Category: Technology

Quick Python Bingo Caller

I keep re-writing the same quick script to implement a bingo “caller” so Anya and I can play a game … figured I’d save it somewhere and save a few minutes next time! We use more words than squares so not every word is on both boards, but you can shorten the list to 24 and just put the words in different squares on each board. 

import random
  
# initializing the word list -- 24 words for the 24 squares but we play with more words than squares!
wordList = ["Hypothesis", "Observation", "Theory", "Variable", "Cat"
, "Fun", "Science", "Happy", "Dog", "Thyme"
, "Rosemary", "Sage", "Time", "Run", "Pot"
, "TV", "Rogue", "Smile", "Black", "Rock"
, "Ash", "Kitten", "Love", "Bingo (but not BINGO like somebody won!)",
"Mom", "Dad", "Anya", "Wood", "Trail", "Tail", "Star"]

# shuffling word list
random.shuffle(wordList)

i = 0  
while i < len(wordList):
    print(wordList[i])
    i += 1
    x= input()

Windows Admin Center – Changing the Port

Where I work, the “OS Support” and “Application Support” functions are different verticals. Sometimes what constitutes an “OS” and what constitutes an “application” is nebulous. In this case, we needed to install a web-based application but found TCP port 443 was already bound to Windows. Unfortunately, the OS support group disclaims any ownership of “Windows Admin Center” and told me I was welcome to fix it myself. So … oddly, there isn’t any easily located configuration for this thing. You have to go through the add/remove programs and modify the installation of Windows Admin Center.

Select “Change”

You will get the configuration panel — here, you can specify a different port for the Admin Center.

Let the installer complete …

Voila — not using port 443!

Kafka – Messages Not Appearing in Topic

I created a few new Kafka topics for a project today — but, in testing, messages sent to the topic weren’t there. I normally echo some string into “kafka-console-producer.sh” to test messages. Evidently, STDERR wasn’t getting rendered back to my screen this way. I ran the producer script to get the “>” prompt and tried again — voila, a useful error:

[2022-10-31 15:36:23,471] ERROR Error when sending message to topic MyTopic with key: null, value: 4 bytes with error: (org.apache.kafka.clients.pro.internals.ErrorLoggingCallback)
org.apache.kafka.common.InvalidRecordException: Compacted topic cannot accept message without key in topic partition MyTopic-0.

Ohhh — that makes sense! They’ve got an existing process on a different Kafka server, and I just mirrored the configuration without researching what the configuration meant. They use “compact” as their cleanup policy — so messages don’t really age out of the topic. They age out when a newer message with that key gets posted. It’s a neat algorithm that I remember encountering when I first started reading the Kafka documentation … but it’s not something I had a reason to use. The other data we have transiting our Kafka cluster is time-series data where we want all of the info for trending. Having just the most recent, say, CPU utilization on my server isn’t terribly useful. But it makes sense — if I instruct the topic to clean up old data but retain the most recent message for each key … I need to be giving it a key!

Adding a parameter to parse the string into a key/value pair and provide the separator led to data being published to the clients:

echo “test:EchoTest” | /kafka/bin/kafka-console-producer.sh –bootstrap-server $(hostname):9092 –topic MyTopic –property “parse.key=true” –property “key.separator=:”

Unable to Use JMX Remotely for Kafka Stats

I noticed, today, that our Kafka Manager interface only shows details from one server — the one where we run Kafka Manager. We’ve done everything that we need to do in order to get this working — the port shows as open with nmap, the command to run Kafka includes all of the settings. I’ve even tried setting the JMX hostname, but still there is just one server reporting data

Then I happened across an article online that detailed how JMX actually uses three ports — the configured port 9999 and two other randomly selected and non-configurable ports. I used netstat to list all of the ports in use by the Java PID running my Kafka server and, voila, there were two odd-ball high ports (30000’s and 40000’s). I added those additional ports to the firewall rules and … I’ve got data for all of the Kafka servers!

This is obviously a short-term solution as the two randomly selected ports will be different when I restart the service next time. I’d prefer to leave the firewall in place (i.e. not just open all ports >1024 between the Kafka Manager host and all of the Kafka servers) so might put together a script to identify the “oddball” ports associated to the Java pid and add them to transient firewalld rules. But the last server restart was back in 2021 … so I might just manually add them after the upgrade next week and worry about something ‘better’ next year!

KDE Dolphin — Unable to Move Files and Folders

Scott was trying to move some backup files from /a/path/to/backup to /a/path/to-a-different/backup — he’s using Dolphin & has a tab open to each of the folders in question. He chown’d /a/path to his account, chmod’d /a/path so user can read and write. But using the copy/paste option … nothing happens.

I came across a few old (and closed) bugs that seemed to produce errors in this same situation — but the reporters were able to perform their copy/move operations when they used the same tab instead of having one folder open in each tab. It worked … inexplicable, but we have success!

Samba Server Not Appearing In Network Locations (Fedora)

One of our Samba servers — unfortunately the file server — did not show up when browsing the network locations in Dolphin. I map drives from Windows, so it’s not something I’ve really noticed … but Scott is trying to avoid using network mounts and wanted to access everything through “Network”. Several other servers — ones that Scott built — show up, but not the one where we actually store our files.

There’s no salient difference in the samba configurations. But … it turns out that the “newer” way Samba advertises its presence is through mDNS. And I routinely disable the avahi-daemon because, well, I “don’t use” mDNS for anything. Turns out I do use mDNS … so I had to enable and start the avahi-daemon (and restart Samba). Voila, the file server is visible in the list of network places.

Running a Docker Container without *RUNNING* The Container

I needed to get files from a container image that I couldn’t actually start (not enough memory, and finding a box with more memory wasn’t a reasonable option) — fortunately, you can override the container entrypoint to start the container without actually running whatever the container would normally run.

docker run -ti --entrypoint=bash imageName

Yum Does Not Work On CentOS

Since this is the fifth time this month that I’ve spun up some CentOS image and been stymied by the inability to install new packages … I’m going to write down the sed commands that magic the default yum repository configuration to something that’s still functional. 

cd /etc/yum.repos.d/
sed -i 's/mirrorlist/#mirrorlist/g' /etc/yum.repos.d/CentOS-*
sed -i 's|#baseurl=http://mirror.centos.org|baseurl=http://vault.centos.org|g' /etc/yum.repos.d/CentOS-*

Using PG_CRON In PostgreSQL

The pg_cron extension allows you to schedule tasks from within your database (or, to those who didn’t know it was a thing, it allows you to hide {really well} jobs that mutate or remove data leading to absolutely inexplicable database content). While the project documents how to create or remove a scheduled job, I had quite the time figuring out how to see what was scheduled.

To see jobs scheduled in pg_cron:

To see the result of scheduled jobs: