This commit adds some Prometheus metrics to /metrics in headscale.
It will add the standard go metrics, some automatic gin metrics and some
initial headscale specific ones.
Some of them has been added to aid debugging #97 (loop bug)
In the future, we can use the metrics to get rid of the sleep in the
integration tests by checking that our expected number of nodes has been
registered:
```
headscale_machine_registrations_total
```
This commit moves toNode to the bottom of the file, and adds a helper
function for lists of Machines to be converted.
It also adds string helpers for Machines and lists of machines.
Lastly it splits getPeers into getDirectPeers, which exist in the same
namespace, and getShared, which is nodes shared with the namespace.
getPeers is kept as a function putting together the two lists for
convenience.
This commit rewrites a bunch of the code to always use *Machine instead
of a mix of both, and a mix of tailcfg.Node and Machine.
Now we use *Machine, and if tailcfg.Node is needed, it is converted just
before needed.
If a node does not have an update channel, it is probably not connected,
clarify the log messages and make sure we dont print that it was updated
successfully (continue, not return)
This commit tries to address the possible raceondition that can happen
if a client closes its connection after we have fetched it from the
syncmap before sending the message.
To try to avoid introducing new dead lock conditions, all messages sent
to updateChannel has been moved into a function, which handles the
locking (instead of calling it all over the place)
The same lock is used around the delete/close function.
This commit adds a new field to machine, lastSuccessfulUpdate which
tracks when we last was able to send a proper mapupdate to the node. The
purpose of this is to be able to compare to a "global" last updated time
and determine if we need to send an update map request to a node.
In addition it allows us to create a scheduled check to see if all known
nodes are up to date.
Also, add a helper function to send a message to the update channel of a
machine.
tests for that feature.
Other fixes: clean up a few typos in comments. Fix a bug that caused the
tests to run four times each. Be more consistent in the use of log
rather than fmt to print errors and notices.
