Packages definition

hooks/upgrade-charm

@@ -1,9 +1,13 @@
 #!/usr/bin/env python3
 
 # Load modules from $CHARM_DIR/lib
+import os
 import sys
 sys.path.append('lib')
 
+# This is an upgrade-charm context, make sure we install latest deps
+os.unlink('wheelhouse/.bootstrapped')
+
 from charms.bootstrap import bootstrap_charm_deps
 bootstrap_charm_deps()
 

layer.yaml

@@ -0,0 +1,5 @@
+defines:
+  packages:
+    type: array
+    description: Additional packages to be installed at time of bootstrap
+

lib/charms/bootstrap.py

@@ -9,7 +9,9 @@ def bootstrap_charm_deps():
         return
     # bootstrap wheelhouse
     if os.path.exists('wheelhouse'):
-        check_call(['apt-get', 'install', '-yq', 'python3-pip'])
+        apt_install(['python3-pip', 'python3-yaml'])
+        # install packages defined in layer.yaml
+        install_charm_deps()
         # need newer pip, to fix spurious Double Requirement error https://github.com/pypa/pip/issues/56
         check_call(['pip3', 'install', '-U', '--no-index', '-f', 'wheelhouse', 'pip'])
         # install the rest of the wheelhouse deps
@@ -21,3 +23,26 @@ def bootstrap_charm_deps():
         # Non-namespace-package libs (e.g., charmhelpers) are available
         # without having to reload the interpreter. :/
         os.execl(sys.argv[0], sys.argv[0])
+
+
+def install_charm_deps():
+    from charms import layer
+
+    cfg = layer.options('basic')
+    apt_install(cfg.get('packages', []))
+
+
+def apt_install(packages):
+    if isinstance(packages, basestring):
+        packages = [packages]
+
+    env = os.environ.copy()
+
+    if 'DEBIAN_FRONTEND' not in env:
+        env['DEBIAN_FRONTEND'] = 'noninteractive'
+
+    cmd = ['apt-get',
+           '--option=Dpkg::Options::=--force-confold',
+           '--assume-yes',
+           'install']
+    check_call(cmd + packages, env=env)

lib/charms/layer.py

@@ -0,0 +1,22 @@
+
+import os
+import yaml
+
+
+class LayerOptions(dict):
+    def __init__(self, layer_file, section=None):
+        with open(layer_file) as f:
+            layer = yaml.safe_load(f.read())
+        opts = layer.get('options', {})
+        if section and section in opts:
+            super(LayerOptions, self).__init__(opts.get(section))
+        else:
+            super(LayerOptions, self).__init__(opts)
+
+
+def options(section=None, layer_file=None):
+    if not layer_file:
+        base_dir = os.environ.get('CHARM_DIR', os.getcwd())
+        layer_file = os.path.join(base_dir, 'layer.yaml')
+
+    return LayerOptions(layer_file, section)