Honor SCM checkout retry count

src/main/java/org/jenkinsci/plugins/workflow/steps/scm/SCMStep.java

@@ -25,14 +25,17 @@
 package org.jenkinsci.plugins.workflow.steps.scm;
 
 import com.google.common.collect.ImmutableSet;
+import hudson.AbortException;
 import hudson.FilePath;
+import hudson.Functions;
 import hudson.Launcher;
 import hudson.model.Run;
 import hudson.model.TaskListener;
 import hudson.model.listeners.SCMListener;
 import hudson.scm.SCM;
 import hudson.scm.SCMRevisionState;
 import java.io.File;
+import java.io.InterruptedIOException;
 import java.nio.file.FileSystems;
 import java.nio.file.Files;
 import java.nio.file.attribute.PosixFilePermissions;
@@ -42,6 +45,7 @@
 import java.util.logging.Level;
 import java.util.logging.Logger;
 import edu.umd.cs.findbugs.annotations.NonNull;
+import jenkins.model.Jenkins;
 import org.jenkinsci.plugins.workflow.steps.Step;
 import org.jenkinsci.plugins.workflow.steps.StepContext;
 import org.jenkinsci.plugins.workflow.steps.StepDescriptor;
@@ -62,11 +66,11 @@
     public boolean isPoll() {
         return poll;
     }
-    
+
     @DataBoundSetter public void setPoll(boolean poll) {
         this.poll = poll;
     }
-    
+
     public boolean isChangelog() {
         return changelog;
     }
@@ -126,7 +130,30 @@
                 }
                 }
             }
-            scm.checkout(run, launcher, workspace, listener, changelogFile, baseline);
+
+            for (int retryCount = Jenkins.get().getScmCheckoutRetryCount(); retryCount >= 0; retryCount--) {
+                try {
+                    scm.checkout(run, launcher, workspace, listener, changelogFile, baseline);
+                    break;
+                } catch (InterruptedIOException e) {
+                    throw e;
+                } catch (Exception e) {
+                    // We follow the same exception output behavior as jenkinsci/workflow-cps-plugin#147,
+                    // but throw up the original exception if this is the last attempt
+                    if (e instanceof AbortException && e.getMessage() != null) {
+                        listener.error(e.getMessage());
+                    } else {
+                        Functions.printStackTrace(e, listener.error("Checkout failed"));
+                    }
+                    if (retryCount == 0) {
+                        listener.error("Maximum checkout retry attempts reached, aborting");// all attempts failed
+                        throw e;
+                    }
+                }
+                listener.getLogger().println("Retrying after 10 seconds");
+                Thread.sleep(10000);
+            }
+
             if (changelogFile != null && changelogFile.length() == 0
                     && changelogOriginalModifiedDate != null && changelogFile.lastModified() == changelogOriginalModifiedDate) {
                 // JENKINS-57918/JENKINS-59560/FakeChangeLogSCM: Some SCMs don't write anything to the changelog file in some

src/test/java/org/jenkinsci/plugins/workflow/steps/scm/SCMStepTest.java

@@ -238,4 +238,26 @@ public ChangeLogSet<? extends ChangeLogSet.Entry> parse(Run build, RepositoryBro
         public static class DescriptorImpl extends NullSCM.DescriptorImpl { }
     }
 
+
+
+    @Test
+    public void scmRetryFromFakeUnstableChangeLogSCM() {
+        rr.then(r -> {
+            r.jenkins.setScmCheckoutRetryCount(2);
+            WorkflowJob p = r.jenkins.createProject(WorkflowJob.class, "p");
+            p.setDefinition(new CpsFlowDefinition(
+                    "import org.jenkinsci.plugins.workflow.steps.scm.UnstableSCM\n" +
+                            "def testSCM = new UnstableSCM(2)\n" +
+                            "testSCM.addChange().withAuthor(/alice$BUILD_NUMBER/)\n" +
+                            "node() {\n" +
+                            "  checkout(testSCM)\n" +
+                            "}", false));
+            WorkflowRun b = r.buildAndAssertSuccess(p);
+            assertThat(b.getCulpritIds(), Matchers.equalTo(Collections.singleton("alice1")));
+            r.assertLogContains("Checkout failed", b);
+            r.assertLogContains("IO Exception happens", b);
+            r.assertLogContains("Retrying after 10 seconds", b);
+            assertThat(b.getCulpritIds(), Matchers.equalTo(Collections.singleton("alice1")));
+        });
+    }
 }

src/test/java/org/jenkinsci/plugins/workflow/steps/scm/UnstableSCM.java

@@ -0,0 +1,30 @@
+package org.jenkinsci.plugins.workflow.steps.scm;
+
+import hudson.FilePath;
+import hudson.Launcher;
+import hudson.model.Run;
+import hudson.model.TaskListener;
+import hudson.scm.SCMRevisionState;
+
+import java.io.File;
+import java.io.IOException;
+
+public class UnstableSCM extends org.jvnet.hudson.test.FakeChangeLogSCM {
+    private int failedCount;
+
+    public UnstableSCM(int failedCount) {
+        this.failedCount = failedCount;
+    }
+
+    @Override
+    public void checkout(Run<?, ?> build, Launcher launcher, FilePath remoteDir, TaskListener listener, File changeLogFile, SCMRevisionState baseline) throws IOException, InterruptedException {
+        try {
+            if (failedCount > 0) {
+                throw new IOException("IO Exception happens");
+            }
+            super.checkout(build, launcher, remoteDir, listener, changeLogFile, baseline);
+        } finally {
+            failedCount--;
+        }
+    }
+}