ensure correct locale on 035 update

core/src/version/v0_3_6_alpha_0.rs

@@ -40,6 +40,102 @@ lazy_static::lazy_static! {
     );
 }
 
+/// Detect the LC_COLLATE / LC_CTYPE the cluster was created with and generate
+/// those locales if they are missing from the running system.  Older installs
+/// may have been initialized with a locale (e.g. en_GB.UTF-8) that the current
+/// image does not ship.  Without it PostgreSQL starts but refuses
+/// connections, breaking the migration.
+async fn ensure_cluster_locale(pg_version: u32) -> Result<(), Error> {
+    let cluster_dir = format!("/var/lib/postgresql/{pg_version}/main");
+    let pg_controldata = format!("/usr/lib/postgresql/{pg_version}/bin/pg_controldata");
+
+    let output = Command::new(&pg_controldata)
+        .arg(&cluster_dir)
+        .kill_on_drop(true)
+        .stdout(std::process::Stdio::piped())
+        .stderr(std::process::Stdio::piped())
+        .output()
+        .await
+        .with_kind(crate::ErrorKind::Database)?;
+    if !output.status.success() {
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        tracing::warn!("pg_controldata failed, skipping locale check: {stderr}");
+        return Ok(());
+    }
+
+    let stdout = String::from_utf8_lossy(&output.stdout);
+    let mut locales_needed = Vec::new();
+    for line in stdout.lines() {
+        let locale = if let Some(rest) = line.strip_prefix("LC_COLLATE:") {
+            rest.trim()
+        } else if let Some(rest) = line.strip_prefix("LC_CTYPE:") {
+            rest.trim()
+        } else {
+            continue;
+        };
+        if !locale.is_empty() && locale != "C" && locale != "POSIX" {
+            locales_needed.push(locale.to_owned());
+        }
+    }
+    locales_needed.sort();
+    locales_needed.dedup();
+
+    if locales_needed.is_empty() {
+        return Ok(());
+    }
+
+    // Check which locales are already available.
+    let available = Command::new("locale")
+        .arg("-a")
+        .kill_on_drop(true)
+        .stdout(std::process::Stdio::piped())
+        .stderr(std::process::Stdio::null())
+        .output()
+        .await
+        .map(|o| String::from_utf8_lossy(&o.stdout).to_string())
+        .unwrap_or_default();
+
+    let mut need_gen = false;
+    for locale in &locales_needed {
+        // locale -a normalizes e.g. "en_GB.UTF-8" → "en_GB.utf8"
+        let normalized = locale.replace("-", "").to_lowercase();
+        if available.lines().any(|l| l.replace("-", "").to_lowercase() == normalized) {
+            continue;
+        }
+        // Debian's locale-gen ignores positional args — the locale must be
+        // uncommented in /etc/locale.gen or appended to it.
+        tracing::info!("Enabling missing locale for PostgreSQL cluster: {locale}");
+        let locale_gen_path = Path::new("/etc/locale.gen");
+        let contents = tokio::fs::read_to_string(locale_gen_path)
+            .await
+            .unwrap_or_default();
+        // Try to uncomment an existing entry first, otherwise append.
+        let entry = format!("{locale} UTF-8");
+        let commented = format!("# {entry}");
+        if contents.contains(&commented) {
+            let updated = contents.replace(&commented, &entry);
+            tokio::fs::write(locale_gen_path, updated).await?;
+        } else if !contents.contains(&entry) {
+            use tokio::io::AsyncWriteExt;
+            let mut f = tokio::fs::OpenOptions::new()
+                .create(true)
+                .append(true)
+                .open(locale_gen_path)
+                .await?;
+            f.write_all(format!("\n{entry}\n").as_bytes()).await?;
+        }
+        need_gen = true;
+    }
+
+    if need_gen {
+        Command::new("locale-gen")
+            .invoke(crate::ErrorKind::Database)
+            .await?;
+    }
+
+    Ok(())
+}
+
 #[tracing::instrument(skip_all)]
 async fn init_postgres(datadir: impl AsRef<Path>) -> Result<PgPool, Error> {
     let db_dir = datadir.as_ref().join("main/postgresql");
@@ -91,6 +187,12 @@ async fn init_postgres(datadir: impl AsRef<Path>) -> Result<PgPool, Error> {
 
     crate::disk::mount::util::bind(&db_dir, "/var/lib/postgresql", false).await?;
 
+    // The cluster may have been created with a locale not present on the
+    // current image (e.g. en_GB.UTF-8 on a server that predates the trixie
+    // image).  Detect and generate it before starting PostgreSQL, otherwise
+    // PG will start but refuse connections.
+    ensure_cluster_locale(pg_version).await?;
+
     Command::new("systemctl")
         .arg("start")
         .arg(format!("postgresql@{pg_version}-main.service"))