Programming – Page 4 – A nice guy's view on life

"funfair action" by "Jon Bunting" on Flickr

Improving the speed of Azure deployments in Ansible with Async

2019-05-152019-05-15 JonTheNiceGuy Leave a comment

Recently I was building a few environments in Azure using Ansible, and found this stanza which helped me to speed things up.

  - name: "Schedule UDR Creation"
    azure_rm_routetable:
      resource_group: "{{ resource_group }}"
      name: "{{ item.key }}_udr"
    loop: "{{ routetables | dict2items }}"
    loop_control:
        label: "{{ item.key }}_udr"
    async: 1000
    poll: 0
    changed_when: False
    register: sleeper

  - name: "Check UDRs Created"
    async_status:
      jid: "{{ item.ansible_job_id }}"
    register: sleeper_status
    until: sleeper_status.finished
    retries: 500
    delay: 4
    loop: "{{ sleeper.results|flatten(levels=1) }}"
    when: item.ansible_job_id is defined
    loop_control:
      label: "{{ item._ansible_item_label }}"

What we do here is to start an action with an “async” time (to give the Schedule an opportunity to register itself) and a “poll” time of 0 (to prevent the Schedule from waiting to be finished). We then tell it that it’s “never changed” (changed_when: False) because otherwise it always shows as changed, and to register the scheduled item itself as a “sleeper”.

After all the async jobs get queued, we then check the status of all the scheduled items with the async_status module, passing it the registered job ID. This lets me spin up a lot more items in parallel, and then “just” confirm afterwards that they’ve been run properly.

It’s not perfect, and it can make for rather messy code. But, it does work, and it’s well worth giving it the once over, particularly if you’ve got some slow-to-run tasks in your playbook!

Featured image is “funfair action” by “Jon Bunting” on Flickr and is released under a CC-BY license.

A web browser with the example.com web page loaded

Working around the fact that Ansible’s URI module doesn’t honour the no_proxy variable…

2019-05-142019-05-14 JonTheNiceGuy Leave a comment

An Ansible project I’ve been working on has tripped me up this week. I’m working with some HTTP APIs and I need to check early whether I can reach the host. To do this, I used a simple Ansible Core Module which lets you call an HTTP URI.

- uri:
    follow_redirects: none
    validate_certs: False
    timeout: 5
    url: "http{% if ansible_https | default(True) %}s{% endif %}://{{ ansible_host }}/login"
  register: uri_data
  failed_when: False
  changed_when: False

This all seems pretty simple. One of the environments I’m working in uses the following values in their environment:

http_proxy="http://192.0.2.1:8080"
https_proxy="http://192.0.2.1:8080"
no_proxy="10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, 192.0.2.0/24, 198.51.100.0/24, 203.0.113.0/24"

And this breaks the uri module, because it tries to punt everything through the proxy if the “no_proxy” contains CIDR values (like 192.0.2.0/24) (there’s a bug raised for this)… So here’s my fix!

- set_fact:
    no_proxy_match: |
      {
        {% for no_proxy in (lookup('env', 'no_proxy') | replace(',', '') ).split() %}
          {% if no_proxy| ipaddr | type_debug != 'NoneType' %}
            {% if ansible_host | ipaddr(no_proxy) | type_debug != 'NoneType' %}
              "match": "True"
            {% endif %}
          {% endif %}
        {% endfor %}
      }

- uri:
    follow_redirects: none
    validate_certs: False
    timeout: 5
    url: "http{% if ansible_https | default(True) %}s{% endif %}://{{ ansible_host }}/login"
  register: uri_data
  failed_when: False
  changed_when: False
  environment: "{ {% if no_proxy_match.match | default(False) %}'no_proxy': '{{ ansible_host }}'{% endif %} }"

So, let’s break this down.

The key part to this script is that we need to override the no_proxy environment variable with the IP address that we’re trying to address (so that we’re not putting 16M addresses for 10.0.0.0/8 into no_proxy, for example). To do that, we use the exact same URI block, except for the environment line at the end.

In turn, the set_fact block steps through the no_proxy values, looking for IP Addresses to check ({% if no_proxy | ipaddr ... %}‌ says “if the no_proxy value is an IP Address, return it, but if it isn’t, return a ‘None’ value”) and if it’s an IP address or subnet mask, it checks to see whether the IP address of the host you’re trying to reach falls inside that IP Address or Subnet Mask ({% if ansible_host | ipaddr(no_proxy) ... %} says “if the ansible_host address falls inside the no_proxy range, then return it, otherwise return a ‘None’ value”). Both of these checks say “If this previous check returns anything other than a ‘None’ value, do the next thing”, and on the last check, the “next” thing is to set the flag ‘match’ to ‘true’. When we get to the environment variable, we say “if match is not true, it’s false, so don’t put a value in there”.

So that’s that! Yes, I could merge the set_fact block into the environment variable, but I do end up using that a fair amount. And really, if it was merged, that would be even MORE complicated to pick through.

I have raised a pull request on the Ansible project to update the documentation, so we’ll see whether we end up with people over here looking for ways around this issue. If so, let me know in the comments below! Thanks!!

Creating Self Signed certificates in Ansible

2018-11-232019-01-23 JonTheNiceGuy 1 Comment

In my day job, I sometimes need to use a self-signed certificate when building a box. As I love using Ansible, I wanted to make the self-signed certificate piece something that was part of my Ansible workflow.

Here follows a bit of basic code that you could use to work through how the process of creating a self-signed certificate would work. I would strongly recommend using something more production-ready (e.g. LetsEncrypt) when you’re looking to move from “development” to “production” :)

Log Levels in code (and SYSLOG)

2018-10-172018-10-17 JonTheNiceGuy Leave a comment

Saw this picture showing what your log levels should actually be and figured it was awesome. Thought you might like it too! (Also Jamie’s content is fab generally)

@dylanbeattie has advised some new names for common log levels #TechNott pic.twitter.com/tVu5AJ0b9I

— Jamie Tanna | www.jvt.me (@JamieTanna) October 8, 2018

One to read: A Beginner’s Guide to IPFS

2018-09-202018-09-21 Leave a comment

One to read: “A Beginner’s Guide to IPFS”

Ever wondered about IPFS (the “Inter Planetary File System”) – a new way to share and store content. This doesn’t rely on a central server (e.g. Facebook, Google, Digital Ocean, or your home NAS) but instead uses a system like bittorrent combined with published records to keep the content in the system.

If your host goes down (where the original content is stored) it’s also cached on other nodes who have visited your site.

These caches are cleared over time, so are suitable for short outages, or you can have other nodes who “pin” your content (and this can be seen as a paid solution that can fund hosts).

IPFS is great at hosting static content, but how to deal with dynamic content? That’s where PubSub comes into play (which isn’t in this article). There’s a database service which sits on IPFS and uses PubSub to sync data content across the network, called Orbit-DB.

It’s looking interesting, especially in light of the announcement from CloudFlare about their introduction of an available IPFS gateway.

It’s looking good for IPFS!

This was automatically posted from my RSS Reader, and may be edited later to add commentary.

Setting UK keyboards in Vagrant Ubuntu Machines, using Ansible

2018-05-152018-05-23 JonTheNiceGuy Leave a comment

Wow, now there’s a specific post title…

I use Ansible… quite a bit :) and one of the things I do with Ansible is to have a standard build desktop that I can create using Vagrant. Recently I upgraded the base to Ubuntu 18.04, and it annoyed me that I still didn’t have a working keyboard combination, so I kept getting US keyboards. I spent 20 minutes sorting it out, and here’s how to do it.

- name: Set keyboard layout debconf: name: "keyboard-configuration" question: "keyboard-configuration/{{ item.key }}" value: "{{ item.value }}" vtype: "{{ item.type|default('string') }}" with_items: - { key: "altgr", value: "The default for the keyboard layout", vtype: "select" } - { key: "compose", value: "No compose key", vtype: "select" } - { key: "ctrl_alt_bksp", value: "false", type: "boolean" } - { key: "variant", value: "English (UK)", vtype: "select" } - { key: "layout", value: "English (UK)", vtype: "select" } - { key: "model", value: "Generic 105-key PC (intl.)", vtype: "select" }

I posted how I got to this point over at the Server Fault post that got me most of the way. https://serverfault.com/a/912342/14832

Ansible Behaviour Change

2018-04-062018-04-06 JonTheNiceGuy Leave a comment

For those of you who are working with #Ansible… Ansible 2.5 is out, and has an unusual documentation change around a key Ansible concept – `with_` loops Where you previously had:

with_dict: "{{ your_fact }}"
or
with_subelements: - "{{ your_fact }}" - some_subkey

This now should be written like this:

loop: "{{ lookup('dict', your_fact) }}"
and
loop: "{{ lookup('subelements', your_fact, 'some_subkey') }}"

Fear not, I hear you say, It’s fine, of course the documentation suggests that this is “how it’s always been”…… HA HA HA Nope. This behaviour is new as of 2.5, and needs ansible to be updated to the latest version. As far as I can tell, there’s no way to indicate to Ansible “Oh, BTW, this needs to be running on 2.5 or later”… so I wrote a role that does that for you.

ansible-galaxy install JonTheNiceGuy.version-check

You’re welcome :)

More useful URLs:

Creating OpenStack “Allowed Address Pairs” for Clusters with Ansible

2018-04-052018-04-05 JonTheNiceGuy Leave a comment

This post came about after a couple of hours of iterations, so I can’t necessarily quote all the sources I worked from, but I’ll do my best!

In OpenStack (particularly in the “Kilo” release I’m working with), if you have a networking device that will pass traffic on behalf of something else (e.g. Firewall, IDS, Router, Transparent Proxy) you need to tell the virtual NIC that the interface is allowed to pass traffic for other IP addresses, as OpenStack applies by default a “Same Origin” firewall rule to the interface. Defining this in OpenStack is more complex than it could be, because for some reason, you can’t define 0.0.0.0/0 as this allowed address pair, so instead you have to define 0.0.0.0/1 and 128.0.0.0/1.

Here’s how you define those allowed address pairs (note, this assumes you’ve got some scaffolding in place to define things like “network_appliance”):

allowed_address_pairs: "{% if (item.0.network_appliance|default('false')|lower() == 'true') or (item.1.network_appliance|default('false')|lower() == 'true') %}[{'ip_address': '0.0.0.0/1'}, {'ip_address': '128.0.0.0/1'}]{% else %}{{ item.0.allowed_address_pairs|default(omit) }}{% endif %}"

OK, so we’ve defined the allowed address pairs! We can pass traffic across our firewall. But (and there’s always a but), the product I’m working with at the moment has a floating MAC address in a cluster, when you define an HA pair. They have a standard schedule for how each port’s floating MAC is assigned… so here’s what I’ve ended up with (and yes, I know it’s a mess!)

allowed_address_pairs: "{% if (item.0.network_appliance|default('false')|lower() == 'true') or (item.1.network_appliance|default('false')|lower() == 'true') %}[{'ip_address': '0.0.0.0/1'},{'ip_address': '128.0.0.0/1'}{% if item.0.ha is defined and item.0.ha != '' %}{% for vdom in range(0,40, 10) %},{'ip_address': '0.0.0.0/1','mac_address': '{{ item.0.floating_mac_prefix|default(item.0.image.floating_mac_prefix|default(floating_mac_prefix)) }}:{% if item.0.ha.group_id|default(0) < 16 %}0{% endif %}{{ '%0x' | format(item.0.ha.group_id|default(0)|int) }}:{% if vdom+(item.1.interface|default('1')|replace('port', '')|int)-1 < 16 %}0{% endif %}{{ '%0x' | format(vdom+(item.1.interface|default('1')|replace('port', '')|int)-1) }}'}, {'ip_address': '128.0.0.0/1','mac_address': '{{ item.0.floating_mac_prefix|default(item.0.image.floating_mac_prefix|default(floating_mac_prefix)) }}:{% if item.0.ha.group_id|default(0) < 16 %}0{% endif %}{{ '%0x' | format(item.0.ha.group_id|default(0)|int) }}:{% if vdom+(item.1.interface|default('0')|replace('port', '')|int)-1 < 16 %}0{% endif %}{{ '%0x' | format(vdom+(item.1.interface|default('1')|replace('port', '')|int)-1) }}'}{% endfor %}{% endif %}]{% else %}{{ item.0.allowed_address_pairs|default(omit) }}{% endif %}"

Let's break this down a bit. The vendor says that each port gets a standard prefix, (e.g. DE:CA:FB:AD) then the penultimate octet is the "Cluster ID" number in hex, and then the last octet is the sum of the port number (zero-indexed) added to a VDOM number, which increments in 10's. We're only allowed to assign 10 "allowed address pairs" to an interface, so I've got the two originals (which are assigned to "whatever" the defined mac address is of the interface), and four passes around. Other vendors (e.g. this one) do things differently, so I'll probably need to revisit this once I know how the next one (and the next one... etc.) works!

So, we have here a few parts to make that happen.

The penultimate octet, which is the group ID in hex needs to be two hex digits long, and without adding more python modules to our default machines, we can't use a "pad" filter (to add 0's to the beginning of the mac octets), so we do that by hand:

{% if item.0.ha.group_id|default(0) < 16 %}0{% endif %}

And here's how to convert the group ID into a hex number:

{{ '%0x' | format(item.0.ha.group_id|default(0)|int) }}

Then the next octet is the sum of the VDOM and PortID. First we need to loop around the VDOMs. We don't always know whether we're going to be adding VDOMs until after deployment has started, so here we will assume we've got 3 VDOMs (plus VDOM "0" for management) as it doesn't really matter if we don't end up using them. We create the vdom variable like this:

{% for vdom in range(0, 40, 10) %} STUFF {% endfor %}

We need to put the actual port ID in there too. As we're using a with_subelement loop we can't create an increment, but what we can do is ensure we're recording the interface number. This only works here because the vendor has a sequential port number (port1, port2, etc). We'll need to experiment further with other vendors! So, here's how we're doing this. We already know how to create a hex number, but we do need to use some other Jinja2 filters here:

{{ '%0x' | format(vdom+(item.1.interface|default('1')|replace('port', '')|int)-1) }}

Let's pull this apart a bit further. item.1.interface is the name of the interface, and if it doesn't exist (using the |default('1') part) we replace it with the string "1". So, let's replace that variable with a "normal" value.

{{ '%0x' | format(vdom+("port1"|replace('port', '')|int)-1) }}

Next, we need to remove the word "port" from the string "port1" to make it just "1", so we use the replace filter to strip part of that value out. Let's do that:

{{ '%0x' | format(vdom+("1"|int)-1) }}

After that, we need to turn the string "1" into the literal number 1:

{{ '%0x' | format(vdom+1-1) }}

We loop through vdom several times, but let's pick one instance of that at random - 30 (the fourth iteration of the vdom for-loop):

{{ '%0x' | format(30+1-1) }}

And then we resolve the maths:

{{ '%0x' | format(30) }}

And then the |format(30) turns the '%0x' into the value "1e"

Assuming the vendor prefix is, as I mentioned, 'de:ca:fb:ad:' and the cluster ID is 0, this gives us the following resulting allowed address pairs:

[ {"ip_address": "0.0.0.0/1"}, {"ip_address": "128.0.0.0/1"}, {"ip_address": "0.0.0.0/1", "mac_address": "de:ca:fb:ad:00:00"}, {"ip_address": "128.0.0.0/1", "mac_address": "de:ca:fb:ad:00:00"}, {"ip_address": "0.0.0.0/1", "mac_address": "de:ca:fb:ad:00:0a"}, {"ip_address": "128.0.0.0/1", "mac_address": "de:ca:fb:ad:00:0a"}, {"ip_address": "0.0.0.0/1", "mac_address": "de:ca:fb:ad:00:14"}, {"ip_address": "128.0.0.0/1", "mac_address": "de:ca:fb:ad:00:14"}, {"ip_address": "0.0.0.0/1", "mac_address": "de:ca:fb:ad:00:1e"}, {"ip_address": "128.0.0.0/1", "mac_address": "de:ca:fb:ad:00:1e"} ]

I hope this has helped you!

Sources of information:

Defining Networks with Ansible

2018-03-212018-03-21 JonTheNiceGuy Leave a comment

In my day job, I’m using Ansible to provision networks in OpenStack. One of the complaints I’ve had about the way I now define them is that the person implementing the network has to spell out all the network elements – the subnet size, DHCP pool, the addresses of the firewalls and names of those items. This works for a manual implementation process, but is seriously broken when you try to hand that over to someone else to implement. Most people just want something which says “Here is the network I want to implement – 192.0.2.0/24″… and let the system make it for you.

So, I wrote some code to make that happen. It’s not perfect, and it’s not what’s in production (we have lots more things I need to add for that!) but it should do OK with an IPv4 network.

Hope this makes sense!

--- - hosts: localhost vars: - networks: # Defined as a subnet with specific router and firewall addressing external: subnet: "192.0.2.0/24" firewall: "192.0.2.1" router: "192.0.2.254" # Defined as an IP address and CIDR prefix, rather than a proper network address and CIDR prefix internal_1: subnet: "198.51.100.64/24" # A valid smaller network and CIDR prefix internal_2: subnet: "203.0.113.0/27" # A tiny CIDR network internal_3: subnet: "203.0.113.64/30" # These two CIDR networks are unusable for this environment internal_4: subnet: "203.0.113.128/31" internal_5: subnet: "203.0.113.192/32" # A massive CIDR network internal_6: subnet: "10.0.0.0/8" tasks: # Based on https://stackoverflow.com/a/47631963/5738 with serious help from mgedmin and apollo13 via #ansible on Freenode - name: Add router and firewall addressing for CIDR prefixes < 30 set_fact: networks: > {{ networks | default({}) | combine( {item.key: { 'subnet': item.value.subnet | ipv4('network'), 'router': item.value.router | default((( item.value.subnet | ipv4('network') | ipv4('int') ) + 1) | ipv4), 'firewall': item.value.firewall | default((( item.value.subnet | ipv4('broadcast') | ipv4('int') ) - 1) | ipv4), 'dhcp_start': item.value.dhcp_start | default((( item.value.subnet | ipv4('network') | ipv4('int') ) + 2) | ipv4), 'dhcp_end': item.value.dhcp_end | default((( item.value.subnet | ipv4('broadcast') | ipv4('int') ) - 2) | ipv4) } }) }} with_dict: "{{ networks }}" when: item.value.subnet | ipv4('prefix') < 30 - name: Add router and firewall addressing for CIDR prefixes = 30 set_fact: networks: > {{ networks | default({}) | combine( {item.key: { 'subnet': item.value.subnet | ipv4('network'), 'router': item.value.router | default((( item.value.subnet | ipv4('network') | ipv4('int') ) + 1) | ipv4), 'firewall': item.value.firewall | default((( item.value.subnet | ipv4('broadcast') | ipv4('int') ) - 1) | ipv4) } }) }} with_dict: "{{ networks }}" when: item.value.subnet | ipv4('prefix') == 30 - debug: var: networks

Using inspec to test your ansible

2018-02-122018-02-12 JonTheNiceGuy Leave a comment

Over the past few days I’ve been binge listening to the Arrested Devops podcast. In one of the recent episodes (“Career Change Into DevOps With Michael Hedgpeth, Annie Hedgpeth, And Megan Bohl (ADO102)“) one of the interviewees mentions that she got started in DevOps by using Inspec.

Essentially, inspec is a way of explaining “this is what my server must look like”, so you can then test these statements against a built machine… effectively letting you unit test your provisioning scripts.

I’ve already built a fair bit of my current personal project using Ansible, so I wasn’t exactly keen to re-write everything from scratch, but it did make me think that maybe I should have a common set of tests to see how close my server was to the hardening “Benchmark” guides from CIS… and that’s pretty easy to script in inspec, particularly as the tests in those documents list the “how to test” and “how to remediate” commands to execute.

These are in the process of being drawn up (so far, all I have is an inspec test saying “confirm you’re running on Ubuntu 16.04″… not very complex!!) but, from the looks of things, the following playbook would work relatively well!

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