aetherscale

commit 8a78602e851415f794bab4545e8e6d65547c67f9
parent 00c33bcbddf89f8ce81a5ea210d7400f50cae02b
Author: Stefan Koch <programming@stefan-koch.name>
Date:   Sat, 19 Dec 2020 11:11:57 +0100

check for binary dependencies before startup

Diffstat:
A
aetherscale/dependencies.py
 | 
37
+++++++++++++++++++++++++++++++++++++
M
aetherscale/server.py
 | 
16
+++++++++++++---
A
tests/test_dependencies.py
 | 
26
++++++++++++++++++++++++++

3 files changed, 76 insertions(+), 3 deletions(-)
diff --git a/aetherscale/dependencies.py b/aetherscale/dependencies.py
@@ -0,0 +1,37 @@
+import shutil
+from typing import List
+
+
+BINARY_DEPENDENCIES = {
+    'systemctl':
+        'systemd is required by aetherscale. For support of other '
+        'service managers a new ServiceManager subclass is required. '
+        'Feel free to open an issue at Github.',
+    'guestmount':
+        'libguestfs is required by aetherscale. You can install it:\n\n'
+        '    On Ubuntu: apt install libguestfs-tools\n'
+        '    On Arch Linux: pacman -S libguestfs',
+    'qemu-img':
+        'QEMU is required by aetherscale. You can install it:\n\n'
+        '    On Ubuntu: apt install qemu-utils qemu-kvm\n'
+        '    On Arch Linux: pacman -S qemu-headless',
+    'vde_switch':
+        'VDE2 is required by aetherscale. You can install it:\n\n'
+        '    On Ubuntu: apt install vde2\n'
+        '    On Arch Linux: pacman -S vde2'
+}
+
+
+def find_missing_dependencies(dependency_commands: List[str]) -> List[str]:
+    return [cmd for cmd in dependency_commands if not shutil.which(cmd)]
+
+
+def build_dependency_help_text(missing_dependencies: List[str]) -> str:
+    full_help = []
+    for dependency in missing_dependencies:
+        try:
+            full_help.append(BINARY_DEPENDENCIES[dependency])
+        except KeyError:
+            full_help.append(f'{dependency} is required by aetherscale.')
+
+    return '\n\n'.join(full_help)
diff --git a/aetherscale/server.py b/aetherscale/server.py
@@ -1,8 +1,18 @@
-from . import __version__
-from .computing import run
+import sys
+
+from aetherscale import __version__
+from aetherscale.computing import run
+from aetherscale import dependencies
 
 
 def main():
     print(f'Executing aetherscale version {__version__}.')
 
-    run()
+    missing_deps = dependencies.find_missing_dependencies(
+        dependencies.BINARY_DEPENDENCIES.keys())
+
+    if len(missing_deps) > 0:
+        help_text = dependencies.build_dependency_help_text(missing_deps)
+        print(help_text, file=sys.stderr)
+    else:
+        run()
diff --git a/tests/test_dependencies.py b/tests/test_dependencies.py
@@ -0,0 +1,26 @@
+from aetherscale.dependencies \
+    import find_missing_dependencies, build_dependency_help_text
+
+
+def test_existing_binary():
+    missing = find_missing_dependencies(['sh'])
+    assert len(missing) == 0
+
+
+def test_missing_binary():
+    missing = find_missing_dependencies(['9c4f52e32803b906214f6059a8e2850f'])
+    assert len(missing) == 1
+
+
+def test_build_help():
+    help_text = build_dependency_help_text(['systemctl'])
+    assert help_text != ''
+
+
+def test_unknown_missing_dependency():
+    """if the dependency is not known, it should still be listed with a generic
+    help text"""
+
+    missing_command = '9c4f52e32803b906214f6059a8e2850f'
+    help_text = build_dependency_help_text([missing_command])
+    assert missing_command in help_text