Closes#536.
This removes:
- the user-agent (we can add a mechanism to specify extra BIP14 components later, if any users ask us for that feature);
- the EWMA parameters (these were put in the config just to avoid making a choice);
- the peer connection timeout (we can change the default value if anyone ever has a problem with it);
- the peer set request buffer size (setting this too low can make the application deadlock);
The new peer interval is left in.
Prior to this change, the service returned by `zebra_network::init` would spawn background tasks that could silently fail, causing unexpected errors in the zebra_network service.
This change modifies the `PeerSet` that backs `zebra_network::init` to store all of the `JoinHandle`s for each background task it depends on. The `PeerSet` then checks this set of futures to see if any of them have exited with an error or a panic, and if they have it returns the error as part of `poll_ready`.
Co-authored-by: Jane Lusby <jane@zfnd.org>
Prior to this change, the seed subcommand would consistently encounter a panic in one of the background tasks, but would continue running after the panic. This is indicative of two bugs.
First, zebrad was not configured to treat panics as non recoverable and instead defaulted to the tokio defaults, which are to catch panics in tasks and return them via the join handle if available, or to print them if the join handle has been discarded. This is likely a poor fit for zebrad as an application, we do not need to maximize uptime or minimize the extent of an outage should one of our tasks / services start encountering panics. Ignoring a panic increases our risk of observing invalid state, causing all sorts of wild and bad bugs. To deal with this we've switched the default panic behavior from `unwind` to `abort`. This makes panics fail immediately and take down the entire application, regardless of where they occur, which is consistent with our treatment of misbehaving connections.
The second bug is the panic itself. This was triggered by a duplicate entry in the initial_peers set. To fix this we've switched the storage for the peers from a `Vec` to a `HashSet`, which has similar properties but guarantees uniqueness of its keys.
The previous outbound peer connection logic got requests to connect to new
peers and processed them one at a time, making single connection attempts
and retrying if the connection attempt failed. This was quite slow, because
many connections fail, and we have to wait for timeouts. Instead, this logic
connects to new peers concurrently (up to 50 at a time).
Henry de Valence
teor
Dimitris Apostolou
Jane Lusby
Jane Lusby