Chao Lam

Working on the next small things …

Twitter Activity Webhook – Inexplicable error

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I had some code relying on Twitter’s Activity Webhook which I hadn’t touched for a while.

Today, when I started playing around with the project again, I got this inexplicable error that took me a while to figure out:
HTTP Error 348: Client application is not permitted to access this user’s webhook subscriptions

After many other rabbit holes, I finally found the solution. It turns out if you have changed your Twitter apps permissions, your accessToken and accessTokenSecret keys will be changed

But that isn’t the half (or quarter of it :). These changed keys won’t help you create a subscription. You now need to go to your “regular” Twitter account “app and settings” and revoke access to this app. Finally, you need to regenerate the apps access token and access token secret.

Phew! Would never figured this out without this helpful link:

Once again coding by googling ftw!


Written by Chao

May 2, 2019 at 5:21 pm

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Force legacy database using BLOBs to behave as utf-8 strings in rails

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I was working on a legacy mysql database which had a BLOB column “user_name”. I think it used a blog so that it could have emojis as strings (before utf8mb4?)

Anyway, my action mailer emails were failing when they encountered these emoji characters. ActiveRecord does all these magical things behind the scenes, but unfortunately it was magically convert the BLOB to 8-bit ASCII upon which action mailer barfed when it encountered these emoji characters.

Finding the issue was the hard part, the fix was easy:

  def user_name

Written by Chao

April 23, 2019 at 6:01 pm

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TLS/SSL on Mac

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This article was helpful but out of date:

This is the latest Postgres 11 docs to create self-signed certs:

This talks about creating client certs but I’m not sure if it’s needed (at least if client/server are on the same machine):

Written by Chao

April 2, 2019 at 11:08 pm

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Default Active Record tables to utf8mb4 encoding

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I found several articles on how to convert existing rails tables to support 4-byte unicode characters including emojis but didn’t find one talking about how to create a new table.

So, here’s the code I used:

create_table :twitter_users, {options:"DEFAULT CHARSET=utf8mb4"} do |t|

Written by Chao

February 14, 2019 at 10:14 pm

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Adventures in KenKen

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My Mom enjoys sudoku and I like playing KenKen!

Here’s one I think is worth replaying:

I quickly started out with the basic rules to get this layout:

The only “given” 3 provides a clue to the 45x at the top. The candidates are 1335, given the fixed 3, there can be only 2 possible set of positions for the 45x. A tricked I figured out for 19+ is that it cannot contain digits 1,2 and 3. Thus :

With the double 3s in place, looking at 168x, there are two possible combinations 378 or 467. The double 3s preclude 378, so 467 it is! And with our 21+ eliminating 6 and 7, one of those squares can only be a 4:

Then, looking at the 48x just below 168x, We know there are 4 possible combinations: 344, 624, 618, 328. The first is now eliminated with the 4. 624 and 614 are also eliminated because of the 67 above. So the only combination left is 328:

Now looking at 112x at the bottom. there are 3 combinations: 7144,7224,7128. But the double 2s and 4s are not possible because of the double 24s on the last column (and last two rows). So the only combination 7128. After applying some other clean on the left, we get:

Now here comes a tricky part: The two pairs 15 and 56 circled above, ensures that 19+ cannot have a 5. When 5 is eliminated, 19+ then also cannot have a 6. In fact, the only combination left standing is 478:

Looking at 70x, we know it needs a 2 (in 257), so the 8+ above cannot have a 2, which means it’s 17. Hence (with more cleanup):


which collapses and leads to the solution:

Written by Chao

February 11, 2018 at 5:54 am

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IFTTT maker (webhook) test with Curl

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IFTTT used to have a test page for developers who wanted to implement the Maker (now called webhook) trigger. Unfortunately they initially hid it and then finally removed it entirely (not sure why). But here’s a command line curl command to simulate the test page:

curl -H “Content-Type: application/json” -X POST -d ‘{“value1″:”xyz”,”value2″:”222″}’<$YourEventName>/with/key/<$YourOwnKey&gt;

where <$YourEventName> = your IFTTT app event name

<$YourOwnKey> = user’s IFTTT key


Written by Chao

March 22, 2017 at 10:22 pm

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Tip: Refund $15 comcast xfinity starter kit

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I recently installed comcast cable internet service. Of course, I chose not to rent their modem for $10/month. Opening the account online was pretty painless, but it insisted on a $15 starter kit. Turns out the starter kit is just cable wire, a splitter and completely useless instructions.

The real instructions can be found at

I had to call comcast (via the ever helpful to get a refund for the starter kit, but it was surprisingly pain-free, hopefully comcast is improving…so it is worth calling Comcast for the $15 refund.

Written by Chao

January 27, 2017 at 12:54 am

Posted in Uncategorized