Struct Aggregate 

pub struct Aggregate { /* private fields */ }

The read-only multi-city view.

Deliberately not generic and deliberately without a transport: the merge order is the part that must be deterministic and testable, and it needs no socket to be either.

Implementations

impl Aggregate

pub fn new() -> Self

pub fn attach(&mut self, upstream: Upstream)

Registers an upstream. Re-registering the same label replaces its settings rather than adding a second entry, so a corrected address does not silently leave the old one attached.

pub fn detach(&mut self, label: &CityLabel) -> bool

pub fn cities(&self) -> impl Iterator<Item = &Upstream>

Every attached city, in label order. BTreeMap rather than a hash map because iteration order reaching an interface must not depend on hashing.

pub fn ask(&self, label: &CityLabel, query: Query) -> Result<Forwarded, AxError>

Forwards a read to one upstream.

This is the only method that sends anything, and it accepts a Query. There is no sibling that accepts a Command, which is how “never forwards a Command” is held.

Errors

Refuses a label that was never attached, rather than guessing.

pub fn merge(streams: Vec<(CityLabel, Vec<EventRecord>)>) -> Vec<Sighting>

Interleaves per-city event streams into one readable sequence.

Ordering is (t, city, seq). Sequence numbers are meaningless across cities - each Ledger numbers its own history - so time leads, and the label breaks ties. The label is in the key rather than a tiebreak of last resort because two cities can genuinely stamp the same millisecond, and the merged view must still be the same twice.

Trait Implementations

impl Debug for Aggregate

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Aggregate

fn default() -> Self

Returns the “default value” for a type.