Move initial timeline creation into pytest (#3270)

For every Python test, we start the storage first, and expect that
later, in the test, when we start a compute, it will work without
specific timeline and tenant creation or their IDs specified.

For that, we have a concept of "default" branch that was created on the
control plane level first, but that's not needed at all, given that it's
only Python tests that need it: let them create the initial timeline
during set-up.

Before, control plane started and stopped pageserver for timeline
creation, now Python harness runs an extra tenant creation request on
test env init.

I had to adjust the metrics test, turns out it registered the metrics
from the default tenant after an extra pageserver restart.
New model does not sent the metrics before the collection time happens,
and that was 30s before.

control_plane/src/background_process.rs

@@ -136,22 +136,6 @@ where
     anyhow::bail!("{process_name} did not start in {RETRY_UNTIL_SECS} seconds");
 }
 
-/// Send SIGTERM to child process
-pub fn send_stop_child_process(child: &std::process::Child) -> anyhow::Result<()> {
-    let pid = child.id();
-    match kill(
-        nix::unistd::Pid::from_raw(pid.try_into().unwrap()),
-        Signal::SIGTERM,
-    ) {
-        Ok(()) => Ok(()),
-        Err(Errno::ESRCH) => {
-            println!("child process with pid {pid} does not exist");
-            Ok(())
-        }
-        Err(e) => anyhow::bail!("Failed to send signal to child process with pid {pid}: {e}"),
-    }
-}
-
 /// Stops the process, using the pid file given. Returns Ok also if the process is already not running.
 pub fn stop_process(immediate: bool, process_name: &str, pid_file: &Path) -> anyhow::Result<()> {
     let pid = match pid_file::read(pid_file)

control_plane/src/bin/neon_local.rs

@@ -284,8 +284,6 @@ fn parse_timeline_id(sub_match: &ArgMatches) -> anyhow::Result<Option<TimelineId
 }
 
 fn handle_init(init_match: &ArgMatches) -> anyhow::Result<LocalEnv> {
-    let initial_timeline_id_arg = parse_timeline_id(init_match)?;
-
     // Create config file
     let toml_file: String = if let Some(config_path) = init_match.get_one::<PathBuf>("config") {
         // load and parse the file
@@ -309,30 +307,16 @@ fn handle_init(init_match: &ArgMatches) -> anyhow::Result<LocalEnv> {
         LocalEnv::parse_config(&toml_file).context("Failed to create neon configuration")?;
     env.init(pg_version)
         .context("Failed to initialize neon repository")?;
-    let initial_tenant_id = env
-        .default_tenant_id
-        .expect("default_tenant_id should be generated by the `env.init()` call above");
 
     // Initialize pageserver, create initial tenant and timeline.
     let pageserver = PageServerNode::from_env(&env);
-    let initial_timeline_id = pageserver
-        .initialize(
-            Some(initial_tenant_id),
-            initial_timeline_id_arg,
-            &pageserver_config_overrides(init_match),
-            pg_version,
-        )
+    pageserver
+        .initialize(&pageserver_config_overrides(init_match))
         .unwrap_or_else(|e| {
             eprintln!("pageserver init failed: {e:?}");
             exit(1);
         });
 
-    env.register_branch_mapping(
-        DEFAULT_BRANCH_NAME.to_owned(),
-        initial_tenant_id,
-        initial_timeline_id,
-    )?;
-
     Ok(env)
 }
 
@@ -928,9 +912,8 @@ fn cli() -> Command {
         .version(GIT_VERSION)
         .subcommand(
             Command::new("init")
-                .about("Initialize a new Neon repository")
+                .about("Initialize a new Neon repository, preparing configs for services to start with")
                 .arg(pageserver_config_args.clone())
-                .arg(timeline_id_arg.clone().help("Use a specific timeline id when creating a tenant and its initial timeline"))
                 .arg(
                     Arg::new("config")
                         .long("config")

control_plane/src/pageserver.rs

@@ -7,7 +7,7 @@ use std::path::PathBuf;
 use std::process::{Child, Command};
 use std::{io, result};
 
-use anyhow::{bail, ensure, Context};
+use anyhow::{bail, Context};
 use pageserver_api::models::{
     TenantConfigRequest, TenantCreateRequest, TenantInfo, TimelineCreateRequest, TimelineInfo,
 };
@@ -130,83 +130,15 @@ impl PageServerNode {
         overrides
     }
 
-    /// Initializes a pageserver node by creating its config with the overrides provided,
-    /// and creating an initial tenant and timeline afterwards.
-    pub fn initialize(
-        &self,
-        create_tenant: Option<TenantId>,
-        initial_timeline_id: Option<TimelineId>,
-        config_overrides: &[&str],
-        pg_version: u32,
-    ) -> anyhow::Result<TimelineId> {
+    /// Initializes a pageserver node by creating its config with the overrides provided.
+    pub fn initialize(&self, config_overrides: &[&str]) -> anyhow::Result<()> {
         // First, run `pageserver --init` and wait for it to write a config into FS and exit.
         self.pageserver_init(config_overrides).with_context(|| {
             format!(
                 "Failed to run init for pageserver node {}",
                 self.env.pageserver.id,
             )
-        })?;
-
-        // Then, briefly start it fully to run HTTP commands on it,
-        // to create initial tenant and timeline.
-        // We disable the remote storage, since we stop pageserver right after the timeline creation,
-        // hence most of the uploads will either aborted or not started: no point to start them at all.
-        let disabled_remote_storage_override = "remote_storage={}";
-        let mut pageserver_process = self
-            .start_node(
-                &[disabled_remote_storage_override],
-                // Previous overrides will be taken from the config created before, don't overwrite them.
-                false,
-            )
-            .with_context(|| {
-                format!(
-                    "Failed to start a process for pageserver node {}",
-                    self.env.pageserver.id,
-                )
-            })?;
-
-        let init_result = self
-            .try_init_timeline(create_tenant, initial_timeline_id, pg_version)
-            .context("Failed to create initial tenant and timeline for pageserver");
-        match &init_result {
-            Ok(initial_timeline_id) => {
-                println!("Successfully initialized timeline {initial_timeline_id}")
-            }
-            Err(e) => eprintln!("{e:#}"),
-        }
-        background_process::send_stop_child_process(&pageserver_process)?;
-
-        let exit_code = pageserver_process.wait()?;
-        ensure!(
-            exit_code.success(),
-            format!(
-                "pageserver init failed with exit code {:?}",
-                exit_code.code()
-            )
-        );
-        println!(
-            "Stopped pageserver {} process with pid {}",
-            self.env.pageserver.id,
-            pageserver_process.id(),
-        );
-        init_result
-    }
-
-    fn try_init_timeline(
-        &self,
-        new_tenant_id: Option<TenantId>,
-        new_timeline_id: Option<TimelineId>,
-        pg_version: u32,
-    ) -> anyhow::Result<TimelineId> {
-        let initial_tenant_id = self.tenant_create(new_tenant_id, HashMap::new())?;
-        let initial_timeline_info = self.timeline_create(
-            initial_tenant_id,
-            new_timeline_id,
-            None,
-            None,
-            Some(pg_version),
-        )?;
-        Ok(initial_timeline_info.timeline_id)
+        })
     }
 
     pub fn repo_path(&self) -> PathBuf {