# Running a SharedExtension without Entrypoint

**URL:** <https://discourse.nameko.io/t/running-a-sharedextension-without-entrypoint/507>\
**Category:** Uncategorized\
**Created:** [October 16, 2019, 6:20pm UTC](https://discourse.nameko.io/t/running-a-sharedextension-without-entrypoint/507 "2019-10-16T18:20:26Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![litmax](https://yyz1.discourse-cdn.com/flex031/user_avatar/discourse.nameko.io/litmax/32/67_2.png) [@litmax](https://discourse.nameko.io/u/litmax)\
**Post date:** [October 16, 2019, 6:20pm UTC](https://discourse.nameko.io/t/running-a-sharedextension-without-entrypoint/507/1 "2019-10-16T18:20:26Z")

</div>

Hi!  
I am developing a ban system based on iptables.  
So I need to run a service that will accept incoming rpc for settings & querying iptables rules.  
On nameko run some setup procedures should be called like creating new iptables chains etc.  
But this must be run only once on startup.  
So I am trying to use a SharedExtension. Like this:

```auto
class SecurityExtension(DependencyProvider):
    def get_dependency(self, worker_ctx):
        for ext in self.container.extensions:
            if isinstance(ext, SecurityManager):
                return ext
        logger.error('Cannot find SecurityManager!')

class SecurityManager(SharedExtension, ProviderCollector):
    filter_ports = []

    def setup(self):
        self.filter_ports = ['5060'] # TODO: Get from server or directly from asterisk AMI
        logger.info('Security filter ports: %s', self.filter_ports)

class SecurityBroker:
    name = 'security'
    manager = SecurityExtension()

    @rpc
    def test(self):
        return self.manager.filter_ports

```

But test() always returns [] and setup never is called.  
So if I add a new Entrypoint class it works:

```auto
class SecurityEvent(Entrypoint):
    manager = SecurityManager()

security = SecurityEvent.decorator

```

and add the following method to SecurityBroker class:

```auto
    @security
    def security_stub():
        pass

```

And all works.

But I have a question if there is another way to setup some code on startup of nameko run.  
Thanks.

---

<div class="post-metadata">

**Author:** ![mattbennett](https://yyz1.discourse-cdn.com/flex031/user_avatar/discourse.nameko.io/mattbennett/32/13_2.png) [@mattbennett](https://discourse.nameko.io/u/mattbennett)\
**Post date:** [October 16, 2019, 7:03pm UTC](https://discourse.nameko.io/t/running-a-sharedextension-without-entrypoint/507/2 "2019-10-16T19:03:46Z")

</div>

I don’t think you want a `SharedExtension` here. `SharedExtension` is used where you want a single extension instance to be shared by multiple other extension instances (e.g. all `Rpc` entrypoint instances share one `RpcConsumer`, because there is one queue from which they all consume).

The pattern you want, where something runs once at service startup, can be achieved with a simple `DependencyProvider`:

```auto
class SecurityManager(DependencyProvider):
    filter_ports = []

    def setup(self):
        # do one-time setup here
        self.filter_ports = ['5060']

    def get_dependency(self, worker_ctx):
        # return anything you want the service methods to access here
        return self.filter_ports

class SecurityBroker:
    name = 'security'
    manager = SecurityManager()

    @rpc
    def test(self):
        return self.manager.filter_ports

```

Your later example works by accident, and is not the intended way.

It’s normally nice to return a proper class instance from `get_dependency` so that you can expose a rich API to the service method (while still hiding the complexity of the `DependencyProvider` internals) but if a simple dict or list is sufficient that’s fine too.

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<div class="post-metadata">

**Author:** ![litmax](https://yyz1.discourse-cdn.com/flex031/user_avatar/discourse.nameko.io/litmax/32/67_2.png) [@litmax](https://discourse.nameko.io/u/litmax)\
**Post date:** [October 19, 2019, 11:27am UTC](https://discourse.nameko.io/t/running-a-sharedextension-without-entrypoint/507/3 "2019-10-19T11:27:37Z")

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Thank you Matt!  
It worked.