DependencyProvider get_dependency specific to request

googlegroup
1

I have a use case where we have isolated databases for each client. That
means, when a request from a specific client comes in, I want to get access
to that client's specific database.

Let's say I have a database DependencyProvider (similar to
nameko_sqlalchemy), where the *setup *function instantiates all of my
connections to all of the client databases. I'm not entirely clear how I
can alter the worker_ctx in *get_dependency *so that I can return the
connection for a specific client. It seems like I somehow need to alter
worker_ctx so that I end up doing something like:

class Database(DependencyProvider):

    def setup(self):
        #Start all client connections

    def get_dependency(self, worker_ctx):
        client = worker_ctx['client_id']
        session_cls = sessionmaker(bind=self.connections[client])
        session = session_cls()
        self.session[worker_ctx] = session
        return session
       
Do you have any suggestions for how to do this?

Thanks!

2

You've got the right approach.

The WorkerContext has a `context_data` dict for carrying request-contextual
data like `session_id`, `locale` etc between calls. If you put the
`client_id` in there, it'll be available to all DependencyProviders in the
current service. It will also pass along between service calls if your
inter-service DependencyProviders and Entrypoints pass it along. See my
reply to your question here
<Redirecting to Google Groups; for more.

···

On Wednesday, April 19, 2017 at 2:29:52 AM UTC+1, di...@clearmetal.com wrote:

I have a use case where we have isolated databases for each client. That
means, when a request from a specific client comes in, I want to get access
to that client's specific database.

Let's say I have a database DependencyProvider (similar to
nameko_sqlalchemy), where the *setup *function instantiates all of my
connections to all of the client databases. I'm not entirely clear how I
can alter the worker_ctx in *get_dependency *so that I can return the
connection for a specific client. It seems like I somehow need to alter
worker_ctx so that I end up doing something like:

class Database(DependencyProvider):

    def setup(self):
        #Start all client connections

    def get_dependency(self, worker_ctx):
        client = worker_ctx['client_id']
        session_cls = sessionmaker(bind=self.connections[client])
        session = session_cls()
        self.session[worker_ctx] = session
        return session
       
Do you have any suggestions for how to do this?

Thanks!

3

Hi Matt,

Thanks for the response. That's a solution I hadn't thought of, thanks for
posting it.

I'm curious whether you can achieve the same functionality with "logging
in" with a session. Can you alter the context data when you are making a
call from one service to another? For example, could I do something similar
to the following:

class Service1(object):
    name = 'service_1'
    service_2 = RpcProxy('service_2')

    @rpc
    def client_endpoint(self, client_id):
        data = {"data": "blah"}

        # SOME HOW PASS IN CONTEXT DATA HERE ??
        # self.worker_ctx.context_data['client_id'] = client_id
        self.service_2.write_to_database(client_id, data)

class Service2(object):
    name = 'service_2'
    session = Session(Base)

    @rpc
    def write_to_database(self):
        session = self.session # Uses context_data from client_endpoint to
get session specific to client

···

On Wednesday, April 19, 2017 at 12:26:32 AM UTC-7, Matt Yule-Bennett wrote:

You've got the right approach.

The WorkerContext has a `context_data` dict for carrying
request-contextual data like `session_id`, `locale` etc between calls. If
you put the `client_id` in there, it'll be available to all
DependencyProviders in the current service. It will also pass along between
service calls if your inter-service DependencyProviders and Entrypoints
pass it along. See my reply to your question here
<Redirecting to Google Groups; for more.

On Wednesday, April 19, 2017 at 2:29:52 AM UTC+1, di...@clearmetal.com > wrote:

I have a use case where we have isolated databases for each client. That
means, when a request from a specific client comes in, I want to get access
to that client's specific database.

Let's say I have a database DependencyProvider (similar to
nameko_sqlalchemy), where the *setup *function instantiates all of my
connections to all of the client databases. I'm not entirely clear how I
can alter the worker_ctx in *get_dependency *so that I can return the
connection for a specific client. It seems like I somehow need to alter
worker_ctx so that I end up doing something like:

class Database(DependencyProvider):

    def setup(self):
        #Start all client connections

    def get_dependency(self, worker_ctx):
        client = worker_ctx['client_id']
        session_cls = sessionmaker(bind=self.connections[client])
        session = session_cls()
        self.session[worker_ctx] = session
        return session
       
Do you have any suggestions for how to do this?

Thanks!

4

Yes, you can do exactly this.

The only caveat is that service classes can't access the worker context
directly -- you'd need to modify it via a DependencyProvider (or use one to
expose it directly).

With this pattern, we sometimes use a context manager around the RPC proxy
call to set context data for that call and remove it again afterwards.

···

On Saturday, April 22, 2017 at 9:55:34 PM UTC+1, di...@clearmetal.com wrote:

Hi Matt,

Thanks for the response. That's a solution I hadn't thought of, thanks
for posting it.

I'm curious whether you can achieve the same functionality with "logging
in" with a session. Can you alter the context data when you are making a
call from one service to another? For example, could I do something similar
to the following:

class Service1(object):
    name = 'service_1'
    service_2 = RpcProxy('service_2')

    @rpc
    def client_endpoint(self, client_id):
        data = {"data": "blah"}

        # SOME HOW PASS IN CONTEXT DATA HERE ??
        # self.worker_ctx.context_data['client_id'] = client_id
        self.service_2.write_to_database(client_id, data)

class Service2(object):
    name = 'service_2'
    session = Session(Base)

    @rpc
    def write_to_database(self):
        session = self.session # Uses context_data from client_endpoint to
get session specific to client

On Wednesday, April 19, 2017 at 12:26:32 AM UTC-7, Matt Yule-Bennett wrote:

You've got the right approach.

The WorkerContext has a `context_data` dict for carrying
request-contextual data like `session_id`, `locale` etc between calls. If
you put the `client_id` in there, it'll be available to all
DependencyProviders in the current service. It will also pass along between
service calls if your inter-service DependencyProviders and Entrypoints
pass it along. See my reply to your question here
<Redirecting to Google Groups; for
more.

On Wednesday, April 19, 2017 at 2:29:52 AM UTC+1, di...@clearmetal.com >> wrote:

I have a use case where we have isolated databases for each client.
That means, when a request from a specific client comes in, I want to get
access to that client's specific database.

Let's say I have a database DependencyProvider (similar to
nameko_sqlalchemy), where the *setup *function instantiates all of my
connections to all of the client databases. I'm not entirely clear how I
can alter the worker_ctx in *get_dependency *so that I can return the
connection for a specific client. It seems like I somehow need to alter
worker_ctx so that I end up doing something like:

class Database(DependencyProvider):

    def setup(self):
        #Start all client connections

    def get_dependency(self, worker_ctx):
        client = worker_ctx['client_id']
        session_cls = sessionmaker(bind=self.connections[client])
        session = session_cls()
        self.session[worker_ctx] = session
        return session
       
Do you have any suggestions for how to do this?

Thanks!