Define a proxy for plugin installation

Address the issue [ansible-elasticsearch
#4](https://github.com/elastic/ansible-elasticsearch/issues/4) which
add proxy for plugin installation and more generally es_proxy_host and
es_proxy_port for global usage.

Right now, it’s only used for plugins installation. In the futur, it
can be used (or defined) in the java_opts within the default file for
instance (elasticsearch.j2)

README.md

@@ -100,6 +100,8 @@ A more complex example:
         - plugin: marvel-agent
         - plugin: lmenezes/elasticsearch-kopf
           version: master
+          proxy_host: proxy.example.com
+          proxy_port: 8080
 ```
 
 ### Multi Node Server Installations
@@ -166,8 +168,7 @@ Following variables affect the versions installed:
     - plugin: elasticsearch-cloud-aws
       version: 2.5.0
 ```
- 
+
- 
 Earlier examples illustrate the installation of plugins for 2.x.  The correct use of this parameter varies depending on the version of Elasticsearch being installed:
  
  - 2.x. - For officially supported plugins no version or source delimiter is required. The plugin script will determine the appropriate plugin version based on the target Elasticsearch version.  
@@ -188,6 +189,25 @@ controlled by the following parameters:
 * ```es_work_dir``` - defaults to "/tmp/elasticsearch".
 * ```es_plugin_dir``` - defaults to "/usr/share/elasticsearch/plugins".
 
+### Proxy
+
+To define proxy globaly, set the following variables:
+
+* ```es_proxy_host``` - global proxy host
+* ```es_proxy_port``` - global proxy port
+
+To define proxy only for a particular plugin during its installation:
+
+```
+  es_plugins:
+    - plugin: elasticsearch-cloud-aws
+      version: 2.5.0
+      proxy_host: proxy.example.com
+      proxy_port: 8080
+```
+
+> For plugins installation, proxy_host and proxy_port are used first if they are defined and fallback to the global proxy settings if not.
+
 ## Notes
 
 * The role assumes the user/group exists on the server.  The elasticsearch packages create the default elasticsearch user.  If this needs to be changed, ensure the user exists.

tasks/checkParameters.yml

@@ -3,6 +3,9 @@
 - fail: msg="es_instance_name must be specified and cannot be blank"
   when: es_instance_name is not defined or es_instance_name == ''
 
+- fail: msg="es_proxy_port must be specified and cannot be blank when es_proxy_host is defined"
+  when: (es_proxy_port is not defined or es_proxy_port == '') and (es_proxy_host is defined and es_proxy_host != '')
+
 - set_fact: multi_cast={{ (es_version | version_compare('2.0', '<') and es_config['discovery.zen.ping.multicast.enabled'] is not defined) or (es_config['discovery.zen.ping.multicast.enabled'] is defined and es_config['discovery.zen.ping.multicast.enabled'])}}
 
 - debug: msg="WARNING - It is recommended you specify the parameter 'http.port' when multicast is disabled"

tasks/elasticsearch-plugins.yml

@@ -20,7 +20,15 @@
 
 - name: Install elasticsearch plugins
   #debug: var=item
-  command: "{{es_home}}/bin/plugin install {{ item.plugin }}{% if item.version is defined and item.version != '' %}/{{ item.version }}{% endif %} --silent"
+  command: >
+    {{es_home}}/bin/plugin install
+    {{ item.plugin }}{% if item.version is defined and item.version != '' %}/{{ item.version }}{% endif %}
+    {% if item.proxy_host is defined and item.proxy_host != '' and item.proxy_port is defined and item.proxy_port != ''%}
+      -DproxyHost={{ item.proxy_host }} -DproxyPort={{ item.proxy_port }}
+    {% elif es_proxy_host is defined and es_proxy_host != '' %}
+      -DproxyHost={{ es_proxy_host }} -DproxyPort={{ es_proxy_port }}
+    {% endif %}
+    --silent
   register: plugin_installed
   failed_when: "'Failed to install' in plugin_installed.stderr"
   changed_when: plugin_installed.rc == 0