Author / Maik

by Maik

OpenShift: “systemd” is different from docker cgroup driver: “cgroupfs”

Messing around with OpenShift Origin 3.6.0 and their Docker Quickstart guide I stumbled upon some configuration incompatibilities with Kubernetes:

F0819 08:47:34.208186    9065 node.go:282] failed to run Kubelet: failed to create kubelet: misconfiguration: kubelet cgroup driver: "systemd" is different from docker cgroup driver: "cgroupfs"

The issue is caused due to using cgrougfs as Cgroup Driver for Docker. You can verify your Docker config by running docker info | grep Cgroup. You can change your Cgroup Driver to systemd using the native.cgroupdriver parameter for the Docker Daemon. Add the following arg to your /etc/systemd/system/docker.service.d/docker-thinpool.conf (ExecStart) file and /etc/default/docker (DOCKER_OPTS):

--exec-opt native.cgroupdriver=systemd

Relaunch the dockerd afterwards and verify your changes:

systemctl daemon-reload
systemctl restart docker.service
docker info | grep Cgroup

Further references

docker change cgroup driver to systemd

I want to docker to start with systemd cgroup driver. for some reason it using only cgroupfs on my centos 7 server. here is startup config file. # systemctl cat docker # /usr/lib/systemd/system/d…

openshift/origin docker container fails to start: failed to create kubelet: misconfiguration: kubelet cgroup driver: “systemd” is different from docker cgroup driver: “cgroupfs” · Issue #14766 · openshift/origin

Affected System configuration

$ docker version

Client:
 Version:      17.06.1-ce
 API version:  1.30
 Go version:   go1.8.3
 Git commit:   874a737
 Built:        Thu Aug 17 22:51:12 2017
 OS/Arch:      linux/amd64

Server:
 Version:      17.06.1-ce
 API version:  1.30 (minimum version 1.12)
 Go version:   go1.8.3
 Git commit:   874a737
 Built:        Thu Aug 17 22:50:04 2017
 OS/Arch:      linux/amd64
 Experimental: false

$ lsb_release -a
Distributor ID: Ubuntu
Description:    Ubuntu 16.04.3 LTS
Release:    16.04
Codename:   xenial
by Maik

fastlane supply: Google Api Error (Google Play)

fastlane is an awesome tool to release your iOS and Android apps. It handles all your tedious tasks, like generating screenshots, dealing with code signing, and releasing your application. From my experience fastlane is pretty reliable and a true blessing when developing mobile applications. supply is the component of fastlane that is responsible for updating Android apps (binaries), release management (e.g. beta & alpha tracks) and the respective metadata (store listing and screenshots) on the Google Play Store.

Using supply to automate the alpha releases, I had to deal with the following error message:

[10:04:54]: Updating track 'alpha'...
[10:04:55]: Uploading all changes to Google Play...

[!] Google Api Error: multiApkShadowedActiveApk: Version 2100384 of this app can not be downloaded by any devices as they will all receive APKs with higher version codes.

Not only does this complication keep the builds failing, it also prevents releasing new alpha builds – therefore effectively jamming the release cycle. According to a related GitHub Issues the error gets triggered after promoting a release directly from alpha to production (skipping the beta track). As of this writing there is a pretty fresh (14 hours old) Pull Request, which tries to circumvent the outlined problem. Until the possible fix is released, you can workaround the problem by manually uploading a new APK to the alpha track. All subsequent builds should be fixed.

  • The described problem could be reproduced with supply 2.19.0 on Ubuntu 16.04.
by Maik

Debian Recovery Mode: Turn on networking

Sometime things go wrong… and sometimes things go terribly wrong. So you might find yourself in the depths of your favorite distribution’s recovery mode late in the night. Depending on the nature of your Linux distribution you might be served with the possibility to enable networking foresighted (e.g. via GRUB). Or… there is no such option at all and you are on your own to figure out how to fix your failed update, missing dependencies or incompatible packages — all that, without the plethora of solutions offered by the almighty internet.

Fortunately there is a straight-forward way to get your Ethernet bits flowing:

ifconfig eth0 up
dhclient eth0

# Validate local IP / network config
ifconfig
by Maik

Building OpenCL on macOS: CL/cl.h not found

Compiling a third party project on macOS, I stumbled upon the following compilation error after running make:

Scanning dependencies of target[...]
[ 33%] Building CXX object CMakeFiles/[...].dir/main.cpp.o
In file included from /Users/[...]/main.cpp:11:
/Users/[...]/CLCalculator.h:14:10: fatal error: 'CL/cl.h' file not found
#include <CL/cl.h>
         ^
1 error generated.
make[2]: *** [CMakeFiles/[...].dir/main.cpp.o] Error 1
make[1]: *** [CMakeFiles/[...].dir/all] Error 2
make: *** [all] Error 2

Unfortunately the application was originally not intended for macOS / OS X platforms. There are quite some examples of similar encounters in the vastness of the internet. But… there is a simple way to make your the respective code cross-plattform and compatible with macOS / OS X:

#if defined(__APPLE__) || defined(__MACOSX)
#include <OpenCL/cl.h>
#else
#include <CL/cl.h>
#endif

Just replace the #include <CL/cl.h> statement with the snippet above and run make again – great…

by Maik

Error Logging for Ionic 2 with Sentry (Raven.js)

Sentry is a realtime, platform-agnostic error logging and aggregation platform, that helps me catch errors across different projects. Raven.js is Sentry’s official browser JavaScript client and supports „quite a few“ technologies and frameworks (like plain-old JavaScript, Node.js: Express, Koa, Connect, Angular.js 1, Angular, Ember, React, Vue,…).

Ionic 2 comes with an excellent Error-Handling by default. It simply smashes all exceptions right into the developer’s face (the „React approach“ to handle things). This in itself is alright for development, but in production you should probably log all exceptions with solutions like Sentry.

To log exceptions with Sentry on Ionic 2, I decided to extend the existing IonicErrorHandler to additionally forward the logs to Sentry. The snippet below gives an example:

import * as Raven from 'raven-js';
import {NgModule, ErrorHandler} from '@angular/core';
import {IonicApp, IonicModule, IonicErrorHandler} from 'ionic-angular';
import {MyApp} from './app.component';
import {FoobarPage} from '../pages/home/home';

Raven
  .config('*YOUR DSN*')
  .install();

class RavenErrorHandler extends IonicErrorHandler implements ErrorHandler {
  handleError(err: any): void {
    super.handleError(err)
    Raven.captureException(err.originalError);
  }
}

@NgModule({
  declarations: [MyApp, FoobarPage],
  imports: [
    IonicModule.forRoot(MyApp)
  ],
  bootstrap: [IonicApp],
  entryComponents: [MyApp, FoobarPage],
  providers: [{provide: ErrorHandler, useClass: RavenErrorHandler}]
})
export class AppModule {}
by Maik

Python Pillow 3 with Alpine Linux

Using Alpine Linux as a base for Docker images does have some implications and odd bugs. Trying to get Taiga (Backend) running with Alpine Linux I stumbled upon the following error log:

ValueError: --enable-zlib requested but zlib not found, aborting.

Even explicitly installing zlib (as required) does not help getting rid of the issue:

apk add --no-cache zlib zlib-dev

To get it working / recognizing the system’s zlib you need to

  • extend the CFLAGS environmental variable
CFLAGS="$CFLAGS -L/lib"
  • or create a softlink for the zlib library before executing the Pillow installation:
ln -s /lib/libz.so /usr/lib/

Further References:

by Maik

ERROR ITMS-90071: CodeResources file must be a symbolic link

Using a continuous integration solution to efficiently develop iOS applications, I stumble upon the following issue when trying to upload an .ipa file using Apple’s Application Loader (Version 3.0)

ERROR ITMS-90071: “This bundle is invalid. The CodeResources file must be a symbolic link to _CodeSignature/CodeResources. Make certain that the bundle is on a locally-mounted volume [not a remote SMB volume], and be certain to use the Mac OS X Finder to compress it.”

The error might be caused by the way your CI solution creates your resulting archive or just due to running the build process from a command line instead of old-fashioned XCode with GUI.

To fix this issue you need to manually change the structure of your application file.

# extract your application archive file (ends with .ipa)
unzip Foobar.ipa -d tmp/

# change to the application folder (ends with .app)
cd tmp/Payload/Foobar.app

# overwrite or create the mentioned symbolic link
ln -fs _CodeSignature/CodeResources CodeResources

# change to the tmp/ folder
cd ../..

# recreate the application archive file (.ipa)
zip -yr9 Foobar.ipa Payload/

You should then be able to successfully upload your iOS application with Apple’s gorgeous Application Loader.

You can also use the copy’n’pastable example below (resulting file is called Fixed.ipa).

unzip *.ipa -d tmp/
cd tmp/Payload/*.app
ln -fs _CodeSignature/CodeResources CodeResources
cd ../..
zip -yr9 Fixed.ipa Payload/
cd ..
mv tmp/Fixed.ipa .
rm -r tmp
ls -lah
by Maik

WordPress API v2 with Polylang and ACF

Using WordPress with Custom Post Types enriched with Advanced Custom Fields offers a simple solution to provide an intuitive Database management solution. With WP REST API v2 it’s even possible to use WordPress as a simple mobile backend. ACF to WP-API allows accessing the ACF attributes.
But using WP REST API v2 with ACF (through ACF to WP-API) does not work by default if you add Multilanguage support through Polylang. Even though you can filter post types through the filter parameter (e.g. filter[lang]=de) the ACF attributes are not resolved properly (AFAICT this only affects relationship fields).

Fortunately there are some smart folks out there that already figured out how to set the language for REST requests:

<?php
function polylang_json_api_init() {
  global $polylang;

  $default = pll_default_language();
  $langs = pll_languages_list();

  $cur_lang = $_GET['lang'];

  if (!in_array($cur_lang, $langs)) {
    $cur_lang = $default;
  }

  $polylang->curlang = $polylang->model->get_language($cur_lang);
  $GLOBALS['text_direction'] = $polylang->curlang->is_rtl ? 'rtl' : 'ltr';
}

add_action('rest_api_init', 'polylang_json_api_init');
?>
by Maik

ADB over network with Android 2.3

For testing purposes I use an old Android 2.3 device that runs an old version of Cyanogenmod. Unfortunately I could not find an option to enable ADB over network in the device’s settings. I am not a fan of plugging in the device every time I would like to debug an application. But, fortunately, there is a way to enable ADB over network via Terminal if your device is rooted:

su
setprop service.adb.tcp.port 5555
stop adbd
start adbd

Afterwards you can connect as usual by running adb connect device-ip on your development machine.

To disable ADB over network you can set the TCP port option to -1:

setprop service.adb.tcp.port -1
stop adbd
start adbd
by Maik

Cordova 5: Building signed Android applications

Even though signing Android applications is quite simpler than signing iOS applications, it’s sometimes annoying to set it up and reliably automate it (without using Phonegap or comparable services). Recently I tried automating singing a Cordova application for Android and struggled finding a reliable documentation.

The official Cordova documentation states, that you can easily append a bunch of arguments to the build command to automatically sign your Android application:

Keystore (--keystore): Path to a binary file which can hold a set of keys.
Keystore password (--storePassword): Password to the keystore
Alias (--alias): The id specifying the private key used for singing.
Password (--password): Password for the private key specified.
Type of the keystore (--keystoreType): pkcs12, jks (Default: auto-detect based on file extension)

The catch is, you need to append these arguments as platformopts (POPTS):

cordova build [PROD] [TARGET] [EXP] [PLATS] [BUILDCONFIG] [-- POPTS]

  PROD:   --debug|--release
  TARGET: --device|--emulator|--target=FOO
  EXP:    --experimental [EXPERIMENTALFLAGS]
  PLATS:  PLATFORM [...]
  BUILDCONFIG: --buildConfig=CONFIGFILE
  POPTS:  platformopts

Therefore the command to build a signed Cordova android application becomes:

cordova build --release android -- --keystore=my.keystore --storePassword=K3ySt0reP4ssw0rd --alias=foobar --password=K3yP4ssw0rd

Alternatively, you could specify them in a build configuration file (build.json) using (–buildConfig) argument. 

{
     "android": {
         "release": {
             "keystore": "my.keystore",
             "storePassword": "K3ySt0reP4ssw0rd",
             "alias": "foobar",
             "password" : "K3yP4ssw0rd",
             "keystoreType": ""
         }
     }
 }

and respectively

cordova build --release android --buildConfig=buildConfig.json

I tested all those commands with Cordova 5.4.0