Dariusz on Software Quality & Performance

02/12/2013

JPA + ObjectDB example

Filed under: en — Tags: java, jee, orm — dariusz.cieslak @

JPA stands for "Java Persistence API" – an API that tries to replace direct Hibernate (or other ORM) usage with more generic layer that allows to replace underlying ORM with no application code changes.

Although ORM (object relational mappers) typically use relational database under the hood JPA is not restricted to relational databases. I'll present how object database (objectdb) can be used using JPA interface.

All the source code can be located here: https://github.com/dcieslak/jee-samples/tree/master/jpa.

Classes

Firstly, you have to define your model and relations using POJO with JPA annotations. We try to make model as simple as possible, so no getters/setters pairs if not really required.

@Entity
class SystemUser implements Serializable {

    @Id @Column @GeneratedValue(strategy=GenerationType.AUTO)
    public Integer userId;

    @Column
    public String systemUserName;

    @Column
    public Departament department;

    public String toString() {
        return "SystemUser(" + systemUserName + ", " + department + ")";
    }
}

(more…)

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29/11/2013

Check current network bandwidth used on a Linux/Unix box

Filed under: en — Tags: linux, network — dariusz.cieslak @

Sometimes you need to quickly measure current bandwidth used by your Linux box and don't have dedicated command installed. You can use standard /proc/ file entries to get that info from the system.

Example of a embedded device with a TS stream as an input:

( cat /proc/net/dev; sleep 1; cat /proc/net/dev; ) | awk '/eth0/ { b=$1; sub(/eth0:/,"",b); if(bp){ print (b-bp)/1024/1024, "MB/s" }; bp=b }'
1.00053 MB/s

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28/11/2013

The simplest MySQL setup, ever

Filed under: en,pl — Tags: mysql, sql — dariusz.cieslak @

First of all: you have to install the server (I assume you use Debian / Ubuntu):

apt-get install mysql-server

Then you have to create database, user and password (for sake of simplicity, not security, name, login and password are the same):

N=<DB_NAME>; echo "create database $N; grant usage on *.* to $N@localhost identified by '$N'; grant all privileges on $N.* to $N@localhost ;" | mysql -u root

Then you should configure your program:

db_name=<DB_NAME>
db_user=<DB_NAME>
db_password=<DB_NAME>
host=localhost

Beware (SECURITY): I assume you have MySQL external connection closed (only local) and you trust every user from your Linux installation, they will have access to your database easily in such setup.

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31/10/2013

Secure PostgreSQL setup on Debian/Ubuntu

Filed under: en — Tags: postgresql, sql — dariusz.cieslak @

PostgreSQL is an OpenSource database server that is sometimes slower, but more powerful when compared to MySQL for example. For typical MySQL user complicated authentication system of PostgreSQL may be a bit confusing (they expect just login/password) but it has some advantages over password-based mechanisms: security. I'll show you how to setup ident-based authentication for your applications (authentication method that uses underlying operating system mechanisms).

Installation, assuming version 8.4 is available for your OS (may be different):

$ sudo apt-get install postgresql-8.4

Switch to postgres operating system account for database management, all the following commands are executed from postgresql account:

$ sudo su - postgres

First, create database as a namespace for your tables:

postgres:$ createdb mydatabase

Secondly, create application PostgreSQL user. We do not want to grant too much permissions to this user:

postgres:$ createuser myuser --no-superuser --no-createdb --no-createrole

Right now we have to grant access to newly created database access to PostgreSQL user (just access to single database):

postgres:$ psql mydatabase -c 'GRANT ALL PRIVILEGES ON DATABASE mydatabase TO myuser'

Finally we have to allow connections from operating system account darek to PostgreSQL account myuser:

/etc/postgresql/8.4/main/pg_ident.conf
 mymap  darek   myuser

/etc/postgresql/8.4/main/pg_hba.conf
 local   all         all                               ident map=mymap

In order the changes to have effect you have to reload PSQL configuration files:

postgres:$ /etc/init.d/postgresql reload

What is happening here requires a bit of explanation:

A mapping is created from local Linux user (darek) to PostgreSQL account (myuser) called "mymap"
Local connections by socket allow to authenticate user darek using mapping "mymap"

As a result "darek" can login as myuser from his account, let's test this:

$ psql mydatabase myuser -c "CREATE TABLE mytable(x int)"
 CREATE TABLE

As you probably have noticed no passwords were set. Authentication is done by operating system. This is much safer than storing passwords in configuration files of application.

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13/10/2013

A new site: RandomTest.net

Filed under: en — Tags: testing — dariusz.cieslak @

A new site has been just born: RandomTest.net. Based on current experiences in IPTV industry I'm going to create set of libraries for different environments that will allow to:

make random input to any application (web-based, smartphone, thick client-type, …)
collect errors found
send them to central server
prepare useful reports for stability analysis

The rationale:

Manual integration tests are expensive, unit developers tests are hard to implement properly and your latest click’n'play tool requires more and more maintenance effort for failing test cases along development?

What if we forget for a moment about scripting your UI by static scripts and replace it with totally random input? You will get for free coverage in almost whole application. “Wait” – you will say - “but there’s no way to check results as the input is random, is there?”.

Sure, here Design By Contract + Continuous Integration comes to play. You embed assertions in your system in many places. Failed assertions do not crash application, but are reported immediately to central server and aggregated into reports every day. Crashes, warnings, errors are reported, too. Then you can measure quality of your system-under-test by observing changes in number of errors, day by day. No scripting required to cover any new line of code! It will be tested automatically!

The source code will be open, the project has just started on github.com.

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