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Web Application as a Microservice
Sota Sugiura
Tech Lead (Backend)
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Tech Lead
Backend
Sota Sugiura
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Web Application as a Microservice
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https://www.mercari.com/jp/
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JP Web Re-architect
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Improve scalability of the development team
Goals
A flexible architecture that is resilient to change
1
2
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Flexible architecture that is resilient to change
● Keeping up to date with trends
● Scrap and Build
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No content
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Improving scalability of the development team
● Architecture that can handle the increasing
number of engineers
● Providing freedom for each team to choose their
own technology stack
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Single PHP Server
Te m ar Te m ar
Box
Te m ar G i
Now
Mercari
Mercari
Box
Mercari
Guide
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SSR
GraphQL
SPA
REST API
Simple HTTP server
Mic r i s
Te m ar
Mic r i s
Te m ar
Box
Mic r i s
Te m ar G i
Goal
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How to Carry Out the Re-architecture
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1 Monolithic Service
to
4 Microservices
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Wait, can you migrate all features
from a Monolithic Service at once? :P
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1 Monolithic Service
to with
4 Microservices
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Monolithic
Service
Feture
・
・
・
Monolithic
Service
Feature
・
・
・
Microservice
Microservice
Microservice
Microservice
Microservice
Microservice
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Why?
● This is a re-architecture, not a redesign
● Limiting the scope of migration at first
● We will start by taking on many small
challenges and failures
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Limiting the migration scope
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Monolithic
Service
Feature
・
・
・
/jp/*
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Monolithic
Service
Feature
・
・
・
Microservice
Microservice
/jp/* /jp/top
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How we decided the order of migration
● Difficulty
● Clashes with other tasks and changes
● Amount of traffic
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Challenges
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Challenges
Monolithic Service + Microservices
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2 Separating Frontend and Backend
3 Session synchronization
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GraphQL
SSR
mercari-web
mercari-api
Web Gateway
Session service
CDN
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GraphQL
SSR
mercari-web
mercari-api
Web Gateway
Session service
CDN
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2
3
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GraphQL
SSR
mercari-web
mercari-api
Web Gateway
Session service
CDN
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2
3
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Web Gateway
● Balancing for each service
● Initially for both new and old architectures to co-exist
● In the future, for Web Microservices
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● Mapping with path
control
● Scoped release
● Session persistence
Web Gateway
mercari-web
Service A Service B
/hoge /moge /others
CDN
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● Mapping with path
control
● Scoped release
● Session persistence
Web Gateway
mercari-web
Service A Service B
/hoge /moge /others
CDN
/hoge=”Service A”
/moge=”Service B”
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● Mapping with path
control
● Scoped release
● Session persistence
Web Gateway
mercari-web
Service A
Service B
/hoge /moge /others
0% 100%
WI
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● Mapping with path
control
● Scoped release
● Session persistence
Web Gateway
mercari-web
Service A
Service B
/hoge /moge /others
10% 90%
WI
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● Mapping with path
control
● Scoped release
● Session persistence
Web Gateway
mercari-web
Service A
Service B
/hoge /moge /others
100% 0%
WI
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● Mapping with path
control
● Scoped release
● Session persistence
Web Gateway
mercari-web
Service A
Service B
/hoge /moge /others
10% 90%
A B
WI
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● Mapping with path
control
● Scoped release
● Session persistence
Web Gateway
mercari-web
Service A
Service B
/hoge /moge /others
10% 90%
A B
WI
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● Mapping with path
control
● Scoped release
● Session persistence
Web Gateway
mercari-web
Service A
Service B
/hoge /moge /others
10% 90%
A B
WI
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● Mapping with path
control
● Scoped release
● Session persistence
Web Gateway
mercari-web
Service A
Service B
/hoge /moge /others
10% 90%
A B
WI
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GraphQL
SSR
mercari-web
mercari-api
Web Gateway
Session service
CDN
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2
3
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How is frontend affected by the backend migration to
Microservices?
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mercari-web
mercari-api
JSON over HTTPs
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mercari-web
mercari-api
JSON over HTTPs
SSR
JSON over HTTPs
New!
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mercari-web
mercari-api
JSON over HTTPs
SSR
Offer service
JSON over HTTPs
gRPC
New!
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mercari-web
mercari-api
JSON over HTTPs
SSR
Offer service
JSON over HTTPs
gRPC
Listing service
gRPC
New!
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mercari-web
mercari-api
JSON over HTTPs
SSR
Offer service
JSON over HTTPs
gRPC
Listing service
gRPC
New!
Buying service
New!
Live service
New!
User service
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mercari-web
mercari-api
JSON over HTTPs
SSR
Offer service
JSON over HTTPs
gRPC
Listing service
gRPC
New!
Buying service
New!
Live service
New!
User service
● We need to keep up to date with the
specs for every new microservice
● We need to write high-performance code
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mercari-web
mercari-api
JSON over HTTPs
BFF
Listing Service
JSON over HTTPs
gRPC
Offer Service
gRPC
Our strategy
SSR
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mercari-web
mercari-api
JSON over HTTPs
BFF
Listing Service
JSON over HTTPs
gRPC
Offer Service
gRPC
Our strategy
SSR
Frontend Engineer
Backend Engineer
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Backends for Frontends in our JP Web
Re-architecture
● Our definition of BFF: “a layer to aggregate
backend microservices”
● To improve the development experience for
frontend engineers
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What to implement as BFF
● GraphQL - works well with SPAs
● a
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GraphQL
SSR
mercari-web
mercari-api
Web Gateway
Session service
CDN
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2
3
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Session synchronization issues
● Several microservices will exist in the same
domain
● Need to maintain consistency with the longin
state of the Monolithic Service
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mercari-web
Logged-out user
SSR server
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mercari-web
POST /login
SSR server
Logged-out user
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mercari-web
Logged-in user
Success!
SSR server
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mercari-web
Logged-in user
GET /
SSR server
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mercari-web
Should show page
for logged in
users
SSR server
Logged-in user
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Microservice for managing session
● Create a microservice to manage sessions
● Maintaining session consistency and data
preservation, etc.
● Assume multiple microservices will use this
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How we will manage synchronization
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mercari-web
Session service
Request
Call to get session
every time
Response
Session
data
SSR server
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mercari-web
Session service
Request
Call to get session
every time
Response
Session
data
SSR server
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https://gist.github.com/jboner/2841832
Latency Numbers Every Programmer Should Know
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mercari-web
Session service
Q. What’s the distance
here?
SSR server
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About 800km
※だいたいです
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Data transmission between
Hokkaido and Tokyo
● We use GKE in Tokyo region
● The exisiting Monolithic Service will run from Hokkaido
● We need to design the architecture with latency in mind
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● Making Storage to
store cache data
● Minimize amount of
back-and-forth data
transmission in Japan
mercari-web
Session service
New!
Cache storage
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mercari-web
Session service
New!
Cache storage
● We chose gRPC via
Node.js
● Based on technical
expertise of our
members
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mercari-web
Session service
mercari-api
Cache storage
SSR server
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mercari-web
Session service
mercari-api
Cache storage
Firstly, check the Cache and DB
at hand to check for existing
session data
SSR server
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mercari-web
Session service
mercari-api
Cache storage
If no session data can be found, check
for the session in Monolithic Service
SSR server
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mercari-web
Session service
mercari-api
Cache storage
With the session data, request
authentication data to the Monolithic API
SSR server
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mercari-web
Session service
mercari-api
Cache storage
Save session data
SSR server
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● Use cache data if it exists, but if not, get from Hokkaido
● No access to Tokyo from Hokkaido
● This ensures security and consistency
Simple is the best!
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Conclusion
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Sowing the seeds of success
● Implement a supreme architecture
● Make it possible to develop at explosive speeds
● And provide the ultimate developer experience
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So many challenges!
● Tech stack
● Re-architecture
● Evolving and scaling our development structure
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Al or One
All for the ultimate Web
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Thank you :)
Feel free to ask me any questions
at the “Ask the speaker” booth
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