email: Only send the first x bytes of detail in email

npbackup/__env__.py

@@ -51,3 +51,6 @@ ALLOWED_UPGRADE_SERVER_IDS = ("npbackup.upgrader", "npbackup.deployment_server")
 
 # Replacement string for sensitive data
 HIDDEN_BY_NPBACKUP = "_[o_O]_hidden_by_npbackup"
+
+# Maximum number of characters for details content in emails
+MAX_EMAIL_DETAIL_LENGTH = 1000

npbackup/core/metrics.py

@@ -24,6 +24,7 @@ from npbackup.restic_metrics import (
 from npbackup.__version__ import __intname__ as NAME, version_dict
 from npbackup.__debug__ import fmt_json
 from resources.customization import OEM_STRING
+from npbackup.__env__ import MAX_EMAIL_DETAIL_LENGTH
 
 logger = getLogger()
 
@@ -325,7 +326,17 @@ def send_metrics_mail(
     body += f"\nDate: {date}"
 
     if isinstance(restic_result, dict):
-        body += f"\n\nDetail: {fmt_json(restic_result)}"
+        try:
+            restic_result = fmt_json(restic_result)
+        except TypeError:
+            # TypeError may happen on ls command which contains a json of LSNodes when HAVE_MSGSPEC is True
+            pass
+        # Convert the dict to a string so we can analyze its length
+        restic_result = str(restic_result)
+        if len(restic_result) > MAX_EMAIL_DETAIL_LENGTH:
+            body += f"\n\nDetail:\n{restic_result[0:MAX_EMAIL_DETAIL_LENGTH]} [... truncated]"
+        else:
+            body += f"\n\nDetail:\n{restic_result}"
 
     body += f"\n\nGenerated by {OEM_STRING} {version_dict['version']}\n"