sambacc: extend rados pseudo-uris to include getting mon config keys

There are cases where certain configuration items may not be stored in
the Ceph cluster's  rados pool but rather in the Ceph MON's
configuration key store. This can be accessed via a mon command. Add
support for new pseudo uri's formed like:
  rados:mon-config-key:foo/bar/baz

Instead of fetching an item from a rados pool, this will try to fetch a
key in a manner equivalent to running the following CLI command:
  `ceph config-key get foo/bar/baz`

This idea is borrowed from the ceph iscsi support.

Signed-off-by: John Mulligan <[email protected]>

Author: phlogistonjohn

sambacc/rados_opener.py

@@ -18,6 +18,8 @@
 
 from __future__ import annotations
 
+import io
+import json
 import typing
 import urllib.request
 
@@ -39,6 +41,10 @@ class _RADOSHandler(urllib.request.BaseHandler):
     def rados_open(self, req: urllib.request.Request) -> typing.IO:
         if self._rados_api is None:
             raise RADOSUnsupported()
+        if req.selector.startswith("mon-config-key:"):
+            return _get_mon_config_key(
+                self._rados_api, req.selector.split(":", 1)[1]
+            )
         sel = req.selector.lstrip("/")
         if req.host:
             pool = req.host
@@ -171,6 +177,25 @@ def writelines(self, ls: typing.Iterable[typing.Any]) -> None:
         raise NotImplementedError()
 
 
+def _get_mon_config_key(rados_api: _RADOSModule, key: str) -> io.BytesIO:
+    mcmd = json.dumps(
+        {
+            "prefix": "config-key get",
+            "key": str(key),
+        }
+    )
+    with rados_api.Rados(conffile=rados_api.Rados.DEFAULT_CONF_FILES) as rc:
+        ret, out, err = rc.mon_command(mcmd, b"")
+        if ret == 0:
+            # We need to return a file like object. Since we are handed just
+            # bytes from this api, use BytesIO to adapt it to something valid.
+            return io.BytesIO(out)
+        # ensure ceph didn't send us a negative errno
+        ret = ret if ret > 0 else -ret
+        msg = f"failed to get mon config key: {key!r}: {err}"
+        raise OSError(ret, msg)
+
+
 def enable_rados_url_opener(cls: typing.Type[url_opener.URLOpener]) -> None:
     """Extend the URLOpener type to support pseudo-URLs for rados
     object storage. If rados libraries are not found the function

tests/test_rados_opener.py

@@ -156,3 +156,29 @@ def test_rados_response_not_implemented():
         rr.write(b"zzzzz")
     with pytest.raises(NotImplementedError):
         rr.writelines([b"zzzzz"])
+
+
+def test_rados_handler_config_key():
+    class RH(sambacc.rados_opener._RADOSHandler):
+        _rados_api = unittest.mock.MagicMock()
+
+    mc = RH._rados_api.Rados.return_value.__enter__.return_value.mon_command
+    mc.return_value = (0, b"rubber baby buggy bumpers", "")
+
+    rh = RH()
+    rq = urllib.request.Request("rados:mon-config-key:aa/bb/cc")
+    rr = rh.rados_open(rq)
+    assert isinstance(rr, io.BytesIO)
+    assert rr.read() == b"rubber baby buggy bumpers"
+    assert mc.called
+    assert "aa/bb/cc" in mc.call_args[0][0]
+
+    mc.reset_mock()
+    mc.return_value = (2, b"", "no passing")
+    rh = RH()
+    rq = urllib.request.Request("rados:mon-config-key:xx/yy/zz")
+    with pytest.raises(OSError) as pe:
+        rh.rados_open(rq)
+    assert getattr(pe.value, "errno", None) == 2
+    assert mc.called
+    assert "xx/yy/zz" in mc.call_args[0][0]