Now creates a backup when migrating LMDB databases

Ticket: None Changelog: Title Signed-off-by: Lars Erik Wik <[email protected]>
cfengine · Oct 23, 2024 · bae0737 · bae0737
1 parent 0293ff3
commit bae0737
Showing 1 changed file with 38 additions and 1 deletion.
diff --git a/libpromises/dbm_migration.c b/libpromises/dbm_migration.c
@@ -26,6 +26,7 @@
 
 #include <lastseen.h>
 #include <string_lib.h>
+#include <files_copy.h>
 
 extern const DBMigrationFunction dbm_migration_plan_lastseen[];
 
@@ -64,10 +65,46 @@ bool DBMigrate(DBHandle *db, dbid id)
         {
             if (step_version == DBVersion(db))
             {
-                if (!(*step)(db))
+                /* Create a backup */
+                char *db_path = DBIdToPath(id);
+                char backup[strlen(db_path) + strlen(".backup") + 1];
+                NDEBUG_UNUSED int ret = snprintf(backup, sizeof(backup),
+                                                 "%s.backup", db_path);
+                assert(ret > 0 && (size_t) ret < sizeof(backup));
+
+                Log(LOG_LEVEL_INFO,
+                    "Backing up '%s' to '%s' before migration.", db_path,
+                    backup);
+
+                if (!CopyRegularFileDisk(db_path, backup))
+                {
+                    Log(LOG_LEVEL_WARNING,
+                        "Failed to backup '%s' before migration", db_path);
+                }
+
+                /* Preform migration */
+                if ((*step)(db))
+                {
+                    /* Migration was successful! We can safely remove the
+                     * backup */
+                    Log(LOG_LEVEL_INFO,
+                        "Deleting backup of '%s' after successful migration.",
+                        backup);
+                    unlink(backup);
+                }
+                else
                 {
+                    /* Migration failed! Error is already logged. Delete DB so
+                     * that we can start fresh. It's not ideal, but it's the
+                     * best we can do. */
+                    Log(LOG_LEVEL_INFO,
+                        "Deleting '%s' due to failed migration. "
+                        "A backup is available in '%s'.", db_path, backup);
+                    unlink(db_path);
+                    free(db_path);
                     return false;
                 }
+                free(db_path);
             }
         }
     }