client.py 文件源码

def _resolve_signature_version(self, service_name, resolved):
        # Client config overrides everything.
        client = self.client_config
        if client and client.signature_version is not None:
            return client.signature_version
        # Scoped config overrides picking from the endpoint metadata.
        scoped = self.scoped_config
        if scoped is not None:
            service_config = scoped.get(service_name)
            if service_config is not None and isinstance(service_config, dict):
                version = service_config.get('signature_version')
                if version:
                    logger.debug(
                        "Switching signature version for service %s "
                        "to version %s based on config file override.",
                        service_name, version)
                    return version
        # Pick a signature version from the endpoint metadata if present.
        if 'signatureVersions' in resolved:
            potential_versions = resolved['signatureVersions']
            if service_name == 's3':
                # We currently prefer s3 over s3v4.
                if 's3' in potential_versions:
                    return 's3'
                elif 's3v4' in potential_versions:
                    return 's3v4'
            if 'v4' in potential_versions:
                return 'v4'
            # Now just iterate over the signature versions in order until we
            # find the first one that is known to Botocore.
            for known in AUTH_TYPE_MAPS:
                if known in potential_versions:
                    return known
        raise UnknownSignatureVersionError(
            signature_version=resolved.get('signatureVersions'))