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[Messenger][RFC] Improve Messenger to support other app consuming/recieving the message #33912
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Isn't the Symfony Serializer integration enough for these cases? When using Serializer, the message is encoded in JSON, and can easily be decode by any app able to deal with JSON. |
We’re covering this in the coming days in SymfonyCasts: A) symfony Serializer for turning messages into JSON if the worker will be another app. That’s one line of config. B) custom Messenger transport Serializer is your app is consuming messages that originate from another app. That’s one class and one line of config (and if you want, you can use the Serializer component from within the this custom transport Serializer). Could the problem be just a lack of documentation to point this out? Thanks for the convo! |
So, I actually was able to successfully get messenger working with magento 1.x to a symfony application over redis. Both applications send and receive messages from the other. What we ended up doing was just create a third repository for storing our shared message classes between the two, and then installed the repository as a git submodule and used composer path type repositories to include into each of the applications. I think using shared classes is safer than maintaining two separate versions of the class, but, you still have to be careful that any message class changes are done in a backwards compatible way to remove the tight coupling of those apps being deployed together. |
We have an application that is synced up with a .net process. We use a custom Messenger Serializer (described by @weaverryan) for inbound and outbound messages. |
I am struggling with this issue myself currently at work where I have to publish messages onto a queue where another agency will pick up the messages. I tried to create a small package that contains interfaces which would be implemented by the classes that will be published so both of us would end up installing this package. In my messenger config, I bound the interfaces to the different queues but this did not work since the class names were added to the envelope and not the interface names. |
That's one of my main concern with messenger (and symfony/serializer component as well): you cannot give a map of names or aliases that would map to PHP class. In a project we wrote this: https://gist.github.com/pounard/25d2a8d4502a6bb61e660957196a5773 (which is then filled with an alias to PHP class array map, from a custom bundle configuration). Then you specify your messages with business oriented names and not technical ones. One missing bit in my example code is that we also have a custom messenger's serializer that maps the names the other way around to send them instead of PHP class names (PHP classes got converted to business name when published, then converted back into PHP class names when consumed). |
If you have more than two applications (currently we have only one but we are targeting a client environment where we'll have at least 5, each with their own maintainers and release plan, plus one end-user centric dashboard that will arbitrarily consume events to populate a client dashboard). In this future, having other technos than PHP is considered, and having stalling application for 1 or 2 year is also a possibility: we have to specify our messages as a high-level business-oriented specification unbound to the technical aspects. Which means, backward compatibility when possible, having the most recent upgrades able to talk using more than one version of the protocol, etc... In that regard, sharing code with every application is not possible. |
@pounard for sure, you gotta do what works best for your team and roadmap. A custom serializer might be the best way to go if you end up sharing messages across various languages. If you can keep in php, a shard repository that can be updated at its own cadence in the individual repos might be less work. |
That's the usual answer I get :) I do not always agree though. Regarding incoming content type I still think that the messenger component should handle this natively. For the rest, every bit is subject to subjectivity and one's need. But all remain interesting topics to discuss. To go further in this direction, there's still a probability that we'll switch from the messenger to a more bare-metal AMQP implementation instead one day, if the messenger doesn't easily answer our needs; that's why all our business code sends its messages via a custom interface, and messenger, in our project, is completely hidden behind it. It's replaceable. |
Are you suggesting that the message type would be set on the content type and then a system would allow you to map each type to a class in your code (that the Serializer works then use fire deserialization)? Or do I misunderstand? For us, our custom Serializer is a basic switch case statement: we determine what kind is message is coming in (e.g. by reading some info from a header or just looking at the field), then use that in a switch case to create and return different message objects for each. |
content-type and message type are both very different things, I think they can be handled very differently. Message type may or may not be exposed by the bus implementation, for example in AMQP you can retrieve messages with the 'type' property (as of now, the messenger stores it alongside the message header, in the form of the PHP class name). Converting from an arbitrary type to a PHP class could be a feature of component/serializer, or could be handled by the messenger serializer (which I think makes more sense). Regarding content-type (i.e. format in component/serializer semantic) should be handled by the messenger serializer class.
I think that a basic version of that based upon configuration could be in messenger core, all it needs is a map to be injected, using the dic or annotations (either one or both). You then wouldn't even need to implement your own. |
Symfony Messenger's headers are very tightly coupled with not only Symfony Messenger, but also with PHP as a whole through its utilization of PHP namespacees. This is quite the hindrance for us who wish to utilize other programming languages that publish and consume messages from the same RabbitMQ server. The "type" header always points to a PHP class (full namespace). But what if the message is an integration event, consumed by an entirely different code base with a different namespace? It is a very greedy coupling. Stamps are a great feature. I like how they're handled. However, again the coupling to Symfony and PHP is tight, as headers like "X-Message-Stamp-Foo\Bar\Baz" will exist, where "Foo\Bar\Baz" is - again - a PHP class reference. You are completely locked into this naming convention if you use This could be fixed for stamps by introducing a new interface, e.g. "NamedHeaderStampInterface": <?php
namespace Symfony\Component\Messenger\Stamp;
use Symfony\Component\Messenger\Stamp\StampInterface;
interface NamedHeaderStampInterface extends StampInterface
{
public function getHeaderName(): string;
} Stamps that implement this interface will use the string provided by Mapping the header names to their respective classes is another thing which must be handled, such that when consuming, things may get glued back together. A thought on how to handle the "type" header differently Let developers define a core namespace for the messages being sent to an exchange. This namespace is then subtracted from the full class name. Example: <?php
use My\Application\AMQP\Event\Foo\Bar\Baz\UserWasCreatedEvent;
$namespace = 'My\Application\AMQP\Event';
$userWasCreatedEvent = new UserWasCreatedEvent;
if (0 !== stripos(get_class($userWasCreatedEvent), $namespace)) {
throw new \Exception(sprintf(
"Class \\%s must be located under the namespace \\%s, but it is not",
get_class($userWasCreatedEvent),
$namespace
));
}
$type = substr(get_class($userWasCreatedEvent), strlen($namespace));
echo $type; Output:
To stitch it all together again, the consumer will simply have to prepend the namespace. We have now gotten rid of the ultra tight coupling in PHP and to the application from which a message originated. However, the remainder of the namespace will still have to be exactly the same. The above is also very easily converted to namespacing in other programming languages like C#, Java and Node.js. E.g. simply replace the backslashes with dots. Anyone else thinking this would be a great change? I may even be done without backward compatibility breakage by simple writing an alternative |
I just think the messenger component should have a type to class map, per default returning the class name, but configurable, either using some YAML, some static method call, or using annotations (I dislike annotations I would not use them anyway). The messenger's serializer is way too coupled to messenger own logic making it very hard to replace or decorate. We done that for a year, and ended up ditching the messenger component completely, using a 100% custom bus using pgsql now. |
Thank you for this suggestion. |
Carsonbot (🤖 ) I didn't work on this problematic since 1 / 1.5 year. Has this issue improved since ? |
Thank you for this suggestion. |
This is exactly what we've implemented in a separate bundle in my company and it works well. I am in favor of this approach for two reasons:
routing:
super.custom.event: transport
Old\School\Event: transport
events:
super.custom.event: Some\Php\Class Now I can integrate non-Symfony applications, yay! |
Thank you for this suggestion. |
Ryan's message from a year ago still holds: This issue shows there is a need, but we need someone to do the work. Anyone up to starting a PR to implement the ideas discussed in this issue? Otherwise, I'm afraid we'll have to close this as stalled given there apparently hasn't been enough interest for somebody (or some company) to dedicate some time to actually fix this. |
I did, in 2019. I don't want to it a second time, I'm sorry but this has fatigued me it took 3 years for people to understand it's a must have. I sincerely hope someone will do because it's a necessary feature, it would make the messenger component greater ! |
Thank you for this suggestion. |
Yes |
@weaverryan @wouterj can someone outline where one would start? (with the implementation?) |
just adding my 2cts here perhaps related to what I've posted previously we can imagine just having a class in the symfony core messenger component, not being the default, that just serialized the envelope and return a raw json unrelated to php things at all to decouple things ? thus, freely and simply, we can swap the serializer config of any transport requiring this core class |
I have to admit that through all the comments in this issue I have no idea anymore what are the core changes that you all would like to see for the Messenger component. So from my POV crafting an actionable list of things to do would be a good start. |
@xabbuh long time ago when this issue was opened, where I work for we have switched to a completely home-made message dispatcher instead of messenger due to the numerous restrictions it had at that time. Now, we intend to switch back to messenger which has evolved and stabilized during those years, for new projects, so soon enough I'll go deeper in this topic and will be able to help draw pieces of this actionable list. We have a new project coming in the next weeks, so stay tuned. |
@xabbuh First one: add an |
given that message classes are not registered as service, this won't be easy as autoconfiguration attributes are used only on autoconfigured services (unless you suggest reading that attribute at runtime). |
You can read it at runtime with no problems, reflection is lightning fast. We did this in our own bus implementation for routing |
That's a good point! I support this idea, since I myself used to find me three times a day jumping back and forth between message routing configuration files just to tweak a message class after refactoring. Idea with attribute is a good starting point, though, in case of routing configuration files, it's a common thing to define a separate routing (e.g. sync transport) sections for development environments ( |
My opinion is that the bus implementation should be different when dev or test, but not the routing itself, otherwise you don't test in prod condition. But that's an opinion, not an absolute truth. A simple idea to fix that would be either to add an |
I will open an issue and a PR next week if time allows me to do so. |
Hi! This issue is going a bit everywhere, which makes it hard to understand (maybe extra because I'm not that familiar with the Messenger component). I suggest the best way forward is to branch of a couple actionable and scoped issues, and close this one. For now, I've spotted three things in the discussion here:
Are some of you open to start the issue, run some research and experiment with code? |
Agree, this would worth the shot to open a set of smaller issues, lots of the changes requested here are not conflicting with each other. I'll try to reach you on Slack, but I don't open the client often since it likes to eat all my laptop RAM. |
Using the Serializer component instead of using PHP serialization is already possible (the default behavior is to use PHP serialization because it is a simpler setup, which works fine when you don't need to share the message between apps) |
OK nice, that wasn't the case when this issue was created, that's good news. |
I reread the code and it seems what you said is not exactly true: while it seems to be OK in |
Correct me if I'm wrong, but even the json serialization is still called the |
I saw two different ways of solving the intercommunication:
Regarding the first point, there are many ways to skin a cat, but I can see two (which are in the end equivalent) and both easy to implement:
I much prefer the first one, but both are doable quite easily (done it for client projects in https://github.com/makinacorpus/php-normalization) The hardest problem here is that messages are not services, and will never be, hence core developers will not allow abusing the dependency injection registration mechanism to parse class attributes (ie. making messages false services, parse them, register the names, then drop them as being services). |
I opened #57536 for discussion around class name aliases. |
…sage routing (pounard) This PR was merged into the 7.2 branch. Discussion ---------- [Messenger] Introduce `#[AsMessage]` attribute for message routing | Q | A | ------------- | --- | Branch? | 7.2 | Bug fix? | no | New feature? | yes | Deprecations? | no | Issues | Fix #57506 | License | MIT Basic implementation of #57506. * Adds the `Symfony\Component\Messenger\Attribute\AsMessage` attribute, with the `$transport` parameter which can be `string` or `array`. * Implement runtime routing in `Symfony\Component\Messenger\Transport\Sender\SendersLocator`. Rationale: * Messages are not services, it cannot be computed during container compilation. * Reflection is very fast, it shouldn't be significant for performances, yet I don't have measured it yet. * YAML configuration and `Symfony\Component\Messenger\Stamp\TransportNamesStamp` will always override the attribute values, allowing users to change hardcoded routing on a per-environment basis. * This is the simplest implementation I could think of for discussion. Links and references: * #33912 where the discussion started, 5 years ago. * #49143 closed PR that was doing the same, but at compile time, rejected because the actual doctrine is that messages should never be services. * #41179 is stilled opened, and awaiting for modifications, but it was written for an earlier version of Symfony and is inactive for a year or so, yet messenger code has evolved since, and this PR will never merge as-is, it requires to be fully rewrote, reason why I opened this new one. Commits ------- d652842 feature #57506 [Messenger] introduce AsMessage attribute for message routing
…sage routing (pounard) This PR was merged into the 7.2 branch. Discussion ---------- [Messenger] Introduce `#[AsMessage]` attribute for message routing | Q | A | ------------- | --- | Branch? | 7.2 | Bug fix? | no | New feature? | yes | Deprecations? | no | Issues | Fix #57506 | License | MIT Basic implementation of #57506. * Adds the `Symfony\Component\Messenger\Attribute\AsMessage` attribute, with the `$transport` parameter which can be `string` or `array`. * Implement runtime routing in `Symfony\Component\Messenger\Transport\Sender\SendersLocator`. Rationale: * Messages are not services, it cannot be computed during container compilation. * Reflection is very fast, it shouldn't be significant for performances, yet I don't have measured it yet. * YAML configuration and `Symfony\Component\Messenger\Stamp\TransportNamesStamp` will always override the attribute values, allowing users to change hardcoded routing on a per-environment basis. * This is the simplest implementation I could think of for discussion. Links and references: * symfony/symfony#33912 where the discussion started, 5 years ago. * symfony/symfony#49143 closed PR that was doing the same, but at compile time, rejected because the actual doctrine is that messages should never be services. * symfony/symfony#41179 is stilled opened, and awaiting for modifications, but it was written for an earlier version of Symfony and is inactive for a year or so, yet messenger code has evolved since, and this PR will never merge as-is, it requires to be fully rewrote, reason why I opened this new one. Commits ------- d65284239f feature #57506 [Messenger] introduce AsMessage attribute for message routing
Description
Hello,
I'm a new user of Messenger; Thank you to all contributors of this promising component; Yet, it gave me a hard time to solve some basic problematics.
Example
Let's say you have 2 different Symfony applications.
The application A (big, monolithic) is responsible of publishing the message to the queue using messenger. Until here, it's ok, everything is covered by the doc.
Then the queue (Amazon SQS/SNS) triggers a new Lambda execution, passing the message to the function (which is a SF Application B, responsible of generating a PDF); This behaviour is specific to Amazon, but it can be generalized of "messages can be pulled or pushed".
The problematic
A. On all examples on the doc, you assume that the consumer is the application that put the message in the queue itself;
But what if it's not the case ? What if it is another Symfony (smaller) project, responsible of generating the PDF only ? What if it's another language ? (JS ?).
B. The Messenger component sends the messages with some
namespace
inside;So if your message class lives in
App\AwesomeBundle\Message\PdfMessage
in application A, andApp\Message\PdfMessage
in application B, then application B won't be able to decode the Message;C. What if the message is not pulled by the messenger component itself, but somhow is recieved (pull vs pushed) ?
I achieved this scenario, and here's what helped me:
Happyr/message-serializer
Do you think some of these problematic are generic enough to be covered by the component code or by the documentation ?
Thank you :)
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