tael_server/
config.rs

1use std::path::PathBuf;
2
3/// Selected storage backend. `TaelBackend` (the purpose-built tiered engine)
4/// is the default; pass `--storage duckdb` or set `TAEL_STORAGE=duckdb` to use
5/// the legacy embedded-DuckDB backend instead.
6#[derive(Debug, Clone, Copy, PartialEq, Eq)]
7pub enum StorageBackend {
8    Duckdb,
9    TaelBackend,
10}
11
12impl StorageBackend {
13    /// Parse a backend name (from the `--storage` flag or `TAEL_STORAGE`).
14    /// Anything that isn't explicitly `duckdb` selects the default tael-backend.
15    pub fn parse(s: &str) -> Self {
16        match s.trim().to_lowercase().as_str() {
17            "duckdb" | "duck" => StorageBackend::Duckdb,
18            _ => StorageBackend::TaelBackend,
19        }
20    }
21}
22
23pub struct ServerConfig {
24    pub otlp_grpc_addr: String,
25    pub rest_api_addr: String,
26    pub rest_api_socket: Option<String>,
27    pub data_dir: String,
28    pub wal_dir: String,
29    pub storage: StorageBackend,
30    /// When non-empty, this process runs as a stateless **query tier**: reads
31    /// are served by a `FanoutStore` that scatter-gathers across these shard
32    /// base URLs (`http://shard-0:7701,...`) instead of a local engine. Set via
33    /// `TAEL_QUERY_SHARDS`. See `docs/tael-server-scaling-ha.md` §3.
34    pub query_shards: Vec<String>,
35    /// Standby base URLs this node ships its WAL to as a **leader**
36    /// (`http://standby-1:7701,...`). Set via `TAEL_WAL_STANDBYS`. Only honored
37    /// by the tael-backend engine. See §5.1.
38    pub wal_standbys: Vec<String>,
39    /// How many standbys must ack a write before it returns. `None` = all
40    /// (fully synchronous); `Some(0)` = async best-effort. Set via
41    /// `TAEL_WAL_REQUIRED_ACKS`.
42    pub wal_required_acks: Option<usize>,
43    /// Cluster coordination (chitchat) for automatic leader election + epoch
44    /// fencing of WAL replication. `Some` when `TAEL_CLUSTER_LISTEN` is set.
45    /// See `docs/tael-server-scaling-ha.md` §5.1.
46    pub cluster: Option<ClusterSettings>,
47}
48
49/// Gossip-cluster settings for HA leader election (chitchat).
50#[derive(Debug, Clone)]
51pub struct ClusterSettings {
52    /// Stable unique node id within the replication group (election orders on it).
53    pub node_id: String,
54    /// UDP gossip listen address (`TAEL_CLUSTER_LISTEN`).
55    pub listen_addr: String,
56    /// Address peers reach this node on (`TAEL_CLUSTER_ADVERTISE`; default = listen).
57    pub advertise_addr: String,
58    /// Seed peers' gossip addresses (`TAEL_CLUSTER_SEEDS`).
59    pub seeds: Vec<String>,
60    /// Replication-group id peers must share (`TAEL_CLUSTER_ID`, default `tael`).
61    pub cluster_id: String,
62}
63
64impl ServerConfig {
65    pub fn from_env() -> Self {
66        let mut config = Self {
67            otlp_grpc_addr: std::env::var("TAEL_OTLP_GRPC_ADDR")
68                .unwrap_or_else(|_| "127.0.0.1:4317".into()),
69            rest_api_addr: std::env::var("TAEL_REST_API_ADDR")
70                .unwrap_or_else(|_| "127.0.0.1:7701".into()),
71            rest_api_socket: std::env::var("TAEL_REST_API_SOCKET")
72                .ok()
73                .filter(|s| !s.trim().is_empty()),
74            data_dir: std::env::var("TAEL_DATA_DIR").unwrap_or_else(|_| default_data_dir()),
75            wal_dir: std::env::var("TAEL_WAL_DIR")
76                .or_else(|_| std::env::var("WALRUS_DATA_DIR"))
77                .unwrap_or_else(|_| default_wal_dir()),
78            // Default to the tael-backend engine; `TAEL_STORAGE` can override.
79            storage: std::env::var("TAEL_STORAGE")
80                .map(|s| StorageBackend::parse(&s))
81                .unwrap_or(StorageBackend::TaelBackend),
82            query_shards: parse_csv_env("TAEL_QUERY_SHARDS"),
83            wal_standbys: parse_csv_env("TAEL_WAL_STANDBYS"),
84            wal_required_acks: std::env::var("TAEL_WAL_REQUIRED_ACKS")
85                .ok()
86                .and_then(|s| s.trim().parse().ok()),
87            cluster: cluster_from_env(),
88        };
89        // A `--storage <duckdb|tael-backend>` flag (or `--storage=…`) takes
90        // precedence over the env var.
91        if let Some(s) = storage_flag() {
92            config.storage = s;
93        }
94        config
95    }
96}
97
98fn default_data_dir() -> String {
99    default_tael_home().join("data").display().to_string()
100}
101
102fn default_wal_dir() -> String {
103    default_tael_home().join("wal_files").display().to_string()
104}
105
106fn default_tael_home() -> PathBuf {
107    home_dir()
108        .map(|home| home.join(".tael"))
109        .unwrap_or_else(|| PathBuf::from(".tael"))
110}
111
112fn home_dir() -> Option<PathBuf> {
113    std::env::var_os("HOME")
114        .map(PathBuf::from)
115        .or_else(|| std::env::var_os("USERPROFILE").map(PathBuf::from))
116        .or_else(
117            || match (std::env::var_os("HOMEDRIVE"), std::env::var_os("HOMEPATH")) {
118                (Some(drive), Some(path)) => {
119                    let mut home = PathBuf::from(drive);
120                    home.push(path);
121                    Some(home)
122                }
123                _ => None,
124            },
125        )
126}
127
128/// Build cluster settings from `TAEL_CLUSTER_*`. Returns `None` (coordination
129/// off) unless `TAEL_CLUSTER_LISTEN` is set.
130fn cluster_from_env() -> Option<ClusterSettings> {
131    let listen_addr = std::env::var("TAEL_CLUSTER_LISTEN").ok()?;
132    let advertise_addr =
133        std::env::var("TAEL_CLUSTER_ADVERTISE").unwrap_or_else(|_| listen_addr.clone());
134    // Default node id to the advertise address — unique per node, stable.
135    let node_id = std::env::var("TAEL_NODE_ID").unwrap_or_else(|_| advertise_addr.clone());
136    Some(ClusterSettings {
137        node_id,
138        listen_addr,
139        advertise_addr,
140        seeds: parse_csv_env("TAEL_CLUSTER_SEEDS"),
141        cluster_id: std::env::var("TAEL_CLUSTER_ID").unwrap_or_else(|_| "tael".to_string()),
142    })
143}
144
145/// Parse a comma-separated env var into a trimmed, non-empty list.
146fn parse_csv_env(var: &str) -> Vec<String> {
147    std::env::var(var)
148        .ok()
149        .map(|s| {
150            s.split(',')
151                .map(|p| p.trim().to_string())
152                .filter(|p| !p.is_empty())
153                .collect()
154        })
155        .unwrap_or_default()
156}
157
158/// Scan the process args for `--storage <value>` / `--storage=<value>`.
159fn storage_flag() -> Option<StorageBackend> {
160    let mut args = std::env::args().skip(1);
161    while let Some(arg) = args.next() {
162        if arg == "--storage" {
163            return args.next().map(|v| StorageBackend::parse(&v));
164        }
165        if let Some(v) = arg.strip_prefix("--storage=") {
166            return Some(StorageBackend::parse(v));
167        }
168    }
169    None
170}
tael_server/config.rs

tael_server/
config.rs
