Dynamic AWS provider in terraform

Recently I needed to create a backup vault resource in Cape Town region, but only if the region is enabled in the AWS account. Straight approach:

provider "aws" {
   region = "af-south-1"
   alias  = "af-south-1"
}

resource "aws_backup_vault" "af_south_1" {
   provider = aws.af-south-1
   name     = "default"
}

would throw exception if af-south-1 region is not enabled for the account. Terraform has the ability to create a resource only if certain condition is met (via count = meta property), but it cannot conditionally declare providers.

But we can conditionally redirect the provider. Continue reading →

Nested Loops in Terraform: Create a map from 2 lists

Recently I encountered a Terraform task in which I had a list of roles and a list of policies and I needed to create a AWS resource for every combination of role-policy. In a “regular” programming language this would be a simple nested loop. Thankfully Terraform 0.12 added for_each and for attributes to declare recurring resources. But two problems remained:

1. I needed some kind of way to nest these for declarations
2. for_each attributes requires a map with a unique key

So let’s tackle these problems one at a time. Let’s we have 2 lists:

locals {
   ROLES = ["developer", "analyst", "manager"]
   POLICIES = ["arn:1", "arn:2", "arn:3"]
}

Continue reading →

Export Dynamic LINQ to CSV

LINQ allows to perform various queries against different data structures. Wouldn’t it be great if you could easily export result of a LINQ query to CSV? Fortunately you can! This article by Scott Hanselman explain how and culminates in cool in its simplicity code:

namespace FooFoo
{
    public static class LinqToCSV
    {
        public static string ToCsv<T>(this IEnumerable<T> items)
            where T : class
        {
            var csvBuilder = new StringBuilder();
            var properties = typeof(T).GetProperties();
            foreach (T item in items)
            {
                string line = string.Join(",",properties
                      .Select(p => p.GetValue(item, null)
                      .ToCsvValue()).ToArray());
                csvBuilder.AppendLine(line);
            }
            return csvBuilder.ToString();
        }
  
        private static string ToCsvValue<T>(this T item)
        {
            if(item == null) return "\"\"";
  
            if (item is string)
            {
                return string.Format("\"{0}\"", item
                      .ToString().Replace("\"", "\\\""));
            }
            double dummy;
            if (double.TryParse(item.ToString(), out dummy))
            {
                return string.Format("{0}", item);
            }
            return string.Format("\"{0}\"", item);
        }
    }
}

This code adds .ToCsv() extension method to any IEnumerable so you can run something like

string csv = linqQuery.ToCSV()

Unfortunately this doesn’t work if your query is Dynamic LINQ query Continue reading →

Dynamic LINQ to XML

Language Integrated Query (LINQ) is a cool feature of .NET languages like C# that allows you to perform SQL-like query right within the language against language’s data structures (lists, arrays etc.) But one drawback of LINQ – you have to know in advance, at compile time which fields to select, what filter conditions would be. Sometimes there’s a need to supply these at runtime – e.g. user selects which fields they want to see

Thankfully there exists Dynamic LINQ Library that allows you to supply LINQ parameters as a string akin Dynamic SQL. Here’s an example of such query from the library’s homepage:

var query = db.Customers
    .Where("City == @0 and Orders.Count >= @1", "London", 10)
    .OrderBy("CompanyName")
    .Select("new(CompanyName as Name, Phone)");

Now, one thing that LINQ can do is query XML. So in theory if we load, say, this XML:

<DATA_CENTER>
   <SERVER IP="1.2.3.4">
      <OS>Windows</OS>
   </SERVER>
   <SERVER IP="5.6.7.8">
      <OS>Linux</OS>
   </SERVER>
</DATA_CENTER>

into an XElement and run something like this

var query0 = myXElement.Elements()
          .AsQueryable()
          .Select("new (Attribute(\"IP\").Value as IP, Element(\"OS\").Value as OS)")

it would produce list of IPs and OSes. Unfortunately this doesn’t work. Continue reading →

Keep animated images after uploading to WordPress

Haven’t written in a while. Not that nothing interesting happened, but never got around to. But I finally moved my blogs to AWS Lightsail (very smooth process, by the way) and experienced only one hurdle I wanted to write about (surprisingly, not related to AWS).

After the migration, I noticed that all images on my site lost their animation. When I inspected an image – I found that it’s source goes thru some kind of a proxy “i1.wp.com”. After digging a bit I found that it is used by JetPack site acceleration service – it caches images to serve them faster. Unfortunately cached copies seem to lose some of their properties (like animation).

To fix it – go to JetPack settings and turn “Speed up image load times” off

Happy blogging!

Copy/Paste image into an editable DOM element in Chrome

All major browsers allow to paste image directly into a DOM element with contentEditable property set to true. They automatically convert it into IMG element with source pointing to base64 encoded DataURI of the pasted image. That is all browsers, but Chrome. Chrome needs a little help.

In my particular case I need to be able to paste image into an IFRAME with editable body of the content document (for some reason Infragistics WebHtmlEditor ASP.NET control renders itself as this contraption). But the code below applies (with small changes) to any editable DOM element.

To achieve the result we need to perform 3 tasks:

1. Capture image from the clipboard
2. Convert the image to DataURI format
3. Create IMG element with the DataURI source and insert it into the DOM

Take a look at the code below: Continue reading →

Fling a random insult at Trump after every tweet

Ok time to get political. I hate many things that Trump tweets these days and would love to reply to each tweet personally, but have neither time not desire to read his delusions. Fortunately in these modern times robots take many of our jobs. And this looked like a perfect job for a bot. Similarly to the bot described in the previous post it will be IFTTT + Scriptr combo. But this time in reverse, here’s intended flow:

  1. Twitter service at IFTTT detects when @realDonaldTrump tweets
  2. It triggers Maker service that makes HTTP request to Scriptr code
  3. Scriptr code generates random insult and posts a reply to Trump’s tweet

Here’s what IFTTT applet looks like: Continue reading →

Tweet images with Scriptr and IFTTT

Sev Trek

Looks like everybody is doing Twitter bots these days so I decided to try my hand on one as well. And it had to be something lighthearted – to let people’s mind off things for a while. Way back in early 2000s there was a funny parody comic of Star Trek called Sev Trek. Original site is gone now, but archive of images was saved at http://sevspace.com/stupidarchive/sevtrek.asp.htm. Images are numbered sequentially – ideal for automatic processing. My bot would tweet random images every couple hours.

To host bot’s script I decided to go with Scriptr which offers powerful JavaScript backend and multiple expansion modules. And IFTTT has a cool Twitter service, one that can tweet image from an URL. So the idea was:

  1. Code hosted at Scriptr generates URL pointing to an image at sevspace.com
  2. Code then call Maker service of IFTTT – custom service capable of accepting HTTP requests
  3. Maker service triggers Twitter service and passes URL of image it got from Scriptr code
  4. IFTTT Twitter service tweets the image

Continue reading →