Vestigial variable DataUpload::lastConnectTime

[ntlhui]

smartfin-fw3/src/cellular/dataUpload.hpp

Line 48 in 91b5bb9

system_tick_t lastConnectTime;

In smartfin-fw, there was a limitation that we could not connect to the Particle network more than once a second. There was some logic to rate limit the number of connections made.

1. Investigate whether such a limitation exists in Tracker SOM/Gen3 Particle devices.
2. Ensure that the logic of DataUpload and sf::cloud consolidates network connections to minimize churn on network state.

[charliekush]

According to the docs the limit is now "Maximum of 10,000 requests every 5 minutes".

[ntlhui]

So this corresponds to 33 requests per second across the entire fleet. We can probably incur many connect/disconnect events in rapid succession per device, but we want to avoid this anyhow to conserve energy. So we want to probably implement a per device limit. I think it will probably suffice to do a limitation of one publish per second, and an exponential back off for connect from once per second to once every 6 hours on connection failure. Probably want to do a connection timeout of 1 second or so, that way the system isn't sitting there churning, maybe an exponential gain of 2 or 3?

[ntlhui]

This should probably go into a decision log

[charliekush]

Sleep recommendations from particle docs:

• If you are sleeping for less than 10 seconds, shouldn't use sleep at all, and instead just stay awake.
• If you are sleeping less than 10 minutes, you should never use a cellular off mode because frequently reconnecting to cellular may use more power than it saves, and also your SIM may be banned from the cellular network for aggressive reconnection.
• If you are sleeping more than 15 minutes, using cellular off mode uses the least power.
• From 10 to 15 minutes, generally speaking, using cellular standby or cellular off is a toss-up, and will depend on other factors.

Also from same page: "Particle Device OS is not intended to handle very short sleep cycles. Practically speaking, the minimum is about 10 seconds."