Add git/gerrit-on-borg utilities.

gerrit_util.py

Index: gerrit_util.py
diff --git a/gerrit_util.py b/gerrit_util.py
new file mode 100755
index 0000000000000000000000000000000000000000..7c44f03107468de934940bd1bf7646630818c53f
--- /dev/null
+++ b/gerrit_util.py
@@ -0,0 +1,394 @@
+# Copyright (c) 2013 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""
+Utilities for requesting information for a gerrit server via https.
+
+https://gerrit-review.googlesource.com/Documentation/rest-api.html
+"""
+
+import base64
+import httplib
+import json
+import logging
+import netrc
+import os
+import time
+import urllib
+from cStringIO import StringIO
+
+try:
+  NETRC = netrc.netrc()
+except (IOError, netrc.NetrcParseError):
+  NETRC = netrc.netrc(os.devnull)
+LOGGER = logging.getLogger()
+TRY_LIMIT = 5
+
+# Controls the transport protocol used to communicate with gerrit.
+# This is parameterized primarily to enable GerritTestCase.
+GERRIT_PROTOCOL = 'https'
+
+
+class GerritError(Exception):
+  """Exception class for errors commuicating with the gerrit-on-borg service."""
+  def __init__(self, http_status, *args, **kwargs):
+    super(GerritError, self).__init__(*args, **kwargs)
+    self.http_status = http_status
+    self.message = '(%d) %s' % (self.http_status, self.message)
+
+
+def _QueryString(param_dict, first_param=None):
+  """Encodes query parameters in the key:val[+key:val...] format specified here:
+
+  https://gerrit-review.googlesource.com/Documentation/rest-api-changes.html#list-changes
+  """
+  q = [urllib.quote(first_param)] if first_param else []
+  q.extend(['%s:%s' % (key, val) for key, val in param_dict.iteritems()])
+  return '+'.join(q)
+
+
+def GetConnectionClass(protocol=None):
+  if protocol is None:
+    protocol = GERRIT_PROTOCOL
+  if protocol == 'https':
+    return httplib.HTTPSConnection
+  elif protocol == 'http':
+    return httplib.HTTPConnection
+  else:
+    raise RuntimeError(
+        "Don't know how to work with protocol '%s'" % protocol)
+
+
+def CreateHttpConn(host, path, reqtype='GET', headers=None, body=None):
+  """Opens an https connection to a gerrit service, and sends a request."""
+  headers = headers or {}
+  bare_host = host.partition(':')[0]
+  auth = NETRC.authenticators(bare_host)
+  if auth:
+    headers.setdefault('Authorization', 'Basic %s' % (
+        base64.b64encode('%s:%s' % (auth[0], auth[2]))))
+  else:
+    LOGGER.debug('No authorization found')
+  if body:
+    body = json.JSONEncoder().encode(body)
+    headers.setdefault('Content-Type', 'application/json')
+  if LOGGER.isEnabledFor(logging.DEBUG):
+    LOGGER.debug('%s %s://%s/a/%s' % (reqtype, GERRIT_PROTOCOL, host, path))
+    for key, val in headers.iteritems():
+      if key == 'Authorization':
+        val = 'HIDDEN'
+      LOGGER.debug('%s: %s' % (key, val))
+    if body:
+      LOGGER.debug(body)
+  conn = GetConnectionClass()(host)
+  conn.req_host = host
+  conn.req_params = {
+      'url': '/a/%s' % path,
+      'method': reqtype,
+      'headers': headers,
+      'body': body,
+  }
+  conn.request(**conn.req_params)
+  return conn
+
+
+def ReadHttpResponse(conn, expect_status=200, ignore_404=True):
+  """Reads an http response from a connection into a string buffer.
+
+  Args:
+    conn: An HTTPSConnection or HTTPConnection created by CreateHttpConn, above.
+    expect_status: Success is indicated by this status in the response.
+    ignore_404: For many requests, gerrit-on-borg will return 404 if the request
+                doesn't match the database contents.  In most such cases, we
+                want the API to return None rather than raise an Exception.
+  Returns: A string buffer containing the connection's reply.
+  """
+
+  sleep_time = 0.5
+  for idx in range(TRY_LIMIT):
+    response = conn.getresponse()
+    # If response.status < 500 then the result is final; break retry loop.
+    if response.status < 500:
+      break
+    # A status >=500 is assumed to be a possible transient error; retry.
+    http_version = 'HTTP/%s' % ('1.1' if response.version == 11 else '1.0')
+    msg = (
+        'A transient error occured while querying %s:\n'
+        '%s %s %s\n'
+        '%s %d %s' % (
+            conn.host, conn.req_params['method'], conn.req_params['url'],
+            http_version, http_version, response.status, response.reason))
+    if TRY_LIMIT - idx > 1:
+      msg += '\n... will retry %d more times.' % (TRY_LIMIT - idx - 1)
+      time.sleep(sleep_time)
+      sleep_time = sleep_time * 2
+      req_host = conn.req_host
+      req_params = conn.req_params
+      conn = GetConnectionClass()(req_host)
+      conn.req_host = req_host
+      conn.req_params = req_params
+      conn.request(**req_params)
+    LOGGER.warn(msg)
+  if ignore_404 and response.status == 404:
+    return StringIO()
+  if response.status != expect_status:
+    raise GerritError(response.status, response.reason)
+  return StringIO(response.read())
+
+
+def ReadHttpJsonResponse(conn, expect_status=200, ignore_404=True):
+  """Parses an https response as json."""
+  fh = ReadHttpResponse(
+      conn, expect_status=expect_status, ignore_404=ignore_404)
+  # The first line of the response should always be: )]}'
+  s = fh.readline()
+  if s and s.rstrip() != ")]}'":
+    raise GerritError(200, 'Unexpected json output: %s' % s)
+  s = fh.read()
+  if not s:
+    return None
+  return json.loads(s)
+
+
+def QueryChanges(host, param_dict, first_param=None, limit=None, o_params=None,
+                 sortkey=None):
+  """
+  Queries a gerrit-on-borg server for changes matching query terms.
+
+  Args:
+    param_dict: A dictionary of search parameters, as documented here:
+        http://gerrit-documentation.googlecode.com/svn/Documentation/2.6/user-search.html
+    first_param: A change identifier
+    limit: Maximum number of results to return.
+    o_params: A list of additional output specifiers, as documented here:
+        https://gerrit-review.googlesource.com/Documentation/rest-api-changes.html#list-changes
+  Returns:
+    A list of json-decoded query results.
+  """
+  # Note that no attempt is made to escape special characters; YMMV.
+  if not param_dict and not first_param:
+    raise RuntimeError('QueryChanges requires search parameters')
+  path = 'changes/?q=%s' % _QueryString(param_dict, first_param)
+  if sortkey:
+    path = '%s&N=%s' % (path, sortkey)
+  if limit:
+    path = '%s&n=%d' % (path, limit)
+  if o_params:
+    path = '%s&%s' % (path, '&'.join(['o=%s' % p for p in o_params]))
+  # Don't ignore 404; a query should always return a list, even if it's empty.
+  return ReadHttpJsonResponse(CreateHttpConn(host, path), ignore_404=False)
+
+
+def MultiQueryChanges(host, param_dict, change_list, limit=None, o_params=None,
+                      sortkey=None):
+  """Initiate a query composed of multiple sets of query parameters."""
+  if not change_list:
+    raise RuntimeError(
+        "MultiQueryChanges requires a list of change numbers/id's")
+  q = ['q=%s' % '+OR+'.join([urllib.quote(str(x)) for x in change_list])]
+  if param_dict:
+    q.append(_QueryString(param_dict))
+  if limit:
+    q.append('n=%d' % limit)
+  if sortkey:
+    q.append('N=%s' % sortkey)
+  if o_params:
+    q.extend(['o=%s' % p for p in o_params])
+  path = 'changes/?%s' % '&'.join(q)
+  try:
+    result = ReadHttpJsonResponse(CreateHttpConn(host, path), ignore_404=False)
+  except GerritError as e:
+    msg = '%s:\n%s' % (e.message, path)
+    raise GerritError(e.http_status, msg)
+  return result
+
+
+def GetGerritFetchUrl(host):
+  """Given a gerrit host name returns URL of a gerrit instance to fetch from."""
+  return '%s://%s/' % (GERRIT_PROTOCOL, host)
+
+
+def GetChangePageUrl(host, change_number):
+  """Given a gerrit host name and change number, return change page url."""
+  return '%s://%s/#/c/%d/' % (GERRIT_PROTOCOL, host, change_number)
+
+
+def GetChangeUrl(host, change):
+  """Given a gerrit host name and change id, return an url for the change."""
+  return '%s://%s/a/changes/%s' % (GERRIT_PROTOCOL, host, change)
+
+
+def GetChange(host, change):
+  """Query a gerrit server for information about a single change."""
+  path = 'changes/%s' % change
+  return ReadHttpJsonResponse(CreateHttpConn(host, path))
+
+
+def GetChangeDetail(host, change, o_params=None):
+  """Query a gerrit server for extended information about a single change."""
+  path = 'changes/%s/detail' % change
+  if o_params:
+    path += '?%s' % '&'.join(['o=%s' % p for p in o_params])
+  return ReadHttpJsonResponse(CreateHttpConn(host, path))
+
+
+def GetChangeCurrentRevision(host, change):
+  """Get information about the latest revision for a given change."""
+  return QueryChanges(host, {}, change, o_params=('CURRENT_REVISION',))
+
+
+def GetChangeRevisions(host, change):
+  """Get information about all revisions associated with a change."""
+  return QueryChanges(host, {}, change, o_params=('ALL_REVISIONS',))
+
+
+def GetChangeReview(host, change, revision=None):
+  """Get the current review information for a change."""
+  if not revision:
+    jmsg = GetChangeRevisions(host, change)
+    if not jmsg:
+      return None
+    elif len(jmsg) > 1:
+      raise GerritError(200, 'Multiple changes found for ChangeId %s.' % change)
+    revision = jmsg[0]['current_revision']
+  path = 'changes/%s/revisions/%s/review'
+  return ReadHttpJsonResponse(CreateHttpConn(host, path))
+
+
+def AbandonChange(host, change, msg=''):
+  """Abandon a gerrit change."""
+  path = 'changes/%s/abandon' % change
+  body = {'message': msg} if msg else None
+  conn = CreateHttpConn(host, path, reqtype='POST', body=body)
+  return ReadHttpJsonResponse(conn, ignore_404=False)
+
+
+def RestoreChange(host, change, msg=''):
+  """Restore a previously abandoned change."""
+  path = 'changes/%s/restore' % change
+  body = {'message': msg} if msg else None
+  conn = CreateHttpConn(host, path, reqtype='POST', body=body)
+  return ReadHttpJsonResponse(conn, ignore_404=False)
+
+
+def SubmitChange(host, change, wait_for_merge=True):
+  """Submits a gerrit change via Gerrit."""
+  path = 'changes/%s/submit' % change
+  body = {'wait_for_merge': wait_for_merge}
+  conn = CreateHttpConn(host, path, reqtype='POST', body=body)
+  return ReadHttpJsonResponse(conn, ignore_404=False)
+
+
+def GetReviewers(host, change):
+  """Get information about all reviewers attached to a change."""
+  path = 'changes/%s/reviewers' % change
+  return ReadHttpJsonResponse(CreateHttpConn(host, path))
+
+
+def GetReview(host, change, revision):
+  """Get review information about a specific revision of a change."""
+  path = 'changes/%s/revisions/%s/review' % (change, revision)
+  return ReadHttpJsonResponse(CreateHttpConn(host, path))
+
+
+def AddReviewers(host, change, add=None):
+  """Add reviewers to a change."""
+  if not add:
+    return
+  if isinstance(add, basestring):
+    add = (add,)
+  path = 'changes/%s/reviewers' % change
+  for r in add:
+    body = {'reviewer': r}
+    conn = CreateHttpConn(host, path, reqtype='POST', body=body)
+    jmsg = ReadHttpJsonResponse(conn, ignore_404=False)
+  return jmsg
+
+
+def RemoveReviewers(host, change, remove=None):
+  """Remove reveiewers from a change."""
+  if not remove:
+    return
+  if isinstance(remove, basestring):
+    remove = (remove,)
+  for r in remove:
+    path = 'changes/%s/reviewers/%s' % (change, r)
+    conn = CreateHttpConn(host, path, reqtype='DELETE')
+    try:
+      ReadHttpResponse(conn, ignore_404=False)
+    except GerritError as e:
+      # On success, gerrit returns status 204; anything else is an error.
+      if e.http_status != 204:
+        raise
+    else:
+      raise GerritError(
+          'Unexpectedly received a 200 http status while deleting reviewer "%s"'
+          ' from change %s' % (r, change))
+
+
+def SetReview(host, change, msg=None, labels=None, notify=None):
+  """Set labels and/or add a message to a code review."""
+  if not msg and not labels:
+    return
+  path = 'changes/%s/revisions/current/review' % change
+  body = {}
+  if msg:
+    body['message'] = msg
+  if labels:
+    body['labels'] = labels
+  if notify:
+    body['notify'] = notify
+  conn = CreateHttpConn(host, path, reqtype='POST', body=body)
+  response = ReadHttpJsonResponse(conn)
+  if labels:
+    for key, val in labels.iteritems():
+      if ('labels' not in response or key not in response['labels'] or
+          int(response['labels'][key] != int(val))):
+        raise GerritError(200, 'Unable to set "%s" label on change %s.' % (
+            key, change))
+
+
+def ResetReviewLabels(host, change, label, value='0', message=None,
+                      notify=None):
+  """Reset the value of a given label for all reviewers on a change."""
+  # This is tricky, because we want to work on the "current revision", but
+  # there's always the risk that "current revision" will change in between
+  # API calls.  So, we check "current revision" at the beginning and end; if
+  # it has changed, raise an exception.
+  jmsg = GetChangeCurrentRevision(host, change)
+  if not jmsg:
+    raise GerritError(
+        200, 'Could not get review information for change "%s"' % change)
+  value = str(value)
+  revision = jmsg[0]['current_revision']
+  path = 'changes/%s/revisions/%s/review' % (change, revision)
+  message = message or (
+      '%s label set to %s programmatically.' % (label, value))
+  jmsg = GetReview(host, change, revision)
+  if not jmsg:
+    raise GerritError(200, 'Could not get review information for revison %s '
+                   'of change %s' % (revision, change))
+  for review in jmsg.get('labels', {}).get(label, {}).get('all', []):
+    if str(review.get('value', value)) != value:
+      body = {
+          'message': message,
+          'labels': {label: value},
+          'on_behalf_of': review['_account_id'],
+      }
+      if notify:
+        body['notify'] = notify
+      conn = CreateHttpConn(
+          host, path, reqtype='POST', body=body)
+      response = ReadHttpJsonResponse(conn)
+      if str(response['labels'][label]) != value:
+        username = review.get('email', jmsg.get('name', ''))
+        raise GerritError(200, 'Unable to set %s label for user "%s"'
+                       ' on change %s.' % (label, username, change))
+  jmsg = GetChangeCurrentRevision(host, change)
+  if not jmsg:
+    raise GerritError(
+        200, 'Could not get review information for change "%s"' % change)
+  elif jmsg[0]['current_revision'] != revision:
+    raise GerritError(200, 'While resetting labels on change "%s", '
+                   'a new patchset was uploaded.' % change)