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.
Instead of providing a (unit path), allows for (list path), which better
supports the "update to path and subpath cases".
For example, if /things wants updates about everything, and
/things/specific wants updates about the specific thing, they'll both
need to receive a %fact when the specific thing changes.
Previously, these would have been two separate moves. Now, gall handles
the multi-targeting for you.
Re-implements the behavior of the previous azimuth-tracker as an app
that pokes and peers eth-watcher. Should have maintained identical
outward semantics to the original.
Uses the logic existing in azimuth-tracker to implement a new
eth-watcher, which can look at Ethereum nodes for _any_ events, as
opposed to exclusively a subset of the Azimuth contract's events.
Azimuth-tracker will be reimplemented as a dependent of this in
forthcoming commits.
