refactor(slog): refactor logging for slog gc (#1992)

Author: empiredan

src/replica/mutation_log.cpp

@@ -1445,47 +1445,51 @@ bool can_gc_replica_slog(const dsn::replication::replica_log_info_map &slog_max_
         // `ERR_INCOMPLETE_DATA`, thus it's possible that `valid_start_offset == 0`.
         CHECK(valid_start_offset == 0 || file->end_offset() <= valid_start_offset,
               "valid start offset must be 0 or greater than the end of this log file");
-        LOG_DEBUG("gc @ {}: max_decree for {} is missing vs {} as garbage max decree, it's "
-                  "safe to delete this and all older logs for this replica",
-                  pid,
-                  file->path(),
-                  garbage_max_decree);
+        LOG_INFO("gc @ {}: max_decree for {} is missing vs {} as garbage max decree, it's "
+                 "safe to delete this and all older logs for this replica",
+                 pid,
+                 file->path(),
+                 garbage_max_decree);
         return true;
-    } else if (file->end_offset() <= valid_start_offset) {
+    }
+
+    if (file->end_offset() <= valid_start_offset) {
         // This file has been invalid for this replica, since `valid_start_offset` was reset
         // to a file with larger index than this file. Thus all decrees of this replica in
         // this file could be deleted.
-        LOG_DEBUG("gc @ {}: log is invalid for {}, as valid start offset vs log end offset = "
-                  "{} vs {}, it is therefore safe to delete this and all older logs for this "
-                  "replica",
-                  pid,
-                  file->path(),
-                  valid_start_offset,
-                  file->end_offset());
+        LOG_INFO("gc @ {}: log is invalid for {}, as valid start offset vs log end offset = "
+                 "{} vs {}, it is therefore safe to delete this and all older logs for this "
+                 "replica",
+                 pid,
+                 file->path(),
+                 valid_start_offset,
+                 file->end_offset());
         return true;
-    } else if (it->second.max_decree <= garbage_max_decree) {
+    }
+
+    if (it->second.max_decree <= garbage_max_decree) {
         // All decrees are no more than the garbage max decree. Since all decrees less than
         // garbage max decree would be deleted, all decrees of this replica in this file
         // could be deleted.
-        LOG_DEBUG("gc @ {}: max_decree for {} is {} vs {} as garbage max decree, it is "
-                  "therefore safe to delete this and all older logs for this replica",
-                  pid,
-                  file->path(),
-                  it->second.max_decree,
-                  garbage_max_decree);
+        LOG_INFO("gc @ {}: max_decree for {} is {} vs {} as garbage max decree, it is "
+                 "therefore safe to delete this and all older logs for this replica",
+                 pid,
+                 file->path(),
+                 it->second.max_decree,
+                 garbage_max_decree);
         return true;
     }
 
     // it->second.max_decree > garbage_max_decree
     //
     // Some decrees are more than garbage max decree, thus this file should not be deleted
     // for now.
-    LOG_DEBUG("gc @ {}: max_decree for {} is {} vs {} as garbage max decree, it "
-              "is therefore not allowed to delete this and all older logs",
-              pid,
-              file->path(),
-              it->second.max_decree,
-              garbage_max_decree);
+    LOG_INFO("gc @ {}: max_decree for {} is {} vs {} as garbage max decree, it "
+             "is therefore not allowed to delete this and all older logs",
+             pid,
+             file->path(),
+             it->second.max_decree,
+             garbage_max_decree);
 
     auto gap = it->second.max_decree - garbage_max_decree;
     if (file->index() < gc_summary.min_file_index || gap > gc_summary.max_decree_gap) {