Module backend 

Backend PostgreSQL client used by TR-management code paths.

ProxyServer::route_and_forward still forwards client frames to backends without ever parsing or originating SQL — that zero-copy path remains untouched. This module is the other direction: the proxy itself acts as a PG client for internal management queries (health checks, pg_is_in_recovery(), pg_promote(), WAL-position probes, failover replay, session-state restoration).

Design goals:

• No tokio-postgres. We reuse crate::protocol for every wire frame so the crate has exactly one PG protocol implementation.
• TLS-capable. tls::negotiate performs the SSLRequest dance and wraps the TCP stream in tokio-rustls when accepted.
• Text format only. All parameter values are interpolated as quoted SQL literals before send; extended-protocol Parse/Bind/Execute is deliberately out of scope for internal management queries.
• Narrow type surface. Seven OIDs — BOOL, INT4, INT8, TEXT, FLOAT8, TIMESTAMPTZ, NUMERIC — plus PG_LSN for WAL positions.

Example

use heliosdb_proxy::backend::{BackendClient, BackendConfig, tls, TlsMode};
use std::time::Duration;

let cfg = BackendConfig {
    host: "primary.db.internal".into(),
    port: 5432,
    user: "postgres".into(),
    password: Some("secret".into()),
    database: Some("app".into()),
    application_name: Some("helios-health".into()),
    tls_mode: TlsMode::Prefer,
    connect_timeout: Duration::from_secs(5),
    query_timeout: Duration::from_secs(5),
    tls_config: tls::default_client_config(),
};
let mut c = BackendClient::connect(&cfg).await?;
let in_recovery = c.query_scalar("SELECT pg_is_in_recovery()").await?;

Re-exports

pub use client::BackendClient;

pub use client::BackendConfig;

pub use client::ColumnMeta;

pub use client::QueryResult;

pub use error::BackendError;

pub use error::BackendResult;

pub use stream::Stream;

pub use tls::TlsMode;

pub use types::encode_literal;

pub use types::oid;

pub use types::ParamValue;

pub use types::TextValue;

Modules

auth

PostgreSQL client-side authentication helpers.

client

Backend PostgreSQL client.

error

Backend client error types.

stream

A pluggable I/O stream — plain TCP or TLS-wrapped TCP.

tls

TLS handshake for backend PostgreSQL connections.

types

PostgreSQL type OIDs and text-format value encoding/decoding.