on disk. This will also rebuild active optional indexes.", ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
@@ -858,8 +858,6 @@ bool AppInitParameterInteraction(const ArgsManager& args, bool use_syscall_sandb
     if (args.GetIntArg("-prune", 0)) {
         if (args.GetBoolArg("-txindex", DEFAULT_TXINDEX))
             return InitError(_("Prune mode is incompatible with -txindex."));
-        if (args.GetBoolArg("-coinstatsindex", DEFAULT_COINSTATSINDEX))
-            return InitError(_("Prune mode is incompatible with -coinstatsindex."));
         if (args.GetBoolArg("-reindex-chainstate", false)) {
             return InitError(_("Prune mode is incompatible with -reindex-chainstate. Use full -reindex instead."));
         }