Fix the canonical chain is deleted

CHANGES.md

@@ -26,8 +26,11 @@ To be released.
 ### Behavioral changes
 
 ### Bug fixes
+ -  Fixed a bug where the canonical chain could be deleted if `Swarm<T>` failed
+    to download blocks due to network connection.  [[#675]]
 
 [#662]: https://github.com/planetarium/libplanet/pull/662
+[#675]: https://github.com/planetarium/libplanet/pull/675
 
 
 Version 0.7.0

Libplanet.Tests/Net/SwarmTest.cs

@@ -2388,6 +2388,40 @@ public async Task CreateNewChainWhenBranchPointNotExist()
             }
         }
 
+        [Fact(Timeout = Timeout)]
+        public async Task DoNotDeleteCanonicalChainWhenBlockDownloadFailed()
+        {
+            var chainA = _blockchains[0];
+            var chainB = _blockchains[1];
+
+            var swarmA = _swarms[0];
+            var swarmB = _swarms[1];
+
+            var genesis = await chainA.MineBlock(_fx1.Address1);
+            chainB.Append(genesis);
+
+            var block = await chainA.MineBlock(_fx1.Address1);
+
+            try
+            {
+                await StartAsync(swarmA);
+                await StartAsync(swarmB);
+                await BootstrapAsync(swarmA, swarmB.AsPeer);
+
+                swarmA.BroadcastBlocks(new[] { block });
+                await swarmB.FillBlocksAsyncStarted.WaitAsync();
+                await swarmA.StopAsync();
+                await swarmB.FillBlocksAsyncFailed.WaitAsync();
+
+                Assert.NotEmpty(chainB.GetState(_fx1.Address1));
+            }
+            finally
+            {
+                await swarmA.StopAsync();
+                await swarmB.StopAsync();
+            }
+        }
+
         private static async Task<(Address, Block<DumbAction>[])>
             MakeFixtureBlocksForPreloadAsyncCancellationTest()
         {

Libplanet/Net/Swarm.cs

@@ -264,6 +264,10 @@ private set
 
         internal int FindNextHashesChunkSize { get; set; } = 500;
 
+        internal AsyncAutoResetEvent FillBlocksAsyncStarted { get; } = new AsyncAutoResetEvent();
+
+        internal AsyncAutoResetEvent FillBlocksAsyncFailed { get; } = new AsyncAutoResetEvent();
+
         /// <summary>
         /// Waits until this <see cref="Swarm{T}"/> instance gets started to run.
         /// </summary>
@@ -1560,18 +1564,7 @@ CancellationToken cancellationToken
                         );
                         break;
                     }
-
-                    // We can't recover with OperationCanceledException and
-                    // ObjectDisposedException. so just re-throw them.
-                    catch (ObjectDisposedException)
-                    {
-                        throw;
-                    }
-                    catch (OperationCanceledException)
-                    {
-                        throw;
-                    }
-                    catch (Exception e)
+                    catch (TimeoutException e)
                     {
                         if (retry > 0)
                         {
@@ -1678,6 +1671,7 @@ private async Task<BlockChain<T>> FillBlocksAsync(
             CancellationToken cancellationToken
         )
         {
+            FillBlocksAsyncStarted.Set();
             BlockChain<T> workspace = blockChain;
             var scope = new List<Guid>();
 
@@ -1791,12 +1785,13 @@ await GetBlocksAsync(peer, hashesAsArray)
             }
             catch
             {
-                if (!(workspace is null))
+                if (!(workspace is null) && !workspace.Id.Equals(BlockChain.Id))
                 {
                     IStore store = blockChain.Store;
                     store.DeleteChainId(workspace.Id);
                 }
 
+                FillBlocksAsyncFailed.Set();
                 throw;
             }
             finally

Menees.Analyzers.Settings.xml

@@ -2,5 +2,5 @@
 <Menees.Analyzers.Settings>
   <MaxLineColumns>100</MaxLineColumns>
   <MaxMethodLines>200</MaxMethodLines>
-  <MaxFileLines>2500</MaxFileLines>
+  <MaxFileLines>2600</MaxFileLines>
 </Menees.Analyzers.Settings>