Re: [Proposal] Adding Log File Capability to pg_createsubscriber - Mailing list pgsql-hackers

On Mon, 26 Jan 2026 at 07:08, Gyan Sreejith <gyan.sreejith@gmail.com> wrote:
>
> Thank you, I have made the changes and attached the patch.

Few comments:
1) Adding \n at the end will assert as pg_log_generic_v has the
following Assert:
Assert(fmt[strlen(fmt) - 1] != '\n');

@@ -1106,7 +1220,7 @@ check_subscriber(const struct LogicalRepInfo *dbinfo)
        int                     max_reporigins;
        int                     max_wprocs;

-       pg_log_info("checking settings on subscriber");
+       INFO("checking settings on subscriber\n");

You can run in verbose mode without -l to see this issue

2) There is a chance that directory creation can fail, it should be
checked and error should be thrown:
+                               if (stat(opt.log_dir, &statbuf) != 0)
+                               {
+                                       if (errno == ENOENT)
+                                       {
+                                               mkdir(opt.log_dir, S_IRWXU);
+                                               INFO("log directory created");

3) Can you include an fflush after the fprintf so that there is no log
content lost in case of abrupt failure:
+               va_start(args, format);
+               vfprintf(internal_log_file_fp, format, args);
+               fprintf(internal_log_file_fp, "\n");
+               va_end(args);

4) Since you are closing the log file early, the logs after this point
like the drop publication/drop replication slot in error flow will be
lost. They will neither appear in the console nor in the log file:
  * Clean up objects created by pg_createsubscriber.
@@ -212,6 +315,9 @@ cleanup_objects_atexit(void)
        if (success)
                return;

+       if (internal_log_file_fp != NULL)
+               fclose(internal_log_file_fp);
+

5) Since there is only one caller for this function and not needed by
anyone else, this code can be moved to the caller:
+static void
+populate_timestamp(char *timestr, size_t ts_len)
+{
+       struct timeval tval;
+       time_t          now;
+       struct tm       tmbuf;
+
+       gettimeofday(&tval, NULL);
+
+       /*
+        * MSVC's implementation of timeval uses a long for tv_sec, however,
+        * localtime() expects a time_t pointer.  Here we'll assign tv_sec to a
+        * local time_t variable so that we pass localtime() the correct pointer
+        * type.
+        */
+       now = tval.tv_sec;
+       strftime(timestr, ts_len,
+                        "%Y-%m-%d-%H-%M-%S",
+                        localtime_r(&now, &tmbuf));
+       /* append microseconds */
+       snprintf(timestr + strlen(timestr), ts_len - strlen(timestr),
+                        ".%06u", (unsigned int) (tval.tv_usec));
+}

Regards,
Vignesh