How I Fixed: Server channel error: 406, message: PRECONDITION_FAILED – inequivalent arg ‘type’ for exchange ‘my_exchange’ in vhost ‘/’: received ‘fanout’ but current is ‘direct’

Not a fun way to start a Saturday morning. With a bit of spare time this morning I wanted to continue some refactoring work on a tool I’ve been working on for checking broken links on any given website.

The project is quite cool (in my opinion), using a bunch of interesting software / tech such as RabbitMQ with Symfony’s Messenger component, STOMP for real time stuff, React with Hooks, Tailwinds for CSS… and a bunch more buzz-wordy, CV helping stuff that keeps me gainfully employed.

Anyway, the first thing I did was spin up the Symfony docker containers that run the various services to handle incoming broken link checking requests. And as ever, I ran a composer update to bring Symfony up to 4.3.x.

I’m not sure if bumping up to Symfony 4.3 was the cause of this problem. I suspect not. It’s been a while since I’ve worked on this part of the code, but it was all working the last time I brought the project up. And it’s working live and online, too, so something has gone awry.

Anyway, after the composer update completed successfully:

I tried to run my messenger consumer:

Knickers. It all blew up quite badly.

There’s a lot of info to process, and without some nice terminal colouring it’s all a bit of a blur.

The interesting line is:

What I think has gone wrong is that at some point in the past, I’ve switched over my RabbitMQ exchange to use direct, and by default, Symfony’s Messenger component will try to create an exchange with the type of fanout.

To clarify, my exchange and queue combo already exists at: amqp://{username}:{password}@rabbitmq:5672/%2f/fetch

It exists because I have previously configured my RabbitMQ instance to boot up with this exchange / queue combo ready and good to go.

Because Symfony’s Messenger component is not immediately aware that this queue will already exist, it tries to create it.

It cannot create it because the default type of exchange that Symfony’s Messenger component will try to use is fanout.

In order to make this work, I needed to manually specify the config that explicitly sets this exchange / queue combo to the desired setting of direct.

Finding this out via the documentation wasn’t super straightforward. Here’s a few of the steps I took:

bin/console config:dump-reference framework

This shows that for each framework.messenger.transports entry in your config/packages/messenger.yaml file, you can have a variety of additional settings.

As it was, my original config looked like this:

By providing just a DSN (by way of environment variables), all the default config would be used.

What I needed to do was swap over to this:

And after doing so, it all started working again:

In short, this isn’t directly a Symfony / Symfony Messenger problem. It’s a config problem. The messaging could be a little more clear, as could the documentation for what things are viable as options.

Symfony 4: Removing the Mystery

The Beginners Symfony 4 tutorial is in progress. I have all but the final video recorded now. I ended up re-recording a number of sections in both of the recent video uploads:

Why?

One of the areas I found most confusing when first starting with Symfony was in the widespread use of Interfaces.

You may have encountered the following problem:

Let’s say you’re working under a tight deadline. You’re writing some Symfony Controller code and working with a form. It’s not going quite as smoothly as you’d like. You reckon something is going awry with the form submission.

Being the inquisitive developer, you remember the oft touted advice:

Read the source, Luke

The thing is, when you ctrl+click on $form->submit($request); you’re taken to… an interface.

This is good stuff.

Your life will be much easier if you code to an interface, rather than tie your methods to specific implementations.

However, with that deadline looming over your shoulder, such things are nice to know, but right now, just show me the code!

Finding An Implementation

When I first recorded this video I initially just said what the outcome of a call to the submit  method would be.

Watching back, I couldn’t help but think about that stuck, and stressed developer. Sat in a noisy office, headphones in, listening to music when you’d rather have peace and quiet.

Everyone around you seems to be goofing off whilst you’re struggling to think through this really important problem.

The last thing you need is to be met with this weird interface  thing. If only you could find the implementation then life would be a lot less stressful.

How can you find out what is really happening when you call $form->submit($request);?

And what happens when you find the implementation and even then the code is tricky to follow?

I know these feels.

That’s why when recording this video I worked hard to make sure you come out at the end with a good understanding of the code that makes this happen.

This is a beginners series for Symfony 4. This is the stuff that will make working with, and understanding Symfony that much easier.

I hope you enjoy it.


Site Stuff

There’s a ton of work going on behind the scenes at the moment.

Can I pay by PayPal?

This is one of the most frequently asked questions that I get.

Currently: no.

That sucks. I appreciate that.

The reasoning for this is that Stripe is super shiny and as a developer, they were high on my wish list of cool things to implement.

Also, from a code perspective Stripe is actually a joy to work with. They really are awesome.

But still, I get asked a lot for PayPal.

I’m adding PayPal.

It’s quite a big job, but I’m about 65% of the way through the implementation.

Here’s a sneak peak:

That’s the Stripe form using Stripe’s React elements.

PayPal functionality is provided through Braintree.

There’s a nice transition between the two options too, which came for free via Bootstrap 4 and I really like it.

I’ve been working on completely extracting the membership code.

Would you have any interest in seeing video tutorials on how to make your own Symfony bundles?

Leave a comment and let me know.

There’s some other cool features that this work enables, which I’ll share with you in a future update.

Until next time, have a great weekend and happy coding.

Chris

Merry Christmas and a Happy New Year for 2018

This is the last you will be hearing from me – newsletter wise, at least – for 2017.

With that in mind I’d like to take this opportunity to say firstly a very big and sincere thank you to you for your support this year.

Whether your are a subscriber currently, have subscribed to the site in the past, or will be subscribing in the future, your support means a lot to me.

I’m really pleased with how things have progressed with CodeReviewVideos.com this year.

I launched the new site version, which whilst still a work-in-progress (and likely always will be) now is in line with almost everything new I’ve learned in the last four years.

I share everything I know on CodeReviewVideos.com, and from the feedback I’ve had this year (thank you!) I know it’s really helpful to many of you, too.

This site is all about saving you weeks, months, or even years off the amount of time it takes to learn a framework as big and (potentially) complex as Symfony.

There’s other great stuff on here too, like learning how to use Docker in the real world, and another of my personal favourites, React with Redux and Redux Saga all connected to a Symfony JSON API.

Video Update

This week saw three new videos added to the site.

#1 – Fixing Third Party Bundle Deprecations (Indirectly)

We’ve fixed the issues with Symfony’s code.

We’ve fixed the issues with our own code.

Now we must fix the issues with any third party bundles we are using.

In our case we have just one bundle – eightpoints/guzzle-bundle.

The issue we have is fairly common. If a bundle you use adds ‘stuff’ to the sidebar in the profiler, then you are almost certainly going to need to fix this issue. Well, I say you. What I really mean is you will need to hope your bundle maintainer has updated their code appropriately, or you have a few options:

  1. Don’t upgrade
  2. Fix it yourself (which may take a while to get merged)
  3. Fork it, and fix it yourself (hoorah, now you’re in open source)
  4. Be lucky and have the bundle maintainer already have updated it for you

We all hope for number 4, right?

Fortunately on eightpoints/guzzle-bundle we get lucky. This is fixed for us… but:

Always a but. This will mean we need to be on at least PHP 7. Actually thought, Symfony 4 needs PHP 7.1, so yeah… either way it’s time to come kicking and screaming in to the modern world of PHP. Good.

#2 – [Part 1/2] Migrating to Symfony 4.0 with Flex

The recommended approach for upgrading to Symfony 4 with Flex is to start a brand new Flex project, and then migrate code between the old project, and the new.

This brings a potential problem:

When you create the new Flex project you will, by default, get a git repo created on your local computer.

For the love of Mike, don’t do what I did and accidentally copy that git directory over your existing git directory. Whoops. I share for the comedy, and fortunately it didn’t cost me any, because that was during the write up, and I re-do the whole thing again for the video. I bet you don’t want to do things twice though 🙂

There’s a bunch of steps to work through, some easier than others. You won’t believe step 5! Ho, ho, a buzz feed style bit of link bait title nonsense.

No, but seriously, step 5 needs some extra attention so be sure to watch the video to learn what that is.

#3 – [Part 2/2] Migrating to Symfony 4.0 with Flex

Finally we finish up the Symfony 4 migration by moving over the src  directory contents from the old Symfony 3.4 project to the new Symfony 4 Flex approach.

We then move over the Twig templates. There’s more work to be done here, and some of the problems we will face are not very intuitive. I guess it depends on how much you’ve been following the changes made in Symfony 4.

It really does feel good to have migrated a complete project, regardless of the project’s size, from Symfony 3 to Symfony 4. There’s some serious sense of satisfaction in seeing everything continue to work, even with such a massive amount of change behind the scenes.

Here’s to 2018

Whatever you are up to in 2018 I sincerely wish you every success.

Thank you and happy Christmas!

Chris