[YSQL] Add UUID to yb_servers() function

[xenown]

Jira Link: DB-2753

Context

This is the 1st change in a series of diffs for porting the Postgres extension pg_cron to yugabyte. The following summary assumes you understand how the original pg cron extension worked.

Unlike the original extension, we intend for this port to have all Postgres instances act as workers as opposed to a single worker which will complete the scheduled pg cron jobs. A job runs on one of the workers in a YB cluster. The cron.job_run_details table shows information about each individual job run. Example:

system_platform=# SELECT * from cron.job_run_details;
 jobid | runid | job_pid |    database     | username |        command         |  status   | return_message |          start_time           |           end_time            |  node_uuid        
-------+-------+---------+-----------------+----------+------------------------+-----------+----------------+-------------------------------+-------------------------------+-------------
     1 |   212 | 3820788 | system_platform | yugabyte | select pg_sleep(20), 1 | succeeded | SELECT 1       | 2022-07-21 19:36:02.241619+00 | 2022-07-21 19:36:24.754601+00 |  aedf2-dfs
     2 |   211 | 3820766 | system_platform | yugabyte | select pg_sleep(20), 1 | succeeded | SELECT 1       | 2022-07-21 19:36:02.069145+00 | 2022-07-21 19:36:24.712906+00 |  sedf7-bbs

The cron.job_run_details table exists in the original extension. However, we add a node_uuid column, which is the UUID of the node on which a job ran. The purpose behind this extra column is it'll be easier for the user to find which logs to look at in the case of a job failure/issue/debugging/etc.

Problem

However, the UUID field is currently not accessible in YB Managed. As an open-source feature, YB support for the pg_cron extension should be available across all tiers (YB OSS/Anywhere/Managed).

Solution

We will add a node_uuid column to the yb_servers() function so users can map UUIDs to a specific node.

yugabyte=# select * from yb_servers();
   host    | port | uuid                                 | node_type | cloud  |   region    | zone  | public_ip 
-----------+------+--------------------------------------+-------------+-------+-------------------------------
 127.0.0.2 | 5433 | 123e4567-e89b-12d3-a456-426614174000 | primary   | cloud1 | datacenter1 | rack1 | 13.512.12
(3 rows)

[sushantrmishra]

Testing

[paullee-yb]

Resolved here