When you first boot, if you try talk to someone before your azimuth is
up-to-date (for example by import), then if they've ever breached
(twice) then you'll get breach notification, cancelling your message.
This changes is it so that if we haven't heard anything about this ship,
we don't signal a breach.
The implementation complexity is primarily because we need
eth-watcher/azimuth-tracker to produce an update of a list instead of a
list of updates. This way, Jael can keep a "state as of the beginning
of this move" variable to check when deciding whether to signal a
breach.
Previously, when the refresh-rate timer activated, and the thread from
the previous activation was still running, we would kill it and start
a new one. For low refresh rates, on slower machines, nodes, or network
connections, this could cause the update to never conclude.
Here we add a timeout-time to eth-watcher's config. If the refresh-rate
timer activates, and a thread exists, but hasn't been running for at
least the specified timeout-time yet, we simply take no action, and wait
for the next refresh timer.
Note that we opted for "at least timeout-time", instead of killing &
restarting directly after the specified timeout-time has passed, to
avoid having to handle an extra timer flow.
In the +on-load logic, we configure the timeout-time for existing
watchdogs as six times the refresh-rate. We want to set
azimuth-tracker's timeout-time to ~m30, and don't care much about other,
less-likely-to-be-active use cases of eth-watcher.
These were deprecated in favor of azimuth-tracker in #1320.
(Azimuth-tracker, however, isn't a general-purpose Ethereum log watcher
tool. Commits to transform it into a more broadly useful tool are
forthcoming.)
