The context that is passed into the block fetch protocol client when it is started.

The policy used by the fetch clients. It is set by the central block fetch logic, and passed to them via the FetchClientRegistry.

A set of variables shared between the block fetch logic thread and each thread executing the client side of the block fetch protocol. That is, these are the shared variables per peer. The FetchClientRegistry contains the mapping of these for all peers.

The variables are used for communicating from the protocol thread to the decision making thread the status of things with that peer. And in the other direction one shared variable is for providing new fetch requests.

The status of the block fetch communication with a peer. This is maintained by fetch protocol threads and used in the block fetch decision making logic. Changes in this status trigger re-evaluation of fetch decisions.

Whether this mini protocol instance is in the Idle State

The number of requests in-flight and the amount of data in-flight with a peer. This is maintained by fetch protocol threads and used in the block fetch decision making logic.

Add a new fetch request for a single peer. This is used by the fetch decision logic thread to add new fetch requests.

We have as a pre-condition that all requested blocks are new, i.e. none should appear in the existing peerFetchBlocksInFlight. This is a relatively easy precondition to satisfy since the decision logic can filter its requests based on this in-flight blocks state, and this operation is the only operation that grows the in-flight blocks, and is only used by the fetch decision logic thread.

This is used by the fetch client threads.

Tracing types for the various events that change the state (i.e. FetchClientStateVars) for a block fetch client.

Note that while these are all state changes, the AddedFetchRequest occurs in the decision thread while the other state changes occur in the block fetch client threads.

A peer label for use in Tracers. This annotates tracer output as being associated with a given peer identifier.

Range of blocks, defined by a lower and upper point, inclusive.

A new type used to emphasize the precondition of headerForgeUTCTime and blockForgeUTCTime at each call site.

At time of writing, the a is either a header or a block. The headers are literally from Consensus (ie provided by ChainSync). Blocks, on the other hand, are indirectly from Consensus: they were fetched only because we favored the corresponding header that Consensus provided.