The role of limitations and SLAs in the API industry

Abstract

As software architecture design is evolving to a microservice paradigm, RESTful APIs are being established as the preferred choice to build applications. In such a scenario, there is a shift towards a growing market of APIs where providers ofer diferent service levels with tailored limitations typically based on the cost.In this context, while there are well established standards to describe the functional elements of APIs (such as the OpenAPI Speciication), having a standard model for Service Level Agreements (SLAs) for APIs may boost an open ecosystem of tools that would represent an improvement for the industry by automating certain tasks during the development such as: SLA-aware scafolding, SLA-aware testing, or SLA-aware requesters.Unfortunately, despite there have been several proposals to describe SLAs for software in general and web services in particular during the past decades, there is an actual lack of a widely used standard due to the complex landscape of concepts surrounding the notion of SLAs and the multiple perspectives that can be addressed.In this paper, we aim to analyze the landscape for SLAs for APIs in two diferent directions: i) Clarifying the SLA-driven API development lifecycle: its activities and participants; 2) Developing a catalog of relevant concepts and an ulterior prioritization based on diferent perspectives from both Industry and Academia. As a main result, we present a scored list of concepts that paves the way to establish a concrete road-map for a standard industry-aligned speciication to describe SLAs in APIs.

Governify for APIs: SLA-driven ecosystem for API governance

“…Concerning the industrial evaluation, some OpenAPI Initiative members have expressed its interest in SLA4OAI, the SLA modeling proposal, and in promoting a working group for evolving and extending it. Indeed, in [4], we collaborated with people from Google, Paypal, AsyncAPI Initiative and Metadev for analyzing, starting from SLA4OAI, the status of SLAs and limitations in the industry. Furthermore, in spite of the fact the SLA4OAI extension and tools have not been widely announced nor promoted, we have disclosed the tooling ecosystem into the main public Node.js artifact repository (i.e., NPM) and this platform provides a set of analytics of usage since their publishing.…”

“…This API does not ofer any explicit information of the nonfunctional properties or limitations besides of an entry in the FAQ 4 in natural language (sic. you should always be ine when waiting for at least one or two seconds between two consecutive requests).…”

Impact of API Rate Limit on Reliability of Microservices-Based Architectures

“…Rate Limit and similar techniques have been introduced as best practices or patterns [2], [3], [4], [5], [20] and in the context of Service-Level Agreements [21], [22]. However, the effects of Rate Limit have not yet been studied empirically in the scientific literature.…”

Call Limit-Based Composite Service Selection

“…The results show that more than 80% of rate limits and quotas are defined over number of requests. In addition, this kind of rate limits and quotas are classified among the three most important API concepts in [9]. This motivated us to focus our work on limits over requests, however, our definitions and algorithms can be easily adapted to other types of limitations.…”

“…This includes, the form of registration, payment plans as well as call limits [6]. There are two different types of call limits: rate limits and quotas [7]- [9]. Rate limits describe limitations of use for a short period of time (e.g., 3 calls per second); their role is to protect servers and infrastructure against overload.…”