Invoke between two device services

[mlz960820]

In device-modbus-go, I added an intermediate layer device service service to parse device parameters and other functions. After parsing, it calls the restful interface in the command service of device-modbus-go. Activating automatic collection for fifty devices would lead to high CPU usage for these two services (each read operation on device resources must go through intermediate layer parsing and forwarding). I wonder if frequent creation of connections for HTTP requests consumes resources, but changing it to messaging's command using message bus mechanism still shows no significant improvement. What optimization suggestions do you have for this situation?

[cloudxxx8]

When you call these 50 devices from the Command APIs, do you need them to return the Event response via REST?
If the purpose is just the trigger read operations, and you have other services subscribe to message bus to receive events.
You can add the query parameter to the REST call: ds-pushevent=true&ds-returnevent=false . It could save lots of CPU for the REST response.
https://docs.edgexfoundry.org/3.1/api/core/Ch-APICoreCommand/

In addition, you can set the environment variable EDGEX_ENCODE_ALL_EVENTS_CBOR: true to use CBOR encoding instead of JSON. It improve the performance as well.

[mlz960820]

I need them to return the Event response via REST.This situation does not apply to rest, right? Should the subscription-publish approach be used?First,I use http.After,I use https://github.com/edgexfoundry/device-sdk-go/blob/main/internal/controller/messaging/command.go,send edgex/device/command/request and subscribe to edgex/response to get the results,but the cpu is still very high.Does this pattern, which sends hundreds of requests per second (50 devices, 5 resources per device), use a lot of CPU?My server has only four cores of CPU. Is it because my other code is not reasonable rather than this service interaction?

[cloudxxx8]

If you need the read operation to keep running, you should use AutoEvent and receive the events from the message bus.
The command service should only be used without high frequency executeion if you have the performance concerns.

[mlz960820]

sure，But why does my messagebus use a high CPU?

[cloudxxx8]

The CPU usage is caused by high volume JSON encoding and decoding in both Command and Device Service, so no matter using REST or message bus, those services have to encoding and decode lots of JSON constantly.
If you use AutoEvent, only Device Service needs to encode the JSON for each event. As I mentioned, using CBOR encoding can save CPU usage as well.