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