This commit addresses a bug in the channel event store
where the opened time of a channel event log was not
set for peers that were offline on startup.
Previously, opened time was set to the time of the first
event in the event log. This worked for online peers,
because the eventlog was created with an initial online
event. However, offline peers had no inital event so had
no open time set.
This commit simplifies the creation of an event log by
removing the initial event and setting open time for all
event logs. This has the effect of potentially introducing
a gap between opened time for a log and the first peer
online event for peers with channels that exist at startup
if a peer takes time to reconnect. However, the cost of this
is less than the benefit of reducing the bug-prone custom
code path that was previously in place.
In this commit, the channelEventStore in the channel
fitness subsystem is changed to identify channels
by their outpoint rather than short channel id. This
change is made made becuase outpoints are the preferred
way to expose references over rpc, and easier to perform
queries within lnd.
This commit adds a chanfitness package which will be used to track
channel health and performance metrics. It adds a channel event
structure which will be used to track channel opens/closes and peer
uptime.
The eventLog implements an uptime function which calcualtes uptime
over a given period and a lifespan function which returns the time
when the log began monitoring the channel and, if the channel is
closed, the time when it stopped moitoring it.
