neon_local: support force init (#4363)

When we use local SSD for bench and create `.neon` directory before we
do `cargo neon init`, the initialization process will error due to
directory already exists. This PR adds a flag `--force` that removes
everything inside the directory if `.neon` already exists.

---------

Signed-off-by: Alex Chi Z. <chi@neon.tech>

control_plane/src/bin/neon_local.rs

@@ -308,7 +308,8 @@ fn handle_init(init_match: &ArgMatches) -> anyhow::Result<LocalEnv> {
 
     let mut env =
         LocalEnv::parse_config(&toml_file).context("Failed to create neon configuration")?;
-    env.init(pg_version)
+    let force = init_match.get_flag("force");
+    env.init(pg_version, force)
         .context("Failed to initialize neon repository")?;
 
     // Initialize pageserver, create initial tenant and timeline.
@@ -1013,6 +1014,13 @@ fn cli() -> Command {
         .help("If set, the node will be a hot replica on the specified timeline")
         .required(false);
 
+    let force_arg = Arg::new("force")
+        .value_parser(value_parser!(bool))
+        .long("force")
+        .action(ArgAction::SetTrue)
+        .help("Force initialization even if the repository is not empty")
+        .required(false);
+
     Command::new("Neon CLI")
         .arg_required_else_help(true)
         .version(GIT_VERSION)
@@ -1028,6 +1036,7 @@ fn cli() -> Command {
                         .value_name("config"),
                 )
                 .arg(pg_version_arg.clone())
+                .arg(force_arg)
         )
         .subcommand(
             Command::new("timeline")

control_plane/src/local_env.rs

@@ -364,7 +364,7 @@ impl LocalEnv {
     //
     // Initialize a new Neon repository
     //
-    pub fn init(&mut self, pg_version: u32) -> anyhow::Result<()> {
+    pub fn init(&mut self, pg_version: u32, force: bool) -> anyhow::Result<()> {
         // check if config already exists
         let base_path = &self.base_data_dir;
         ensure!(
@@ -372,11 +372,29 @@ impl LocalEnv {
             "repository base path is missing"
         );
 
-        ensure!(
-            !base_path.exists(),
-            "directory '{}' already exists. Perhaps already initialized?",
-            base_path.display()
-        );
+        if base_path.exists() {
+            if force {
+                println!("removing all contents of '{}'", base_path.display());
+                // instead of directly calling `remove_dir_all`, we keep the original dir but removing
+                // all contents inside. This helps if the developer symbol links another directory (i.e.,
+                // S3 local SSD) to the `.neon` base directory.
+                for entry in std::fs::read_dir(base_path)? {
+                    let entry = entry?;
+                    let path = entry.path();
+                    if path.is_dir() {
+                        fs::remove_dir_all(&path)?;
+                    } else {
+                        fs::remove_file(&path)?;
+                    }
+                }
+            } else {
+                bail!(
+                    "directory '{}' already exists. Perhaps already initialized? (Hint: use --force to remove all contents)",
+                    base_path.display()
+                );
+            }
+        }
+
         if !self.pg_bin_dir(pg_version)?.join("postgres").exists() {
             bail!(
                 "Can't find postgres binary at {}",
@@ -392,7 +410,9 @@ impl LocalEnv {
             }
         }
 
-        fs::create_dir(base_path)?;
+        if !base_path.exists() {
+            fs::create_dir(base_path)?;
+        }
 
         // Generate keypair for JWT.
         //