class RequestBuilder(object):
"""
The request builder is responsible for building the PutMetricData requests using HTTP GET.
Keyword arguments:
credentials -- The AWSCredentials object containing access and secret keys
region -- The region to which the data should be published
namespace -- The namespace used for grouping of the published metrics.
"""
_SERVICE = "monitoring"
_ACTION = "PutMetricData"
_API_VERSION = "2010-08-01"
_ALGORITHM = "AWS4-HMAC-SHA256"
_V4_TERMINATOR = "aws4_request"
def __init__(self, credentials, region):
self.credentials = credentials
self.region = region
self.namespace = ""
self.datestamp = None
self.aws_timestamp = None
self.payload = "" # for HTTP GET payload is always empty
self.querystring_builder = QuerystringBuilder()
self.signer = Signer(credentials, region, self._SERVICE,
self._ALGORITHM)
def create_signed_request(self, namespace, metric_list):
""" Creates a ready to send request with metrics from the metric list passed as parameter """
self.namespace = namespace
self._init_timestamps()
canonical_querystring = self._create_canonical_querystring(metric_list)
signature = self.signer.create_request_signature(
canonical_querystring, self._get_credential_scope(),
self.aws_timestamp, self.datestamp, self._get_canonical_headers(),
self._get_signed_headers(), self.payload)
canonical_querystring += '&X-Amz-Signature=' + signature
return canonical_querystring
def _init_timestamps(self):
""" Initializes timestamp and datestamp values """
self.datestamp = get_datestamp()
self.aws_timestamp = get_aws_timestamp()
def _create_canonical_querystring(self, metric_list):
"""
Creates a canonical querystring as defined in the official AWS API documentation:
http://docs.aws.amazon.com/general/latest/gr/sigv4-create-canonical-request.html
"""
return self.querystring_builder.build_querystring(
metric_list, self._get_request_map())
def _get_request_map(self):
"""
Creates a map of request parameters and values which can be used
to build a canonical querystring
"""
canonical_map = {
"Action":
self._ACTION,
"Namespace":
self.namespace,
"Version":
self._API_VERSION,
"X-Amz-Algorithm":
self._ALGORITHM,
"X-Amz-Credential":
self.credentials.access_key + '/' + self._get_credential_scope(),
"X-Amz-Date":
self.aws_timestamp,
"X-Amz-SignedHeaders":
self._get_signed_headers()
}
if self.credentials.token:
canonical_map["X-Amz-Security-Token"] = self.credentials.token
return canonical_map
def _get_credential_scope(self):
""" Builds credential scope string used in querystring and signing """
return self.datestamp + '/' + self.region + '/' + self._SERVICE + '/' + self._V4_TERMINATOR
def _get_canonical_headers(self):
""" Returns a list of canonical headers separated with new line characters """
return "host:" + self._get_host() + "\n"
def _get_signed_headers(self):
""" Returns comma delimited list of signed headers """
return "host"
def _get_host(self):
""" Returns the endpoint's hostname derived from the region """
if self.region == "localhost":
return "localhost"
elif self.region.startswith("cn-"):
return "monitoring." + self.region + ".amazonaws.com.cn"
return "monitoring." + self.region + ".amazonaws.com"
