The per-watcher channels for reobservation requests don't have a
buffer, which means that if sending on any one channel blocks then _all_
reobservation requests get blocked. Make the send fallible and log if
it blocks instead.
The wormhole sdk is a new go module in the sdk/ directory. This
initially contains the *_consts.go files from the common package in the
top-level sdk package and the entire vaa package as a sub-package.
For go reasons this needs to be in the sdk directory itself (rather than
a sdk/go subdir). To prevent the go tooling from looking into the other
non-go subdirs, add an empty go.mod file in each one. See
golang issue 42965 for more details on why we can't have nice
things (I'm deliberately not linking to stop github from spamming that
issue).
Commit `1753bb3: Send re-observation request when re-broadcasting local
observations` changed the processor code to automatically send
re-observation requests. If multiple guardians do this around the same
time that would lead to multiple re-observation requests for the same
transaction.
Deduplicate re-observation requests by keeping a cache of the requests
that were received in the last 11 minutes. Any request that's already
in the cache will not be forwarded to the chain-specific observation
code. The 11 minute value was chosen because the guardians will send
these requests approximately every 5 minutes.
Also move the re-observation code into a standalone function so that it
can be more easily tested.
Chirantan Ekbote