Use pg_upgrade to upgrade projects from one Postgres major version to the next

libs/compute_api/src/requests.rs

@@ -12,3 +12,9 @@ use serde::Deserialize;
 pub struct ConfigurationRequest {
     pub spec: ComputeSpec,
 }
+
+/// Request body of the /upgrade API
+#[derive(Deserialize, Debug)]
+pub struct UpgradeRequest {
+    pub pg_version: String,
+}

libs/compute_api/src/responses.rs

@@ -44,10 +44,15 @@ pub enum ComputeStatus {
     // Compute node has spec and initial startup and
     // configuration is in progress.
     Init,
+    // Compute has been prepared, meaning that remote extensions have been
+    // downloaded and the data directory has been prepared.
+    Prepared,
     // Compute is configured and running.
     Running,
     // New spec is being applied.
     Configuration,
+    // Compute is upgrading Postgres.
+    Upgrading,
     // Either startup or configuration failed,
     // compute will exit soon or is waiting for
     // control-plane to terminate it.

libs/compute_api/src/spec.rs

@@ -199,6 +199,11 @@ pub enum ComputeMode {
     /// Future versions may want to distinguish between replicas with hot standby
     /// feedback and other kinds of replication configurations.
     Replica,
+    /// An upgrade-only node
+    ///
+    /// This node will not accept remote Postgres connections. It's only
+    /// purpose is to upgrade a timeline.
+    Upgrade,
 }
 
 #[derive(Clone, Debug, Default, Deserialize, Serialize)]