Struct Cache 

pub struct Cache {
    pub max_capacity: CacheCapacity,
    pub ttl: Duration,
    pub cache_articles: bool,
    pub adaptive_precheck: bool,
    pub disk: Option<DiskCache>,
}

Cache configuration for article caching

Fields

max_capacity: CacheCapacity

Maximum cache size in bytes (memory tier for hybrid cache)

Supports human-readable formats:

• "1gb" = 1 GB
• "500mb" = 500 MB
• "64mb" = 64 MB (default)
• 10000 = 10,000 bytes

ttl: Duration

Time-to-live for cached articles

cache_articles: bool

Whether to cache article bodies (default: true)

When false:

• Cache still tracks backend availability (smart routing, 430 retry)
• Article bodies are NOT stored (saves ~750KB per article)
• Useful for availability-only mode with limited memory

When true:

• Full caching mode (bodies + availability tracking)
• Can serve articles from cache without backend query

adaptive_precheck: bool

Enable adaptive availability prechecking for STAT/HEAD commands (default: false)

When true:

• STAT/HEAD commands with message-ID check all backends simultaneously
• Returns optimistic response to client immediately (assumes article exists)
• Updates availability cache in background based on actual backend responses
• Improves future routing decisions by learning which backends have articles
• For HEAD with cache_articles=true, also caches the headers

When false:

• STAT/HEAD commands use normal routing (single backend check)

Trade-off: Uses more backend connections but builds accurate availability data

disk: Option<DiskCache>

Disk cache configuration (requires hybrid-cache feature)

When enabled, articles evicted from memory are written to disk, creating a two-tier cache (memory → disk → backend).

Trait Implementations

impl Clone for Cache

fn clone(&self) -> Cache

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Cache

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

Formats the value using the given formatter.

impl Default for Cache

fn default() -> Self

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for Cache

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl PartialEq for Cache

fn eq(&self, other: &Cache) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Serialize for Cache

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for Cache