CPS-821 Spike: Support Async read-write operations on CPS-NCMP interface

New/Open

Reopened

Agreed/Closed

1

What topic to use for client?

Topic provided by client as a parameter which will be injected into our environment and used for asynchronous requests sent back to client.

Feb 17, 2022  Update: @Toine Siebelink had a conversation with @Tony Finnerty it has been agreed CPS is to configure a (temporary) dedicated client-topic as final destination for the async replies: we now want to propose to use a common ‘cps-broadcast’ topic which also will used for broadcasting messages like cm handles being added o removed etc.

Still it is only a temporary solution until the client have a better way of declaring their own topics. It does not affect our proposed interfaces, just the name of the topic that will be accepted by NCMP (for now)

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Feb 16, 2022  Update: After discussion with @Fiachra Corcoran regarding Kafka-strimzi it has been agreed that we will define a topic for client responses in advance (defined upfront). After release K it is envisioned that auto creation of topics will be disbaled by default thus the client will have to use our predefined topic.

Agreement on topic name outstanding 

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To be supplied by cient

2

What topic to use for private DMI-NCMP?

Contact Fiachra Corcoran regarding ONAP conventions.

Response was that there aren't any conventions to speak of but we would use dashes (i.e. my-new-topic) instead of dot notation (i.e. my.new.topic) for topic name

ncmp-async-m2m

3

Are adding a new REST endpoint for async or modifying an existing endpoint?

To facilitate asynchronous requests to DMI we will need to either create a new endpoint or modify existing endpoint to include /async flag. The second solution may not be backwards compatible. However creating a new endpoint solely for a flag is also not ideal. We could add async to list of options (but this might interfere with the purpose of /options.

Additionally, considered adding a new endpoint for async which simply re-routes the response to the original endpoint while adding the logic for OK response to the client. However, would this lead to a change in the schema? If so, would this be backwards compatible?

https://lf-onap.atlassian.net/browse/CPS-830

/ncmp/v1/data/ch/123ee5/ds/ncmp-datastore:*?topic=<topic-name> 

4

Agree URL for async once #2 is clarified

CPS R10 Release Planning#NCMPRequirements #11. 

/ncmp/v1/data/ch/123ee5/ds/ncmp-datastore:*?topic=<topic-name> 

5

Passthrough request need to be able to handle different response types (using accept header) but the async option would have a fixed and possibly different response type.

CPS R10 Release Planning#NCMPRequirements #11.

The async response can 'wrap' the native response inside a json object identical to the synchronous response

6

Should we create a standalone app to demo or are tests sufficient?

CSIT tests may require more involved effort - perhaps we could add standalone app to nexus and use it as part of CSIT test?

See #13

7

Do we need to persist the generated requestID?

We should be be stateless

No - Further disc

8

Error Reporting - Topic Correctness/Availability

At a minimum we should report to the client if a topic was not found or if the topic name was incorrect

In Scope

9

Error Reporting - Kafka Issues

Issues such full buffer/queue, drop messages, failure not in scope

Out of scope

10

Async Request Option using Messaging

See:  https://lf-onap.atlassian.net/wiki/display/DW/CPS-821+Spike%3A+Support+Async+read-write+operations+on+CPS-NCMP+interface#CPS821Spike:SupportAsyncreadwriteoperationsonCPSNCMPinterface-AsyncRequestOptionusingMessaging(OutofScope)

Out of scope

11

Do we actually require futures in this implementation proposal?

It could be argued that the need for futures is made redundant by the fact we call dmi from ncmp through rest and the response will be consumed via Kafka.

What benefit would future give us in this case? 

Not needed

12

ID Generation

Which mechanism to use? Look at CPS-Temporal and follow to keep consistency

See: https://lf-onap.atlassian.net/wiki/display/DW/CPS-821+Spike%3A+Support+Async+read-write+operations+on+CPS-NCMP+interface#CPS821Spike:SupportAsyncreadwriteoperationsonCPSNCMPinterface-CanRobotFrameworkverifyKafkaEvents

13

Can robot framework verify if Kafka events have been sent/received

This would be less work and overhead (rather than creating/.maintaining client app)

Will need to verify if 3PP libraries are safe to introduce into codebase. If so, what is the process? Do they need to be FOSSed?

Integration testing should be carried out by a client of NCMP. Demo can be performed up the point NCMP produces message for the client.

14

Can Webflux do this work with less code/impl?

@Sourabh Sourabh suggested using this to compliment our existing approach. By adding webflux we add an event loop to synchronize and access I/O connections to the database.

No, It will compliment the design by adding an event loop for I/O synchronization and access. See: CPS-850

15

ONAP may be deprecating PLAINTEXT for Kafka. Strimzi Kafka might need to be used

No relevant information could be found relating to this. See: https://lf-onap.atlassian.net/wiki/display/DW/CPS-821+Spike%3A+Support+Async+read-write+operations+on+CPS-NCMP+interface#CPS821Spike:SupportAsyncreadwriteoperationsonCPSNCMPinterface-KafkaStrimziInvestigation

The underlying implementation won't be affected. The config will contain relevant configuration for protocol (e.g. PLAINTEXT, SASL) and connections. 

This information needs to be made configurable when implementing.

16

Should we have something like the message count in the response or an indication of the last message at least.?

On the topic=Xyz async analysis, One item I forgot to mention was when a client might know when they have received the last response message for a request.  

If async there may be many responses (otherwise there's no need for async) 

Therefore should it not have something like the message count in it or an indication of the last message at least. 

This is another step in an evolution of the product. Multiple response messages might become a necessity for asycnc bulk operations and maybe that is when we can discuss it in more detail. I don’t think it has to affect our current implementation additional field to handle that can always be added in a backward compatible way.

17

Do we need Kafka messaging between DMI and NCMP?

This was discussed as it was argued that the client and CPS ecosystem is decoupled and async using only bus between ncmp and client. However, this would not rectify blocking calls between ncmp and dmi.

It was decided to have two separate kafka topics for client → ncmp & ncmp → dmi

Can NCMP list all existing topics

https://lf-onap.atlassian.net/browse/CPS-828

AC Point 3 : Topic does not exists (not allowed to create new topics, assuming NCMP can 'list' existing topics)

@Gareth Roper Need your suggestion.

19

https://lf-onap.atlassian.net/browse/CPS-828

Async: NCMP Rest impl. including Request ID generation

AC Points : 

2. cm handle does not exists

3. No DMI registration for CM Handle

AC point 2 : We agreed to check only if cm handle exists. If cm does not exists will get Http status 404 as below.

{
    "status": "404 NOT_FOUND",
    "message": "DataNode not found",
    "details": "DataNode with xpath /dmi-registry/cm-handles[@id='my-cm-handle1'] was not found for anchor ncmp-dmi-registry and dataspace NCMP-Admin."
}

AC point 3 . Is not valid.

Client Kafka User & Privileges

 Feb 16, 2022 After discussion with @Fiachra Corcoran regarding Kafka-strimzi we will need to ensure client can access Kafka user and be allocated sufficient privileges (principle of least privilege)

agree client response format 

Message gets forwarded to original Client Topic

See  https://lf-onap.atlassian.net/wiki/display/DW/CPS-821+Spike%3A+Support+Async+read-write+operations+on+CPS-NCMP+interface#CPS821Spike:SupportAsyncreadwriteoperationsonCPSNCMPinterface-ProposedMessageFormat

22

Async Ack

{
    "headers": {},
    "body": {
        "requestId": "f1aa75c6-e9ad-4072-bf19-659a66b3e0ff"
    },
    "statusCode": "OK",
    "statusCodeValue": 200
}

Agreed & implemented

@renu kumari 

[Relates to point 3 from high-level steps]

It would be good to have async implementation only dependent on NCMP. So that it does not break or work with only few DMI plugins. 
I think a DMI plugin independent async flow would be like 
1. Once request is received, check if  dmi plugin exist. If exists, generate request uuid, send the message to the Kafka topic (or store it in DB), and send an accepted response back to client.
2. NCMP will listen to the same topic or read from the DB. Process it by calling appropriate DMI Plugins synchronously. After it receives the response back, it sends to to Kafka topic provided in the input by user. 

In this implementation, we are not dependent on the DMI implementation. 
We do need persistence for storing async request. It can be a stored in DB or Kafka, it does not matter as long as we can read it in the same order. 

The main points are
1. No dependency on the DMI for async behavior

2. No async request get lost because of pod restart or JVM crash. 

NCMP standard event schema

Event payload schema as per org.onap.ncmp:async-request-response-event:v1

Response payload schema.  The payload schema is an onap one if non-passthrough but may be either an onap published or other (oran, proprietary, etc) schema if the original call received by the dmi plugin is a ncmp:passthrough-*.