CENTOS Postgres pg_upgrade 9 to 11 – In Place – Link – No Copy – Limited Disk Space

I wanted to share my experience with upgrading postgres database server from major version 9 to 11. I am showing the steps that I took to get many servers in dev and production upgraded with limited disk space(not enough space to copy). I am hoping this will help with the problems I faced when testing this procedure. Using the –link parameter has drawbacks as noted in the documentation, however we perform full VM backups of each server so we can always restore from backup if the upgrade fails and we will not need to start the pg9.3 database again.

https://www.postgresql.org/docs/11/pgupgrade.html

-k
--link

use hard links instead of copying files to the new cluster
If you ran pg_upgrade with --link, the data files are shared between the old and new cluster. If you started the new cluster, the new server has written to those shared files and it is unsafe to use the old cluster.

Before we get started make a backup of the files pg_hba.conf and postgresql.conf for later use, you will need to use them later to reconstruct the pg11 configs.

Use WGET to grab the RPMS from https://yum.postgresql.org

Install the RPMS for postgres11 that we just downloaded

We will create the data location for postgres11 where the files will be hardlinked and not copied. You can see the tablespace disk locations and the index locations from the pg9.3 install. Its important to create the new pg11 data directory on the same filesystem since we will be using the –link parameter and it uses hardlinks which will not traverse filesystems.

We will need to init a postgres database in our new location on disk data11.

Now we are ready to stop pg9.3 and check pg_upgrade compatibility. pg_upgrade ships with a –check argument that will check the compatibility of the clusters and be sure the upgrade will work before changing any files. Lets stop pg9.3 and run the pg_upgrade with the –check parameter.


Ok checks have passed and the cluster versions are ready for upgrade, lets run this without the –check parameter and upgrade postgres.

OK the pg_upgrade code completed successfully and has generated 2 scripts. One to analyze the new pg11 cluster to get stats for the query planner and vacuum. The other to cleanup and remove the old pg9.3 locations on disk. Let’s start pg11, we will need to create an override file to tell pg11 where the data11 data lives, then we should be able to start postgres and check some things and verify our upgrade.


OK we can see we have pg11 running and we can run the generated scripts to cleanup, but lets take a look at the data and index directories to see what the upgrade produced.

We can view the shell scripts that pg_upgrade produced and cleanup the old pg9.3 references and run the analyze vacuums.


This looks good, lets execute them and cleanup any pg9.3 references as well as remove the pg9.3 rpms.

You can now view the pg_hba.conf and postgresql.conf you saved in /root and add whats needed to the new pg11 configs.

That’s it!!

SINOPIA NPM allow connections to GITHUB as well as the NPM registry

SINOPIA LINK HERE
We use SINOPIA as a proxy on our internal network behind the firewall to allow users to install NODE packages without an internet connection. We basically run sinopia on a machine that has access to the internet and the clients point to the server to install packages that are not locally available. We have been running into issues where installs that needed access to github would fail with something like this:

As you can see, we are getting choked at:

To get around this we need to change the config.yml on the server to allow proxies to github, here is the final configuration. Hope this helps other users as we had a fun time trying to figure it out. Pay attention to the uplinks section and the proxy requests where github is defined.

PSQL Connect To AWS Redshift From Windows 10 PowerShell

Coming from a completely Linux background, I was tasked with connecting to a aws redshift cluster or a postgres cluster via Windows powershell and PSQL. I knew it was possible and searching the internet came up with CMD prompt solutions, when I attempted via powershell, I was faced with the following error:

Turns out a colleague of mine and I figured out you will need to set the variable PGCLIENTENCODING via the powershell command line. This was expected but we could not nail down the syntax, we found it.

Once this is set, you can connect to PG as normal.

Python Generator Find Files With Wildcard

This is a neat way to generate file names in a directory that match a specific pattern, I use this to generate a list of files exported out of hive to load into S3.

Nagios Python Plugin Check If File Is Stale

Wrote this simple plugin to check if a log file was stale on a server using nagios and nrpe. This plugin checks multiple files with the app. naming convention.

POSTGRES – Top 100 Tables In Tablespace

I had a situation where I needed to find the top 100 largest tables in a certain tablespace on a postgres 9 database, in my case we archive tables into an archive1 tablespace. This query will find all the largest relations in the archive1 tablespace. Its important to swap out ‘archive1’ with whatever tablespace you are trying to list.

Hope this helps you out, took some time to get it to work.

Nagios Check Postgres Table Date Column Against now()

I had a situation where a daily sync of a table from one database to another was failing. This table was updated daily so the query should return something like this when it was synced correctly:

I use Nagios very heavily and I setup a custom plugin to check the query’s date against today’s date, this should warn or critical based on user supplied arguments. Here is what a failure looks like when running from the nagios servers command line. This worked well at alerting me when the sync failed, this was integrated into the nagios subsystem and emails and slack alerts are generated as expected.

Nagios Python Plugin Check Lock File Exists

Code Highlighting Test

I just installed the crayon code highlight plugin from the link below, man you got to give credit where credit is due. This plugin was simple to install on my site and it has endless code highlighting capabilities.
Crayon Highlight
OMG: This is some pretty code highlighting if I must say so myself. Have a look:

PYTHON:

PHP:

C++:

BASH:

PERL:

JAVA:

CYGWIN – clear.exe from scratch C Program

Hello all,

TL;DR – I wrote a C program to use as clear.exe on cygwin, I know about CTRL-L but I wanted a binary for scripts, and I am used to typing clear at a terminal

I was recently enforced to use Windows as my daily computer at work for all types of compliance PCI reasons, reasons that I do not wish to dive into. However I am now on Windows, I spend most of my day in a BASH shell on a remote system, so it’s not that bad. However traversing around Windows with CMD or PS sucked. I was introduced to cygwin and I was really impressed, I was able to use a ton of tools that I was already familiar with on the Linux CLI. Native SSH,SCP were huge for me at this time, also the ability to customize the colors with the TTY settings was awesome.

One issue I ran into was I liked to use the clear command in my scripts and from the CLI when I want a fresh terminal. Well, I figured I could just re launch the cygwin installer and search for clear.exe and install it. This was not the case, unfortunately I was instructed to install ncurses and the associated libraries. I followed these recommendations and never got clear.exe to work.

So I did what any computer scientist would do, research how to write a C program on this and compile it and copy it to my $PATH and wouldn’t you know it works!!.

So Here it is in all it’s glory. clear.exe for Windows and CYGWIN:

### Clear no workie ###

Ok so we can see the clear program was not working in the above example. So I wrote the following lines of C code below and compiled them.

OK, cool, now you will need to get GCC on your Windows machine from the CYGWIN installer, so just re run the installer and search GCC, you can install it from there like so.

View post on imgur.com

Ok now for the awesome stuff, it’s time to compile this with GCC and create a new clear.exe binary for Windows and CYGWIN.

Now that we see we can use the new executable to clear out cygwin shell, let’s copy it somewhere so we can just type “clear” to get what we want.

And there you have it, have fun!!!

Jason