qa/tasks: add templating functions to cephadm module

Add functions to cephadm.py that will be later used to template
strings within the yaml files in the cephadm suites. This will be used
to replace the specific subst_vip call with generic calls that let
tests access "any" variables stored on the test ctx.

Signed-off-by: John Mulligan <jmulligan@redhat.com>

qa/tasks/cephadm.py

@@ -4,13 +4,16 @@
 import argparse
 import configobj
 import contextlib
+import functools
+import json
 import logging
 import os
-import json
 import re
 import uuid
 import yaml
 
+import jinja2
+
 from copy import deepcopy
 from io import BytesIO, StringIO
 from tarfile import ReadError
@@ -34,6 +37,62 @@
 log = logging.getLogger(__name__)
 
 
+def _convert_strs_in(o, conv):
+    """A function to walk the contents of a dict/list and recurisvely apply
+    a conversion function (`conv`) to the strings within.
+    """
+    if isinstance(o, str):
+        return conv(o)
+    if isinstance(o, dict):
+        for k in o:
+            o[k] = _convert_strs_in(o[k], conv)
+    if isinstance(o, list):
+        o[:] = [_convert_strs_in(v, conv) for v in o]
+    return o
+
+
+def _apply_template(jinja_env, rctx, template):
+    """Apply jinja2 templating to the template string `template` via the jinja
+    environment `jinja_env`, passing a dictionary containing top-level context
+    to render into the template.
+    """
+    if '{{' in template or '{%' in template:
+        return jinja_env.from_string(template).render(**rctx)
+    return template
+
+
+def _template_transform(ctx, config, target):
+    """Apply jinja2 based templates to strings within the target object,
+    returning a transformed target. Target objects may be a list or dict or
+    str.
+
+    Note that only string values in the list or dict objects are modified.
+    Therefore one can read & parse yaml or json that contain templates in
+    string values without the risk of changing the structure of the yaml/json.
+    """
+    jenv = getattr(ctx, '_jinja_env', None)
+    if jenv is None:
+        loader = jinja2.BaseLoader()
+        jenv = jinja2.Environment(loader=loader)
+        setattr(ctx, '_jinja_env', jenv)
+    rctx = dict(ctx=ctx, config=config, cluster_name=config.get('cluster', ''))
+    _vip_vars(rctx)
+    conv = functools.partial(_apply_template, jenv, rctx)
+    return _convert_strs_in(target, conv)
+
+
+def _vip_vars(rctx):
+    """For backwards compat with the previous subst_vip function."""
+    ctx = rctx['ctx']
+    if 'vnet' in getattr(ctx, 'vip', {}):
+        rctx['VIPPREFIXLEN'] = str(ctx.vip["vnet"].prefixlen)
+        rctx['VIPSUBNET'] = str(ctx.vip["vnet"].network_address)
+    if 'vips' in getattr(ctx, 'vip', {}):
+        vips = ctx.vip['vips']
+        for idx, vip in enumerate(vips):
+            rctx[f'VIP{idx}'] = str(vip)
+
+
 def _shell(ctx, cluster_name, remote, args, extra_cephadm_args=[], **kwargs):
     teuthology.get_testdir(ctx)
     return remote.run(