Elsys device not rejoining after gateway offline (EU)

ChirpStack Application Server
1

I had a situation where my lora gateway was offline for ~2 months and was brought back online.

I noticed the devices that were active on that gateway did not come back online (these are Elsys ERS motion sensors).

From viewing the uplinks coming from the back-online gateway I noticed that the devaddr of a device doing ConfirmedDataUp is the same as one in the device_activation table on chirpstack_ns postgres server. This leads me to think that the device is not configured to try to rejoin on not receiving downlinks.

  1. How do devices lose the Activation on the chirpstack application server? Is it based on time?
  2. Can I reinstate the existing activation and get the data flowing as expected?
  3. What else should I try?

chirpstack_ns:

image
image2565Ă—197 134 KB

gateway frames:
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image1894Ă—1025 190 KB

2

the app-server keeps a bunch of the shared-keys on redis, if redis is gone or the records expired, you are sort of out of luck, but i might be wrong.

1 Like
3

As far as I can tell, the app_s_key and the network session key are on postgres. I just don’t know how the server decides it is “unactivated” or not

4

@brocaar where is the device activation held specifically? Is it in redis or in the databases? What causes it to expire and can I reinstate it?

5

The device-session (holding the snapshot of the all the device configuration at that moment) is held in Redis. The expiration is triggered by the configured device_session_ttl config option (default 31 days).

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6

we also have Elsys ERS sensors. The big problem with these is, that by default, there is no timeout mechanism active which would force the sensor to retry a JOIN after not being able to communicate with any network server for a long time. I’d rather have devices always try to JOIN again just in case the encryption keys disappear to /dev/null etc. Redis is not my idea of a “stable” data store.

7

Is it possible to re-build the “device-session” (the snapshot of all device configuration) onto Redis after the event of disappearance of the Redis backing store at /var/lib/redis ?

There are plenty of network keys, etc, in psql::chirpstack_as::device_keys table.