Move compute_ctl structs used in HTTP API and spec file to separate crate.

This is in preparation of using compute_ctl to launch postgres nodes
in the neon_local control plane. And seems like a good idea to
separate the public interfaces anyway.

One non-mechanical change here is that we now use a RwLock rather than
atomics to protect the ComputeNode::metrics field. We were not using
atomics for performance but for convenience here, and an RwLock is now
more convenient.

libs/compute_api/src/lib.rs

@@ -0,0 +1,2 @@
+pub mod models;
+pub mod spec;

libs/compute_api/src/models.rs

@@ -0,0 +1,39 @@
+//! Structs representing the JSON formats used in the compute_ctl's HTTP API.
+use chrono::{DateTime, Utc};
+use serde::{Serialize, Serializer};
+
+/// Response of the /status API
+///
+#[derive(Serialize)]
+#[serde(rename_all = "snake_case")]
+pub struct ComputeState {
+    pub status: ComputeStatus,
+    /// Timestamp of the last Postgres activity
+    #[serde(serialize_with = "rfc3339_serialize")]
+    pub last_active: DateTime<Utc>,
+    pub error: Option<String>,
+}
+
+#[derive(Serialize, Clone, Copy, PartialEq, Eq)]
+#[serde(rename_all = "snake_case")]
+pub enum ComputeStatus {
+    Init,
+    Running,
+    Failed,
+}
+
+fn rfc3339_serialize<S>(x: &DateTime<Utc>, s: S) -> Result<S::Ok, S::Error>
+where
+    S: Serializer,
+{
+    x.to_rfc3339().serialize(s)
+}
+
+/// Response of the /metrics.json API
+#[derive(Clone, Default, Serialize)]
+pub struct ComputeMetrics {
+    pub sync_safekeepers_ms: u64,
+    pub basebackup_ms: u64,
+    pub config_ms: u64,
+    pub total_startup_ms: u64,
+}

libs/compute_api/src/spec.rs

@@ -0,0 +1,94 @@
+//! `ComputeSpec` represents the contents of the spec.json file.
+//!
+//! The spec.json file is used to pass information to 'compute_ctl'. It contains
+//! all the information needed to start up the right version of PostgreSQL,
+//! and connect it to the storage nodes.
+use serde::Deserialize;
+use std::collections::HashMap;
+
+/// String type alias representing Postgres identifier and
+/// intended to be used for DB / role names.
+pub type PgIdent = String;
+
+/// Cluster spec or configuration represented as an optional number of
+/// delta operations + final cluster state description.
+#[derive(Clone, Deserialize)]
+pub struct ComputeSpec {
+    pub format_version: f32,
+    pub timestamp: String,
+    pub operation_uuid: Option<String>,
+    /// Expected cluster state at the end of transition process.
+    pub cluster: Cluster,
+    pub delta_operations: Option<Vec<DeltaOp>>,
+
+    pub storage_auth_token: Option<String>,
+
+    pub startup_tracing_context: Option<HashMap<String, String>>,
+}
+
+#[derive(Clone, Deserialize)]
+pub struct Cluster {
+    pub cluster_id: String,
+    pub name: String,
+    pub state: Option<String>,
+    pub roles: Vec<Role>,
+    pub databases: Vec<Database>,
+    pub settings: GenericOptions,
+}
+
+/// Single cluster state changing operation that could not be represented as
+/// a static `Cluster` structure. For example:
+/// - DROP DATABASE
+/// - DROP ROLE
+/// - ALTER ROLE name RENAME TO new_name
+/// - ALTER DATABASE name RENAME TO new_name
+#[derive(Clone, Deserialize)]
+pub struct DeltaOp {
+    pub action: String,
+    pub name: PgIdent,
+    pub new_name: Option<PgIdent>,
+}
+
+/// Rust representation of Postgres role info with only those fields
+/// that matter for us.
+#[derive(Clone, Deserialize)]
+pub struct Role {
+    pub name: PgIdent,
+    pub encrypted_password: Option<String>,
+    pub options: GenericOptions,
+}
+
+/// Rust representation of Postgres database info with only those fields
+/// that matter for us.
+#[derive(Clone, Deserialize)]
+pub struct Database {
+    pub name: PgIdent,
+    pub owner: PgIdent,
+    pub options: GenericOptions,
+}
+
+/// Common type representing both SQL statement params with or without value,
+/// like `LOGIN` or `OWNER username` in the `CREATE/ALTER ROLE`, and config
+/// options like `wal_level = logical`.
+#[derive(Clone, Deserialize)]
+pub struct GenericOption {
+    pub name: String,
+    pub value: Option<String>,
+    pub vartype: String,
+}
+
+/// Optional collection of `GenericOption`'s. Type alias allows us to
+/// declare a `trait` on it.
+pub type GenericOptions = Option<Vec<GenericOption>>;
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::fs::File;
+
+    #[test]
+    fn parse_spec_file() {
+        let file = File::open("tests/cluster_spec.json").unwrap();
+        let _spec: ComputeSpec = serde_json::from_reader(file).unwrap();
+    }
+}