Support environment variables as CLI opts defaults

CHANGELOG.md

@@ -9,13 +9,21 @@ and this project adheres to
 ## [unreleased]
 
 ### Added
-- docs: Mention support of RHEL 10, Fedora 43, SLES and openSUSE 15 and 16.
+- cli: Environment variables `RACKSDB_DB`, `RACKSDB_SCHEMA`,
+  `RACKSDB_EXTENSIONS`, and to set default schema, extensions, and database
+  paths when the matching `racksdb` / `racksdb-web` option is omitted (#149).
+- web: Support the same environment variables as CLI.
+- docs:
+  - Mention support of RHEL 10, Fedora 43, SLES and openSUSE 15 and 16.
+  - Mention support of `RACKSDB_DB`, `RACKSDB_SCHEMA` and `RACKSDB_EXTENSIONS`
+    environment variables in `racksdb` and `racksdb-web` manpages.
+
+### Fixed
+- docs: Add missing system dependency `libpango1.0-dev` to install from sources,
+  reported by @astappiev (#148).
 
 ### Removed
-- docs:
-  - Drop support of Fedora 41.
-  - Add missing system dependency `libpango1.0-dev` to install from sources,
-    reported by @astappiev (#148).
+- docs: Drop support of Fedora 41.
 
 ## [0.6.0] - 2025-10-16
 

docs/modules/usage/pages/racksdb-web.adoc

@@ -27,16 +27,19 @@ endif::[]
   Path to database. Both files and directories paths are accepted. If the path
   is a directory, all YAML files in this directory are loaded, recursively. If
   the path does not exist, an error is reported. Default value is
-  [.path]#`/var/lib/racksdb/`# directory.
+  [.path]#`/var/lib/racksdb/`# directory or environment variable
+  [.cli-opt]#*RACKSDB_DB*# if set.
 
 [.cli-opt]#*-s, --schema*=#[.cli-optval]##_SCHEMA_##::
   Path to RacksDB schema YAML file. If the file does not exist, an error is
-  reported. Default value is [.path]#`/usr/share/racksdb/schemas/racksdb.yml`#.
+  reported. Default value is [.path]#`/usr/share/racksdb/schemas/racksdb.yml`#
+  or environment variable [.cli-opt]#*RACKSDB_SCHEMA*# if set.
 
 [.cli-opt]#*-e, --ext*=#[.cli-optval]##_EXT_##::
   Path to optional RacksDB schema extensions. If the file does not exist,
   it is silently ignored by RacksDB. Default value is
-  [.path]#`/etc/racksdb/extensions.yml`#.
+  [.path]#`/etc/racksdb/extensions.yml`# or environment variable
+  [.cli-opt]#*RACKSDB_EXTENSIONS*# if set.
 
 [.cli-opt]#*--host*=#[.cli-optval]##_HOST_##::
   The hostname to listen for incoming requests. Set to `0.0.0.0` to listen on
@@ -61,6 +64,22 @@ endif::[]
   without value, default UI path [.path]#`/usr/share/racksdb/frontend`# is used.
   When a path is provided, `racksdb-web` loads UI files from this path.
 
+== Environment variables
+
+When a command-line option above is omitted, `racksdb-web` uses the following
+environment variables if they are set to a non-empty value:
+
+[.cli-opt]#*RACKSDB_SCHEMA*#::
+  Path to the RacksDB schema YAML file.
+
+[.cli-opt]#*RACKSDB_EXTENSIONS*#::
+  Path to optional schema extensions.
+
+[.cli-opt]#*RACKSDB_DB*#::
+  Path to the database.
+
+Command-line options always override environment variables.
+
 == Exit status
 
 *0*::

docs/modules/usage/pages/racksdb.adoc

@@ -28,16 +28,19 @@ endif::[]
   Path to database. Both files and directories paths are accepted. If the path
   is a directory, all YAML files in this directory are loaded, recursively. If
   the path does not exist, an error is reported. Default value is
-  [.path]#`/var/lib/racksdb/`# directory.
+  [.path]#`/var/lib/racksdb/`# directory or environment variable
+  [.cli-opt]#*RACKSDB_DB*# if set.
 
 [.cli-opt]#*-s, --schema*=#[.cli-optval]##_SCHEMA_##::
   Path to RacksDB schema YAML file. If the file does not exist, an error is
-  reported. Default value is [.path]#`/usr/share/racksdb/schemas/racksdb.yml`#.
+  reported. Default value is [.path]#`/usr/share/racksdb/schemas/racksdb.yml`#
+  or environment variable [.cli-opt]#*RACKSDB_SCHEMA*# if set.
 
 [.cli-opt]#*-e, --ext*=#[.cli-optval]##_EXT_##::
   Path to optional RacksDB schema extensions. If the file does not exist,
   it is silently ignored by RacksDB. Default value is
-  [.path]#`/etc/racksdb/extensions.yml`#.
+  [.path]#`/etc/racksdb/extensions.yml`# or environment variable
+  [.cli-opt]#*RACKSDB_EXTENSIONS*# if set.
 
 == Commands
 
@@ -373,6 +376,22 @@ Generate graphical representation of _noisy_ datacenter room and dump
 coordinates of racks in JSON format in a file named `noisy-coordinates.json`.
 ====
 
+== Environment variables
+
+When a command-line option above is omitted, `racksdb` uses the following
+environment variables if they are set to a non-empty value:
+
+[.cli-opt]#*RACKSDB_SCHEMA*#::
+  Path to the RacksDB schema YAML file.
+
+[.cli-opt]#*RACKSDB_EXTENSIONS*#::
+  Path to optional schema extensions.
+
+[.cli-opt]#*RACKSDB_DB*#::
+  Path to the database.
+
+Command-line options always override environment variables.
+
 == Exit status
 
 *0*::

racksdb/env.py

@@ -0,0 +1,25 @@
+# Copyright (c) 2025 Rackslab
+#
+# This file is part of RacksDB.
+#
+# SPDX-License-Identifier: MIT
+
+"""Environment variable names and helpers for RacksDB CLI entry points."""
+
+import os
+from pathlib import Path
+import typing as t
+
+
+class RacksDBEnv:
+    SCHEMA = "RACKSDB_SCHEMA"
+    EXTENSIONS = "RACKSDB_EXTENSIONS"
+    DB = "RACKSDB_DB"
+
+
+def env_or_default(env_key: str, fallback: t.Union[str, Path]) -> Path:
+    """Path from ``os.environ[env_key]`` if set and non-empty, else *fallback*."""
+    val = os.environ.get(env_key)
+    if val:
+        return Path(val)
+    return Path(fallback)

racksdb/exec.py

@@ -22,6 +22,7 @@
 )
 from .generic.dumpers import DBDumperFactory, SchemaDumperFactory
 from . import RacksDB
+from .env import RacksDBEnv, env_or_default
 from .drawers import InfrastructureDrawer, AxonometricInfrastructureDrawer, RoomDrawer
 from .drawers.parameters import DrawingParameters
 from .errors import RacksDBError
@@ -57,21 +58,21 @@ def __init__(self, cmd_args: t.Optional[t.List[str]] = None):
             "-s",
             "--schema",
             help="Schema to load (default: %(default)s)",
-            default=RacksDB.DEFAULT_SCHEMA,
+            default=env_or_default(RacksDBEnv.SCHEMA, RacksDB.DEFAULT_SCHEMA),
             type=Path,
         )
         parser.add_argument(
             "-e",
             "--ext",
             help="Path to extensions of schema (default: %(default)s)",
-            default=RacksDB.DEFAULT_EXT,
+            default=env_or_default(RacksDBEnv.EXTENSIONS, RacksDB.DEFAULT_EXT),
             type=Path,
         )
         parser.add_argument(
             "-b",
             "--db",
             help="Database to load (default: %(default)s)",
-            default=RacksDB.DEFAULT_DB,
+            default=env_or_default(RacksDBEnv.DB, RacksDB.DEFAULT_DB),
             type=Path,
         )
 

racksdb/tests/test_env.py

@@ -0,0 +1,39 @@
+# Copyright (c) 2025 Rackslab
+#
+# This file is part of RacksDB.
+#
+# SPDX-License-Identifier: MIT
+
+import os
+import unittest
+from pathlib import Path
+from unittest import mock
+
+from racksdb.env import env_or_default
+
+
+class TestEnvOrDefault(unittest.TestCase):
+    def test_uses_fallback_when_key_missing(self):
+        key = "RACKSDB_TEST_ENV_OR_DEFAULT_MISSING"
+        self.assertNotIn(key, os.environ)
+        p = env_or_default(key, "/tmp/fallback")
+        self.assertEqual(p, Path("/tmp/fallback"))
+
+    def test_uses_fallback_when_empty_string(self):
+        key = "RACKSDB_TEST_ENV_OR_DEFAULT_EMPTY"
+        with mock.patch.dict(os.environ, {key: ""}, clear=False):
+            p = env_or_default(key, "/tmp/fallback")
+        self.assertEqual(p, Path("/tmp/fallback"))
+
+    def test_uses_environment_when_set(self):
+        key = "RACKSDB_TEST_ENV_OR_DEFAULT_SET"
+        with mock.patch.dict(os.environ, {key: "/from/env"}, clear=False):
+            p = env_or_default(key, "/tmp/fallback")
+        self.assertEqual(p, Path("/from/env"))
+
+    def test_fallback_accepts_path(self):
+        key = "RACKSDB_TEST_ENV_OR_DEFAULT_PATH_FALLBACK"
+        fb = Path("/tmp/fallback_path")
+        with mock.patch.dict(os.environ, {key: ""}, clear=False):
+            p = env_or_default(key, fb)
+        self.assertEqual(p, fb)

racksdb/tests/test_exec.py

@@ -4,6 +4,7 @@
 #
 # SPDX-License-Identifier: MIT
 
+import unittest
 from unittest import mock
 import io
 import tempfile
@@ -15,6 +16,7 @@
 import yaml
 
 from racksdb import RacksDB
+from racksdb.env import RacksDBEnv
 from racksdb.exec import RacksDBExec
 from racksdb.version import get_version
 
@@ -695,3 +697,78 @@ def test_autopager_used_in_views(self):
                 RacksDBExec(CMD_BASE_ARGS + ["datacenters"])
             autopager.assert_called_once()
             autopager.return_value.__enter__.assert_called_once()
+
+
+class TestRacksDBExecLoadArguments(unittest.TestCase):
+    """``RacksDB.load()`` receives paths from argparse defaults (env + fallbacks)."""
+
+    @staticmethod
+    def _mock_db_for_dump():
+        mdb = mock.MagicMock()
+        mdb._loader.content = {}
+        return mdb
+
+    def test_load_args_use_class_defaults_when_env_keys_empty(self):
+        with mock.patch.dict(
+            os.environ,
+            {
+                RacksDBEnv.SCHEMA: "",
+                RacksDBEnv.EXTENSIONS: "",
+                RacksDBEnv.DB: "",
+            },
+            clear=False,
+        ):
+            with mock.patch("racksdb.exec.RacksDB.load") as load_mock:
+                load_mock.return_value = self._mock_db_for_dump()
+                with mock.patch("sys.stdout", new=io.StringIO()):
+                    RacksDBExec(["dump"])
+        load_mock.assert_called_once_with(
+            Path(RacksDB.DEFAULT_SCHEMA),
+            Path(RacksDB.DEFAULT_EXT),
+            Path(RacksDB.DEFAULT_DB),
+        )
+
+    def test_load_args_use_environment_when_set(self):
+        env = {
+            RacksDBEnv.SCHEMA: "/env/schema.yml",
+            RacksDBEnv.EXTENSIONS: "/env/extensions.yml",
+            RacksDBEnv.DB: "/env/db",
+        }
+        with mock.patch.dict(os.environ, env, clear=False):
+            with mock.patch("racksdb.exec.RacksDB.load") as load_mock:
+                load_mock.return_value = self._mock_db_for_dump()
+                with mock.patch("sys.stdout", new=io.StringIO()):
+                    RacksDBExec(["dump"])
+        load_mock.assert_called_once_with(
+            Path("/env/schema.yml"),
+            Path("/env/extensions.yml"),
+            Path("/env/db"),
+        )
+
+    def test_load_args_prefer_cli_over_environment(self):
+        with mock.patch.dict(
+            os.environ,
+            {
+                RacksDBEnv.SCHEMA: "/wrong/schema.yml",
+                RacksDBEnv.EXTENSIONS: "",
+                RacksDBEnv.DB: "/wrong/db",
+            },
+            clear=False,
+        ):
+            with mock.patch("racksdb.exec.RacksDB.load") as load_mock:
+                load_mock.return_value = self._mock_db_for_dump()
+                with mock.patch("sys.stdout", new=io.StringIO()):
+                    RacksDBExec(
+                        [
+                            "--schema",
+                            "/cli/schema.yml",
+                            "--db",
+                            "/cli/db",
+                            "dump",
+                        ]
+                    )
+        load_mock.assert_called_once_with(
+            Path("/cli/schema.yml"),
+            Path(RacksDB.DEFAULT_EXT),
+            Path("/cli/db"),
+        )