fix: collapse redundant stack trace lines in error logs

extensions/data-transfer/portability-data-transfer-google/src/main/java/org/datatransferproject/datatransfer/google/common/GoogleErrorLogger.java

@@ -1,7 +1,7 @@
 package org.datatransferproject.datatransfer.google.common;
 
-import com.google.common.base.Throwables;
 import com.google.common.collect.ImmutableList;
+import org.datatransferproject.types.common.ExceptionUtils;
 import java.io.IOException;
 import java.util.UUID;
 import org.datatransferproject.spi.cloud.storage.JobStore;
@@ -30,7 +30,7 @@ public static ErrorDetail createErrorDetail(String idempotentId, String title, E
     return ErrorDetail.builder()
         .setId(idempotentId)
         .setTitle(title)
-        .setException(Throwables.getStackTraceAsString(e))
+        .setException(ExceptionUtils.getStackTraceAsString(e))
         .setCanSkip(canSkip).build();
   }
 }

portability-api-launcher/src/main/java/org/datatransferproject/launcher/monitor/ConsoleMonitor.java

@@ -16,7 +16,7 @@
 package org.datatransferproject.launcher.monitor;
 
 import static com.google.common.base.Strings.isNullOrEmpty;
-import static com.google.common.base.Throwables.getStackTraceAsString;
+import static org.datatransferproject.types.common.ExceptionUtils.getStackTraceAsString;
 
 import java.util.UUID;
 import org.datatransferproject.api.launcher.Monitor;

portability-spi-transfer/src/main/java/org/datatransferproject/spi/transfer/idempotentexecutor/InMemoryIdempotentImportExecutor.java

@@ -19,8 +19,8 @@
 import static java.lang.String.format;
 
 import com.google.common.base.Joiner;
-import com.google.common.base.Throwables;
 import com.google.common.collect.ImmutableList;
+import org.datatransferproject.types.common.ExceptionUtils;
 import java.util.UUID;
 import org.datatransferproject.api.launcher.Monitor;
 import org.datatransferproject.types.transfer.errors.ErrorDetail;
@@ -81,7 +81,7 @@ public <T extends Serializable> T executeOrThrowException(
           ErrorDetail.builder()
               .setId(idempotentId)
               .setTitle(itemName)
-              .setException(Throwables.getStackTraceAsString(e))
+              .setException(ExceptionUtils.getStackTraceAsString(e))
               .build();
       errors.put(idempotentId, errorDetail);
       recentErrors.put(idempotentId, errorDetail);

portability-spi-transfer/src/main/java/org/datatransferproject/spi/transfer/idempotentexecutor/RetryingInMemoryIdempotentImportExecutor.java

@@ -19,8 +19,8 @@
 import static java.lang.String.format;
 
 import com.google.common.base.Joiner;
-import com.google.common.base.Throwables;
 import com.google.common.collect.ImmutableList;
+import org.datatransferproject.types.common.ExceptionUtils;
 import java.io.IOException;
 import java.io.Serializable;
 import java.time.Clock;
@@ -90,10 +90,10 @@ public <T extends Serializable> T executeOrThrowException(
       errors.remove(idempotentId);
       return result;
     } catch (RetryException e) {
-      ErrorDetail.Builder errorDetailBuilder = ErrorDetail.builder();
-      errorDetailBuilder.setId(idempotentId)
+      ErrorDetail.Builder errorDetailBuilder = ErrorDetail.builder()
+          .setId(idempotentId)
           .setTitle(itemName)
-          .setException(Throwables.getStackTraceAsString(e));
+          .setException(ExceptionUtils.getStackTraceAsString(e));
       if(e.canSkip()){
         ErrorDetail errorDetail = errorDetailBuilder.setCanSkip(true).build();
         errors.put(idempotentId, errorDetail);

portability-types-common/src/main/java/org/datatransferproject/types/common/ExceptionUtils.java

@@ -0,0 +1,87 @@
+package org.datatransferproject.types.common;
+
+/** Utility class for handling exceptions. */
+public class ExceptionUtils {
+
+  /**
+   * Formats a Throwable's stack trace to collapse consecutive identical frames.
+   * This handles highly recursive calls (e.g. repeated copyHelper invocations)
+   * by logging the first occurrence and annotating how many times it was repeated.
+   */
+  public static String getStackTraceAsString(Throwable t) {
+    if (t == null) {
+      return "";
+    }
+    StringBuilder sb = new StringBuilder();
+    sb.append(t.toString()).append('\n');
+    StackTraceElement[] trace = t.getStackTrace();
+    int duplicateCount = 0;
+    StackTraceElement lastElement = null;
+
+    for (StackTraceElement element : trace) {
+      if (lastElement != null && element.equals(lastElement)) {
+        duplicateCount++;
+      } else {
+        if (duplicateCount > 0) {
+          sb.append("\t... repeated ").append(duplicateCount).append(" times more\n");
+          duplicateCount = 0;
+        }
+        sb.append("\tat ").append(element.toString()).append('\n');
+        lastElement = element;
+      }
+    }
+    if (duplicateCount > 0) {
+      sb.append("\t... repeated ").append(duplicateCount).append(" times more\n");
+    }
+
+    // Now handle Caused by recursively
+    Throwable cause = t.getCause();
+    if (cause != null) {
+      appendCause(cause, trace, sb);
+    }
+
+    return sb.toString();
+  }
+
+  private static void appendCause(Throwable cause, StackTraceElement[] enclosingTrace, StringBuilder sb) {
+    sb.append("Caused by: ").append(cause.toString()).append('\n');
+    StackTraceElement[] trace = cause.getStackTrace();
+
+    // Find common suffix between trace and enclosingTrace
+    int m = trace.length - 1;
+    int n = enclosingTrace.length - 1;
+    while (m >= 0 && n >= 0 && trace[m].equals(enclosingTrace[n])) {
+      m--;
+      n--;
+    }
+    int framesInCommon = trace.length - 1 - m;
+
+    int duplicateCount = 0;
+    StackTraceElement lastElement = null;
+
+    for (int i = 0; i <= m; i++) {
+      StackTraceElement element = trace[i];
+      if (lastElement != null && element.equals(lastElement)) {
+        duplicateCount++;
+      } else {
+        if (duplicateCount > 0) {
+          sb.append("\t... repeated ").append(duplicateCount).append(" times more\n");
+          duplicateCount = 0;
+        }
+        sb.append("\tat ").append(element.toString()).append('\n');
+        lastElement = element;
+      }
+    }
+    if (duplicateCount > 0) {
+      sb.append("\t... repeated ").append(duplicateCount).append(" times more\n");
+    }
+    if (framesInCommon != 0) {
+      sb.append("\t... ").append(framesInCommon).append(" more\n");
+    }
+
+    Throwable nextCause = cause.getCause();
+    if (nextCause != null) {
+      appendCause(nextCause, trace, sb);
+    }
+  }
+}

portability-types-transfer/src/main/java/org/datatransferproject/types/transfer/retry/RetryMapping.java

@@ -17,7 +17,7 @@
 package org.datatransferproject.types.transfer.retry;
 
 import static com.google.common.base.Preconditions.checkArgument;
-import static com.google.common.base.Throwables.getStackTraceAsString;
+import static org.datatransferproject.types.common.ExceptionUtils.getStackTraceAsString;
 
 import com.fasterxml.jackson.annotation.JsonProperty;
 import java.util.Arrays;