=Paper=
{{Paper
|id=Vol-1859/emisa-06-paper
|storemode=property
|title=Microservices-based Business Process Model Execution
|pdfUrl=https://ceur-ws.org/Vol-1859/emisa-06-paper.pdf
|volume=Vol-1859
|authors=Agnes Koschmider
|dblpUrl=https://dblp.org/rec/conf/emisa/Koschmider17
}}
==Microservices-based Business Process Model Execution==
https://ceur-ws.org/Vol-1859/emisa-06-paper.pdf
158
Microservices-based Business Process Model Execution
Agnes Koschmider1
Abstract: Recently, microservices evolved as a new software architecture paradigm allowing to
build independently deployable software systems. In the context of Business Process Management
microservices could be used to automate the execution of highly distributed business process
models as required within the digital transformation. This paper sketches a microservices-based
business process model execution and discusses challenges.
Keywords: Microservices, business process automation, business process execution
1 Introduction
WSBPEL [WS] is the widely-used standard for business process model execution. It lays
the foundation for a process engine automating the execution of business processes
specified as web services. Recently, microservices [LeFo14] evolved as a new software
architecture paradigm allowing a flexible execution and an independent deployment of
software systems. Microservice (architecture style)…”is an approach to developing a
single application as a suite of small services, each running in its own process and
communicating with lightweight mechanisms” [LeFo14]. Initial discussions can be found
how microservices might support business scenarios. Particularly, their use for an agile
development of software systems has been attested [DDEF16]. In the context of
Business Process Management (BPM) microservices could complement or even replace
WSBPEL for business process model execution.
Contrary to WSBPEL the characteristics of microservices support the execution of
highly distributed business process models and do not require any centralized
management. Particularly, process model activities or events could be specified as a
microservice addressing its own technology stack. A microservices-based business
process model execution would be performed upon a container technology (e.g.,
Docker2) and thus would replace or complement a process engine-based execution. Such
a microservices-based business process model execution would have several advantages.
From a technological perspective it would allow a scalable and reliable execution of
business process models. From a customer perspective it would support a real-time
individualized and personalized production of products. However, several challenges
must be solved in order to exploit these benefits.
1
Institute AIFB, KIT, 76128 Karlsruhe, agnes.koschmider@kit.edu
2
https://www.docker.com/
Microservices-based BP Model Execution 159
This paper sketches a microservices-based business process model execution and
discusses the challenges to be met.
2 Microservices
Microservices are characterized by services that are built around business capabilities,
they are independently deployable, have little centralized management of services, and
can use its own technology stack (the programming language and data storage are not
centrally specified). Often microservices are illustrated by means of a comparison with a
monolithic style. A monolithic style (on the left hand side of Fig. 1) is considered as a
large “stone” where all functions run in a single process. An application includes all
modules, libraries and dependencies, which are necessary to ensure the proper function.
Changes on the application require to test and compile the entire application. In contrast,
a microservices style consists of several independent services that together build the
application. The modifications of a service do not directly affect the properties and
functions of other services thus ensuring independence of services. The main difference
between web services and microservices is the automatic deployment. Generally, a
deeper understanding is required which service is large (microservice vs. web service).
Fig. 1: Monolithic style (left) versus Microservices style (right) [Fowl15]
The main benefits of microservices are (1) improved scalability: services are capable of
scaling independent of the use of other services, (2) improved agility: changes on
services can be performed without affecting other services, (3) improved availability of
the application: a partial failure of a service might not directly affect the entire
application, (4) continuous delivery: changes of services do not set the entire application
to the maintenance mode.
These benefits of microservices can be exploited for business process model execution
allowing more agile and scalable application as discussed in the next section.
160 Agnes Koschmider
3 Microservices-based Business Process Model Execution
A microservices-based business process model execution is performed on the
microservices framework (i.e., in a container on an orchestrator). This means that a
container technology (e.g., Docker) is required to execute the application code (any
programming language can be used to specify the service). Then an orchestrator (e.g.,
kubernetes3) is necessary to automate the deployment of containerized applications.
Finally, a monitoring tool can be used to control the distributed environment. Applying
this framework to a microservices-based business process model execution means that
the orchestration of services is no longer exclusively performed by a process engine but
(also) by containerized application orchestrator, which is set on a different abstraction
level. This raises two challenges
Challenge 1: What are appropriate strategies for business process model orchestration
(e.g., routing of business process activities). The control-flow of process models could
make the unpredictable flow of microservices instances more transparent.
Challenge 2: How to deal with processes containing “automatic tasks” and “semi-
automatic tasks” and thus how to combine process-based engines and containerized
application orchestrator?
Also, it is open:
Challenge 3: How to specify the dependencies of microservices executed within
distributed business process models? Microservices require only a minimum of central
control, which also raises the challenge of
Challenge 4: Who takes care of the process? Microservices communicate with
lightweight mechanisms but have so called “dumb pipes“ (i.e., only the endpoints are
smart and pipes only forward information) raising the challenge of:
Challenge 5: How to implement processes according to „smart endpoints and dumb
pipes“ characteristic?
Finally it remains to address:
Challenge 6: What is an appropriate visualization and assignment of microservices in a
business process model? Fig. 2 shows one alternative. Two microservices (depicted as
MS events) are specified in a book flight BPMN diagram. It remains to investigate if
microservices are specified as events (see Fig. 2) or as a new type of process activities
(then an icon is attached to the activity) or if a process model fragment defines a
microservice.
Fig. 2 also uses choreography (between Client and System). If microservices are used in
such setting it remains to investigate if timer event would implement the routing of
3
https://kubernetes.io/
Microservices-based BP Model Execution 161
activities addressed by the challenge:
Challenge 7: What is an efficient solution for choreography in microservices-based
business process model execution?
Fig. 2: One option of visualization and assignment of microservices in a business process model
4 Conclusion
Microservices can be seen as an architectural style for the design of distributed software
systems having several benefits in contract to common architecture styles. This paper
illustrated the use of microservices for business process model execution. A research
agenda should cover the following points (1) elaborate the difference between
microservices and web services for business process model automation, (2) discuss if a
microservices-based business process model execution is complementary to existing
solutions or even might dominate them, (3) discuss use cases for a microservices-based
business process model execution, and (4) provide a testbed for experiments.
Bibliography
[DDEF16] Daya, S.; Van Duy, N.; Eati, K.; Ferreira, C.M.; Glozic, D.; Gucer, V.; Gupta, M.;
Joshi, S.; Lampkin, V.; Martins, M.; Narain, S.; Vennam, R.: Microservices from
Theory to Practice: Creating Applications in IBM Bluemix Using the Microservices
Approach. IBM Redbooks, 2016
[Fowl15] Fowler, M.: Microservices: Nur ein weiteres Konzept in der Softwarearchitektur oder
mehr? OBJEKTspektrum, vol. 01, 2015.
[LeFo14] Lewis, J.; Fowler, M.: Microservices: a definition of this new architectural term.
https://martinfowler.com/articles/microservices.html
[WS] OASIS Standard WS-BPEL 2.0: https://www.oasis-
open.org/committees/tc_home.php?wg_abbrev=wsbpel