core-data Retention question

[mlz960820]

When the message reaches Retention's MaxCap, it will delete old data, won't it not group by each device? If I have a device configuration with autoevent onchange set to true, and this device has a very low status update frequency, would this cause the device's status to be lost, and how can this issue be resolved? What I am thinking now is that if I want to use this mechanism, I need to set all device onchange to false

[jiekechoo]

@mlz960820 I don't understand your point actually.
Here is the AutoEvents specification that you can refer.
If you have an issue please create it in the device SDK repo or the specific device repo.

[mlz960820]

我有一个服务B想通过restful定时从core-data中读取设备资源，Retention达到MaxCap，就会清除历史信息，那么这时候我的服务B就读取不到设备信息了，假如设备B资源不会频繁变化，autoevent设置为true，这时候core-data中就不会有设备B的资源数据了

[jiekechoo]

@cloudxxx8 Can you help with this question?

[cloudxxx8]

@mlz960820 this is a valid requirement, and the current mechanism doesn't support your scenario.
the workaround is to execute core command to GET that device resource value if it doesn't exist in the core-data.
you can open an issue in edgex-go repository and see if there is anyone could enhance the retention policy.