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Ansible and string comparisation for IDs

Was running in a stupid problem where Ansible (version 2.9.x) throws an error when a variable is defined. The Play:

- name: Check if id is defined
  fail:
    msg: "No id defined for {{ inventory_hostname }}!"
  when: id is not defined or id|length == 0

And the error:

TASK [Check if id is defined] *****************************************
fatal: [xxx.xxx.xxx.xxx]: FAILED! => {"msg": "The conditional check 'id is not defined or id|length == 0' failed. The error was: Unexpected templating type error occurred on ({% if id is not defined or id|length == 0 %} True {% else %} False {% endif %}): object of type 'int' has no len()\n\nThe error appears to be in '/path/to/playbook/configuration.yml': line 57, column 7, but may\nbe elsewhere in the file depending on the exact syntax problem.\n\nThe offending line appears to be:\n\n\n    - name: Check if id is defined\n      ^ here\n"}

Ok, it tries to compare an integer, fine. There are two ways to fix this problem:

1: Change the type to a string by updating the inventory:

From:

id=1

to:

id="1"

But this might have other consequences, as the other parts of the Playbook might depend on this being an integer.

2: Compare as string

when: id is not defined or id|string|length == 0

This casts the integer to a string, and then the length() function works.

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Ansible, "copy" module and "become"

For testing I did spin up a couple of new virtual (Ubuntu 20.04 LTS) instances, installed PostgreSQL, and wanted to copy over a .sql file to install in the database:

- name: copy files to PostgreSQL data directory
  copy:
    src: "files/{{ item }}"
    dest: "{{ item }}"
    mode: 0700
  become: yes
  become_user: postgres
  loop:
    - file1.sql
    - file2.sql

And ran into a meaningless error message:

TASK [copy files to PostgreSQL data directory] ***********
fatal: [xxx.xxx.xxx.xxx]: FAILED! => {"msg": "Failed to set permissions on the temporary files Ansible needs to create when becoming an unprivileged user (rc: 1, err: chown: changing ownership of '/var/tmp/ansible-tmp-1618521951.848439-176484068031965/': Operation not permitted\nchown: changing ownership of '/var/tmp/ansible-tmp-1618521951.848439-176484068031965/source': Operation not permitted\n}). For information on working around this, see https://docs.ansible.com/ansible/become.html#becoming-an-unprivileged-user"}

 

 

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Make Ansible "postgresql_ping" fail if the database does not exist

Ansible has a very useful module "postgresql_ping" which checks connectivity to the database server. I'm using it in quite a few Playbooks as first step just to ensure that the database server is present - this fails early if there is a problem which otherwise just prevents the rest of the Playbook to work properly.

TASK [Check if database is available]
[WARNING]: PostgreSQL server is unavailable: could not connect to server: No such file or directory         Is the server running locally and accepting         connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?
fatal: [127.0.0.1]: FAILED! => {"changed": false, "failed_when_result": true, "is_available": false, "server_version": {}}

 

However this module does not check if the database exists, just if the server is reachable. Example Playbook:

- name: Check if database is available
  postgresql_ping:
    db: "testdb"
  become: yes
  become_user: postgres

When I run the Playbook:

TASK [Check if database is available]
[WARNING]: PostgreSQL server is unavailable: FATAL:  database "testdb" does not exist
ok: [127.0.0.1]

 

As you can see, the database "testdb" does not exist. Which for the module is a reason to raise a warning, but not  a reason to fail.

One possible solution is to let this module do it's work, and add a "postgresql_db" call next, which ensures that the database is created. But not every Playbook is supposed to create and populate a database, and has all the required parameters (owner, encoding, template ect) available. Therefore it would be nice if "postgresql_ping" fails early if the database in question doesn't exist. That's possible, with two more lines of code:

- name: Check if database is available
  postgresql_ping:
    db: "testdb"
  become: yes
  become_user: postgres
  register: ping_database
  failed_when: ping_database.warnings is defined

And the Playbook run:

TASK [Check if database is available]
[WARNING]: PostgreSQL server is unavailable: FATAL:  database "testdb" does not exist
fatal: [127.0.0.1]: FAILED! => {"changed": false, "failed_when_result": true, "is_available": false, "server_version": {}}

Together with "any_errors_fatal: True" this ends the entire Playbook early enough before I have to debug the problem later on.

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Blog website crawlers and bots in Apache2

Found a couple more bots crawling my website, and from the look at online resources it seems I catched a few of the bad guys. Crawlers which ignore the robots.txt standard, and just crawl a website for content.

Decided to do something against it, and added a filter in Apache2.

The way I have my webserver setup is that I have templates for every website (they all have different configs), and deploy them using Ansible. Parts of the website configuration which are the same, or at least similar, are handled by includes.

 

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Create child pages in Redmine

Once or twice a year I have to setup a new Redmine project, which we use to organize conferences for PostgreSQL Europe.

Every single time I'm trying to figure out how the child pages for the meeting notes work.

Steps required:

  • Create a page "MeetingMinutes", doesn't need to have any content, but it must exist
  • Create the first child page with meeting minutes, as parent page select "MeetingMinutes"
  • On the main wiki page insert a link with: "{{child_pages(MeetingMinutes)}}"

Every time I forget step 1), because this page is only required as parent page, and serves no further purpose. And then I'm wondering why I can't create child pages.

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