API/YAML: Support using env vars to define file_mounts.

examples/using_file_mounts_with_env_vars.yaml

@@ -0,0 +1,52 @@
+# Example showcasing how env vars can be used in the file_mounts section.
+
+# You can set the default values for env vars in this 'envs' section.
+# When launching, `sky launch --env ENV=val` will override the default.
+envs:
+  MY_BUCKET: skypilot-temp-gcs-test
+  MY_LOCAL_PATH: tmp-workdir
+  MODEL_SIZE: 13b
+
+resources:
+  cloud: gcp
+
+# You can use env vars in
+#   - the destination: source paths
+#   - for SkyPilot Storage
+#     - the "name" (bucket name) and "source" (local dir/file to upload) fields.
+#
+# Both syntaxes work: ${MY_BUCKET} and $MY_BUCKET.
+file_mounts:
+  /mydir:
+    name: ${MY_BUCKET}  # Name of the bucket.
+    store: gcs
+    mode: MOUNT
+
+  /mydir2:
+    name: $MY_BUCKET  # Name of the bucket.
+    store: gcs
+    mode: MOUNT
+
+  /another-dir:
+    name: ${MY_BUCKET}-2
+    source: ["~/${MY_LOCAL_PATH}"]
+    store: gcs
+    mode: MOUNT
+
+  /another-dir2:
+    name: $MY_BUCKET-2
+    source: ["~/${MY_LOCAL_PATH}"]
+    store: gcs
+    mode: MOUNT
+
+  /checkpoint/${MODEL_SIZE}: ~/${MY_LOCAL_PATH}
+
+run: |
+  echo Env var MY_BUCKET has value: ${MY_BUCKET}
+  echo Env var MY_LOCAL_PATH has value: ${MY_LOCAL_PATH}
+
+  ls -lthr /mydir
+  ls -lthr /mydir2
+  ls -lthr /another-dir
+  ls -lthr /another-dir2
+  ls -lthr /checkpoint/${MODEL_SIZE}

sky/backends/backend_utils.py

@@ -2502,17 +2502,28 @@ def validate_schema(obj, schema, err_msg_prefix=''):
         validator.SchemaValidator(schema).validate(obj)
     except jsonschema.ValidationError as e:
         if e.validator == 'additionalProperties':
-            err_msg = err_msg_prefix + 'The following fields are invalid:'
-            known_fields = set(e.schema.get('properties', {}).keys())
-            for field in e.instance:
-                if field not in known_fields:
-                    most_similar_field = difflib.get_close_matches(
-                        field, known_fields, 1)
-                    if most_similar_field:
-                        err_msg += (f'\nInstead of {field!r}, did you mean '
-                                    f'{most_similar_field[0]!r}?')
-                    else:
-                        err_msg += f'\nFound unsupported field {field!r}.'
+            if tuple(e.schema_path) == ('properties', 'envs',
+                                        'additionalProperties'):
+                # Hack. Here the error is Task.envs having some invalid keys. So
+                # we should not print "unsupported field".
+                #
+                # This will print something like:
+                # 'hello world' does not match any of the regexes: <regex>
+                err_msg = (err_msg_prefix +
+                           'The `envs` field contains invalid keys:\n' +
+                           e.message)
+            else:
+                err_msg = err_msg_prefix + 'The following fields are invalid:'
+                known_fields = set(e.schema.get('properties', {}).keys())
+                for field in e.instance:
+                    if field not in known_fields:
+                        most_similar_field = difflib.get_close_matches(
+                            field, known_fields, 1)
+                        if most_similar_field:
+                            err_msg += (f'\nInstead of {field!r}, did you mean '
+                                        f'{most_similar_field[0]!r}?')
+                        else:
+                            err_msg += f'\nFound unsupported field {field!r}.'
         else:
             # Example e.json_path value: '$.resources'
             err_msg = (err_msg_prefix + e.message +

sky/cli.py

@@ -941,15 +941,23 @@ def _check_yaml(entrypoint: str) -> Tuple[bool, Optional[Dict[str, Any]]]:
         entrypoint: Path to a YAML file.
     """
     is_yaml = True
-    config = None
+    config: Optional[List[Dict[str, Any]]] = None
+    result = None
     shell_splits = shlex.split(entrypoint)
-    yaml_file_provided = len(shell_splits) == 1 and \
-        (shell_splits[0].endswith('yaml') or shell_splits[0].endswith('.yml'))
+    yaml_file_provided = (len(shell_splits) == 1 and
+                          (shell_splits[0].endswith('yaml') or
+                           shell_splits[0].endswith('.yml')))
     try:
         with open(entrypoint, 'r') as f:
             try:
-                config = list(yaml.safe_load_all(f))[0]
-                if isinstance(config, str):
+                config = list(yaml.safe_load_all(f))
+                if config:
+                    # FIXME(zongheng): in a chain DAG YAML it only returns the
+                    # first section. OK for downstream but is weird.
+                    result = config[0]
+                else:
+                    result = {}
+                if isinstance(result, str):
                     # 'sky exec cluster ./my_script.sh'
                     is_yaml = False
             except yaml.YAMLError as e:
@@ -977,7 +985,7 @@ def _check_yaml(entrypoint: str) -> Tuple[bool, Optional[Dict[str, Any]]]:
                 f'{entrypoint!r} looks like a yaml path but {invalid_reason}\n'
                 'It will be treated as a command to be run remotely. Continue?',
                 abort=True)
-    return is_yaml, config
+    return is_yaml, result
 
 
 def _make_task_or_dag_from_entrypoint_with_overrides(
@@ -1041,7 +1049,7 @@ def _make_task_or_dag_from_entrypoint_with_overrides(
     if is_yaml:
         assert entrypoint is not None
         usage_lib.messages.usage.update_user_task_yaml(entrypoint)
-        dag = dag_utils.load_chain_dag_from_yaml(entrypoint)
+        dag = dag_utils.load_chain_dag_from_yaml(entrypoint, env_overrides=env)
         if len(dag.tasks) > 1:
             # When the dag has more than 1 task. It is unclear how to
             # override the params for the dag. So we just ignore the
@@ -1052,7 +1060,9 @@ def _make_task_or_dag_from_entrypoint_with_overrides(
                     'since the yaml file contains multiple tasks.',
                     fg='yellow')
             return dag
-        task = sky.Task.from_yaml(entrypoint)
+        assert len(dag.tasks) == 1, (
+            f'If you see this, please file an issue; tasks: {dag.tasks}')
+        task = dag.tasks[0]
     else:
         task = sky.Task(name='sky-cmd', run=entrypoint)
         task.set_resources({sky.Resources()})

sky/clouds/gcp.py

@@ -622,7 +622,7 @@ def get_credential_file_mounts(self) -> Dict[str, str]:
         # be modified on the remote cluster by ray causing authentication
         # problems. The backup file will be updated to the remote cluster
         # whenever the original file is not empty and will be applied
-        # appropriately on the remote cluster when neccessary.
+        # appropriately on the remote cluster when necessary.
         if (os.path.exists(os.path.expanduser(GCP_CONFIG_PATH)) and
                 os.path.getsize(os.path.expanduser(GCP_CONFIG_PATH)) > 0):
             subprocess.run(f'cp {GCP_CONFIG_PATH} {GCP_CONFIG_SKY_BACKUP_PATH}',

sky/data/storage.py

@@ -1321,11 +1321,10 @@ def _validate(self):
         if not _is_storage_cloud_enabled(str(clouds.GCP())):
             with ux_utils.print_exception_no_traceback():
                 raise exceptions.ResourcesUnavailableError(
-                    'Storage \'store: gcs\' specified, but ' \
-                    'GCP access is disabled. To fix, enable '\
-                    'GCP by running `sky check`. '\
-                    'More info: https://skypilot.readthedocs.io/en/latest/getting-started/installation.html.' # pylint: disable=line-too-long
-                    )
+                    'Storage \'store: gcs\' specified, but '
+                    'GCP access is disabled. To fix, enable '
+                    'GCP by running `sky check`. '
+                    'More info: https://skypilot.readthedocs.io/en/latest/getting-started/installation.html.')  # pylint: disable=line-too-long
 
     @classmethod
     def validate_name(cls, name) -> str:

sky/task.py

@@ -1,5 +1,6 @@
 """Task: a coarse-grained stage in an application."""
 import inspect
+import json
 import os
 import re
 import typing
@@ -68,6 +69,35 @@ def _is_valid_env_var(name: str) -> bool:
     return bool(re.fullmatch(_VALID_ENV_VAR_REGEX, name))
 
 
+def _fill_in_env_vars_in_file_mounts(
+    file_mounts: Dict[str, Any],
+    task_envs: Dict[str, str],
+) -> Dict[str, Any]:
+    """Detects env vars in file_mounts and fills them with task_envs.
+
+    Use cases of env vars in file_mounts:
+    - dst/src paths; e.g.,
+        /model_path/llama-${SIZE}b: s3://llama-weights/llama-${SIZE}b
+    - storage's name (bucket name)
+    - storage's source (local path)
+
+    We simply dump file_mounts into a json string, and replace env vars using
+    regex. This should be safe as file_mounts has been schema-validated.
+
+    Env vars of the following forms are detected:
+        - ${ENV}
+        - $ENV
+    where <ENV> must appear in task.envs.
+    """
+    # TODO(zongheng): support ${ENV:-default}?
+    file_mounts_str = json.dumps(file_mounts)
+    for key, value in task_envs.items():
+        pattern = r'\$\{?\b' + key + r'\b\}?'
+        env_var_pattern = re.compile(pattern)
+        file_mounts_str = env_var_pattern.sub(value, file_mounts_str)
+    return json.loads(file_mounts_str)
+
+
 class Task:
     """Task: a computation to be run on the cloud."""
 
@@ -231,10 +261,37 @@ def _validate(self):
                         f'a symlink to a directory). {self.workdir} not found.')
 
     @staticmethod
-    def from_yaml_config(config: Dict[str, Any]) -> 'Task':
+    def from_yaml_config(
+        config: Dict[str, Any],
+        env_overrides: Optional[List[Tuple[str, str]]] = None,
+    ) -> 'Task':
+        if env_overrides is not None:
+            # We must override env vars before constructing the Task, because
+            # the Storage object creation is eager and it (its name/source
+            # fields) may depend on env vars.
+            #
+            # FIXME(zongheng): The eagerness / how we construct Task's from
+            # entrypoint (YAML, CLI args) should be fixed.
+            new_envs = config.get('envs', {})
+            new_envs.update(env_overrides)
+            config['envs'] = new_envs
+
+        # More robust handling for 'envs': explicitly convert keys and values to
+        # str, since users may pass '123' as keys/values which will get parsed
+        # as int causing validate_schema() to fail.
+        envs = config.get('envs')
+        if envs is not None and isinstance(envs, dict):
+            config['envs'] = {str(k): str(v) for k, v in envs.items()}
+
         backend_utils.validate_schema(config, schemas.get_task_schema(),
                                       'Invalid task YAML: ')
 
+        # Fill in any Task.envs into file_mounts (src/dst paths, storage
+        # name/source).
+        if config.get('file_mounts') is not None:
+            config['file_mounts'] = _fill_in_env_vars_in_file_mounts(
+                config['file_mounts'], config.get('envs', {}))
+
         task = Task(
             config.pop('name', None),
             run=config.pop('run', None),
@@ -269,8 +326,7 @@ def from_yaml_config(config: Dict[str, Any]) -> 'Task':
         all_storages = fm_storages
         for storage in all_storages:
             mount_path = storage[0]
-            assert mount_path, \
-                'Storage mount path cannot be empty.'
+            assert mount_path, 'Storage mount path cannot be empty.'
             try:
                 storage_obj = storage_lib.Storage.from_yaml_config(storage[1])
             except exceptions.StorageSourceError as e:
@@ -649,7 +705,7 @@ def update_storage_mounts(
 
         Different from set_storage_mounts(), this function updates into the
         existing storage_mounts (calls ``dict.update()``), rather than
-        overwritting it.
+        overwriting it.
 
         This should be called before provisioning in order to take effect.
 

sky/utils/common_utils.py

@@ -182,7 +182,11 @@ def read_yaml(path) -> Dict[str, Any]:
 def read_yaml_all(path: str) -> List[Dict[str, Any]]:
     with open(path, 'r') as f:
         config = yaml.safe_load_all(f)
-        return list(config)
+        configs = list(config)
+        if not configs:
+            # Empty YAML file.
+            return [{}]
+        return configs
 
 
 def dump_yaml(path, config) -> None:

sky/utils/dag_utils.py

@@ -1,11 +1,29 @@
 """Utilities for loading and dumping DAGs from/to YAML files."""
+from typing import List, Optional, Tuple
+
 from sky import dag as dag_lib
 from sky import task as task_lib
 from sky.backends import backend_utils
 from sky.utils import common_utils
 
 
-def load_chain_dag_from_yaml(path: str) -> dag_lib.Dag:
+def load_chain_dag_from_yaml(
+    path: str,
+    env_overrides: Optional[List[Tuple[str, str]]] = None,
+) -> dag_lib.Dag:
+    """Loads a chain DAG from a YAML file.
+
+    Has special handling for an initial section in YAML that contains only the
+    'name' field, which is the DAG name.
+
+    'env_overrides' is in effect only when there's exactly one task. It is a
+    list of (key, value) pairs that will be used to update the task's 'envs'
+    section.
+
+    Returns:
+      A chain Dag with 1 or more tasks (an empty entrypoint would create a
+      trivial task).
+    """
     configs = common_utils.read_yaml_all(path)
     dag_name = None
     if set(configs[0].keys()) == {'name'}:
@@ -14,12 +32,22 @@ def load_chain_dag_from_yaml(path: str) -> dag_lib.Dag:
     elif len(configs) == 1:
         dag_name = configs[0].get('name')
 
+    if len(configs) == 0:
+        # YAML has only `name: xxx`. Still instantiate a task.
+        configs = [{'name': dag_name}]
+
+    if len(configs) > 1:
+        # TODO(zongheng): in a chain DAG of N tasks, cli.py currently makes the
+        # decision to not apply overrides. Here we maintain this behavior. We
+        # can listen to user feedback to change this.
+        env_overrides = None
+
     current_task = None
     with dag_lib.Dag() as dag:
         for task_config in configs:
             if task_config is None:
                 continue
-            task = task_lib.Task.from_yaml_config(task_config)
+            task = task_lib.Task.from_yaml_config(task_config, env_overrides)
             if current_task is not None:
                 current_task >> task  # pylint: disable=pointless-statement
             current_task = task

sky/utils/schemas.py

@@ -170,7 +170,13 @@ def get_task_schema():
             'envs': {
                 'type': 'object',
                 'required': [],
-                'additionalProperties': True,
+                'patternProperties': {
+                    # Checks env keys are valid env var names.
+                    '^[a-zA-Z_][a-zA-Z0-9_]*$': {
+                        'type': 'string'
+                    }
+                },
+                'additionalProperties': False,
             },
             # inputs and outputs are experimental
             'inputs': {