Set extra headers for outbound messaging as late as possible

[iky]

Allows for in-entrypoint context data updates. This is useful when setting a language for example:

class LanguageContext(DependencyProvider):

    def get_dependency(self, worker_ctx):
        @contextmanager
        def set_language(language):
            original_language = worker_ctx.data.get('language')
            worker_ctx.data['language'] = language
            yield
            worker_ctx.data['language'] = original_language
        return set_language

class ExampleService(object):

    name = 'exampleservice'

    language_context = LanguageContext()

    @rpc
    def greet_in_french(self):
        with self.language_context('fr'):
            return self.example_rpc.say_hello()

Another use we have is services signing up outbound calls with its own authentication.

I removed the lazy load and caching of call_id and call_id_stack of worker context. These properties are super-cheap and most of the time loaded anyway (if entrypoint contains an outbound call, or in logging debug call_id_stack is logged by the container, if tracer is on and so on...)

[mattbennett]

Thanks @iky.

I think this same change needs applying to the Publisher and EventDispatcher, because this same issue is in messaging.py:

nameko/nameko/messaging.py

Lines 116 to 124 in b0131f5

	def get_dependency(self, worker_ctx):
	extra_headers = encode_to_headers(worker_ctx.context_data)
	def publish(msg, **kwargs):
	self.publisher.publish(
	msg, extra_headers=extra_headers, **kwargs
	)
	return publish

[timbu]

@mattbennett Is this the same problem from here? https://github.com/nameko/nameko/pull/573/files

[mattbennett]

Gah, yes it is! Sorry @timbu, I completely forgot about that PR.

Interesting that this was introduced for the non-RPC extensions before the big refactor that landed in 3.x.

[mattbennett]

I guess we should land #573 and then bring master into the v3 branch.

[iky]

Ah, did not see that. @timbu @mattbennett It's not just Publisher of messaging module, EventDispatcher of events module needs to be changed too, see 5c416ce

[iky]

I've updated the remaining places. The fixes are tiny, maybe we can merge this to 3.0.0 before #573 lands in master and then dealing with merging the two together?

[mattbennett]

@timbu @mattbennett It's not just Publisher of messaging module, EventDispatcher of events module needs to be changed too, see 5c416ce

Ah, quite right. And that means #573 is missing the equivalent fix for the event dispatcher.

I agree, let's make the fixes here, then #573 can land, then we'll merge master into the v3rc branch.

[kooba]

Just one small thing

[kooba]

Might want to add context_data to :Parameters: doc above.

[iky]

good catch, thanks! .)

[mattbennett]

Awesome!

[kooba]

👍