Auto merge of #2517 - micbou:remove-healthy-check, r=Valloric

[READY] Remove healthy check

This PR removes the code that, if the server is not yet healthy, tries in a separate thread to send the same request at different intervals until it gets a response or reaches 5 failed attempts.

Main issue with that code is that it blocks Vim if a synchronous request (`semantic_completion_available`, `run_completer_command`, etc.)  is sent while the server is not up. See issue #2071.

Other issues are that it's hard to understand how this code behaves (it combines threads and retries), it becomes useless once the server is healthy (because `SERVER_HEALTHY` is cached and never reset), it depends on arbitrary parameters (why 5 retries with a delay of 0.5s multiplied by 1.5 at each attempt?), and it has a package dependency `retries`.

Now that we catch all server exceptions (PR #2453) and define a very short connection timeout (PR #2514), we can just drop this code.

This change gives a huge improvement in startup time on Windows (don't worry, more improvements are coming for all platforms). The reason is that `requests` (probably `urllib3`) tries for ~1s to check if the server is healthy on Windows while it's almost instantaneous on other platforms.
<table>
  <tr>
    <th rowspan="2">Platform</th>
    <th colspan="2">First run (ms)</th>
    <th colspan="2">Subsequent runs (ms)</th>
  </tr>
  <tr>
    <td>Before</td>
    <td>After</td>
    <td>Before</td>
    <td>After</td>
  </tr>
  <tr>
    <td>Ubuntu 16.04 64-bit</td>
    <td>228</td>
    <td>248</td>
    <td>176</td>
    <td>151</td>
  </tr>
  <tr>
    <td>macOS 10.12</td>
    <td>433</td>
    <td>417</td>
    <td>263</td>
    <td>263</td>
  </tr>
  <tr>
    <td>Windows 10 64-bit</td>
    <td>1861</td>
    <td>844</td>
    <td>814</td>
    <td>292</td>
  </tr>
</table>

These results were obtained by running the `prof.py` script from [this branch](https://github.com/micbou/YouCompleteMe/tree/profiling-startup). The difference between first run and subsequent runs is Python bytecode generation (`*.pyc` files).

Fixes #2071.

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python/ycm/client/base_request.py

@@ -30,7 +30,6 @@ import urllib.parse
 import json
 from future.utils import native
 from base64 import b64decode, b64encode
-from retries import retries
 from requests_futures.sessions import FuturesSession
 from ycm.unsafe_thread_pool_executor import UnsafeThreadPoolExecutor
 from ycm import vimsupport
@@ -102,43 +101,20 @@ class BaseRequest( object ):
                            handler,
                            method,
                            timeout = _READ_TIMEOUT_SEC ):
-    def SendRequest( data, handler, method, timeout ):
+    request_uri = _BuildUri( handler )
-      request_uri = _BuildUri( handler )
+    if method == 'POST':
-      if method == 'POST':
+      sent_data = _ToUtf8Json( data )
-        sent_data = _ToUtf8Json( data )
+      return BaseRequest.session.post(
-        return BaseRequest.session.post(
+          request_uri,
-            request_uri,
+          data = sent_data,
-            data = sent_data,
+          headers = BaseRequest._ExtraHeaders( method,
-            headers = BaseRequest._ExtraHeaders( method,
+                                               request_uri,
-                                                 request_uri,
+                                               sent_data ),
-                                                 sent_data ),
+          timeout = ( _CONNECT_TIMEOUT_SEC, timeout ) )
-            timeout = ( _CONNECT_TIMEOUT_SEC, timeout ) )
+    return BaseRequest.session.get(
-      if method == 'GET':
+        request_uri,
-        return BaseRequest.session.get(
+        headers = BaseRequest._ExtraHeaders( method, request_uri ),
-            request_uri,
+        timeout = ( _CONNECT_TIMEOUT_SEC, timeout ) )
-            headers = BaseRequest._ExtraHeaders( method, request_uri ),
-            timeout = ( _CONNECT_TIMEOUT_SEC, timeout ) )
-
-    @retries( 5, delay = 0.5, backoff = 1.5 )
-    def DelayedSendRequest( data, handler, method ):
-      request_uri = _BuildUri( handler )
-      if method == 'POST':
-        sent_data = _ToUtf8Json( data )
-        return requests.post(
-            request_uri,
-            data = sent_data,
-            headers = BaseRequest._ExtraHeaders( method,
-                                                 request_uri,
-                                                 sent_data ) )
-      if method == 'GET':
-        return requests.get(
-            request_uri,
-            headers = BaseRequest._ExtraHeaders( method, request_uri ) )
-
-    if not _CheckServerIsHealthyWithCache():
-      return _EXECUTOR.submit( DelayedSendRequest, data, handler, method )
-
-    return SendRequest( data, handler, method, timeout )
 
 
   @staticmethod
@@ -271,31 +247,6 @@ def _BuildUri( handler ):
                                                 handler ) ) )
 
 
-SERVER_HEALTHY = False
-
-
-def _CheckServerIsHealthyWithCache():
-  global SERVER_HEALTHY
-
-  def _ServerIsHealthy():
-    request_uri = _BuildUri( 'healthy' )
-    response = requests.get( request_uri,
-                             headers = BaseRequest._ExtraHeaders(
-                                 'GET', request_uri, bytes( b'' ) ) )
-    _ValidateResponseObject( response )
-    response.raise_for_status()
-    return response.json()
-
-  if SERVER_HEALTHY:
-    return True
-
-  try:
-    SERVER_HEALTHY = _ServerIsHealthy()
-    return SERVER_HEALTHY
-  except:
-    return False
-
-
 def MakeServerException( data ):
   if data[ 'exception' ][ 'TYPE' ] == UnknownExtraConf.__name__:
     return UnknownExtraConf( data[ 'exception' ][ 'extra_conf_file' ] )

third_party/retries/retries.py

@@ -1,79 +0,0 @@
-#!/usr/bin/env python
-#
-# Copyright 2012 by Jeff Laughlin Consulting LLC
-#
-# Permission is hereby granted, free of charge, to any person obtaining a copy
-# of this software and associated documentation files (the "Software"), to deal
-# in the Software without restriction, including without limitation the rights
-# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-# copies of the Software, and to permit persons to whom the Software is
-# furnished to do so, subject to the following conditions:
-#
-# The above copyright notice and this permission notice shall be included in
-# all copies or substantial portions of the Software.
-#
-# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-# SOFTWARE.
-
-
-import sys
-from time import sleep
-
-# Source: https://gist.github.com/n1ywb/2570004
-
-def example_exc_handler(tries_remaining, exception, delay):
-    """Example exception handler; prints a warning to stderr.
-
-    tries_remaining: The number of tries remaining.
-    exception: The exception instance which was raised.
-    """
-    print >> sys.stderr, "Caught '%s', %d tries remaining, sleeping for %s seconds" % (exception, tries_remaining, delay)
-
-
-def retries(max_tries, delay=1, backoff=2, exceptions=(Exception,), hook=None):
-    """Function decorator implementing retrying logic.
-
-    delay: Sleep this many seconds * backoff * try number after failure
-    backoff: Multiply delay by this factor after each failure
-    exceptions: A tuple of exception classes; default (Exception,)
-    hook: A function with the signature myhook(tries_remaining, exception);
-          default None
-
-    The decorator will call the function up to max_tries times if it raises
-    an exception.
-
-    By default it catches instances of the Exception class and subclasses.
-    This will recover after all but the most fatal errors. You may specify a
-    custom tuple of exception classes with the 'exceptions' argument; the
-    function will only be retried if it raises one of the specified
-    exceptions.
-
-    Additionally you may specify a hook function which will be called prior
-    to retrying with the number of remaining tries and the exception instance;
-    see given example. This is primarily intended to give the opportunity to
-    log the failure. Hook is not called after failure if no retries remain.
-    """
-    def dec(func):
-        def f2(*args, **kwargs):
-            mydelay = delay
-            tries = reversed(range(max_tries))
-            for tries_remaining in tries:
-                try:
-                   return func(*args, **kwargs)
-                except exceptions as e:
-                    if tries_remaining > 0:
-                        if hook is not None:
-                            hook(tries_remaining, e, mydelay)
-                        sleep(mydelay)
-                        mydelay = mydelay * backoff
-                    else:
-                        raise
-                else:
-                    break
-        return f2
-    return dec