Redis + Java + Redisson = Encoding issues

Using Reddison/Java to save to Redis, I noticed when using the redis-cli command-line client, that the saved records were encoded funny, as follows:


127.0.0.1:6379> hgetall SessionMap
 1) "\xfc(gB2muKkpNJVgDhiXQA5fGELNcFkFcBszLh5wqcXX"
 2) "\xfc\x0214"
 3) "\xfc(lh9wm3gpV767f6KrvZfVnHO5gKKUFMHfL1KJEsRC"
 4) "\xfc\x0214"

Following from their online documentation, in Java code, I had the following:

RMap map = redisson.getMap("SessionMap");

Turns out we need to specify the encoding of the string by using this bit of code instead:

RMap map = redisson.getMap("SessionMap", new StringCodec("UTF-8"));

Docker Containers Missing!

For many months we've been trying to track down the cause for the sudden termination of our docker containers.

When running the "docker container ls" command, nothing is shown. It almost looks like they're missing.

  docker container ls  
 CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES  

However running the process command "docker ps -a" does indeed indicate that our containers were exited:

 [root@patient-archive-cpi centos]# docker ps -a  
 CONTAINER ID    IMAGE            COMMAND         CREATED       STATUS            PORTS        NAMES  
 4a9b66fdd624    aehrc/ontoserver:ctsa-5.2  "/run.sh run"      7 weeks ago     Exited (143) 2 days ago            ontoserver  
 9e8314f52de2    postgres          "docker-entrypoint.s…"  7 weeks ago     Exited (0) 2 days ago         5432/tcp      docker_db_1  

The command for viewing "dockers logs ", indicated that the container was being shutdown. But there were no errors or reason for the shutdown.

 2019-06-28 03:41:48.302Z INFO 1 --- [ Thread-4] s.b.w.s.c.AnnotationConfigServletWebServerApplicationContext : Closing org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext@63d4e2ba: startup date [Fri May 10 04:11:42 GMT 2019]; root of context hierarchy  
 2019-06-28 03:41:48.313Z INFO 1 --- [ Thread-4] o.s.jmx.export.annotation.AnnotationMBeanExporter : Unregistering JMX-exposed beans on shutdown  
 2019-06-28 03:41:48.314Z INFO 1 --- [ Thread-4] o.s.jmx.export.annotation.AnnotationMBeanExporter : Unregistering JMX-exposed beans  
 2019-06-28 03:41:48.316Z INFO 1 --- [ Thread-4] o.s.scheduling.concurrent.ThreadPoolTaskExecutor : Shutting down ExecutorService 'batchRunner'  
 2019-06-28 03:41:48.319Z INFO 1 --- [ Thread-4] o.s.scheduling.concurrent.ThreadPoolTaskExecutor : Shutting down ExecutorService 'jobRunner'  
 2019-06-28 03:41:48.319Z INFO 1 --- [ Thread-4] o.s.scheduling.concurrent.ThreadPoolTaskExecutor : Shutting down ExecutorService 'auditReportJobRunner'  
 2019-06-28 03:41:48.329Z INFO 1 --- [ Thread-4] o.s.orm.jpa.LocalContainerEntityManagerFactoryBean : Closing JPA EntityManagerFactory for persistence unit 'default'  
 2019-06-28 03:41:48.331Z INFO 1 --- [ Thread-4] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Shutdown initiated...  
 2019-06-28 03:41:48.343Z INFO 1 --- [ Thread-4] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Shutdown completed.  

Running the docker command for viewing events showed nothing of interest

 docker events --filter container=ontoserver --since '2019-06-27'  

After some digging around it turns out that there was an automated yum update to docker in the /var/log/yum.log

 Jun 28 03:41:44 Updated: docker-ce-cli.x86_64 1:18.09.7-3.el7  
 Jun 28 03:41:48 Updated: containerd.io.x86_64 1.2.6-3.3.el7  
 Jun 28 03:41:52 Updated: docker-ce.x86_64 3:18.09.7-3.el7  

Turns out in docker there's a feature for re-enabling the docker containers after a docker update called 'live-restore'

Added a file /etc/docker/daemon.json with the following contents

{
  "live-restore": true
}

Then restarted docker

systemctl reload docker

‌

Reference: https://docs.docker.com/config/containers/live-restore/

flutter Android dependency 'androidx.core:core' has different version for the compile (1.0.0) and runtime (1.0.1) classpath

In the android/build.gradle file set the gradle version to 3.3.2 as follows:

dependencies {
    classpath 'com.android.tools.build:gradle:3.3.2'
}

Reference: https://github.com/flutter/flutter/issues/27254

flutter "detected problems with api compatibility"

In the android/app/build.gradle file change the targetSdkVersion from 27 to 28.

Reference: https://stackoverflow.com/questions/49957255/espresso-test-on-android-p-preview-detected-problems-with-api-compatibility-err

flutter "unable to start activity" "ensureInitializationComplete must be called after startInitialization"

Flutter app fails to launch with the following error:

 Caused by: java.lang.IllegalStateException: ensureInitializationComplete must be called after startInitialization  
     at io.flutter.view.FlutterMain.ensureInitializationComplete(FlutterMain.java:190)  
     at io.flutter.app.FlutterActivityDelegate.onCreate(FlutterActivityDelegate.java:156)  
     at io.flutter.app.FlutterActivity.onCreate(FlutterActivity.java:89)  
     at net.pawpalflutter.MainActivity.onCreate(MainActivity.java:10)  
     at android.app.Activity.performCreate(Activity.java:6672)  
     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1140)  
     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2612)  
     ... 9 more  

This error occurred when loading app from Android Studio to a mobile phone. It seems the transfer of the app may have been interrupted abruptly and didn't close properly, causing all subsequent transfers to fail.

The Solution

Power off and on the phone

Reference: https://github.com/flutter/flutter/issues/14513

Intellij Dart Analysis Server Bad State: Too many elements

This error was also causing an issue "cannot find declaration to go to"

After doing a flutter upgrade, I had to do the following:

1. Close IntelliJ
2. delete the project's .idea folder and any *.iml files
3. Reopen the project in intellij

If that doesn't work try File -> Invalidate caches / restart and repeat the steps above

PlatformException(sign_in_failed, com.google.android.gms.common.api.ApiException: 8: null)

Using the flutter framework for android development, I received the following error during google signin:

PlatformException(sign_in_failed, com.google.android.gms.common.api.ApiException: 8: null)

While it wasn't obvious from the error message what the problem was, it turns out there was no network connection available. So if you get this error, check that you have access to the internet!!

Node.js Centos 7 production configuration

Install nodejs

Download

wget --no-check-certificate https://nodejs.org/dist/v10.15.1/node-v10.15.1-linux-x64.tar.xz

Move the downloaded file /usr/local

Then unpack

tar xf node-v10.15.1-linux-x64.tar.xz

Add node executables to the path by adding symlinks to /usr/bin

ln -s /usr/local/node/bin/node /usr/bin/node

ln -s /usr/local/node/bin/npm /usr/bin/npm

ln -s /usr/local/node/bin/npx /usr/bin/npx

Install pm2

To run node as service we need to install a nodejs package

npm install pm2@latest –g

We need to run set the path to pm2

ln -s /usr/local/node/bin/pm2 /usr/bin/pm2

ln -s /usr/local/node/bin/pm2 /usr/bin/pm2-runtime

For security reasons we should run our app NOT as root. We create a new user nodejs to run our app

useradd nodejs

chown -R nodejs:nodejs /usr/local/node

chown –R nodejs:nodejs /usr/local/node-v10.15.1-linux-x64

# as root

pm2 startup system –u nodejs –-hp /home/nodjs

To start the application as the nodejs user, switch to the user nodejs

su nodejs

pm2 start /usr/local/node/apps/chat/server.js

pm2 list

# to automatically start the app on reboots

pm2 save

You should see that the app is running as user nodejs 

Likewise to stop

#other commands

pm2 stop /usr/local/node/apps/chat/server.js

pm2 delete /usr/local/node/apps/chat/server.js

Install ArangoDB on Centos 7

The instructions on the official arangodb website do not work, so I’m documenting the steps I took so that it may help others.

The first problem is adding arangodb as a repo due to invalid SSL certificates. To get around the issue:

cd /etc/yum.repos.d/

curl -OLk https://download.arangodb.com/arangodb34/RPM/arangodb.repo

The added ‘k’ parameter connects to the repo insecurely skipping the step of verifying the certificates.

Before we can run the yum command to install arangodb, we need to configure the arangodb.repo to skip SSL checks by adding the following to the file /etc/yum.repos.d/arangodb.repo

sslverify=0

Then run the command to install:

yum install arangodb3

References:

https://superuser.com/questions/1057905/adding-no-check-certificate-to-yum-repositories

https://www.arangodb.com/download-major/centos/