fb_apt: Add ability to log output of apt-get update (#232)

Test Plan:
Imported from GitHub, without a `Test Plan:` line.
Tested with a basic regression test on a twshared host, though this cookbook
isn't used internally and this should be a no-op

Differential Revision: D52880450

fbshipit-source-id: 1c4a1cc20837cb0cafd95f432f73639fce3a4eb6

cookbooks/fb_apt/README.md

@@ -22,6 +22,7 @@ Attributes
 * node['fb_apt']['want_source']
 * node['fb_apt']['preserve_unknown_keyrings']
 * node['fb_apt']['allow_modified_pkg_keyrings']
+* node['fb_apt']['apt_update_log_path']
 
 Usage
 -----
@@ -107,3 +108,8 @@ As mentioned above, `fb_apt` can assemble the basic sources for you. It uses
 the LSB "codename" of the current systemd to build the URLs. In the event you
 want to use Chef to upgrade across distros, however, you can set
 `node['fb_apt']['distro']` to the appropriate name and it will be used instead.
+
+### Logging `apt-get update`
+Set `node['fb_apt']['apt_update_log_path']` to log stdout and stderr of the
+`apt-get update` command invoked by this cookbook. This may be useful for
+debugging purposes. The caller must handle log rotation.

cookbooks/fb_apt/attributes/default.rb

@@ -38,6 +38,7 @@
   'want_source' => false,
   'preserve_unknown_keyrings' => false,
   'allow_modified_pkg_keyrings' => false,
+  'apt_update_log_path' => nil,
 }
 # fb_apt must be defined for this to work...
 keys = FB::Apt.get_official_keyids(node).map { |id| [id, nil] }.to_h

cookbooks/fb_apt/recipes/default.rb

@@ -18,6 +18,8 @@
 # limitations under the License.
 #
 
+require 'shellwords'
+
 unless node.debian? || node.ubuntu?
   fail 'fb_apt is only supported on Debian and Ubuntu.'
 end
@@ -94,7 +96,11 @@
 end
 
 execute 'apt-get update' do
-  command 'apt-get update'
+  command lazy do
+    log_path = node['fb_apt']['apt_update_log_path']
+    cmd_suffix = " >>#{Shellwords.shellescape(log_path)} 2>&1" if log_path
+    "apt-get update#{cmd_suffix}"
+  end
   action :nothing
 end