Crate rusmes_storage 

Storage abstraction layer for RusMES

This crate provides a unified storage interface for the RusMES mail server, covering mailbox management, message delivery, metadata tracking, and quota enforcement.

Architecture

The storage layer is composed of three orthogonal trait abstractions:

• MailboxStore — Create, rename, delete, subscribe, and list mailboxes per user.
• MessageStore — Append, retrieve, copy, flag, search, and delete messages.
• MetadataStore — Manage per-user quotas and per-mailbox counters (exists/recent/unseen).

These three stores are obtained from a single StorageBackend factory, which bundles them together and can be shared across protocol handlers (IMAP, JMAP, POP3, SMTP).

Backends

Backend	Module	Notes
Filesystem / Maildir	backends::filesystem	Atomic delivery via tmp/ → new/ rename; flag encoding in filenames
AmateRS distributed KV	backends::amaters	Mock implementation with circuit-breaker and exponential-backoff retry logic
PostgreSQL	backends::postgres	Full connection pool via sqlx, full-text search, migrations

Example — Filesystem backend

use rusmes_storage::{StorageBackend, MailboxStore, MailboxPath};
use rusmes_storage::backends::filesystem::FilesystemBackend;

let backend = FilesystemBackend::new("/var/mail/rusmes");
let mb_store = backend.mailbox_store();

let user: rusmes_proto::Username = "alice@example.com".parse()?;
let path = MailboxPath::new(user, vec!["INBOX".to_string()]);
let id = mb_store.create_mailbox(&path).await?;

let mailbox = mb_store.get_mailbox(&id).await?;
println!("Created: {:?}", mailbox);

ModSeq (Modification Sequence Numbers)

ModSeqGenerator produces monotonically increasing sequence numbers suitable for IMAP CONDSTORE / QRESYNC extensions. Both mailbox-level and message-level ModSeq values are tracked via MailboxModSeq and MessageModSeq wrappers.

Metrics

StorageMetrics records per-operation histograms for timing storage calls from higher-level protocol handlers, enabling Prometheus-compatible export.

Re-exports

pub use metrics::Histogram;

pub use metrics::MetricsSummary;

pub use metrics::StorageMetrics;

pub use metrics::StorageTimer;

pub use modseq::MailboxModSeq;

pub use modseq::MessageModSeq;

pub use modseq::ModSeq;

pub use modseq::ModSeqGenerator;

Modules

backends

Storage backend implementations

metrics

Storage metrics collection and tracking

modseq

MODSEQ (Modification Sequence) tracking for IMAP CONDSTORE

Structs

Mailbox

Mailbox metadata

MailboxCounters

Mailbox counters

MailboxId

Unique identifier for a mailbox

MailboxPath

Mailbox path (hierarchical)

MessageFlags

Message flags (IMAP standard flags)

MessageMetadata

Message metadata in a mailbox

Quota

User quota information

SpecialUseAttributes

Special-use mailbox attributes (RFC 6154)

Enums

SearchCriteria

Search criteria for messages

Traits

MailboxStore

Mailbox storage operations

MessageStore

Message storage operations

MetadataStore

Metadata storage operations

StorageBackend

Combined storage backend