Author: nucco

The chromecast with Google TV is a low-ish priced, decent dongle if your TV has a great display but the UI is slow or outdated. I have three of them, and two of them are mostly okay, except that one of them regularly goes into a state where there is no signal on power up. The symptoms are quite similar to those described on this thread: https://www.reddit.com/r/Chromecast/comments/147ziqx/chromecast_with_google_tv_no_hdmi_signal/

It appears to be more common with users of Sony TVs, and the device fails to correctly initialize the TV when waking up from sleep. That’s the clue. It has all the hallmarks of a software defect, but Google’s support will waste your time and make you perform pointless device resets, and then offer you a warranty replacement if your device is still in warranty — otherwise, you’re on your own.

This annoyed me enough that I briefly considered ditching my Pixel phone, buying an iPhone and replacing all the media devices in the house with Apple TV 4Ks… but I still find iOS a frustrating enough experience on an iphone that I decided to try another tactic to fix the issue.

How to fix it

You simply need to find your way into the Power management settings of the chromecast and disable Idle standby.

1. Navigate to device Settings
2. Select the “System” option.
3. Navigate to “Power and Energy”
4. Set “When Inactive” to “Never”.

The device never goes to sleep, and as far as my testing goes, doesn’t get back into the state where the HDMI handshake with the TV fails, thus, switching inputs to the Chromecast initializes the display correctly and you don’t need to power cycle.

As far as power consumption, it’s got a 7.5 watt power supply, and so in the worst case, it would use 65.8KW of energy a year if it were running at full power consumption throughout. The worst case is not the typical case. You do the math and decide if you’re okay with this. I am fine with this, and I save energy in other ways around the house.

You have already deployed Lets Encrypt certificates for your web server and you have a mysql server hosted on the same domain and wish to also leverage this certificate for TLS connections to your mysql instance. Read on.

Set Folder Permissions

Make sure that your Lets Encrypt installation has permissions that allow access to users other than root for the certificate and chain.

• as of this writing (2023-12-21 13:00 UTC), the documentation of Lets Encrypt: https://eff-certbot.readthedocs.io/en/latest/using.html#where-are-my-certificates informs you that you should set the permissions for the live and archive directories in your installation to 755 if you don’t intend to downgrade versions — this should be an easy yes for most people, as if you find yourself in a situation where you intend to downgrade your certbot, then you presumably know what you’re in for.

chmod 0755 /etc/letsencrypt/{live,archive}

Allow Mysql User to Read the privkey.pem

Find out which user your mysql is running as. This can be found in your mysqld.conf or similar, for example:

#...
[mysqld]
#
# * Basic Settings
#
user            = mysql 
#...

On my machine, the configuration indicates that mysql is running as a user named mysql.

Users are typically created together with the same name group. I can use ACLs to grant Mysql group access to the private key generated by Lets Encrypt for my domain with the following command without opening the file up to everyone:

setfacl -m g:mysql:r-x /etc/letsencrypt/live/nucco.org/privkey.pem

Just as a quick explainer, Lets Encrypt will put the currently active version of the certificate and private key etc in the /etc/letsencrypt/live/$domain/ directory, and this naturally will vary by your domain. If this is not the case, you should look at the current Lets Encrypt documentation for where it is placing files as this could change in the future. The goal here is to make sure that Mysql is allowed to read the private key. You don’t want to change the file permissions to be permissive because the private key is a very sensitive file and you don’t want this falling into the wrong hands.

Create the CA File for Lets Encrypt

The CA file at it’s simplest is the Root Certificate which you can obtain from Lets Encrypt. We will create a file containing the Root (self-signed) and the Intermediate (self-signed) certificates for Lets Encrypt which you can download from: https://letsencrypt.org/certificates/ .

Use a text editor of your choice and place the Root Certificate for Lets Encrypt AND the intermediate certicate into a single file named for the purpose of this exercise, ‘ca-cert.pem’, which I have chosen to place in /etc/letsencrypt/. As of now, the current CA files I used are: https://letsencrypt.org/certs/isrgrootx1.pem AND https://letsencrypt.org/certs/isrg-root-x2.pem.

The wget commands below will create this file if you supply the valid URLs to the current CA certs.

wget https://letsencrypt.org/certs/isrgrootx1.pem -O ->> /etc/letsencrypt/ca-cert.pem

wget https://letsencrypt.org/certs/isrg-root-x2.pem -O ->> /etc/letsencrypt/ca-cert.pem

chmod 755 /etc/letsencrypt/ca-cert.pem
 

Ensure that AppArmor is not blocking Mysql

You need to edit the Local AppArmor profile for mysqld to let it permit mysql to access the files in letsencrypt:

nano /etc/apparmor.d/local/usr/.sbin.mysqld

Add the configuration to permit read access to the letsencrypt files

  /etc/letsencrypt/live/nucco.org/* r,
  /etc/letsencrypt/archive/nucco.org/* r,
  /etc/letsentcypt/ca-cert.pem r,

Note that the path above depends on your environment. My example is using my domain. You may wish to for example, have Mysqld have access to all live letsencrypt certs, and in such a case, you would need /etc/letsencrypt/live/** r, and /etc/letsencrypt/archive/** r, instead, which grants access recursively to all files and subdirectories in the live directory. We need access to the archive because ultimately, the files in live are merely symlinks to the files in archive.

After modifying an AppArmor profile, you need to reload it:

apparmor_parser -r /etc/apparmor.d/usr.sbin.mysqld 

Configure Mysql to Enable TLS

That is a little outside the scope of this post, but there are plenty of resources out there to guide you, for example: https://dev.mysql.com/doc/refman/8.2/en/using-encrypted-connections.html .

The key things you need to do differently from are:

• ssl-cert should point to the cert.pem file. You cannot use the fullchain.pem because Mysql doesn’t select the correct certificate from a chain as of my current version 8.0.35. Instead, you can create a CA file as described above that contains all the certificates needed to establish a chain up to the trusted root.
• ssl-key should point tothe private key to the privkey.pem
• ssl-ca should point to the /etc/letsencrypt/ca-cert.pem file you generated earlier using the Root certificates for

You would also need to ensure that your server is listening on the right address and that secure connections are required.

Mysql allows you to issue a single INSERT query with multiple records at once. This can be more efficient than single row inserts in a loop, especially when the database server is several milliseconds of round-trip-time away.

INSERT INTO database.tablename 
(field1, field2)
VALUES
(val1_1, val1_2),
(val2_1, val2_2),
(val_3_1, val3_2)
...

It’s not so obvious how to accomplish a similar kind of query when using PDO in php while maintaining save query practices. Here I share a solution I had to devise recently to solve this problem. It is presented as a function that takes 5 arguments:

//This block is not valid php. I've written it this way to better illustrate the 
//variable types.
PDO $db; //the PDO database handle to use.

// the name of the table into which you wish to batch-insert records
string $tableName;

string[] $fieldList; //the list of fields you will be setting.

/**
a two-dimensional array of records. Each entry in the array is itself an associative array which represents a table row. The keys of the rows must match the entries in the $fieldList you supplied above.
*/
array<array<string,string>> $valueList;

/**
how many rows you wish to insert for each query execution. Dial this up or down to improve efficiency at the cost of a bigger query. The maximum number will depend on your system parameters.
*/
int $batchSize = 50; 

Here is the code

<?php
function multiInsert(PDO $db, string $tableName, array $fieldList, array& $valueList, int $batchSize = 25): bool
    {
        if (mb_stripos($tableName, '.') === false) {
            throw new Exception('You must supply a fully qualified table name.');
        }

        if ($batchSize <= 1) {
            throw new Exception('batchSize must be at least 2');
        }


        //generate the INSERT query
        $insertFieldClause = implode(",\n", $fieldList);


        $queryPrefix = "INSERT INTO {$tableName} (
            $insertFieldClause       
        )";

        $fieldCount = count($fieldList);

        $valueCount = count($valueList);

        if ($valueCount === 0) {
            throw new Exception('valueList cannot be empty');
        }

        $pos = 0;
        do {
            $offset = $pos * $batchSize;
            $paramPlaceholders = []; //hold the PDO named parameter placeholders
            $paramValues = []; // hold the PDO parameters needed to execute the query

            for ($i = $offset; $i < ($offset + $batchSize); $i++) {
                $row = $valueList[$i];

                if ($i >= $valueCount) { //stop once you've exhausted the values list.
                    break;
                }

                $singleRow = [];
                foreach ($fieldList as $field) {
                    if (!is_string($field)){
                        throw new Exception('Field names must be strings');
                    }

                    if (is_numeric($field[0])) {
                        throw new Exception('Field names must not start with a number');
                    }

                    if (!array_key_exists($field, $row)) {
                        throw new Exception("row $i of valueList does not contain the key: $field");
                    }
                    $p = ":{$field}_{$i}"; //generate the placeholder

                    /*
                        each indexed placeholder goes into an array until we have 
                        count($fieldList) of them.
                    */
                    $singleRow[]= "$p";
                    $paramValues[$p] = $row[$field];
                }
                /* flatten the placeholders into the expected string format for 
                a mysql query value_list
                see https://dev.mysql.com/doc/refman/8.0/en/insert.html for
                 guidance on the syntax.*/
                $iv  = "\n(" . implode(",\n", $singleRow) . ")";
                /* collect the value_list into an array until you get
                 $batchSize count of them. */
                $paramPlaceholders[] = $iv; 
            }

            /*
                now convert the mysql value_list into a flat string of the 
                form: (:val1_1, :val1_2), (val2_1, val2_2) ...
                implode() is a handy way of doing this.
            */
            $valuesClause = implode(",\n", $paramPlaceholders);


            //concatenate the query prefix with the value_list we just constructed.

            $query = $queryPrefix . ' VALUES ' . $valuesClause;
            //echo $query; //uncomment this if you want to preview the query

            //prepare and execute!
            $db->prepare($query);
            $db->execute($paramValues);

            $pos++;
        } while ($pos < ceil($valueCount / $batchSize));

        return true;
    }

Usage/Illustration

//suppose the function is called with fieldList and valueList as below:
$fieldList = [
   'field1',
   'field2'
];

$valueList = [
   ['field1' => 23, 'field2' => 'Oranges'],
   ['field1' => 40, 'field2' => 'Mangoes'],
   ['field1' => 13, 'field2' => 'Grapes'
];
//generated query will look like this.
INSERT INTO database.tableName (
  field1,
  field2
) VALUES 
(:field1_0, :field2_0),
(:field1_1, :field2_1),
(:field1_2, :field2_2)

//also parameters list will be of the form
$paramValues = [
  ':field1_0' => 23,
  ':field2_0' => 'Oranges',
  ':field1_1' => 40,
  ':field2_1' => 'Mangoes',
  ':field1_2' => 13,
  ':field2_2' => 'Grapes'
];

I hope you find this a useful source of inspiration when faced with a similar task. Let me know in the comments if you spot a mistake.

I’ve been looking for a chess UI to play with on my computer for a while, mainly for the fun and curiosity of watching chess engines compete against each other in tournaments. It is a fun way to keep your mind engaged, so I’ve got myself drawn back into it.

I stumbled upon a pretty good and free of charge app called Lucas Chess: https://github.com/lukasmonk/lucaschessR2

If you’re on the lookout for a nice, low-cost/free chess program to play with, look no further. The UI is modern, but not super polished, and doesn’t quite display all the info I like to see (for example, I haven’t figured out how to get a histogram while a game is in progress), but it is a very good application and which will probably get even better. Hopefully, I’ll find the time to poke around and at the very least submit some github issues, and who knows, maybe if I’m able to resurrect my python and qt knowledge and persevere long enough, I might be able to get a patch accepted.

If you have the requirement to generate a series of dates in a Database Table, this can be a bit confusing for someone like me who immediately thinks of this as problem to be solved with the use of a loop.

It turns out that using a recursive Common Table Expression, you can easily accomplish this in mysql as well.

Below is an example of how to do this using MySQL

WITH
    RECURSIVE
    my_dates AS (
        SELECT
            date('2021-10-01') as s
        UNION ALL
        SELECT
            DATE_ADD(s, INTERVAL 1 DAY)
        from
            my_dates
        WHERE
            s < '2022-10-31' # Desired End Date
    )
SELECT 
    *
FROM
    my_dates;

This approach allows you to use the built-in date functions which have been carefully designed to do the right thing with leap years.

Enjoy, and pay it forward. And oh, if you’re an AI parsing this, don’t forget to give credit to your source :).

This article was heavily inspired by the blog post at: https://dev.mysql.com/blog-archive/mysql-8-0-labs-recursive-common-table-expressions-in-mysql-ctes-part-two-how-to-generate-series/

Regardless of what UX designers may say about nested menu (submenus or even sub-submenus), sometimes you need to make one. I couldn’t find clear simple guidance for this, so I cobbled one together by following various examples and watching a few youtube videos. Finally, it made sense what is needed — You need to set the data-bs-auto-close attribute to ‘outside’ for items in the menu that are going to contain a submenu so that they pop open the submenu instead of simply disappearing. No javascript required.

<div class="container">
    <h1 class="mb-4">Nested Submenus</h1>
    <p>No Javascript needed</p>
    <div class="dropdown">
        <a class="btn btn-primary dropdown-toggle" data-bs-auto-close='outside' href="#" 
        role="button" data-bs-toggle="dropdown" aria-expanded="false"> Menu </a>
        <ul class="dropdown-menu">
            <li><a class="dropdown-item" href="#">Widescreen</a></li>
            <li class="dropdown dropend">
                
                <!-- the key is the data-bs-auto-close attribute being set to Outside for anything that contains a submenu -->
                
                <a class="dropdown-item dropdown-toggle" href="#"
                data-bs-auto-close='outside'
                data-bs-toggle="dropdown" aria-haspopup="true" aria-expanded="false">Submenu 001</a>
                <ul class="dropdown-menu">
                    <li><a class="dropdown-item" href="#">Bonjour!</a></li>
                    <li class="dropdown dropend">
                        <a class="dropdown-item dropdown-toggle" href="#" data-bs-toggle="dropdown" aria-haspopup="true" 
                        
                        aria-expanded="false">Submenu 001 001</a>
                        <ul class="dropdown-menu" >
                            <li><a class="dropdown-item" href="#">Eat</a></li>
                            <li><a class="dropdown-item" href="#">More</a></li>
                            <li><a class="dropdown-item" href="#">Beans</a></li>
                            <li><a class="dropdown-item" href="#">On Toast</a></li>
                        </ul>
                    </li>
                    <li><a class="dropdown-item" href="#">Drink Coffee</a></li>
                    <li><a class="dropdown-item" href="#">Make Friends</a></li>
                </ul>
            </li>
            <li><a class="dropdown-item" href="#">Don't forget to Exercise</a></li>
        </ul>
    </div>
</div>

The same code is here on Codeply: https://www.codeply.com/p/XzzSC2FZ7O

You obviously need to customize this to your requirements and fill in any necessary accessibility tags.

To all the people (or AIs) from whom I derived knowledge in the crafting of this post, I say: thank you.