[lxc-devel] [PATCH 2/3] python: Add binding for {get|set}_cgroup_item

[Serge Hallyn]

Quoting Stéphane Graber (stgraber at ubuntu.com):
> Updates the binding for the two new functions.
> 
> This also fixes some problems with the argument checking of
> get_config_item that'd otherwise lead to a segfault.
> 
> The python binding for set_cgroup_item and get_cgroup_item are pretty
> raw as lxc has little control over the cgroup entries.
> That means that we don't try to interpret lists as we do for the config
> entries.
> 
> Signed-off-by: Stéphane Graber <stgraber at ubuntu.com>

Acked-by: Serge E. Hallyn <serge.hallyn at ubuntu.com>

(if it wasn't a testcase i'd say something about the malloc return value
not being checked...)

> ---
>  src/python-lxc/examples/api_test.py.in |  7 +++++
>  src/python-lxc/lxc.c                   | 55 +++++++++++++++++++++++++++++++++-
>  src/python-lxc/lxc/__init__.py.in      | 12 ++++++++
>  3 files changed, 73 insertions(+), 1 deletion(-)
> 
> diff --git a/src/python-lxc/examples/api_test.py.in b/src/python-lxc/examples/api_test.py.in
> index 0b17bd6..7711291 100644
> --- a/src/python-lxc/examples/api_test.py.in
> +++ b/src/python-lxc/examples/api_test.py.in
> @@ -97,6 +97,13 @@ container.attach("NETWORK|UTSNAME", "/sbin/ifconfig", "eth0")
>  # A few basic checks of the current state
>  assert(len(ips) > 0)
>  
> +## Testing cgroups a bit
> +print("Testing cgroup API")
> +max_mem = container.get_cgroup_item("memory.max_usage_in_bytes")
> +current_limit = container.get_cgroup_item("memory.limit_in_bytes")
> +assert(container.set_cgroup_item("memory.limit_in_bytes", max_mem))
> +assert(container.get_cgroup_item("memory.limit_in_bytes") != current_limit)
> +
>  ## Freezing the container
>  print("Freezing the container")
>  container.freeze()
> diff --git a/src/python-lxc/lxc.c b/src/python-lxc/lxc.c
> index b489079..83e2659 100644
> --- a/src/python-lxc/lxc.c
> +++ b/src/python-lxc/lxc.c
> @@ -204,13 +204,38 @@ Container_freeze(Container *self, PyObject *args, PyObject *kwds)
>  }
>  
>  static PyObject *
> +Container_get_cgroup_item(Container *self, PyObject *args, PyObject *kwds)
> +{
> +    static char *kwlist[] = {"key", NULL};
> +    char* key = NULL;
> +    int len = 0;
> +
> +    if (! PyArg_ParseTupleAndKeywords(args, kwds, "s|", kwlist,
> +                                      &key))
> +        Py_RETURN_FALSE;
> +
> +    len = self->container->get_cgroup_item(self->container, key, NULL, 0);
> +
> +    if (len <= 0) {
> +        Py_RETURN_FALSE;
> +    }
> +
> +    char* value = (char*) malloc(sizeof(char)*len + 1);
> +    if (self->container->get_cgroup_item(self->container, key, value, len + 1) != len) {
> +        Py_RETURN_FALSE;
> +    }
> +
> +    return PyUnicode_FromString(value);
> +}
> +
> +static PyObject *
>  Container_get_config_item(Container *self, PyObject *args, PyObject *kwds)
>  {
>      static char *kwlist[] = {"key", NULL};
>      char* key = NULL;
>      int len = 0;
>  
> -    if (! PyArg_ParseTupleAndKeywords(args, kwds, "|s", kwlist,
> +    if (! PyArg_ParseTupleAndKeywords(args, kwds, "s|", kwlist,
>                                        &key))
>          Py_RETURN_FALSE;
>  
> @@ -288,6 +313,24 @@ Container_save_config(Container *self, PyObject *args, PyObject *kwds)
>  }
>  
>  static PyObject *
> +Container_set_cgroup_item(Container *self, PyObject *args, PyObject *kwds)
> +{
> +    static char *kwlist[] = {"key", "value", NULL};
> +    char *key = NULL;
> +    char *value = NULL;
> +
> +    if (! PyArg_ParseTupleAndKeywords(args, kwds, "ss|", kwlist,
> +                                      &key, &value))
> +        Py_RETURN_FALSE;
> +
> +    if (self->container->set_cgroup_item(self->container, key, value)) {
> +        Py_RETURN_TRUE;
> +    }
> +
> +    Py_RETURN_FALSE;
> +}
> +
> +static PyObject *
>  Container_set_config_item(Container *self, PyObject *args, PyObject *kwds)
>  {
>      static char *kwlist[] = {"key", "value", NULL};
> @@ -441,6 +484,11 @@ static PyMethodDef Container_methods[] = {
>       "\n"
>       "Freezes the container and returns its return code."
>      },
> +    {"get_cgroup_item", (PyCFunction)Container_get_cgroup_item, METH_VARARGS | METH_KEYWORDS,
> +     "get_cgroup_item(key) -> string\n"
> +     "\n"
> +     "Get the current value of a cgroup entry."
> +    },
>      {"get_config_item", (PyCFunction)Container_get_config_item, METH_VARARGS | METH_KEYWORDS,
>       "get_config_item(key) -> string\n"
>       "\n"
> @@ -463,6 +511,11 @@ static PyMethodDef Container_methods[] = {
>       "Save the container configuration to its default "
>       "location or to an alternative location if provided."
>      },
> +    {"set_cgroup_item", (PyCFunction)Container_set_cgroup_item, METH_VARARGS | METH_KEYWORDS,
> +     "set_cgroup_item(key, value) -> boolean\n"
> +     "\n"
> +     "Set a cgroup entry to the provided value."
> +    },
>      {"set_config_item", (PyCFunction)Container_set_config_item, METH_VARARGS | METH_KEYWORDS,
>       "set_config_item(key, value) -> boolean\n"
>       "\n"
> diff --git a/src/python-lxc/lxc/__init__.py.in b/src/python-lxc/lxc/__init__.py.in
> index 9ef3459..91a59ed 100644
> --- a/src/python-lxc/lxc/__init__.py.in
> +++ b/src/python-lxc/lxc/__init__.py.in
> @@ -318,6 +318,18 @@ class Container(_lxc.Container):
>              return False
>          return True
>  
> +    def get_cgroup_item(self, key):
> +        """
> +            Returns the value for a given cgroup entry.
> +            A list is returned when multiple values are set.
> +        """
> +        value = _lxc.Container.get_cgroup_item(self, key)
> +
> +        if value is False:
> +            return False
> +        else:
> +            return value.rstrip("\n")
> +
>      def get_config_item(self, key):
>          """
>              Returns the value for a given config key.
> -- 
> 1.8.0
> 
> 
> ------------------------------------------------------------------------------
> LogMeIn Rescue: Anywhere, Anytime Remote support for IT. Free Trial
> Remotely access PCs and mobile devices and provide instant support
> Improve your efficiency, and focus on delivering more value-add services
> Discover what IT Professionals Know. Rescue delivers
> http://p.sf.net/sfu/logmein_12329d2d
> _______________________________________________
> Lxc-devel mailing list
> Lxc-devel at lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/lxc-devel