fabric: retry download when IO exception (#517)

Author: itzg

src/main/java/me/itzg/helpers/fabric/FabricLauncherInstaller.java

@@ -65,6 +65,7 @@ public void installUsingVersions(
                                     resolvedLoaderVersion,
                                     resolvedInstallerVersion
                                 ))
+                                .checkpoint("downloadResolvedLauncher")
                         )
                 )
                 .block();

src/main/java/me/itzg/helpers/fabric/FabricMetaClient.java

@@ -1,20 +1,28 @@
 package me.itzg.helpers.fabric;
 
+import java.io.IOException;
 import java.nio.file.Path;
+import java.time.Duration;
 import java.util.List;
 import java.util.function.Predicate;
+import lombok.Setter;
 import me.itzg.helpers.errors.GenericException;
 import me.itzg.helpers.http.FileDownloadStatusHandler;
 import me.itzg.helpers.http.SharedFetch;
 import me.itzg.helpers.http.UriBuilder;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import reactor.core.publisher.Mono;
+import reactor.util.retry.Retry;
 
 public class FabricMetaClient {
 
     private final SharedFetch sharedFetch;
     private final UriBuilder uriBuilder;
+    @Setter
+    private int downloadRetryMaxAttempts = 5;
+    @Setter
+    private Duration downloadRetryMinBackoff = Duration.ofMillis(500);
 
     public FabricMetaClient(SharedFetch sharedFetch, String fabricMetaBaseUrl) {
         this.sharedFetch = sharedFetch;
@@ -106,7 +114,9 @@ public Mono<Path> downloadLauncher(
             )
             .toDirectory(outputDir)
             .handleStatus(statusHandler)
-            .assemble();
+            .assemble()
+            .retryWhen(Retry.backoff(downloadRetryMaxAttempts, downloadRetryMinBackoff).filter(IOException.class::isInstance))
+            .checkpoint("downloadLauncher");
     }
 
     @NotNull