Refactor pgBackRest error handling for clarity

- Replace magic number 82 with PGBACKREST_ARCHIVE_TIMEOUT_ERROR_CODE constant
- Use semicolon separator for multiple error messages (improved readability)
- Document TimeoutError handling to preserve error state for juju resolve
- Update corresponding unit tests

Signed-off-by: Marcelo Henrique Neppel <marcelo.neppel@canonical.com>

Author: marceloneppel

src/backups.py

@@ -36,6 +36,7 @@
     BACKUP_TYPE_OVERRIDES,
     BACKUP_USER,
     PATRONI_CONF_PATH,
+    PGBACKREST_ARCHIVE_TIMEOUT_ERROR_CODE,
     PGBACKREST_BACKUP_ID_FORMAT,
     PGBACKREST_CONF_PATH,
     PGBACKREST_CONFIGURATION_FILE,
@@ -395,7 +396,7 @@ def _extract_error_message(stdout: str, stderr: str) -> str:
 
         # If we found error/warning lines, return them joined
         if error_lines:
-            return " ".join(error_lines)
+            return "; ".join(error_lines)
 
         # Otherwise return the last non-empty line from stderr or stdout
         if stderr.strip():
@@ -737,7 +738,7 @@ def check_stanza(self) -> bool:
                         f"--stanza={self.stanza_name}",
                         "check",
                     ])
-                    if return_code == 82:
+                    if return_code == PGBACKREST_ARCHIVE_TIMEOUT_ERROR_CODE:
                         # Raise an error if the archive command timeouts, so the user has the possibility
                         # to fix network issues and call juju resolve to re-trigger the hook that calls
                         # this method.
@@ -750,6 +751,7 @@ def check_stanza(self) -> bool:
                         raise Exception(stderr)
             self.charm._set_primary_status_message()
         except TimeoutError as e:
+            # Re-raise to put charm in error state (not blocked), allowing juju resolve
             raise e
         except Exception as e:
             # If the check command doesn't succeed, remove the stanza name

src/constants.py

@@ -32,6 +32,10 @@
 
 # Snap constants.
 PGBACKREST_EXECUTABLE = "charmed-postgresql.pgbackrest"
+# pgBackRest error codes
+PGBACKREST_ARCHIVE_TIMEOUT_ERROR_CODE = (
+    82  # Archive timeout - unable to archive WAL files within configured timeout period
+)
 POSTGRESQL_SNAP_NAME = "charmed-postgresql"
 SNAP_PACKAGES = [
     (

tests/unit/test_backups.py

@@ -78,7 +78,7 @@ def test_extract_error_message_with_multiple_errors():
 P00 ERROR: second error"""
     stderr = ""
     result = PostgreSQLBackups._extract_error_message(stdout, stderr)
-    assert result == "ERROR: first error WARN: warning message ERROR: second error"
+    assert result == "ERROR: first error; WARN: warning message; ERROR: second error"
 
 
 def test_extract_error_message_with_empty_output():