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How to build Drupal Applications with APIs and microservices
Ronald Ashri - @ronald_istos technical strategy director - @DeesonAgency
and why
background in agent-based software engineering and distributed AI
an agent is a computer system capable of flexible, autonomous action in a dynamic, unpredictable and open environment
background in agent-based software engineering and distributed AI
an agent is a computer system capable of flexible, autonomous action in a dynamic, unpredictable and open environment
microservice
heterogeneous
what are the problems we are trying to solve
so. many. things.
organisations (humans)
speed
scalability resilience availability
testability
replaceability
the non-microservice way makes it less likely to address these problems
single application / single codebase or badly implemented SOA
leading to tight coupling hard to support concurrency / partitioning hard to support efficient testing fear stops us from moving fast
does not handle the human issues
- control - reliability - consistency - technical debt over time - knowledge management
we’ve been building monoliths long enough to know that despite the best intentions it rarely ends well - especially in large orgs with multiple teams
the microservices way - guiding principles
bounded context
do one thing well
comprehensible
independently deployable
deployed through automated process builds
message-enabled
composable
encourage polyglotism
a system that makes change easy, safely at scale
a cohesive system
“gather together those things that change for the same reason, and separate those things that change for different reasons”
Robert C. Martin’s Single Responsibility Principle
a loosely coupled system
“The greater the cohesion of individual modules in the system, the lower the coupling between modules will be.”
—Larry Constantine and Edward Yourdon, authors of Structured Design: Fundamentals of a Discipline of Computer Program and Systems Design
microservices - architecture
there is no ideal size
the answer is 42 ;-)
29
OPT
ION
AL S
ECTI
ON
TIT
LE
from Microservice Architecture
by Irakli Nadareishvili et al
use domain-driven design principles to identify the right boundaries for your problem
https://www.martinfowler.com/bliki/BoundedContext.html
designing as a monolith with modular / component based design and then breaking it up is a valid strategy
if in order to implement a change you end up touching lots of different microservices something is wrong - couple loosely
Don’t start by designing data models - focus on business capabilities
REST CRUD services are not the objective
If concerned about dependency on data stores delay implementation to the end. Build interfaces, models, mock replies and push back on the final data store.
DO NOT SHARE A DB.
introduces tight coupling reduces cohesion
microservices - integration
message-based
I’m sorry that I long ago coined the term “objects” for this topic because it gets many people to focus on the lesser idea. The big idea is “messaging.” —Alan Kay
“(…) for far too long, developers have viewed APIs and web services as tools to transmit serialized “objects” over the wire. However, a more efficient approach is to look at a complex system as a collection of services exchanging messages over a wire.”
Microservice Architecture by Irakli Nadareishvili et al
Netflix uses protocols like Avro, Protobuf and Thrift internally and JSON over HTTP for external consumers
Hypermedia driven
package data together with description of possible actions HATEOS - Hypermedia as the engine of application state
event-sourcing
a stream of facts about how our entities are changing
- deposited £10 to account - cash - paid £5 for dinner - deposited £5 - salary - paid £3 for cinema
balance: £7
event-sourcing data model vs structural data model
events are the record of all that has happened with current application state being the result
a structural data model shows us the current state with no background information
- deposited £10 to account - cash
- paid £5 for dinner
- deposited £5 - salary
- paid £3 for cinema
balance: £7
asynchronous messaging passing
Events Hub
Publisher Subscriberpublish subscribe
choreography vs orchestration
micro services - in (micro) practice
hotel booking service
channels
hotel booking service
channels
cannot add a channel without redeploying entire site
if a channel changes need to redeploy site
site will be blocked as it is trying to update separate channels
…
channels
hotel booking service
Amazon SQS
channels
hotel booking service
Amazon SQS
coupled drupal to SQS-specific implementation
will need to redeploy hundreds of sites on each change
channels
hotel booking service
Amazon SQS
listener (silex app)
channels
hotel booking service
Amazon SQSlistener
channel manager
channel A channel B
channels
hotel booking service
queuelistener
channel manager
channel A channel B
gateway
channels
hotel booking service
queuelistener
channel manager
channel A channel B
gateway
What next
testing monitoring security API gateways …
if you take one thing away - it is these four things• Make each program do one thing well. To do a new job, build
afresh rather than complicate old programs by adding new features.
• Expect the output of every program to become the input to another, as yet unknown, program. Don’t clutter output with extraneous information. Avoid stringently columnar or binary input formats. Don’t insist on interactive input.
• Design and build software, even operating systems, to be tried early, ideally within weeks. Don’t hesitate to throw away the clumsy parts and rebuild them.
• Use tools in preference to unskilled help to lighten a programming task, even if you have to detour to build the tools and expect to throw some of them out after you’ve finished using them.
From the 1978 Bell Labs UNIX Timesharing system doc
questions?
Ronald Ashri - @ronald_istos technical strategy director - @DeesonAgency
