get stack run config based on template name (#477)

This PR adds a method in stack to return the stackrunconfig object based
on the template name. This will be used to instantiate a direct client
without the need for an explicit run.yaml

---------

Co-authored-by: Dinesh Yeduguru <dineshyv@fb.com>

llama_stack/distribution/server/server.py

@@ -10,7 +10,6 @@ import functools
 import inspect
 import json
 import os
-import re
 import signal
 import sys
 import traceback
@@ -41,7 +40,11 @@ from llama_stack.providers.utils.telemetry.tracing import (
 from llama_stack.distribution.datatypes import *  # noqa: F403
 from llama_stack.distribution.request_headers import set_request_provider_data
 from llama_stack.distribution.resolver import InvalidProviderError
-from llama_stack.distribution.stack import construct_stack
+from llama_stack.distribution.stack import (
+    construct_stack,
+    replace_env_vars,
+    validate_env_pair,
+)
 
 from .endpoints import get_all_api_endpoints
 
@@ -271,77 +274,6 @@ def create_dynamic_typed_route(func: Any, method: str):
     return endpoint
 
 
-class EnvVarError(Exception):
-    def __init__(self, var_name: str, path: str = ""):
-        self.var_name = var_name
-        self.path = path
-        super().__init__(
-            f"Environment variable '{var_name}' not set or empty{f' at {path}' if path else ''}"
-        )
-
-
-def replace_env_vars(config: Any, path: str = "") -> Any:
-    if isinstance(config, dict):
-        result = {}
-        for k, v in config.items():
-            try:
-                result[k] = replace_env_vars(v, f"{path}.{k}" if path else k)
-            except EnvVarError as e:
-                raise EnvVarError(e.var_name, e.path) from None
-        return result
-
-    elif isinstance(config, list):
-        result = []
-        for i, v in enumerate(config):
-            try:
-                result.append(replace_env_vars(v, f"{path}[{i}]"))
-            except EnvVarError as e:
-                raise EnvVarError(e.var_name, e.path) from None
-        return result
-
-    elif isinstance(config, str):
-        pattern = r"\${env\.([A-Z0-9_]+)(?::([^}]*))?}"
-
-        def get_env_var(match):
-            env_var = match.group(1)
-            default_val = match.group(2)
-
-            value = os.environ.get(env_var)
-            if not value:
-                if default_val is None:
-                    raise EnvVarError(env_var, path)
-                else:
-                    value = default_val
-
-            # expand "~" from the values
-            return os.path.expanduser(value)
-
-        try:
-            return re.sub(pattern, get_env_var, config)
-        except EnvVarError as e:
-            raise EnvVarError(e.var_name, e.path) from None
-
-    return config
-
-
-def validate_env_pair(env_pair: str) -> tuple[str, str]:
-    """Validate and split an environment variable key-value pair."""
-    try:
-        key, value = env_pair.split("=", 1)
-        key = key.strip()
-        if not key:
-            raise ValueError(f"Empty key in environment variable pair: {env_pair}")
-        if not all(c.isalnum() or c == "_" for c in key):
-            raise ValueError(
-                f"Key must contain only alphanumeric characters and underscores: {key}"
-            )
-        return key, value
-    except ValueError as e:
-        raise ValueError(
-            f"Invalid environment variable format '{env_pair}': {str(e)}. Expected format: KEY=value"
-        ) from e
-
-
 def main():
     """Start the LlamaStack server."""
     parser = argparse.ArgumentParser(description="Start the LlamaStack server.")

llama_stack/distribution/stack.py

@@ -4,8 +4,13 @@
 # This source code is licensed under the terms described in the LICENSE file in
 # the root directory of this source tree.
 
+import os
+from pathlib import Path
 from typing import Any, Dict
 
+import pkg_resources
+import yaml
+
 from termcolor import colored
 
 from llama_models.llama3.api.datatypes import *  # noqa: F403
@@ -92,6 +97,77 @@ async def register_resources(run_config: StackRunConfig, impls: Dict[Api, Any]):
     print("")
 
 
+class EnvVarError(Exception):
+    def __init__(self, var_name: str, path: str = ""):
+        self.var_name = var_name
+        self.path = path
+        super().__init__(
+            f"Environment variable '{var_name}' not set or empty{f' at {path}' if path else ''}"
+        )
+
+
+def replace_env_vars(config: Any, path: str = "") -> Any:
+    if isinstance(config, dict):
+        result = {}
+        for k, v in config.items():
+            try:
+                result[k] = replace_env_vars(v, f"{path}.{k}" if path else k)
+            except EnvVarError as e:
+                raise EnvVarError(e.var_name, e.path) from None
+        return result
+
+    elif isinstance(config, list):
+        result = []
+        for i, v in enumerate(config):
+            try:
+                result.append(replace_env_vars(v, f"{path}[{i}]"))
+            except EnvVarError as e:
+                raise EnvVarError(e.var_name, e.path) from None
+        return result
+
+    elif isinstance(config, str):
+        pattern = r"\${env\.([A-Z0-9_]+)(?::([^}]*))?}"
+
+        def get_env_var(match):
+            env_var = match.group(1)
+            default_val = match.group(2)
+
+            value = os.environ.get(env_var)
+            if not value:
+                if default_val is None:
+                    raise EnvVarError(env_var, path)
+                else:
+                    value = default_val
+
+            # expand "~" from the values
+            return os.path.expanduser(value)
+
+        try:
+            return re.sub(pattern, get_env_var, config)
+        except EnvVarError as e:
+            raise EnvVarError(e.var_name, e.path) from None
+
+    return config
+
+
+def validate_env_pair(env_pair: str) -> tuple[str, str]:
+    """Validate and split an environment variable key-value pair."""
+    try:
+        key, value = env_pair.split("=", 1)
+        key = key.strip()
+        if not key:
+            raise ValueError(f"Empty key in environment variable pair: {env_pair}")
+        if not all(c.isalnum() or c == "_" for c in key):
+            raise ValueError(
+                f"Key must contain only alphanumeric characters and underscores: {key}"
+            )
+        return key, value
+    except ValueError as e:
+        raise ValueError(
+            f"Invalid environment variable format '{env_pair}': {str(e)}. Expected format: KEY=value"
+        ) from e
+
+
 # Produces a stack of providers for the given run config. Not all APIs may be
 # asked for in the run config.
 async def construct_stack(
@@ -105,3 +181,17 @@ async def construct_stack(
     )
     await register_resources(run_config, impls)
     return impls
+
+
+def get_stack_run_config_from_template(template: str) -> StackRunConfig:
+    template_path = pkg_resources.resource_filename(
+        "llama_stack", f"templates/{template}/run.yaml"
+    )
+
+    if not Path(template_path).exists():
+        raise ValueError(f"Template '{template}' not found at {template_path}")
+
+    with open(template_path) as f:
+        run_config = yaml.safe_load(f)
+
+    return StackRunConfig(**replace_env_vars(run_config))