Docker: Add a dynamic inventory of docker hosts script

This change adds the docker_hosts script that will build an
inventory file from running docker containers.

See the script comments for information on requirments,
usage, and an example.

Change-Id: I80478db3d691d34fc00ee201318e38014bbf726f
Reviewed-on: https://review.linaro.org/23990
Reviewed-by: Benjamin Copeland <ben.copeland@linaro.org>

1 files changed, 109 insertions, 0 deletions

diff --git a/docker_hosts b/docker_hosts
new file mode 100755
index 00000000..6f78ac6f
--- /dev/null
+++ b/docker_hosts
@@ -0,0 +1,109 @@
+#!/usr/bin/env python
+
+import docker
+import re
+import json
+import sys
+
+"""
+ Ansible Docker Dynamic Inventory Script
+
+External components:
+  https://git.linaro.org/infrastructure/docker-ansible-baseimage.git/
+
+Requirements:
+  pip install docker
+  chmod 755 docker_hosts
+
+Example:
+
+  docker-compose -f linaro_dev up -d
+  docker run -d \
+    -e ANSIBLE_GROUP=gerrit \
+    -e ANSIBLE_HOST=review.linaro.org \
+    -e ALIAS=review.linaro.org \
+    --name review ansible/baseimage:14.04
+  ansible-playbook -u root -v -i docker_hosts \
+    -c local -l review.linaro.org gerrit.yml
+
+Options:
+
+ANSIBLE_HOST overrides the container's name in the inventory
+  Let's you use the host_vars for a real server for testing.
+ANSIBLE_GROUP is a comma separated list of groups that the host
+  should belong to.
+ALIAS is a feature of the linaro/devdns container that replaces the
+  local DNS entry for the target with the container's IP address
+
+"""
+
+class DockerInventory():
+    client = None
+    ip_table = {}
+    hosts = {}
+    groups = {}
+
+    def __init__(self):
+        self.client = docker.from_env()
+
+        # build ip lookup table
+        for network_entry in self.client.networks.list():
+            network = self.client.networks.get( network_entry.name )
+            for entry in network.attrs["Containers"]:
+                ip = network.attrs["Containers"][entry]["IPv4Address"]
+                name = network.attrs["Containers"][entry]["Name"]
+                self.ip_table[ name ] = re.sub( u"/\d+$", '', ip)
+
+        # build up all inventory
+        for container in self.client.containers.list():
+
+            # if ANSIBLE_HOST is set, use that instead of the container.name
+            # We should only add hosts that have an ANSIBLE_HOST set
+            #TODO: find a way to set other hostvars
+            hostname = container.name
+            for env_var in container.attrs["Config"]["Env"]:
+                found_ansible = re.match( 'ANSIBLE_HOST=(?P<ansible_host>.*)', env_var )
+                if found_ansible:
+                    hostname = found_ansible.group("ansible_host")
+            self.hosts[hostname] = { "ansible_host": self.ip_table[container.name] }
+
+            # add in any groups listed in ANSIBLE_GROUP and make this
+            #  container a member
+            for env_var in container.attrs["Config"]["Env"]:
+                found_ansible = re.match( 'ANSIBLE_GROUP=(?P<ansible_group>.*)', env_var )
+
+                if found_ansible:
+                    groups = found_ansible.group("ansible_group")
+                    for group in groups.split(','):
+                        if not self.groups.has_key( group ):
+                            self.groups[group] = []
+                        self.groups[group].append( hostname )
+            #TODO: find a way to add in groupvars
+
+    def build_meta(self):
+        meta = {'_meta': { 'hostvars' : {} } }
+
+        for key in self.hosts.keys():
+            meta['_meta']['hostvars'][key] = self.hosts[key]
+
+        return meta
+
+    def list(self):
+        full = self.groups
+        full["_meta"] = self.build_meta()["_meta"]
+        return json.dumps( full )
+
+    def host(self, hostname):
+        try:
+            return json.dumps( self.hosts[hostname] )
+        except IndexError as e:
+            return json.dumps( {} )
+
+if __name__ == '__main__':
+
+    inventory = DockerInventory()
+
+    if len( sys.argv ) <= 2:
+        print inventory.list()
+    elif len(sys.argv ) >= 3:
+        print inventory.host( sys.argv[2] )