tael_server/
config.rs

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

tael_server/
config.rs
