reduce scope of this PR & fix naming

control_plane/src/bin/neon_local.rs

@@ -359,7 +359,7 @@ fn handle_init(init_match: &ArgMatches) -> anyhow::Result<LocalEnv> {
     };
 
     let pageserver_config_overrides: toml_edit::Document =
-        if let Some(path) = init_match.get_one::<PathBuf>("pageserver-config-overrides-file") {
+        if let Some(path) = init_match.get_one::<PathBuf>("pageserver-config") {
             std::fs::read_to_string(path)
                 .context("load pageserver config overrides file")?
                 .parse()
@@ -1444,11 +1444,11 @@ fn cli() -> Command {
                         .value_name("config"),
                 )
                 .arg(
-                    Arg::new("pageserver-config-overrides-file")
-                        .long("pageserver-config-overrides-file")
+                    Arg::new("pageserver-config")
+                        .long("pageserver-config")
                         .required(false)
                         .value_parser(value_parser!(PathBuf))
-                        .value_name("pageserver-config-overrides-file"),
+                        .value_name("pageserver-config"),
                 )
                 .arg(pg_version_arg.clone())
                 .arg(force_arg)

docs/settings.md

@@ -40,10 +40,18 @@ Note the `[remote_storage]` section: it's a [table](https://toml.io/en/v1.0.0#ta
 
 - or can be placed anywhere if rewritten in identical form as [inline table](https://toml.io/en/v1.0.0#inline-table): `remote_storage = {foo = 2}`
 
+### Config values
+
+All values can be passed as an argument to the pageserver binary, using the `-c` parameter and specified as a valid TOML string. All tables should be passed in the inline form.
+
+Example: `${PAGESERVER_BIN} -c "checkpoint_timeout = '10 m'" -c "remote_storage={local_path='/some/local/path/'}"`
+
+Note that TOML distinguishes between strings and integers, the former require single or double quotes around them.
+
 #### broker_endpoint
 
 A storage broker endpoint to connect and pull the information from. Default is
-`'http://127.0.0.1:50051'`.
+`'http://127.0.0.1:50051'`. 
 
 #### checkpoint_distance
 
@@ -150,7 +158,7 @@ The default distrib dir is `./pg_install/`.
 A directory in the file system, where pageserver will store its files.
 The default is `./.neon/`.
 
-This parameter has a special CLI alias (`-D`).
+This parameter has a special CLI alias (`-D`) and can not be overridden with regular `-c` way.
 
 ##### Remote storage
 

pageserver/src/bin/pageserver.rs

@@ -6,7 +6,7 @@ use std::env::{var, VarError};
 use std::io::Read;
 use std::sync::Arc;
 use std::time::Duration;
-use std::{env, ops::ControlFlow};
+use std::{env, ops::ControlFlow, str::FromStr};
 
 use anyhow::{anyhow, Context};
 use camino::Utf8Path;
@@ -153,8 +153,7 @@ fn initialize_config(
 ) -> anyhow::Result<ControlFlow<(), &'static PageServerConf>> {
     let init = arg_matches.get_flag("init");
 
-    // Load the config file from disk or use the default config if in init mode.
-    let config: toml_edit::Document = match std::fs::File::open(cfg_file_path) {
+    let file_contents: Option<toml_edit::Document> = match std::fs::File::open(cfg_file_path) {
         Ok(mut f) => {
             if init {
                 anyhow::bail!("config file already exists: {cfg_file_path}");
@@ -163,33 +162,46 @@ fn initialize_config(
             if md.is_file() {
                 let mut s = String::new();
                 f.read_to_string(&mut s).context("read config file")?;
-                s.parse().context("parse config file toml")?
+                Some(s.parse().context("parse config file toml")?)
             } else {
                 anyhow::bail!("directory entry exists but is not a file: {cfg_file_path}");
             }
         }
-        Err(e) if e.kind() == std::io::ErrorKind::NotFound => {
-            if init {
-                DEFAULT_CONFIG_FILE
-                    .parse()
-                    .expect("unit tests ensure this works")
-            } else {
-                anyhow::bail!("config file not found: {cfg_file_path}");
-            }
-        }
+        Err(e) if e.kind() == std::io::ErrorKind::NotFound => None,
         Err(e) => {
             anyhow::bail!("open pageserver config: {e}: {cfg_file_path}");
         }
     };
 
+    let mut effective_config = file_contents.unwrap_or_else(|| {
+        DEFAULT_CONFIG_FILE
+            .parse()
+            .expect("unit tests ensure this works")
+    });
+
+    // Patch with overrides from the command line
+    if let Some(values) = arg_matches.get_many::<String>("config-override") {
+        for option_line in values {
+            let doc = toml_edit::Document::from_str(option_line).with_context(|| {
+                format!("Option '{option_line}' could not be parsed as a toml document")
+            })?;
+
+            for (key, item) in doc.iter() {
+                effective_config.insert(key, item.clone());
+            }
+        }
+    }
+
+    debug!("Resulting toml: {effective_config}");
+
     // Construct the runtime representation
-    let conf = PageServerConf::parse_and_validate(&config, workdir)
+    let conf = PageServerConf::parse_and_validate(&effective_config, workdir)
         .context("Failed to parse pageserver configuration")?;
 
     if init {
         info!("Writing pageserver config to '{cfg_file_path}'");
 
-        std::fs::write(cfg_file_path, config.to_string())
+        std::fs::write(cfg_file_path, effective_config.to_string())
             .with_context(|| format!("Failed to write pageserver config to '{cfg_file_path}'"))?;
         info!("Config successfully written to '{cfg_file_path}'")
     }
@@ -740,6 +752,16 @@ fn cli() -> Command {
                 .long("workdir")
                 .help("Working directory for the pageserver"),
         )
+        // See `settings.md` for more details on the extra configuration patameters pageserver can process
+        .arg(
+            Arg::new("config-override")
+                .long("config-override")
+                .short('c')
+                .num_args(1)
+                .action(ArgAction::Append)
+                .help("Additional configuration overrides of the ones from the toml config file (or new ones to add there). \
+                Any option has to be a valid toml document, example: `-c=\"foo='hey'\"` `-c=\"foo={value=1}\"`"),
+        )
         .arg(
             Arg::new("enabled-features")
                 .long("enabled-features")

test_runner/fixtures/neon_fixtures.py

@@ -1711,28 +1711,28 @@ class NeonCli(AbstractNeonCli):
     ) -> "subprocess.CompletedProcess[str]":
         remote_storage = self.env.pageserver_remote_storage
 
-        ps_toml = {}
+        ps_config = {}
         if remote_storage is not None:
             remote_storage_toml_table = remote_storage_to_toml_inline_table(remote_storage)
-            ps_toml["remote_storage"] = remote_storage_toml_table
+            ps_config["remote_storage"] = remote_storage_toml_table
 
         env_overrides = os.getenv("NEON_PAGESERVER_OVERRIDES")
         if env_overrides is not None:
             for o in env_overrides.split(";"):
                 override = toml.loads(o)
                 for key, value in override.items():
-                    ps_toml[key] = value
+                    ps_config[key] = value
 
         if pageserver_config_override is not None:
             for o in pageserver_config_override.split(";"):
                 override = toml.loads(o)
                 for key, value in override.items():
-                    ps_toml[key] = value
+                    ps_config[key] = value
 
         with ExitStack() as stack:
-            ps_toml_file = stack.enter_context(tempfile.NamedTemporaryFile(mode="w+"))
-            ps_toml_file.write(toml.dumps(ps_toml))
-            ps_toml_file.flush()
+            ps_config_file = stack.enter_context(tempfile.NamedTemporaryFile(mode="w+"))
+            ps_config_file.write(toml.dumps(ps_config))
+            ps_config_file.flush()
 
             neon_local_config = stack.enter_context(tempfile.NamedTemporaryFile(mode="w+"))
             neon_local_config.write(toml.dumps(config))
@@ -1743,7 +1743,7 @@ class NeonCli(AbstractNeonCli):
                 f"--config={neon_local_config.name}",
                 "--pg-version",
                 self.env.pg_version,
-                f"--pageserver-config-overrides-file={ps_toml_file.name}",
+                f"--pageserver-config={ps_config_file.name}",
             ]
 
             if force is not None: