Http server with PHP on RaspberryPI

byBartek Zdanowski
February 5, 2013
2 minute read

Totally awesome guide is at http://rasberrypibeginnersguide.tumblr.com/post/27283563130/nginx-php5-on-raspberry-pi-debian-wheezyBut instead using provided silex site config file, you should configure root folder of web server to serve php scripts….

Totally awesome guide is at http://rasberrypibeginnersguide.tumblr.com/post/27283563130/nginx-php5-on-raspberry-pi-debian-wheezy
But instead using provided silex site config file, you should configure root folder of web server to serve php scripts. To do so please rm symlink to
silex file and edit

/etc/nginx/sites-available/default

Set root folder to /var/www

# root /usr/share/nginx/www;
root /var/www;

Add index.php as a index file

index index.html index.htm index.php;

And configure all php files to be parsed by fastCGI php bridge set up on port 9000. Just put all below somewhere in default file

## Parse all .php file in the /var/www directory

location ~ \.php$ {

fastcgi_split_path_info ^(.+\.php)(.*)$;

fastcgi_pass 127.0.0.1:9000;

fastcgi_index index.php;

fastcgi_param SCRIPT_FILENAME /var/www/silex$fastcgi_script_name;

include fastcgi_params;

fastcgi_param QUERY_STRING $query_string;

fastcgi_param REQUEST_METHOD $request_method;

fastcgi_param CONTENT_TYPE $content_type;

fastcgi_param CONTENT_LENGTH $content_length;

fastcgi_intercept_errors on;

fastcgi_ignore_client_abort off;

fastcgi_connect_timeout 60;

fastcgi_send_timeout 180;

fastcgi_read_timeout 180;

fastcgi_buffer_size 128k;

fastcgi_buffers 4 256k;

fastcgi_busy_buffers_size 256k;

fastcgi_temp_file_write_size 256k;

}

Now restart ngix as mentioned in original article and enjoy PHP on RPi!

Tags:
hardware

Bartek Zdanowski

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JBoss Envers and Spring transaction managers

byJakub Nabrdalik
September 20, 2011

I've stumbled upon a bug with my configuration for JBoss Envers today, despite having integration tests all over the application. I have to admit, it casted a dark shadow of doubt about the value of all the tests for a moment. I've been practicing TDD since 2005, and frankly speaking, I should have been smarter than that.

My fault was simple. I've started using Envers the right way, with exploratory tests and a prototype. Then I've deleted the prototype and created some integration tests using in-memory H2 that looked more or less like this example:

@Test
public void savingAndUpdatingPersonShouldCreateTwoHistoricalVersions() {
    //given
    Person person = createAndSavePerson();
    String oldFirstName = person.getFirstName();
    String newFirstName = oldFirstName + "NEW";

    //when
    updatePersonWithNewName(person, newFirstName);

    //then
    verifyTwoHistoricalVersionsWereSaved(oldFirstName, newFirstName);
}

private Person createAndSavePerson() {
    Transaction transaction = session.beginTransaction();
    Person person = PersonFactory.createPerson();
    session.save(person);
    transaction.commit();
    return person;
}    

private void updatePersonWithNewName(Person person, String newName) {
    Transaction transaction = session.beginTransaction();
    person.setFirstName(newName);
    session.update(person);
    transaction.commit();
}

private void verifyTwoHistoricalVersionsWereSaved(String oldFirstName, String newFirstName) {
    List<Object[]> personRevisions = getPersonRevisions();
    assertEquals(2, personRevisions.size());
    assertEquals(oldFirstName, ((Person)personRevisions.get(0)[0]).getFirstName());
    assertEquals(newFirstName, ((Person)personRevisions.get(1)[0]).getFirstName());
}

private List<Object[]> getPersonRevisions() {
    Transaction transaction = session.beginTransaction();
    AuditReader auditReader = AuditReaderFactory.get(session);
    List<Object[]> personRevisions = auditReader.createQuery()
            .forRevisionsOfEntity(Person.class, false, true)
            .getResultList();
    transaction.commit();
    return personRevisions;
}

Because Envers inserts audit data when the transaction is commited (in a new temporary session), I thought I have to create and commit the transaction manually. And that is true to some point.

My fault was that I didn't have an end-to-end integration/acceptance test, that would call to entry point of the application (in this case a service which is called by GWT via RPC), because then I'd notice, that the Spring @Transactional annotation, and calling transaction.commit() are two, very different things.

Spring @Transactional annotation will use a transaction manager configured for the application. Envers on the other hand is used by subscribing a listener to hibernate's SessionFactory like this:

<bean id="sessionFactory" class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean" >        
...
 <property name="eventListeners">
     <map key-type="java.lang.String" value-type="org.hibernate.event.EventListeners">
         <entry key="post-insert" value-ref="auditEventListener"/>
         <entry key="post-update" value-ref="auditEventListener"/>
         <entry key="post-delete" value-ref="auditEventListener"/>
         <entry key="pre-collection-update" value-ref="auditEventListener"/>
         <entry key="pre-collection-remove" value-ref="auditEventListener"/>
         <entry key="post-collection-recreate" value-ref="auditEventListener"/>
     </map>
 </property>
</bean>

<bean id="auditEventListener" class="org.hibernate.envers.event.AuditEventListener" />

Envers creates and collects something called AuditWorkUnits whenever you update/delete/insert audited entities, but audit tables are not populated until something calls AuditProcess.beforeCompletion, which makes sense. If you are using org.hibernate.transaction.JDBCTransaction manually, this is called on commit() when notifying all subscribed javax.transaction.Synchronization objects (and enver's AuditProcess is one of them).

The problem was, that I used a wrong transaction manager.

<bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager" >
    <property name="dataSource" ref="dataSource"/>
</bean>

This transaction manager doesn't know anything about hibernate and doesn't use org.hibernate.transaction.JDBCTransaction. While Synchronization is an interface from javax.transaction package, DataSourceTransactionManager doesn't use it (maybe because of simplicity, I didn't dig deep enough in org.springframework.jdbc.datasource), and thus Envers works fine except not pushing the data to the database.

Which is the whole point of using Envers.

Use right tools for the task, they say. The whole problem is solved by using a transaction manager that is well aware of hibernate underneath.

<bean id="transactionManager" class="org.springframework.orm.hibernate3.HibernateTransactionManager" >
    <property name="sessionFactory" ref="sessionFactory"/>
</bean>

Lesson learned: always make sure your acceptance tests are testing the right thing. If there is a doubt about the value of your tests, you just don't have enough of them,

DDevelopment & Design

Log4j and MDC in Grails

byRafał Nowak
November 5, 2013

Log4j provides very useful feature: MDC - mapped diagnostic context. It can be used to store data in context of current thread. It may sound scary a bit but idea is simple.

My post is based on post http://burtbeckwith.com/blog/?p=521 from Burt Beckwith's excellent blog, it's definitely worth checking if you are interested in Grails.

Short background story...

Suppose we want to do logging our brand new shopping system and we want to have in each log customer's shopping basket number. And our system can be used at once by many users who can perform many transactions, actions like adding items and so on. How can we achieve that? Of course we can add basket number in every place where we do some logging but this task would be boring and error-prone.

Instead of this we can use MDC to store variable with basket number in map.

In fact MDC can be treated as map of custom values for current thread that can be used by logger.

How to do that with Grails?

Using MDC with Grails is quite simple. All we need to do is to create our own custom filter which works for given urls and puts our data in MDC.

Filters in Grails are classes in directory grails-app/conf/* which names end with *Filters.groovy postfix. We can create this class manually or use Grails command:

grails create-filters info.rnowak.App.Basket

In result class named BasketFilters will be created in grails-app/conf/info/rnowak/UberApp.

Initially filter class looks a little bit empty:

class BasketFilters {
    def filters = {
        all(controller:'*', action:'*') {
            before = {

            }
            after = { Map model ->

            }
            afterView = { Exception e ->

            }
        }
    }
}

All we need to do is fill empty closures, modify filter properties and put some data into MDC.

all is the general name of our filter, as class BasketFilters (plural!) can contain many various filters. You can name it whatever you want, for this post let assume it will be named basketFilter.

Another thing is change of filter parameters. According to official documentation (link) we can customize our filter in many ways. You can specify controller to be filtered, its actions, filtered urls and so on. In our example you can stay with default option where filter is applied to every action of every controller. If you are interested in filtering only some urls, use uri parameter with expression describing desired urls to be filtered.

Three closures that are already defined in template have their function and they are started in these conditions:

before - as name says, it is executed before filtered action takes place
after - similarly, it is called after the action
afterView - called after rendering of the actions view

Ok, so now we know what are these mysterious methods and when they are called. But what can be done within them? In official Grails docs (link again) under section 7.6.3 there is a list of properties that are available to use in filter.

With that knowledge, we can proceed to implementing filter.

Putting something into MDC in filter

What we want to do is quite easy: we want to retrieve basket number from parameters and put it into MDC in our filter:

class BasketFilters {
    def filters = {
        basketFilter(controller:'*', action:'*') {
            before = {
                MDC.put("basketNumber", params.basketNumber ?: "")
            }
            after = { Map model ->
                MDC.remove("basketNumber")
            }
        }
    }
}

We retrieve basket number from Grails params map and then we put in map under specified key ("basketNumber" in this case), which will be later used in logger conversion pattern. It is important to remove custom value after processing of action to avoid leaks.

So we are putting something into MDC. But how make use of it in logs?

We can refer to custom data in MDC in conversion patter using syntax: %X{key}, where key is our key we used in filter to put data, like:

def conversionPattern = "%d{yyyy-MM-dd HH:mm:ss} %-5p %t [%c{1}] %X{basketNumber} - %m%n"

And that's it :) We've put custom data in log4j MDC and successfully used it in logs to display interesting values.

DDevelopment & Design

Simple trick to DRY your Grails controller

byTomasz Kalkosiński
June 5, 2013

Grails controllers are not very DRY. It's easy to find duplicated code fragments in default generated controller. Take a look at code sample below. It is duplicated four times in show, edit, update and delete actions:

class BookController {
def show() {
def bookInstance = Book.get(params.id)
if (!bookInstance) {
flash.message = message(code: 'default.not.found.message', args: [message(code: 'book.label', default: 'Book'), params.id])
redirect(action: "list")
return
        }
        [bookInstance: bookInstance]
    }
}

Why is it duplicated?

There is a reason for that duplication, though. If you move this snippet to a method, it can redirect to "list" action, but it can't prevent controller from further execution. After you call redirect, response status changes to 302, but after method exits, controller still runs subsequent code.

Solution

At TouK we've implemented a simple trick to resolve that situation:

wrap everything with a simple withStoppingOnRender method,
whenever you want to render or redirect AND stop controller execution - throw EndRenderingException.

We call it Big Return - return from a method and return from a controller at once. Here is how it works:

class BookController {
def show(Long id) {
withStoppingOnRender {
Book bookInstance = Book.get(id)
validateInstanceExists(bookInstance)
            [bookInstance: bookInstance]
        }
    }

protected Object withStoppingOnRender(Closure closure) {
try {
return closure.call()
        } catch (EndRenderingException e) {}
    }

private void validateInstanceExists(Book instance) {
if (!instance) {
flash.message = message(code: 'default.not.found.message', args: [message(code: 'book.label', default: 'Book'), params.id])
redirect(action: "list")
throw new EndRenderingException()
        }
    }
}

class EndRenderingException extends RuntimeException {}

Example usage

For simple CRUD controllers, you can use this solution and create some BaseController class for your controllers. We use withStoppingOnRender in every controller so code doesn't look like a spaghetti, we follow DRY principle and code is self-documented. Win-win-win! Here is a more complex example:

class DealerController {
@Transactional
def update() {
withStoppingOnRender {
Dealer dealerInstance = Dealer.get(params.id)
validateInstanceExists(dealerInstance)
validateAccountInExternalService(dealerInstance)
checkIfInstanceWasConcurrentlyModified(dealerInstance, params.version)
            dealerInstance.properties = params
saveUpdatedInstance(dealerInstance)
redirectToAfterUpdate(dealerInstance)
        }
    }
}