mirror of
https://github.com/kevingruesser/bootstrap-vz.git
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15c7d1ccb3
An environment with AF_INET6 sockets but no loopback interface creates
nothing but pain.
If an IPv4 server binds to 0.0.0.0:8080, clients may connect to
0.0.0.0:8080, which automatically picks 127.0.0.1 as a source address.
However, when a server binds to [::]:8080, the absence of ::1 causes
clients to fail with ENETUNREACH.
For a demonstration, run the following in a python shell:
import socket
s = socket.socket(socket.AF_INET6, socket.SOCK_STREAM, 0)
s.bind(("", 0))
print s.getsockname() # Example: ('::', 39079, 0, 0)
s.listen(10)
c = socket.socket(socket.AF_INET6, socket.SOCK_STREAM, 0)
c.connect(s.getsockname())
print c.getsockname(), c.getpeername()
This yields the following error:
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python2.7/socket.py", line 224, in meth
return getattr(self._sock,name)(*args)
socket.error: [Errno 101] Network is unreachable
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|---|---|---|
| .. | ||
| base | ||
| common | ||
| plugins | ||
| providers | ||
| remote | ||
| __init__.py | ||
| README.rst | ||
How bootstrap-vz works ---------------------- Tasks ~~~~~ At its core bootstrap-vz is based on tasks that perform units of work. By keeping those tasks small and with a solid structure built around them a high degree of flexibility can be achieved. To ensure that tasks are executed in the right order, each task is placed in a dependency graph where directed edges dictate precedence. Each task is a simple class that defines its predecessor tasks and successor tasks via attributes. Here is an example: .. code-block:: python class MapPartitions(Task): description = 'Mapping volume partitions' phase = phases.volume_preparation predecessors = [PartitionVolume] successors = [filesystem.Format] @classmethod def run(cls, info): info.volume.partition_map.map(info.volume) In this case the attributes define that the task at hand should run after the ``PartitionVolume`` task — i.e. after volume has been partitioned (``predecessors``) — but before formatting each partition (``successors``). It is also placed in the ``volume_preparation`` phase. Phases are ordered and group tasks together. All tasks in a phase are run before proceeding with the tasks in the next phase. They are a way of avoiding the need to list 50 different tasks as predecessors and successors. The final task list that will be executed is computed by enumerating all tasks in the package, placing them in the graph and `sorting them topologically <http://en.wikipedia.org/wiki/Topological_sort>`_. Subsequently the list returned is filtered to contain only the tasks the provider and the plugins added to the taskset. System abstractions ~~~~~~~~~~~~~~~~~~~ There are several abstractions in bootstrap-vz that make it possible to generalize things like volume creation, partitioning, mounting and package installation. As a rule these abstractions are located in the ``base/`` folder, where the manifest parsing and task ordering algorithm are placed as well.