Jeff Mesnil
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Writing a Book for O'Reilly about Mobile & Web Messaging

September 9, 2013

The title says it all: I've agreed with O'Reilly Media to write a book about Mobile and Web Messaging.

Almost all my career has been spent developing messaging platforms or clients using messaging. The last few years, I have focused on messaging for Mobile and Web platforms.

  • I added STOMP support to HornetQ to be able to send and receive messages from iOS and Android apps.
  • I wrote stomp.js to send and receive messages from HTML5 Web Browsers1. This small library is now used by the main Open Source messaging brokers (ActiveMQ, Apollo, RabbitMQ in addition to HornetQ).

This book is the result of all this work and will help mobile and Web developers leverage messaging protocols in their applications.

I plan to introduce messaging protocols and write about STOMP (and most likely MQTT too) in details. The book will come with examples for mobile platforms and Web browsers.

I have setup a web site at mobile-web-messaging.net to promote the book and will tweet about it at @mobilewebmsg.

The target release for the book is June 2014.

For a long time, I wanted to write a technical book and it is a chance to do it about an interesting subject and be published by the best editor for programming books. O'Reilly agreed to publish the book under an Open Source license and the source and examples will be hosted on GitHub (when I have some material to show).

This opportunity is only possible because my employer, Red Hat, allows me to spend some of my work time on this book. Red Hat is an awesome company to work for and we are hiring!

I am incredibly excited about this book and look forward to sharing some sample chapters. I just need to start writing them now! :)


  1. That's why I just released a new version of stomp.js. I plan to write a chapter about it and found some shortcomings that I wanted to fix. 

stomp.js 2.1.0 is Released

September 3, 2013

I have released a new version of Stomp over WebSockets.

During my summer holidays, I have simplified its API to make it more object-oriented instead of a simple translation of the protocol frames. The new API is backwards compatible except for the susbcription change.

The documentation has been updated to reflect the new API.

I also created a 2.1.0 release on GitHub to provide a well-known location to download stomp.js (and its minified version).

Connection

The connect() method accepts different number of arguments to provide a simple API to use in most cases:

client.connect(login, passcode, connectCallback);
client.connect(login, passcode, connectCallback, errorCallback);
client.connect(login, passcode, connectCallback, errorCallback, host);

where login, passcode are strings and connectCallback and errorCallback are functions (some brokers also require to pass a host String).

The connect() method also accepts two other variants if you need to pass additional headers:

client.connect(headers, connectCallback);
client.connect(headers, connectCallback, errorCallback);

where header is a map and connectCallback and errorCallback are functions.

Please note that if you use these forms, you must add the login, passcode (and eventually host) headers yourself:

var headers = {
  login: 'mylogin',
  passcode: 'mypasscode',
  // additional header
  'client-id': 'my-client-id'
};
client.connect(headers, connectCallback);

Acknowledgement

The message objects passed to the subscribe callback now have ack() and nack() methods to directly acknowledge (or not) the message.

var sub = client.subscribe("/queue/test",
  function(message) {
    // do something with the message
    ...
    // and acknowledge it
    message.ack();
  },
  {ack: 'client'}
);

Unsubscription

Instead of returning an id from client.subscribe(), subscribe() returns an object with an id property corresponding to the subscription ID and an unsubscribe() method.

var subscription = client.subscribe(...);
...
subscription.unsubscribe();

Transaction

The begin() method returns a JavaScript object with commit() and abort() methods to complete the transaction.

var tx = client.begin();
message.ack({ transaction: tx.id, receipt: 'my-receipt' });
...
tx.commit(); // or tx.abort();

A transaction ID is automatically generated when calling 'begin() and is available in the returned object's id property.

Miscellaneous changes and fixes

  • default onreceive method

    When a subscription is automatically created on the broker-side, the received messages are discarded by the Stomp.client that find no matching callback for the subscription headers. To workaround that, the client can set a default onreceive callback that will be called if no matching subscription is found.

    This is required to support RabbitMQ temporary queue destinations.

  • By default, debug messages are now written in window.console.

  • STOMP can now be used from a WebWorker (an example shows how to use it).

  • STOMP frame fragmentation

    If the STOMP frames are big to send on a single WebSocket frame, some web server may have trouble process them. It is now possible to split a STOMP frame on multiple Web Socket frames by configuring the client.maxWebSocketFrameSize (in bytes). If the STOMP frame is bigger than this size, it will be send over multiple Web Socket frames (default is 16KiB).

  • use the 1st value for repeated headers

    Stomp.js was keeping the last value of repeated headers. This has been fixed according to the specification to take the 1st value of repeated headers.

  • fix generation of timestamp on IE8

Sunset At Saint-Malo

August 8, 2013

Sunset At Saint-Malo
 Sunset At Saint-Malo (France) © Jeff Mesnil

Velours de Mangue

August 5, 2013

We bought a siphon for cooking some time ago and are having fun with it to prepare desserts and starters (we made a mousse de foie gras that was awesome). Yesterday, we prepared a velours de mangue (velvet of mango).

Velours de Mangue
Velours de Mangue © Jeff Mesnil

JMS 2.0: Shared Subscription

June 27, 2013

JMS 2.0 has been released a few weeks ago. We are working hard to support it in HornetQ and WildFly and I plan to write a few articles about it.

The main features are described on Oracle Web site in What's New in JMS 2.0, Part One: Ease of Use and Part Two: New Messaging Features.

One of the most important new features is Shared Subscription.

Let's assume you are using a topic to send messages. There are several components subscribed to this topic that are processing the messages in different fashion (for example to process jobs A and B).

When a message M is sent to the topic, all consumers subscribed to the topic receive it:

                                   M   +--------------+
                                  ---> | consumer CA1 |  < a consumer for the job A >
    +----------+  M   +-------+ /      +--------------+
    | producer | ---> | topic |   
    +----------+      +-------+ \  M   +--------------+
                                  ---> | consumer CB1 | < a consumer for the job B >
                                       +--------------+

The consumer CB1 is subscribed to the topic. Every time, it receives a message, it processes the job B.

Unfortunately, this job is time-consuming and we would like to scale it out by having several consumers for the job B running on different machines.

We can not have several consumers on the topic for this job, otherwise they would all receive copies of the same message and process it several times. What we need is a set of consumers that receives a single message from the topic amongst them.

If the component is running inside a Java EE application server, you can use a Message-Drive Bean for that. If the component is a Java SE application, you are out of luck.

Before JMS 2.0, each messaging brokers has different ways to provide this feature.

With HornetQ, the workaround is to use a divert:

Diverts allow you to transparently divert messages routed to one address to some other address, without making any changes to any client application logic.

We use a divert to route the messages sent to the topic to another queue (let's called it Queue_B since it's for the processing job B). Everytime a message is sent to the topic, a copy is also routed to the queue. Our divert is non-exclusive since we want it to still be received by the topic consumers.

We can then create as many consumers we want for Queue_B. Since this destination is a queue, only one of them will receive a message that was initially sent to the topic:

                                   M   +--------------+
                                  ---> | consumer CA1 |
    +----------+  M   +-------+ /      +--------------+
    | producer | ---> | topic |  
    +----------+      +-------+  
                          \                        +--------------+
                           \ M                ---> | consumer CB1 |
                     divert \               /      +--------------+
                             \ +---------+ /       +--------------+  
                               | Queue_B | -- ---> | consumer CB2 |
                               +---------+ \       +--------------+
                                            \  M   +--------------+
                                              ---> | consumer CB3 |
                                                   +--------------+

Among CB1, CB2 and CB3, only CB3 received the message sent to the topic.

There are still many shortcomings of using diverts (or similar features) to share consumers of a topic.

  • for each set of shared consumers, a system administrator must create and administrate on the server one more divert and one more queue.
  • the shared consumers are no longer consuming from the original topic but from a specific queue. That makes the messaging topology more complex to setup and configure in the client applications.
  • the management of the messaging system becomes also more complex: there is no way to know how many subscribers are "really" listening to the topic, this information is lost when messages are routed by the divert.

Enter JMS 2.0 and its "shared subscription".

A non-durable shared subscription is used by a client which needs to be able to share the work of receiving messages from a topic subscription amongst multiple consumers. A non-durable shared subscription may therefore have more than one consumer. Each message from the subscription will be delivered to only one of the consumers on that subscription.

The basic idea behing sharing a subscription is to have a set of consumers (identified by a shared subscription name) receiving exclusively a message from a topic.

That solves all the issues we originally had in a standard fashion. We can now create many shared consumers with the shared subscription name << sub B >> to have them process messages for the job B and scale out nicely:

                                            M         +--------------+
                                    ----------------> | consumer CA1 |
                                  /                   +--------------+
                                 /                    +--------------+
    +----------+  M   +-------+ /                ---> | consumer CB1 |
    | producer | ---> | topic |                /      +--------------+
    +----------+      +-------+ \             /   M   +--------------+
                                  << sub B >> -- ---> | consumer CB2 |
                                              \       +--------------+
                                               \      +--------------+
                                                 ---> | consumer CB3 |
                                                      +--------------+

Among the shared consumers CB1, CB2 and CB3, only CB2 received the message sent to the topic.

  • all our consumers are directly consuming from the topic
  • there are no additional resources to configure or administrate on the server

The JMS 2.0 API adds new methods to create shared consumer:

    JMSContext.createSharedConsumer(Topic topic, String sharedSubscriptionName)
    JMSContext.createSharedConsumer(Topic topic, String sharedSubscriptionName, String messageSelector)

It is also possible to create shared durable consumers:

    JMSContext.createSharedDurableConsumer(Topic topic, String name)
    JMSContext.createSharedDurableConsumer(Topic topic, String name, String messageSelector)

Sharability and durability of subscriptions are two orthogonal notions and all the combination are possible:

  • a unshared non-durable subscription can only have one consumer that will not receive messages sent while its consumer was offline
  • a unshared durable subscription can only have one consumer that will receive the messages sent while its consumer was offline
  • a shared non-durable subscription can have many consumers that will not receive messages sent while all consumers were offline.
  • a shared durable subscription can have many consumers that will not receive the messages sent while all consumers were offline.

JMS 2.0 is an incremental update to JMS that should simplify any Java application using messages. Shared subscription is one of this interesting new features.

⇨ Tim Duncan — The Big Fundamental

June 3, 2013

Insightful portrait of Tim Duncan on the cusp of his 5th NBA finals (he won his first fours):

Sometimes people will mention the swimming when trying to pinpoint the origin of Duncan’s remarkable discipline and relentless consistency. Duncan swam until he was 14 and seemed on a path toward the Olympics like his sister, Tricia. That was when Hurricane Hugo roared through the Island and wrecked the swimming pool. More, that was the year his mother, Ione, died of cancer. She had been his greatest fan, the loudest cheers at the pool, the voice inside his head. He would talk about the little nursery rhyme that she would repeat to him over and over and over …

Good, better, best
Never let it rest
Until your good is better
And your better is your best

You can’t help but think that if you cut Tim Duncan open, those words would be etched on his heart.

There has never been a basket-ball player so consistent for the whole span of his career (stats per 36 minutes):

  • 1st year - 21 year old, 19.4 points, 11 rebounds, 2.5 assists, 2.4 blocks, 57.7 true shooting %
  • 7th year - 27 year old, 21.9 points, 12.2 rebounds, 3.0 assists, 2.6 blocks, 53.4 true shooting %
  • 17th year - 36 year old, 21.3 points, 11.9 rebounds, 3.2 assists, 3.2, blocks, 55.4 true shooting %

I am rooting for the spurs for these finals! #GoSpursGo

(via kottke)

Uriage Cabriolet Classic

May 27, 2013

This sunday was held the 2013 edition of Uriage Cabriolet Classic, a large gathering of classic (and more recent) cars.

I am not a connaisseur of cars but I can recognize a beautiful one when I see it. I really enjoy the attention to details of these cars and the love and care of their owners (the engines were all shining!).

Leather strap for car hood
Leather strap for car hood © Jeff Mesnil

Star on car hood
Star on car hood © Jeff Mesnil

Car Engine
Car Engine © Jeff Mesnil

This gathering is an opportunity to appreciate all the shapes and colours of cars. Even the most modest cars look fantastic with out of the ordinary colours.

Citroën 2 CV
Citroën 2 CV © Jeff Mesnil

Citroën 2 CV
Citroën 2 CV © Jeff Mesnil

We were lucky having a beautiful weather for the gathering and enjoyed the familial atmosphere.

Blue child & car
Blue child & car © Jeff Mesnil

Tuscany Countryside

May 13, 2013

Tuscany Countryside
 Tuscany Countryside © Jeff Mesnil

My girlfriend and I spent one week in Tuscany. We loved every moment of it.

⇨ David duChemin Reviews the Fuji XE-1

May 13, 2013

Spoiler: he loves the camera and, unsurprisingly, makes beautiful pictures with it.

I bought his book, The Print and the Process, this week-end. It is a beautifully crafted book composed of 4 sections, Venic, Iceland, Kenya, and Antarctica providing a variety of scenes (it's mostly landscapes and portraits though, it's a David duChemin's book after all :) Each section is composed of a set of 20-30 images without any text that helps appreciate the flow of pictures without any interruption. At the end of each section, there is a text for each images where the author describes what his intent or feeling was when he took the picture.

The book is bound along the short edge in landscape mode. This design makes the beautiful landscape images really stand out.

Beautiful book, gorgeous photos and instructive reading. Heartily recommended.

⇨ Yahoo! Weather App

April 19, 2013

The new weather app from Yahoo! looks gorgeous and is a pleasure to use with an intuitive navigation.

ahoo! Weather App
Yahoo! Weather App

The photos are geolocated and taken from Flickr photo pool. That's a great way to leverage Flickr.

With the updated Flickr app and this new weather app, Marissa Meyer is on the right track to hold her promise to make Flick awesome again.

⇨ Updated Fuji XF Lenses Roadmap

April 18, 2013

With the release of the 55-200mm ƒ/3.5-4.8 telephoto lens, the Fuji X system gains enough reach to build a complete system and the announced 56 ƒ/1.2 will make an awesome portrait lens.

Fuji XF Lenses

It's getting harder and harder to resist getting a X-E1...

Macarons

April 16, 2013

Last month, my girlfriend offered me for my birthday a cooking class with a chef to make macarons. We already tried several times to make them without much success. The recipe is simple but not forgiving: one has to pay attention to a lot of details to cook macarons that please both the eyes and the palate.

This week-end, we had the cooking class with the chef and made macarons garnis à la pâte d'amandes et au caramel au beurre salé

Macarons
Macarons © Jeff Mesnil

The chef was friendly and gave us lot of explanation to make the best macarons and we are quite happy with the results. They look good and taste even better!

We heartily recommend anyone in Rhône-Alpes, France who is interested to improve its cooking craftsmanship to take a class with Jean-Luc at http://www.coachculinaire.fr.

Criticism of JavaScript callbacks

April 2, 2013

I read two interesting articles about the shortcomings of JavaScript callbacks. I played a bit with node.js and I find that the use of callbacks makes the code more convoluted that it could be.

I find Erlang's mailbox approach simpler to understand and read (but I can not warm up to Erlang syntax...).

Promises looks... promising but I'd like to try them out on a pet project to get a better feel on them. In France, we have a saying that said that "promises bind only whose that listen to them", so I prefer to be cautious :)

⇨ Awestruct 0.5.0 Released

April 2, 2013

Awestruct is the static web site generator I use for my Web site.

This 0.5.0 release is a big one which simplifies rendering by using Tilt and provides an Amazon S3 deployer (that I contributed) out of the box among other other features.

I upgraded this morning and it worked like a charm.

Saint-Haon-le-Châtel

March 26, 2013

Saint-Haon-le-Châtel
 Saint-Haon-le-Châtel © Jeff Mesnil

Cemetary Tree

March 26, 2013

We spent the week-end near Roanne and visited Saint-Haon-le-Châtel, one of the smallest medieval town of France.

This town is located on the top of a hill. The church is at the very top of the town and offers a nice panorama view of the plain of Roanne. The cemetary near the church was deserted, most graves were moved to a more recent cemetary and only remain a few tombstones and ruins around a tree.

Cemetary Tree
 Cemetary Tree © Jeff Mesnil

Moody place...

Spring is Coming

March 18, 2013

Last Saturday, near home, the city of Gières organized a spectacle to celebrate the end of winter and the beginning of spring.

A local artist created a huge leprechaun representing the winter.

Printemps de Gières
Leprechaun — Printemps de Gières © Jeff Mesnil

A local troop of jugglers, "les Lutins Farceurs", gave a representation after sunset. Their make-up was very well made, they looked half-elves half-daemons.

Printemps de Gières
Les Lutins Farceurs — Printemps de Gières © Jeff Mesnil

Kids were both frightened and in amazement looking at them, especially when they were jumping using stilts and going incredibly high with them.

Printemps de Gières
Les Lutins Farceurs — Printemps de Gières © Jeff Mesnil

Printemps de Gières
Les Lutins Farceurs — Printemps de Gières © Jeff Mesnil

Printemps de Gières
Les Lutins Farceurs — Printemps de Gières © Jeff Mesnil

Once the Lutins Farceurs ended their representation, the Leprechaun was burnt to celebrate the end of winter.

Printemps de Gières
Burnt Leprechaun — Printemps de Gières © Jeff Mesnil

The spectacle was great but it was untimely to celebrate the end of winter: it was snowing again this morning.

Spring will have to wait a bit more to come... :)

Emincé de Brocoli, Vinaigrette au Curry

March 2, 2013

Emincé de Brocoli, Vinaigrette de Curry
Emincé de Brocoli, Vinaigrette de Curry © Jeff Mesnil

Food photography is fun.

I feel a bit limited using a Nikon 35mm ƒ/1.8 DX for it but my other lenses are not bright enough or focus close enough to obtain a shallow depth of field. If I were not thinking about changing my photo gear to something else than Nikon DX system, I would definitively buy the 85mm macro lens.

I also need to work on lighting the food. The light is not soft enough when it hits the broccoli at the foreground. It's time to invest in a good flash...