Hi Aarushi, 

Thanks for the nice problem description. It may also be helpful to understand 
why the sharing and profile services communicate over RabbitMQ while the others 
are direct Thrift calls.

Marlon
 

On 6/10/19, 10:26 AM, "Bisht, Aarushi" <[email protected]> wrote:

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    ?Hi All,
    
    
    For those of you who don't know me, I am a GA in IU Bloomington, working on 
the Custos project. Since the past week I have been working on migrating 
Sharing Service as a standalone Custos service.
    
    
    I have been trying to remove all dependencies of airavata from sharing 
registry service. So far I am able to start it as an independent service but 
there are few code dependencies on airavata's utility modules.
    
    
    On investigating these dependencies I found out few things and would like 
to get advice on some decisions.
    
    
    The sharing registry service is being used by the following services in 
airavata:
    
    1. Group Manager service
    
    2. Services-security
    
    3. Airavata-api-Server
    
    4.Tenant Profile service
    
    5. User Profile service
    
    5. Registry server
    
    
    All the above services are communicating with the sharing service through a 
thrift client except for user/tenant profile service and registry service.
    
    
    The communication between profile service and sharing service is done 
asynchronously through RabbitMQ . When a new user or tenant is registered,  a 
message is added to the PROFILE / TENANT queue which is then consumed by the 
sharing service and corresponding database entries are done in sharing database.
    
    
    Similarly registry service consumes the message from PROFILE queue and 
sends a message to PROJECT queue to create a default project for the new user 
account. This message is consumed by the sharing registry service.
    
    
    I want to seek advice on how the communication with the standalone sharing 
registry service should be handled in future so that it aligns with custos 
project goals.
    
    
    There are couple of approaches that I can think of:
    
    1. Thrift API calls
    
    Any communication with sharing service will be done only through a thrift 
client. This will involve making changes to registry and profile services. This 
makes the call synchronous, and if required, the consuming services will need 
to handle asynchronous calls and error handling.
    
    
    2. Using RabbitMQ
    
    ?The advantage of using this approach is that communication will be 
asynchronous but the services consuming sharing service will have to manage 
RabbitMQ connection.
    
    
    3. Expose Thrift API call which internally use RabbitMQ for asynchronous 
communication
    
    This will involve adding API call in sharing service which can be used by 
other services to add a message to the sharing service queue. The advantage of 
this approach is that other services consuming sharing service will not have to 
manage RabbitMQ connection and the communication will still be asynchronous 
(other than the call to push request in RabbitMQ)
    
    
    The decision mainly boils down to choosing between synchronous and 
asynchronous approach. Asynchronous will mean faster response time for APIs, 
with each service responsible for handling and resolving its own errors. But 
this also means that there might be few seconds delay in processing of requests 
as these are asynchronous. On other hand, synchronous approach will ensure that 
all requests are processed immediately, which increases the API response time 
but also makes it tricky to handle failure edge cases as if any request fails, 
the corresponding DB entries needs to be rolled back which may include another 
thrift call (if entries were made via thrift). If rollback fails due to some 
reason, there is no easy way to ensure data consistency, though this is a edge 
case scenario.
    
    
    Thanks & Regards,
    
    Aarushi Bisht
    
    
    

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