Please clarify documentation on HTTP vs MQTT

[jgoerzen]

Over at https://owntracks.org/booklet/features/android/, it is stated that "it is highly recommended to use HTTP mode on Android 6 and higher". However, it's not stated why, or if that recommendation is still current.

Also, "When using MQTT, the broker connection is not maintained permanently." It's not clear what the consequences of this are. There is a reference to the keepalive interval not changing that behavior. https://owntracks.org/booklet/tech/mqtt/#mqtt says that "MQTT was designed with mobile clients in mind so it doesn't require a persistent TCP connection."

Over at https://owntracks.org/booklet/features/friends/, the discussion is solely about MQTT mode, implying that friends support is impossible with HTTP mode. Yet https://github.com/owntracks/recorder#friends-in-http-mode covers friends in HTTP mode.

I'd like to see:

• Clarification on tradeoffs of MQTT vs HTTP and why MQTT is not recommended
• Clarification of what the broker connection not being maintained means
• Clarification of tradeoffs of MQTT vs HTTP regarding friends
• Documentation of the recommendation to avoid websockets

Some prior discussion on this:

owntracks/android#774 (Dec 2019) implies that MQTT was killing batteries. There was a recommendation in there, not stated in the docs, to avoid websockets. The HTTP recommendation is restated.

owntracks/android#745 (Oct 2019) again restates the aversion to websockets

[rhasselbaum]

I am also looking for a trade-off comparison between MQTT and HTTP. Also using Android.