When the node notifier was replaced with batcher, we removed
its closing, but forgot to add the batchers so it was never
stopping node connections and waiting forever.
Fixes#2751
Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>
Initial work on a nodestore which stores all of the nodes
and their relations in memory with relationship for peers
precalculated.
It is a copy-on-write structure, replacing the "snapshot"
when a change to the structure occurs. It is optimised for reads,
and while batches are not fast, they are grouped together
to do less of the expensive peer calculation if there are many
changes rapidly.
Writes will block until commited, while reads are never
blocked.
Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>
Before this patch, we would send a message to each "node stream"
that there is an update that needs to be turned into a mapresponse
and sent to a node.
Producing the mapresponse is a "costly" afair which means that while
a node was producing one, it might start blocking and creating full
queues from the poller and all the way up to where updates where sent.
This could cause updates to time out and being dropped as a bad node
going away or spending too time processing would cause all the other
nodes to not get any updates.
In addition, it contributed to "uncontrolled parallel processing" by
potentially doing too many expensive operations at the same time:
Each node stream is essentially a channel, meaning that if you have 30
nodes, we will try to process 30 map requests at the same time. If you
have 8 cpu cores, that will saturate all the cores immediately and cause
a lot of wasted switching between the processing.
Now, all the maps are processed by workers in the mapper, and the number
of workers are controlable. These would now be recommended to be a bit
less than number of CPU cores, allowing us to process them as fast as we
can, and then send them to the poll.
When the poll recieved the map, it is only responsible for taking it and
sending it to the node.
This might not directly improve the performance of Headscale, but it will
likely make the performance a lot more consistent. And I would argue the
design is a lot easier to reason about.
Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>
