From abb9d068e6860c57a07487b173c6b1c7d02e6560 Mon Sep 17 00:00:00 2001
From: Eugene Yokota <eed3si9n@gmail.com>
Date: Fri, 2 Apr 2021 12:10:06 -0400
Subject: [PATCH] Retry 5 times

As a workaround to "concurrent download" failure that happens frequently
on an empty cache, this retries the resolution up to 5 times after 100ms
wait.
---
 .../multiversion/commands/ExportCommand.scala |  5 +++--
 .../configs/ThirdpartyConfig.scala            | 19 +++++++++++++++++--
 2 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/multiversion/src/main/scala/multiversion/commands/ExportCommand.scala b/multiversion/src/main/scala/multiversion/commands/ExportCommand.scala
index 92752db..a9a84e9 100644
--- a/multiversion/src/main/scala/multiversion/commands/ExportCommand.scala
+++ b/multiversion/src/main/scala/multiversion/commands/ExportCommand.scala
@@ -55,7 +55,7 @@ case class ExportCommand(
     lintCommand: LintCommand = LintCommand(),
     @Description("Retry limit when fetching a file.")
     @ParseAsNumber
-    retryCount: Int = 2,
+    retryCount: Int = 5,
     @Description("Number of parallel resolves and downloads.")
     @ParseAsNumber
     parallel: Int = 4,
@@ -401,7 +401,8 @@ case class ExportCommand(
       dep,
       cache,
       progressBar,
-      cdep
+      cdep,
+      retryCount
     )
 
     for {
diff --git a/multiversion/src/main/scala/multiversion/configs/ThirdpartyConfig.scala b/multiversion/src/main/scala/multiversion/configs/ThirdpartyConfig.scala
index 3f04e8f..29b3ae2 100644
--- a/multiversion/src/main/scala/multiversion/configs/ThirdpartyConfig.scala
+++ b/multiversion/src/main/scala/multiversion/configs/ThirdpartyConfig.scala
@@ -10,6 +10,7 @@ import coursier.cache.FileCache
 import coursier.core.Dependency
 import coursier.core.Module
 import coursier.core.Reconciliation
+import coursier.core.Resolution
 import coursier.params.ResolutionParams
 import coursier.util.ModuleMatchers
 import coursier.util.Task
@@ -98,7 +99,8 @@ final case class ThirdpartyConfig(
       dep: DependencyConfig,
       cache: FileCache[Task],
       progressBar: ResolveProgressRenderer,
-      cdep: Dependency
+      cdep: Dependency,
+      retryCount: Int
   ): Result[Task[Result[DependencyResolution]]] =
     Result.fromResults(decodeForceVersions(dep)).map { decodedForceVersions =>
       val allDependencies = for {
@@ -116,7 +118,20 @@ final case class ThirdpartyConfig(
           .withRepositories(
             if (repos.isEmpty) Resolve.defaultRepositories else repos
           )
-      resolve.io.map(r => DependencyResolution(dep, r)).toResult
+
+      def retry(m: Int) =
+        Task.tailRecM[Int, Resolution](m) { (n: Int) =>
+          if (n <= 0) resolve.io.map(Right(_))
+          else
+            resolve.io.attempt map {
+              case Right(r) => Right(r)
+              case Left(e) if e.getMessage.contains("concurrent download") =>
+                Thread.sleep(100)
+                Left(n - 1)
+              case Left(e) => throw e
+            }
+        }
+      retry(retryCount).map(r => DependencyResolution(dep, r)).toResult
     }
 
   private type ForceVersionResult =