Implement dynamic inventory based on files only

1 files changed, 194 insertions, 0 deletions

diff --git a/dynamic.py b/dynamic.py
new file mode 100755
index 0000000..78ebdb2
--- /dev/null
+++ b/dynamic.py
@@ -0,0 +1,194 @@
+#!/usr/bin/env python3
+#
+# This is a dynamic inventory script for Ansible at
+# rgoncalves.se infrastructure.
+#
+# Only groups_vars/ and host_vars/ directory are used for setting up devices
+# and nodes.
+# > Files, files, files, ... only files, everything files!
+#
+# The main goal here is to allow flexible code reviews and edits, POSIX
+# compliant actions over files, and using "less is more" moto. Moreover, each
+# host/group/node is individually track on version control.
+
+import os
+import yaml
+import logging
+import json
+
+from typing import Final
+from optparse import OptionParser
+
+
+HOST_DIR: Final = "./host_vars"
+GROUP_DIR: Final = "./group_vars"
+
+
+class AnsibleInput:
+    """
+    AnsibleInput class mixin.
+    Meta methods and inits for reading and processing yaml files.
+    """
+
+    data = None
+    name = None
+
+    def __init__(self, filepath):
+        with open(filepath) as file:
+            self.data = yaml.load(file, Loader=yaml.FullLoader)
+            self.name = os.path.splitext(os.path.basename(filepath))[0]
+
+
+def pprint(data):
+    """
+    Json pretty print for ansible hosts/groups or whatever output we get.
+    """
+
+    try:
+        print(json.dumps(data, indent=4, sort_keys=True))
+    except TypeError:
+        print(data)
+
+
+def create_nodes(directory):
+    """
+    Build-up and ansible node (Host or Group),
+    then return the full type list.
+    """
+
+    nodes = {}
+    for file in os.scandir(directory):
+        node = AnsibleInput(file.path)
+        nodes[node.name] = node
+    return nodes
+
+
+def get_hostvars(host):
+    """
+    Retrieve and build dynamic variables for a specific host.
+    """
+
+    data = host.data
+    if "ansible_host" not in host.data:
+        data["ansible_host"] = host.name
+    return data
+
+
+def get_subgroups(groups, og):
+    """
+    Get and return all children of a specific group, in a given subset.
+    """
+
+    # specific return for group "all" 
+    if og.name in "all":
+        groups = list(groups.keys())
+        groups.remove("all")
+        return groups
+
+    # usual behavior
+    valid_groups = []
+    if "_groups" not in og.data:
+        logging.warning(f"group { og.name } does not have any _groups var!")
+    else:
+        for group in og.data["_groups"]:
+            if group in groups:
+                valid_groups.append(group)
+    return valid_groups
+
+
+def get_meta(hosts):
+    """
+    For performance reasons, return all the hosts in a meta dict.
+    """
+
+    _meta = {}
+    _meta["hostvars"] = {}
+    for hostname, host in hosts.items():
+        _meta["hostvars"][hostname] = get_hostvars(host)
+        # _meta["hostvars"][hostname] = host.data
+    return "{}"
+    return _meta
+
+
+def get_list(hosts, groups):
+    """
+    Return list of groups with all hosts.
+    """
+
+    _list = {}
+    _list["_meta"] = get_meta(hosts)
+    # init group array
+    for groupname, group in groups.items():
+        _list[groupname] = {}
+        _list[groupname]["hosts"] = []
+        _list[groupname]["vars"] = {}
+        _list[groupname]["children"] = get_subgroups(groups, group)
+    # append each hosts to their corresponding groups
+    for hostname, host in hosts.items():
+        _list["all"]["hosts"].append(hostname)
+        if "_groups" not in host.data:
+            logging.info(f"no _groups data found for host { hostname }")
+            continue
+        # retrieve _groups variables and force conversion to list
+        cleangr = host.data["_groups"]
+        cleangr = [cleangr] if isinstance(cleangr, str) else cleangr
+        for group in cleangr:
+            # skip group assignement on non-existence!
+            logging.info(f"searching for group : { group }")
+            if group not in groups:
+                logging.error(f"group { group } does not exist!")
+                continue
+            _list[group]["hosts"].append(hostname)
+    return _list
+
+
+def main():
+    """
+    Main entry.
+    """
+
+    # logging config
+    logging.basicConfig(level=logging.INFO)
+    logging.disable()
+
+    # parse cli arguments
+    parser = OptionParser()
+    parser.add_option("--host",
+                      dest="host",
+                      default="_empty",
+                      help="show specific host")
+    parser.add_option("--list",
+                      action="store_true",
+                      help="list all groups")
+    parser.add_option("--debug",
+                      action="store_true",
+                      help="show logging informations")
+    (options, args) = parser.parse_args()
+
+    # enable debug if required
+    if options.debug:
+        logging.disable(0)
+
+    # retrieve hosts and groups
+    hosts = create_nodes(HOST_DIR)
+    groups = create_nodes(GROUP_DIR)
+
+    # return specific hostname
+    if options.host != "_empty":
+        if options.host in hosts:
+            pprint(get_hostvars(hosts[options.host]))
+        else:
+            pprint("{}")
+        exit(0)
+
+    # return all groups
+    if options.list:
+        pprint(get_list(hosts, groups))
+        exit(0)
+
+    # return all hosts
+    exit(0)
+
+
+if __name__ == "__main__":
+    main()