Struct LogBuffer 

pub struct LogBuffer { /* private fields */ }

Thread-safe, bounded ring buffer of formatted log lines.

Why: shared between the tracing Layer (writer) and the HTTP handler (reader); both hold cheap Arc clones of the same underlying deque. What: wraps Arc<Mutex<VecDeque<String>>>. push appends and evicts the oldest line past capacity; tail snapshots the most recent N lines. Test: capacity_evicts_oldest, tail_returns_last_n.

Implementations

impl LogBuffer

pub fn new(capacity: usize) -> Self

Create an empty buffer with the given line capacity.

Why: callers (daemon startup) choose the cap; tests use a tiny one. What: allocates a VecDeque with capacity.max(1) reserved slots so a zero capacity is treated as one (a zero-cap ring is useless and would panic on the eviction arithmetic). Test: capacity_evicts_oldest.

pub fn push(&self, line: String)

Append a line, evicting the oldest entry when at capacity.

Why: a tracing Layer calls this on every event; it must never panic or block long. A poisoned mutex (a prior panic while logging) is recovered via into_inner so logging itself never cascades a panic into the daemon. What: pushes line to the back; if length now exceeds capacity, pops the front. Test: capacity_evicts_oldest.

pub fn tail(&self, n: usize) -> Vec<String>

Snapshot the most recent n lines (or all, when n exceeds the current length).

Why: the /logs/tail handler returns these as a JSON array. Cloning under the lock keeps the critical section short and lets the caller serialise without holding the mutex. What: returns a Vec<String> of at most n lines, oldest-first. Test: tail_returns_last_n, tail_all_when_n_exceeds_len.

pub fn len(&self) -> usize

Total number of lines currently buffered.

Why: the /logs/tail response reports total so callers can tell whether the buffer has wrapped. What: returns the deque length. Test: tail_returns_last_n asserts len after pushes.

pub fn is_empty(&self) -> bool

Whether the buffer holds no lines.

Why: clippy requires is_empty alongside len; also a convenient readiness check in tests. What: returns len() == 0. Test: covered by capacity_evicts_oldest.

Trait Implementations

impl Clone for LogBuffer

fn clone(&self) -> LogBuffer

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for LogBuffer

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

Formats the value using the given formatter.