Author Archives: karl.kranich

CloudFormation-based S3 Bucket Policies with Conditional Statements and Principals

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I have a project where I needed to build an S3 bucket policy in a CFT, where certain statements should only be in the policy when a user ARN is provided. It’s hard to even Google for this use case, since bucket policies can contain “conditions”, but that’s different from conditionally including or excluding a policy statement.

The linked gists contain one extra feature – if a second user ARN is provided via a parameter, that user is added to one of the policy statements.

I’ve included json and yml versions. The yml is much easier to read, but my use case required json, so I’ve included both: https://gist.github.com/karlkranich/cd27f8bda64aa9e1cdab6cb52eaafcd8

Find Duplicates Across Sheets in Google Spreadsheets

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Someone reached out and asked if I could adapt my Find Duplicates Apps Script to identify duplicates across all of the sheets in a Google Spreadsheet. Because the requirement is to examine a single column across the sheets, I removed the creation of a temp sheet and used an object to track cell contents and location.

This example also contains logic to identify similar URLs by ignoring “https://”, “http://”, leading “www”, and trailing “/” and query parameters.

The code is here on github. You can add it to a Google Spreadsheet by choosing Tools – Script editor and pasting the code in code.gs. Edit the constants at the beginning that indicate which column to examine and how many header rows to ignore. Save and close the Script editor. Reload the spreadsheet, and it will ask for authorization. You will probably need to reload the spreadsheet one more time before you can run the script.

Here’s a brief video demonstration.

Solved: Build failure of Xylophone project in The Complete 2020 Flutter Developer Bootcamp

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I’m really enjoying The Complete 2020 Flutter Development Bootcamp with Dart on Udemy by Angela Yu and London App Brewery. I like how Angela has organized the progression of concepts and challenges. It’s also easy to skip lectures if you’re already an experienced programmer and don’t need to learn concepts like data types and function syntax.

My first big snag came when I added the audioplayers package to the Xylophone project. The run tab fills up with errors, ending with:

Could not build the application for the simulator.
Error launching application on iPhone 12 Pro Max.
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Serverless Podcast Feed Maintainer and Hosting on AWS

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I just finished building a serverless system on AWS that hosts a podcast’s media files and rss feed, and provides a web interface for managing the rss feed.

This is a cost-effective way to host a podcast, and a fun way to learn a bunch of AWS technologies.

Overview

Here are the elements of the system:

  • The media files and rss feed file are stored in an S3 bucket that is configured for static site hosting. The bucket also contains the html, css, and javascript for the feed maintainer app.
  • Podcast and episode info is stored in a DynamoDB table.
  • Lambda functions insert episode info into DynamoDB, create presigned URLs for uploading media files, and create the rss feed file whenever episode info is updated.
  • API Gateway allows the javascript to PUT episode info to a Lambda function.
  • CloudFront allows the static S3 site to be served via https, and redirects http requests to https (not pictured)
  • Route53 connects a custom domain name to S3 and CloudFront

Operation

  1. The system admin loads podcast info (title, author, etc) into an “Episode 0” item in the DynamoDB table.
  2. The podcast maintainer submits episode information via the html form.
  3. The podcast-poster Lambda function adds the episode info to the DynamoDB table and returns a presigned URL that allows uploading the media file to S3.
  4. The S3 upload triggers a Lambda function that updates the rss feed.

More Info…

If there’s interest, I’ll outline the steps for setting up the system. If you want to look at the html, javascript, and lambda functions, refer to these github repositories:

Installing boto3 for python3 in Cloud9

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I’m developing python code in a Cloud9 environment. Tried setting the default python version to 3, but “python” still runs python 2. It’s not a big deal to type “python3” each time, but “pip install boto3” only installed the module for python 2.

Finally, this adaptation of a command I found on stackoverflow worked:

python3 -m pip install --user boto3

Switch your Mac’s online call handler from Skype to Lync

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I had been using Skype for Business as the online call handler for my Mac, but had various problems in online meetings – sometimes not seeing screen shares, sometimes not seeing chat, sometimes others not seeing my screen share.

But when I tried to switch to Lync, it took a while to figure out how to make “Join online meeting” links work – they kept launching Skype. Turns out that it’s simple – go to Lync Preferences > General tab and change the drop-down settings in the Services section (you can click on the image to expand it).

Insert and Delete Cells Google Sheets Add-on is shut down

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If you’re still using my “Insert and Delete Cells” Add-on for Google Sheets, you’re now seeing: “401. That’s an error”, “Error: deleted_client”, and “The OAuth client was deleted”.

I shut down the “Insert and Delete Cells” Google Sheets Add-on yesterday because the functionality has been built into Google Sheets for a few years now.

You will find the Delete functions in the Edit menu and the Insert functions in the Insert menu.

Sorry for the abrupt shut-down of the Add-on.  I was trying to figure out a graceful way to remove the Add-on from the store, and instead made an irrevocable shut down choice.

I’m glad the Add-on was useful to people while it lasted!

Solved: Mac option key not working on Nixeus MODA Pro keyboard

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There are plenty of articles and Youtube videos showing how to switch the Option and Command keys when you adapt a PC keyboard for use on the Mac.  (System Prefs – Keyboard – Modifier Keys – Choose the correct keyboard, then switch Command and Option).

But even after doing that, the Options key wouldn’t work.  I finally noticed the “Win Lk” light at the top right.  Gaming keyboards let you turn off the Windows key in case you accidentally hit it during a game, and that’s the key that is now mapped to Option for my Mac.

Turning if off just requires holding Fn and pressing F8, which also has a “no Windows” symbol.

iPhone tip: disable the extra click needed to unlock your phone

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iphone-touchid-pexels-400In a recent iOS update, Apple started requiring an extra click of the home button to unlock your iPhone, instead of just allowing a “click with finger resting on Touch ID” to unlock the phone.  It’s not a big change, but just different enough to be frustrating.

To go back to the original behavior, go to Settings – General – Accessibility – Home Button and enable “Rest Finger to Open”.

How to move a Windows EC2 instance to another AWS account

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ec2-iconHere are the steps that I’ve used to move some Windows Server EC2 instances to a different AWS account.  This method should work for any OS, but I’ve only tested with Server 2008 R2.

The simple version:

  1. In the source account, stop the instance
  2. Make a snapshot of the instance’s system volume
  3. Share the snapshot with the destination account number
  4. In the destination account, make a volume from the snapshot
  5. Create an instance with the same OS as the source instance
  6. Detach and delete the new instance’s system volume
  7. Attach the volume from step 4
  8. Start the instance

The detailed version:

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