Add MariaDB IPL validation, topology docs in beds.toml, and developer wiki

- Add MariaDB (REL) IPL validation — master required, secondary non-fatal
- Add RelNodeConfig / RelInstanceConfig structs with master/secondary pattern
- Add rel_services section to beds.toml and test fixture
- Add detailed topology commentary to beds.toml covering standalone,
  master/replica, Galera cluster, and multi-DB-per-node configurations
- Add developer wiki (wiki/) covering:
    - Origin story — PHP Namaste history, production record, why Rust
    - Architecture overview — full system diagram, all layers explained
    - The four nodes — appServer, admin, segundo, tercero with real-world context
    - IPL sequence — every step documented with rationale for ordering
    - Configuration system — layering, env selection, adding new sections
    - Queue topology — exchanges, routing keys, broker bindings, vhost isolation
    - Template system — REC/REL, TLA convention, cache map, warehousing
    - Event lineage — compound event IDs, parent/child tracking, msLogs schema
    - Glossary
- Update README with wiki index and MariaDB status

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/config/mod.rs

@@ -26,7 +26,7 @@
 //! * `2026-04-02` - mks - refactored into load() + load_from() for testability
 
 mod structs;
-pub use structs::{BedsConfig, BrokerServicesConfig, RecNodeConfig};
+pub use structs::{BedsConfig, BrokerServicesConfig, RecNodeConfig, RelNodeConfig, RelInstanceConfig};
 
 use config::{Config, File, FileFormat};
 

src/config/structs.rs

@@ -11,6 +11,7 @@ pub struct BedsConfig {
     pub journal_on: bool,
     pub broker_services: BrokerServicesConfig,
     pub rec_services: HashMap<String, RecNodeConfig>,
+    pub rel_services: HashMap<String, RelNodeConfig>,
 }
 
 #[derive(Debug, Deserialize)]
@@ -60,3 +61,18 @@ pub struct RecNodeConfig {
     pub database: String,
     pub use_ssl: bool,
 }
+
+#[derive(Debug, Deserialize)]
+pub struct RelNodeConfig {
+    pub master: RelInstanceConfig,
+    pub secondary: Option<RelInstanceConfig>,
+}
+
+#[derive(Debug, Deserialize, Clone)]
+pub struct RelInstanceConfig {
+    pub host: String,
+    pub port: u16,
+    pub user: String,
+    pub pass: String,
+    pub database: String,
+}

src/lib.rs

@@ -16,4 +16,5 @@
 pub mod amqp;
 pub mod config;
 pub mod logging;
+pub mod mariadb;
 pub mod mongo;

src/main.rs

@@ -24,6 +24,7 @@
 mod amqp;
 mod config;
 mod logging;
+mod mariadb;
 mod mongo;
 
 /// Executes the BEDS Initial Program Load (IPL) sequence.
@@ -81,6 +82,18 @@ fn ipl() -> Result<(), String> {
         }
     }
 
+    // validate MariaDB reachability — fatal in production, non-fatal in all other envs
+    // secondary instance failures are always non-fatal (handled inside validate_all)
+    match mariadb::validate_all(&cfg.rel_services) {
+        Ok(()) => tracing::info!("MariaDB reachable"),
+        Err(e) => {
+            if cfg.id.env_name == "production" {
+                return Err(e);
+            }
+            tracing::warn!("MariaDB unreachable (non-fatal in {}): {}", cfg.id.env_name, e);
+        }
+    }
+
     Ok(())
 }
 

src/mariadb.rs

@@ -0,0 +1,122 @@
+//! # mariadb.rs — MariaDB (REL) Transport Layer
+//!
+//! Manages all MariaDB interactions for the BEDS node. At IPL, validates that
+//! the master instance of each configured REL service node is reachable before
+//! the node proceeds. The secondary instance is optional — its absence or
+//! unreachability is logged but never fatal.
+//!
+//! Future phases will add connection pooling, authentication, and query
+//! dispatch via the adapter layer.
+//!
+//! ## Calling Agents
+//! - `ipl()` in main.rs — calls `validate_all()` during the IPL sequence
+//!
+//! ## Inputs
+//! - `HashMap<String, RelNodeConfig>` from the loaded BEDS configuration
+//!
+//! ## Outputs
+//! - `Ok(())` if all configured REL master nodes are reachable
+//! - `Err(String)` with node name, host:port, and OS error on first master failure
+//!
+//! **Author:** mks
+//! **Version:** 1.0
+//!
+//! ## History
+//! * `2026-04-04` - mks - original coding
+
+use std::collections::HashMap;
+use std::net::TcpStream;
+use std::time::Duration;
+
+use crate::config::{RelInstanceConfig, RelNodeConfig};
+
+/// Validates that all configured MariaDB master nodes are reachable.
+///
+/// Iterates every entry in the `rel_services` config block and validates the
+/// master instance. Secondary instances are checked but their failure is
+/// non-fatal — a missing or unreachable secondary is logged as a warning.
+/// Fails on the first unreachable master.
+///
+/// # Arguments
+///
+/// * `nodes` — map of service name → `RelNodeConfig` from `BedsConfig`
+///
+/// # Returns
+///
+/// `Ok(())` if every master node responds to a TCP connect within the timeout.
+/// `Err(String)` with the service name and address of the first master failure.
+///
+/// # History
+///
+/// * `2026-04-04` - mks - original coding
+pub fn validate_all(nodes: &HashMap<String, RelNodeConfig>) -> Result<(), String> {
+    for (name, node) in nodes {
+        // master is required — failure is propagated to the caller
+        validate(&format!("{}.master", name), &node.master)?;
+
+        // secondary is optional — log absence but do not fail
+        if let Some(secondary) = &node.secondary {
+            if let Err(e) = validate(&format!("{}.secondary", name), secondary) {
+                tracing::warn!("MariaDB secondary unreachable (non-fatal): {}", e);
+            }
+        }
+    }
+    Ok(())
+}
+
+/// Validates that a single MariaDB instance is reachable.
+///
+/// # Arguments
+///
+/// * `label` — descriptive label for error messages (e.g. "app_server.master")
+/// * `instance` — `RelInstanceConfig` for this instance
+///
+/// # Returns
+///
+/// `Ok(())` if the TCP handshake succeeds within 5 seconds.
+/// `Err(String)` with a descriptive message on failure.
+///
+/// # History
+///
+/// * `2026-04-04` - mks - original coding
+pub fn validate(label: &str, instance: &RelInstanceConfig) -> Result<(), String> {
+    let addr_str = format!("{}:{}", instance.host, instance.port);
+
+    let addr: std::net::SocketAddr = addr_str
+        .parse()
+        .map_err(|e| format!("Invalid MariaDB address for rel_services.{} ({}): {}", label, addr_str, e))?;
+
+    TcpStream::connect_timeout(&addr, Duration::from_secs(5))
+        .map_err(|e| format!("MariaDB unreachable at rel_services.{} ({}): {}", label, addr_str, e))?;
+
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::config::load_from;
+
+    fn test_cfg() -> crate::config::BedsConfig {
+        load_from("tests/fixtures/beds_test.toml", "")
+            .expect("test fixture beds_test.toml failed to load")
+    }
+
+    #[test]
+    fn validate_err_on_closed_port() {
+        let cfg = test_cfg();
+        let node = cfg.rel_services.get("app_server").unwrap();
+        let mut bad = node.master.clone();
+        bad.port = 1;
+        assert!(validate("app_server.master", &bad).is_err());
+    }
+
+    #[test]
+    fn validate_err_on_bad_address() {
+        let cfg = test_cfg();
+        let node = cfg.rel_services.get("app_server").unwrap();
+        let mut bad = node.master.clone();
+        bad.host = "not_a_valid_host!!!".to_string();
+        assert!(validate("app_server.master", &bad).is_err());
+    }
+}