I compiled a list of 8 talks from linux.conf.au 2017 that interested me. You can watch it here or just click play on the embedded video below:
Category: Coding
Coding-related stuff
EOY 2016 links
Some links about interesting things I’ve read or watched by the end of 2016. Further comments are provided on each item of the list.
- Single file libraries: open source libraries with minimal dependencies.
- The sorry state of programming world as the end of 2016 AD: food for though regarding how most of development is done nowadays.
- Find my Phone: what happens when your phone is stolen.
- PayPal Cuts Costs 10x With Open Source CI: self descriptive.
- Learning to Read x86 Assembly: self descriptive.
- Json-c tutorial: how to manipulate json in C.
- The 101 of ELF Binaries on Linux: Understanding and Analysis: self descriptive.
- How the Linux kernel knows it’s running in a Virtual Machine: self descriptive.
- Stack Overflow: The Architecture – 2016 Edition: self descriptive.
- AMQP 1.0 in Azure Service Bus and Event Hubs protocol guide: a detailed explanation abou AMQP 1.0.
- 10 Tips for C and C++ Performance Improvement Code Optimization: simple optimization tips.
- Light Weight Protocol: Critical Implications: a talk about MQTT and security.
- Modern C: a book about modern C programming.
Google Sanitizers and Fedora 25
Here’s a tip if you are using Fedora and trying to use one of the Google Sanitizers with clang and is having problems doing so. One of the common problems is not being able to find libclang_rt.asan-x86_64.a:
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/usr/bin/ld: cannot find /usr/bin/../lib64/clang/3.8.0/lib/linux/libclang_rt.asan-x86_64.a: No such file or directory |
This can be resolved by simply installing the compiler-rt package:
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dnf install -y compiler-rt |
Restoring click method behavior on Fedora 25 and libinput
Here’s a quick tip if you need to enable the Software Button Area behavior on an Apple macbook running Fedora 25:
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xinput set-prop bcm5974 "libinput Click Method Enabled" 1 0 |
Some comments about this:
- You have to run it after every reboot
- There’s, probably, a better way to do this. Per documentation, it should be possible to set it up permanently by creating a file on /etc/X11/xorg.conf.d however I did not manage to create a file that works so far.
References:
- Libinput documentation: Clickpad Software Buttons
- Libinput FAQ
- Libinput Man Page
SonarQube 5.6 upgrade
Overall tips for upgrade a SonarQube instance from 5.4 to 5.6 LTS.
- If you are using MariaDB as your database, please make sure to read the post SonarQube database migration: MariaDB 5.5 to MySQL 5.7.
- Ignore the upgrade steps provided by the application. They are incomplete. If you execute them, the upgrade will finish with success but no rules will be enabled after that. Instead, execute the steps provided in this StackOverflow comment.
- If you are using C++ community plugin, make sure that you are using at least version 0.9.6.
- Ensure that you have Java 8.
SonarQube database migration: MariaDB 5.5 to MySQL 5.7
Newer versions of SonarQube have stopped supporting MariaDB and you may need to switch to MySQL instead. While I’d rather use MariaDB, I understand that it is not within the supported matrix. Therefore I am documenting the steps here. The steps are focused on RHEL 7 (they probably would work on Centos 7 as well, but I did not test it).
Before start with this process, shutdown your SonarQube instance as well as any other analysis that may access the database.
The first step is to use mysqldump to create a backup of your MariaDB database:
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mysqldump sonar > sonar.sql |
After the backup is complete, shutdown and disable your MariaDB instance:
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systemctl stop mariadb ; systemctl disable mariadb |
Then install MySQL 5.7 from Software Collections. The process is documented on this page. These steps are for 5.6, however, you can just replace 56 with 57 in all the steps and the result is the same.
With the new MySQL 5.7 installed and running, create the database:
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mysql -u root |
In the MySQL sheel recreate the database with the same credentials and permissions as the old one:
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CREATE USER '[old username]'@'localhost' IDENTIFIED BY '[old password]'; GRANT ALL PRIVILEGES ON *.* TO '[old username]'@'localhost' WITH GRANT OPTION; CREATE USER '[old username]'@'%' IDENTIFIED BY '[old password]'; GRANT ALL PRIVILEGES ON *.* TO '[old username]'@'%' WITH GRANT OPTION; |
Then you can recover the backup into the new MySQL 5.7 instance:
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mysqldump sonar < sonar.sql |
Now you can go to your SonarQube server and start it.
Colors in GDB
I have been on a intense session of C/C++ hacking lately and one of the things I came across is this interesting StackOverflow topic about how to colorize the GDB output. There are plenty of tips there, but since I prefer vanilla GDB, I just stick to the first one and downloaded a customized GDB for myself.
Consolidating multiple git repositories into a single one
Today I decided to reorganize my GitHub repository. In the past, I added a lot of learning projects there and as time passed by, it was growing considerably. Since I currently have some work-related projects there, I thought it deserved some reorganization.
My idea was to consolidate some of the larger projects I had into a single repository where each component is a sub-module of the project. This was a rather natural choice because most of those projects are written in Java and use Maven, therefore being very easy to refactor into a module-based project layout.
One requirement I had was that I wanted to retain the commit history. After looking at some solutions involving git’s submodule or subtree features, I found one that was fairly simple. The process couldn’t be simpler: you have to add the projects as remote to your new project and run a couple of commands to merge, move and commit the files.
Additionally, since my projects usually follow the same standard, it was quite simple to automate. After running the initial steps to configure the new (consolidated) repository, I was able to run the mass import using the following command line:
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for module in $(echo "project1 project2") ; do git merge -m "Merged $module master for repository reorganization" $module/master ; mkdir $module ; (for file in $(echo "README.md pom.xml src test") ; do [[ -e $file ]] && git mv $file $module/ ; done) ; git status ; git commit -m "UPD: moved $module old files from a separate repo to a separate module" . ; done |
I was even able to import the old branches for each of the sub-components I wanted to merge.
Interesting article about AMQP in Azure
If you are interested in the AMQP 1.0 messaging protocol, I recommend this article entitled “AMQP 1.0 in Azure Service Bus and Event Hubs protocol guide“. It’s a very interesting read about the protocol and its details.
Some messaging stuff
Just sharing some messaging tools I have been working with recently.
The first one is this performance test tool: msg-perf-tool. There’s no secret here: you run the tool and it does its best to bring your messaging system to its knees (though this may not be the correct way how to test it … check the testing tips on the Github page). For now it supports only AMQP, but Stomp and MQTT support is on the way. You can find rpms for RHEL/Centos (6 and 7) and Fedora (22, 23 and 24) for i686 and x86_64 on my Copr profile here.
The second one is a web page that can display the performance data stored on an ElasticSearch database and present it in a beautiful way. I call it messaging performance center. Here’s how it looks like:
Some bits are still in progress, but it’s functional.
Lastly, there’s litestomp. A C implementation of the Simple (or Streaming) Text Oriented Messaging Protocol. It was built on top of what-seems-to-be the now defunct libstomp project. There’s a couple of bugfixes, a simpler and higher level API for ease of use. Still a work in progress, but you can download the current rpms for RHEL/Centos (6 and 7) and Fedora (22, 23 and 24) for i686 and x86_64 from my Copr project page on this link.