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`.
* rename zebra-storage to zebra-state
* Setup initial skeleton for zebra-state
* add test
* Apply suggestions from code review
Co-authored-by: Henry de Valence <hdevalence@hdevalence.ca>
* move shared test vectors to a common crate
Co-authored-by: Jane Lusby <jane@zfnd.org>
Co-authored-by: Henry de Valence <hdevalence@hdevalence.ca>
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.
Bitcoin does this either with `getblocks` (returns up to 500 following block
hashes) or `getheaders` (returns up to 2000 following block headers, not
just hashes). However, Bitcoin headers are much smaller than Zcash
headers, which contain a giant Equihash solution block, and many Zcash
blocks don't have many transactions in them, so the block header is
often similarly sized to the block itself. Because we're
aiming to have a highly parallel network layer, it seems better to use
`getblocks` to implement `FindBlocks` (which is necessarily sequential)
and parallelize the processing of the block downloads.
Attempting to implement requests for block data revealed a problem with
the previous connection logic. Block data is requested by sending a
`getdata` message with hashes of the requested blocks; the peer responds
with a sequence of `block` messages with the blocks themselves.
However, this wasn't possible to handle with the previous connection
logic, which could only convert a single Bitcoin message into a
Response. Instead, we factor out the message handling logic into a
Handler, which can statefully accumulate arbitrary data into a Response
and signal completion. This is still pretty ugly but it does work.
As a side effect, the HeartbeatNonceMismatch error is removed; because
the Handler now tries to process messages until it comes to a Response,
it just ignores mismatched nonces (and will eventually time out).
The previous Mempool and Transaction requests were removed but could be
re-added in a different form later. Also, the `Get` prefixes are
removed from `Request` to tidy the name.
The components are accessed by a lock on application state. When some command
calls block_on to enter an async context, it obtained a write lock on the
entire application state. This meant that if the application state were
accessed later in an async context, a deadlock would occur. Instead the
TokioComponent holds an Option<Runtime> now, so that before calling block_on,
the caller can .take() the runtime and release the lock. Since we only ever
enter an async context once, it's not a problem that the component is then
missing its runtime, as once we are inside of a task we can access the runtime.
With a 'Transactions' response that gets turned into an 'Inv(Vec<InventoryHash::Tx>)' message.
We don't yet handle a response from our peer for a 'mempool', which will have to be
a more generic 'Inv' type because we might receive transaction hashes we don't know about yet.
Pertains to #26
Moved SeedService out of the command closure Command currently spawns
a tokio task to DOS the seed service with `Request::GetPeers` every
second.
Pertains to #54
Jane Lusby
Deirdre Connolly
Henry de Valence
Alfredo Garcia
Jane Lusby
Tony Arcieri