Don't stall syncing if gap is too large (#2801)

cc #2793 After trying to analyze the problem, I've decided to leave it to future-me. It is very complicated to determine which entries in the list of "blocks known by a source" should be kept and which can be thrown away. There are several other TODOs related to that in the code. For now, this PR fixes the sync stalling. Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>
paritytech · Oct 4, 2022 · 9e4f257 · 9e4f257
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diff --git a/bin/wasm-node/CHANGELOG.md b/bin/wasm-node/CHANGELOG.md
@@ -4,6 +4,7 @@
 
 ### Fixed
 
+- Syncing no longer stalls if the gap between the finalized and latest block is more than 100 blocks. ([#2801](https://github.com/paritytech/smoldot/pull/2801))
 - CPU-heavy operations such as verifying finality proofs or compiling the runtime will now better respect the CPU rate limit. ([#2803](https://github.com/paritytech/smoldot/pull/2803))
 
 ## 0.7.0 - 2022-09-28

diff --git a/src/sync/all_forks.rs b/src/sync/all_forks.rs
@@ -1402,11 +1402,12 @@ impl<TBl, TRq, TSrc> AddBlockVacant<TBl, TRq, TSrc> {
                 None => break,
             };
 
-            self.inner
-                .inner
-                .inner
-                .blocks
-                .remove_sources_known_block(height, &hash);
+            // TODO: restore this block of code; it is extremely complicated because it is unclear which source-block combinations we can add and keep without making memory usage explode
+            /*self.inner
+            .inner
+            .inner
+            .blocks
+            .remove_sources_known_block(height, &hash);*/
             self.inner
                 .inner
                 .inner
@@ -1631,10 +1632,11 @@ impl<'a, TBl, TRq, TSrc> AnnouncedBlockUnknown<'a, TBl, TRq, TSrc> {
                 None => break,
             };
 
-            self.inner
-                .inner
-                .blocks
-                .remove_sources_known_block(height, &hash);
+            // TODO: restore this block of code; it is extremely complicated because it is unclear which source-block combinations we can add and keep without making memory usage explode
+            /*self.inner
+            .inner
+            .blocks
+            .remove_sources_known_block(height, &hash);*/
             self.inner
                 .inner
                 .blocks