Since we store all-time flap count for a peer, we add a cooldown factor
which will discount poor flap counts in the past. This is only applied
to peers that have not flapped for at least a cooldown period, so that
we do not downgrade our rate limiting for badly behaved peers.
Since we will use peer flap rate to determine how we rate limit, we
store this value on disk per peer per channel. This allows us to
restart with memory of our peers past behaviour, so we don't give badly
behaving peers have a fresh start on restart. Last flap timestamp is
stored with our flap count so that we can degrade this all time flap
count over time for peers that have not recently flapped.
To prevent flapping peers from endlessly dos-ing us with online and
offline events, we rate limit the number of events we will store per
period using their flap rate to determine how often we will add their
events to our in memory list of online events.
Since we are tracking online events, we need to track the aggregate
change over the rate limited period, otherwise we will lose track of
a peer's current state. For example, if we store an online event, then
do not store the subsequent offline event, we will believe that the
peer is online when they actually aren't. To address this, we "stage"
a single event which keeps track of all the events that occurred while
we were rate limiting the peer. At the end of the rate limting period,
we will store the last state for that peer, thereby ensureing that
we maintain our record of their most recent state.
When dealing with online events, we actually need to track our events
by peer, not by channel. All we need to track channels is to have a
set of online events for a peer which at least contain those events.
This change refactors chanfitness to track by peer.
To get our uptime, we first filter our event log to get online periods.
This change updates this code to be tolerant of consecutive online or
offline events in the log. This will be required for rate limiting,
because we will not record every event for anti-dos reasons, so we could
record an online event, ignore an offline event and then record another
offline event. We could just ignore this duplicate event, but we will
also need this tolerance for when we persist uptime and our peers
can have their last event before restart as an online event and record
another online event when we come back up.
Original PR was written with 4 spaces instead of 8, do a once off fix
here rather than fixing bit-by bit in the subsequent commits and
cluttering them for review.
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.
