add option apt_pipelining to cloud-config to address s3 mirrors (LP: #948461)

Thanks to Ben Howard.

ChangeLog

@@ -28,6 +28,8 @@
  - DataSourceNoCloud: support seed from external disk of ISO or vfat (LP: #857378)
  - DataSourceNoCloud: support inserting /etc/network/interfaces
  - DataSourceMaaS: add data source for Ubuntu Machines as a Service (MaaS) (LP: #942061)
+ - add option 'apt_pipelining' to address issue with S3 mirrors 
+   (LP: #948461) [Ben Howard]
 0.6.2:
  - fix bug where update was not done unless update was explicitly set.
    It would not be run if 'upgrade' or packages were set to be installed

cloudinit/CloudConfig/cc_apt_pipelining.py

@@ -0,0 +1,53 @@
+# vi: ts=4 expandtab
+#
+#    Copyright (C) 2011 Canonical Ltd.
+#
+#    Author: Ben Howard <ben.howard@canonical.com>
+#
+#    This program is free software: you can redistribute it and/or modify
+#    it under the terms of the GNU General Public License version 3, as
+#    published by the Free Software Foundation.
+#
+#    This program is distributed in the hope that it will be useful,
+#    but WITHOUT ANY WARRANTY; without even the implied warranty of
+#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#    GNU General Public License for more details.
+#
+#    You should have received a copy of the GNU General Public License
+#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import cloudinit.util as util
+from cloudinit.CloudConfig import per_instance
+
+frequency = per_instance
+default_file = "/etc/apt/apt.conf.d/90cloud-init-pipeling"
+
+
+def handle(_name, cfg, _cloud, log, _args):
+
+    apt_pipe_value = util.get_cfg_option_str(cfg, "apt_pipelining", False)
+    apt_pipe_value = str(apt_pipe_value).lower()
+
+    if apt_pipe_value == "false":
+        write_apt_snippet("0", log)
+
+    elif apt_pipe_value in ("none", "unchanged", "os"):
+        return
+
+    elif apt_pipe_value in str(range(0, 6)):
+        write_apt_snippet(apt_pipe_value, log)
+
+    else:
+        log.warn("Invalid option for apt_pipeling: %s" % apt_pipe_value)
+
+
+def write_apt_snippet(setting, log, f_name=default_file):
+    """ Writes f_name with apt pipeline depth 'setting' """
+
+    acquire_pipeline_depth = 'Acquire::http::Pipeline-Depth "%s";\n'
+    file_contents = ("//Written by cloud-init per 'apt_pipelining'\n"
+                     + (acquire_pipeline_depth % setting))
+
+    util.write_file(f_name, file_contents)
+
+    log.debug("Wrote %s with APT pipeline setting" % f_name)

config/cloud.cfg

@@ -19,6 +19,7 @@ cloud_config_modules:
  - locale
  - set-passwords
  - grub-dpkg
+ - apt-pipelining
  - apt-update-upgrade
  - landscape
  - timezone

doc/examples/cloud-config.txt

@@ -45,6 +45,15 @@ apt_mirror_search:
 # apt_proxy (configure Acquire::HTTP::Proxy)
 apt_proxy: http://my.apt.proxy:3128
 
+# apt_pipelining (configure Acquire::http::Pipeline-Depth)
+# Default: disables HTTP pipelining. Certain web servers, such
+# as S3 do not pipeline properly (LP: #948461).
+# Valid options:
+#   False/default: Disables pipelining for APT
+#   None/Unchanged: Use OS default
+#   Number: Set pipelining to some number (not recommended)
+apt_pipelining: False
+
 # Preserve existing /etc/apt/sources.list
 # Default: overwrite sources_list with mirror.  If this is true
 # then apt_mirror above will have no effect