Implement wait_for_connection on httpapi (#105)

Implement wait_for_connection on httpapi

Reviewed-by: https://github.com/apps/ansible-zuul

Author: Qalthos

changelogs/fragments/105-wait_for_conn-httpapi.yaml

@@ -0,0 +1,5 @@
+---
+minor_changes:
+  - The httpapi connection plugin now works with `wait_for_connection`. This will periodically request
+    the root page of the server described by the plugin's options until the request succeeds.
+    This can only test that the server is reachable, the correctness or usability of the API is not guaranteed.

plugins/connection/httpapi.py

@@ -193,7 +193,6 @@ def __init__(self, play_context, new_stdin, *args, **kwargs):
             play_context, new_stdin, *args, **kwargs
         )
 
-        self._url = None
         self._auth = None
 
         if self._network_os:
@@ -227,6 +226,13 @@ def __init__(self, play_context, new_stdin, *args, **kwargs):
             )
         self.queue_message("log", "network_os is set to %s" % self._network_os)
 
+    @property
+    def _url(self):
+        protocol = "https" if self.get_option("use_ssl") else "http"
+        host = self.get_option("host")
+        port = self.get_option("port") or (443 if protocol == "https" else 80)
+        return "%s://%s:%s" % (protocol, host, port)
+
     def update_play_context(self, pc_data):
         """Updates the play context information for the connection"""
         pc_data = to_bytes(pc_data)
@@ -249,13 +255,6 @@ def update_play_context(self, pc_data):
 
     def _connect(self):
         if not self.connected:
-            protocol = "https" if self.get_option("use_ssl") else "http"
-            host = self.get_option("host")
-            port = self.get_option("port") or (
-                443 if protocol == "https" else 80
-            )
-            self._url = "%s://%s:%s" % (protocol, host, port)
-
             self.queue_message(
                 "vvv",
                 "ESTABLISH HTTP(S) CONNECTFOR USER: %s TO %s"
@@ -337,3 +336,13 @@ def send(self, path, data, **kwargs):
         response_buffer.seek(0)
 
         return response, response_buffer
+
+    def transport_test(self, connect_timeout):
+        """This method enables wait_for_connection to work.
+
+        The sole purpose of this method is to raise an exception if the API's URL
+        cannot be reached. As such, it does not do anything except attempt to
+        request the root URL with no error handling.
+        """
+
+        open_url(self._url, timeout=connect_timeout)