Re: Add jsonlog log_destination for JSON server logs

On Tue, Aug 31, 2021 at 11:34:56AM -0400, Sehrope Sarkuni wrote:
> The second commit adds a TAP test for log_destination "csvlog". This was
> done to both confirm that the previous change didn't break anything and as
> a skeleton for the test in the next commit.

+note "Before sleep";
+usleep(100_000);
+note "Before rotate";
+$node->logrotate();
+note "After rotate";
+usleep(100_000);

Do you really need a rotation of the log files here? Wouldn't it be
better to grab the position of the current log file with a fixed log
file name, and then slurp the file from this position with your
expected output? That would make the test faster, as well.

> The third commit adds the new log_destination "jsonlog". The output format
> is one line per entry with the top level output being a JSON object keyed
> with the log fields. Newlines in the output fields are escaped as \n so the
> output file has exactly one line per log entry. It also includes a new test
> for verifying the JSON output with some basic regex checks (similar to the
> csvlog test).

+ * Write logs in json format.
+ */
+static void
+write_jsonlog(ErrorData *edata)
+{
Rather than making elog.c larger, I think that we should try to split
that into more files. Why not refactoring out the CSV part first?
You could just call that csvlog.c, then create a new jsonlog.c for the
meat of the patch.

The list of fields is not up to date. At quick glance, you are
missing:
- backend type.
- leader PID.
- query ID.
- Session start timestamp (?)
--
Michael