Architecture of Wemlin Hub

22 December 2013 – Ognen Ivanovski & Goran Cvetkoski
What’s Wemlin?

 Wemlin provides access to public transport information
– easy, fast and independent of time and place
iO...
Wemlin Hub in a nutshell

Netcetera | 3
Wemlin Hub – non-functional requirements
- Wemlin Hub shall be a high performance parallelized message processing system

...
What is Software Architecture?

?
Netcetera | 5
Is this Software Architecture?

Netcetera | 6
Is this Software Architecture?

Netcetera | 7
Software Architecture is…

The decisions about software that are hard to change
E.g.
 Use of Jodatime vs. java.util.Date
...
Wemin Hub Architecture

Model
 Pure Java (no dependencies)
 Well defined extensible classes
 Immutable (like Jodatime, ...
Pure Model
- no external dependency
- design not influenced by any technology e.g. Hibernate, RDBMS, MVC

Netcetera | 10
Algebraic, Immutable Model
- algebraic: each object identity is defined by it's contents.
- immutable: each object, once c...
Compositional
pipeElement = PipelineBuilder.from(gtfsInputJunction())
.transform(new StoppingPlaceResolver())
.filter(new ...
Pipeline: Stateless, Functions

boolean accept(Object obj);
Object transform(Object original);

Optional<?> aggregate(Obje...
Pipeline: Implementation
Netcetera | 14
Pipeline: Typical Hub
Netcetera | 15
Memoization
Immutable Model: each object, once created, cannot be modified.
Problem: Big memory consumption, a lot of obje...
Memoization (2)
Implementation:
Constructors are made private and replaced by annotated factory methods:

@DesignatedFacto...
Memoization (3)
@Pointcut("execution(@com.wemlin.hub.memoization.annotations.DesignatedFactoryMeth
od * *(..))")
public vo...
Modularization – components architectural constraints
- The following architectural constrains define a module in Wemlin H...
Station resolver module (1)
-

The Wemlin Hub Station resolver module does station resolving with help of the reference
st...
Station Resolver (2)
- I Every station is resolved by a set of rules:
-

General rules
Station specific rules

General rul...
Cache
-

we don’t use a DB:
- all data is time bounded i.e. all data we keep is temporary (daily)

-

our choice was an in...
REST
-

all data that is in the cache is available via the REST api

-

there are two versions of the api available:
- leg...
Microkernel architectural style

Illustration

Netcetera | 24
Wemlin Hub - Blue-Green deployment
- Requirement: ensure zero downtime of the system.
- Decision: blue-green deployment
- ...
Wemlin Hub today
- currently 4 customers (all in Switzerland)
- they cover nearly 40% of the transport in all Switzerland ...
Contact

Goran Cvetkoski, senior software engineer, Netcetera
goran.cvetkoski@netcetera.com

Ognen Ivanovski, chief archit...
Q&A?

Netcetera | 28
Upcoming SlideShare
Loading in …5
×

Architecture of Wemlin Hub

492 views
356 views

Published on

Presentation about the architecture of Wemlin Hub, part of the Wemlin product.

Published in: Technology
0 Comments
2 Likes
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total views
492
On SlideShare
0
From Embeds
0
Number of Embeds
3
Actions
Shares
0
Downloads
7
Comments
0
Likes
2
Embeds 0
No embeds

No notes for slide
  • So What is Wemlin?According to our marketing, Wemlin is a Passenger Information System that provides access to public transport information – easy, fast and independent of time and place.The Wemlin Product family for the end user consists of mobile applications for iOS, Android, Windows Phone and Web application.All applications display the same data.Transport unitPlan data – schedules (yearly, daily) – which vehicle drives where?Stop – zastanuvanjeTrip – rutaGps – sends data to avms
  • Under the hood, Wemlin also has a Server part called Wemlin Hub whose main purpose is:to gather data from the transport agencies (using different protocols, like: VDV DFI, VDV AUS, GTFS, HAFAS)enrich the acquired data with its own reference data (why? – it’s third party data, often bad quality or not in desired format)serve that data to primarily to Wemlin mobile clients and also to 3-th party clients.convert data between various formats
  • Exstensible - Many clients with different requirements
  • Exstensible - Many clients with different requirements
  • Under the hood, Wemlin also has a Server part called Wemlin Hub whose main purpose is:to gather data from the transport agencies (using different protocols, like: VDV DFI, VDV AUS, GTFS, HAFAS)enrich the acquired data with its own reference data (why? – it’s third party data, often bad quality or not in desired format)serve that data to primarily to Wemlin mobile clients and also to 3-th party clients.convert data between various formats
  • Why microkernel?software systems that must be able to adapt to changing system requirementsit separates a minimal functional core from extended functionality and customer-specific partsmicrokernel also serves as a socket for plugging in these extensions and coordinating their collaborationsize of the microkernel should be kept to a minimum, therefore, only part of the core functionality can be included in itBenefits of the pattern:good portability, since only microkernel need to be modified when porting the system to a new environment.high flexibility and extensibility, as modifications or extensions can be done by modifying or extending internal servers.maintainability and changeability of the system.
  • You want to make your architecture as small as possible (the less things that are “hard to change” the better)Encapsulation: the more you are able t
  • Microkerncel.This is the architecture. Small, easy to remember.
  • - Log free
  • Explain input components responsibilityKeep connections openHandle specific protocolResolversStation resolver, line resolverWe translate data from the protocols to our model formatUniversal model for any protocolBidejkisekojakomponenta se pridrzuva do odredeninterfejs od pajplajnot, se dobivaparalelizacijazabezpari I bezmnogurazmisluvanjepriimplementacijataPrakanjenaporaki od edenna drug sistem: ova e moznobidejkiporakite se immutable Porakite ne moze da se smenat, mozesamo da zastarat
  • Memoization is a optimization technique used primarily to speed up computer programs by having function calls avoid repeating the calculation of results for previously processed inputs.Having immutable model in a system has it’s advantages when it comes to parallelization and concurrency, but also has it’s drawbacks which is big memory consumption, because for every modification of a single field in an object, you need to shallow copy the whole object and create a new one with the modified filed.Because many of the model objects in Wemlin will be recreated with the same data many times, it makes sense to check if we had previously created objects with the specified parameters and return the old object instead of creating a new one.
  • Memoization is a optimization technique used primarily to speed up computer programs by having function calls avoid repeating the calculation of results for previously processed inputs.
  • The pointcut selects all methods that are anotated with the @DesignatedFactoryMethod annotation.We use the Around advice on the selected join points.
  • Memoization is a optimization technique used primarily to speed up computer programs by having function calls avoid repeating the calculation of results for previously processed inputs.Having immutable model in a system has it’s advantages when it comes to parallelization and concurrency, but also has it’s drawbacks which is big memory consumption, because for every modification of a single field in an object, you need to shallow copy the whole object and create a new one with the modified filed.Because many of the model objects in Wemlin will be recreated with the same data many times, it makes sense to check if we had previously created objects with the specified parameters and return the old object instead of creating a new one.
  • forwarding cache browser - forwards all requests to a wrapped cache browser. useful for overriding some logic.lazy loading cache browser - lazy loads data from the cache, saves time for large schedules
  • forwarding cache browser - forwards all requests to a wrapped cache browser. useful for overriding some logic.lazy loading cache browser - lazy loads data from the cache, saves time for large schedules
  • Why microkernel?software systems that must be able to adapt to changing system requirementsit separates a minimal functional core from extended functionality and customer-specific partsmicrokernel also serves as a socket for plugging in these extensions and coordinating their collaborationsize of the microkernel should be kept to a minimum, therefore, only part of the core functionality can be included in itBenefits of the pattern:good portability, since only microkernel need to be modified when porting the system to a new environment.high flexibility and extensibility, as modifications or extensions can be done by modifying or extending internal servers.maintainability and changeability of the system.Apache httpd exampleKarakteristicno e stoparalelizirame
  • Architecture of Wemlin Hub

    1. 1. Architecture of Wemlin Hub 22 December 2013 – Ognen Ivanovski & Goran Cvetkoski
    2. 2. What’s Wemlin?  Wemlin provides access to public transport information – easy, fast and independent of time and place iOS Android Windows Phone Web Netcetera | 2
    3. 3. Wemlin Hub in a nutshell Netcetera | 3
    4. 4. Wemlin Hub – non-functional requirements - Wemlin Hub shall be a high performance parallelized message processing system - low latency – good processing speed throughput – number of messages we can process available - zero downtime! good disaster recovery scalability (horizontal, vertical) modular – component based extensible – 80% usage pattern flexible – adapt to any infrastructure with minimal effort Netcetera | 4
    5. 5. What is Software Architecture? ? Netcetera | 5
    6. 6. Is this Software Architecture? Netcetera | 6
    7. 7. Is this Software Architecture? Netcetera | 7
    8. 8. Software Architecture is… The decisions about software that are hard to change E.g.  Use of Jodatime vs. java.util.Date  What kind of Database will you use  GWT vs. Angular JS Encapsulation Netcetera | 8
    9. 9. Wemin Hub Architecture Model  Pure Java (no dependencies)  Well defined extensible classes  Immutable (like Jodatime, every modification produces a new object)  Algebraic  Inverse References Pipeline  Compositional (All components are wired together using a fixed set of well defined interfaces) Filter (stateless, function) Transformer (stateless, function) Aggregator (stateful, function) Sink (consumer) Tap (producer) Netcetera | 9
    10. 10. Pure Model - no external dependency - design not influenced by any technology e.g. Hibernate, RDBMS, MVC Netcetera | 10
    11. 11. Algebraic, Immutable Model - algebraic: each object identity is defined by it's contents. - immutable: each object, once created, cannot be modified. Each part of the pipeline must copy-and-modify each object to perform it’s processing. This characteristic enables easier reasoning about concurrency. - metadata: classes support arbitrary metadata expressed as key-value pairs. Metadata does not take part in the definition of the object's identity. This allows encoding of format specific information in the model, which can be used in the pipeline. Netcetera | 11
    12. 12. Compositional pipeElement = PipelineBuilder.from(gtfsInputJunction()) .transform(new StoppingPlaceResolver()) .filter(new InvalidStopsFilter()) .transform(new UnresolvedLineVehicleTypeAdder()) .transform(new UnresolvedLineNameAdjuster()) .transform(new LineResolver()) .transform( new LineColorsEnricher(…)) .aggregate(new CacheAggregator(cache())) .to(nullSink()); Netcetera | 12
    13. 13. Pipeline: Stateless, Functions boolean accept(Object obj); Object transform(Object original); Optional<?> aggregate(Object obj); filter, transform are referentially transparent Netcetera | 13
    14. 14. Pipeline: Implementation Netcetera | 14
    15. 15. Pipeline: Typical Hub Netcetera | 15
    16. 16. Memoization Immutable Model: each object, once created, cannot be modified. Problem: Big memory consumption, a lot of objects are created with the same contents Solution: Memoization When a factory method is executed, for example: Station.get("1", "St. Gallen, Bahnhof"); a global cache of objects in searched if a object with the specified data already exists. If object exists, it is returned, if not, new object is created and stored into cache for future use. Netcetera | 16
    17. 17. Memoization (2) Implementation: Constructors are made private and replaced by annotated factory methods: @DesignatedFactoryMethod public static Station get(Map<String, ? extends Serializable> attributes, String referenceId, String name, String localName, String place, GeoPoint location) { return new Station(attributes, referenceId, name, localName, place, location); } Netcetera | 17
    18. 18. Memoization (3) @Pointcut("execution(@com.wemlin.hub.memoization.annotations.DesignatedFactoryMeth od * *(..))") public void designatedFactoryMethodPointcut() { } @Around("designatedFactoryMethodPointcut()") public Object handleMemoize(final ProceedingJoinPoint pjp) throws Exception { // search for object with the specified factory parameters in cache }} Impact: 500 to 1000 times less objects created (depends on how much data is processed) Netcetera | 18
    19. 19. Modularization – components architectural constraints - The following architectural constrains define a module in Wemlin Hub: - it is a maven module, a jar or web fragment - is not allowed to use spring annotations for injection, i.e. all injection is done via constructors - a module provides components, only a few (up to 4) and facades for the 80% usage pattern - each component is allowed to hook into the wemlin pipeline only through the predefined pipeline interfaces Filter, Transformer, Aggregator, input component, output component - components are Spring independent, as far as it is possible. They may implement some spring interfaces, but as few as possible, and provide means to achieve the same functionality without Spring. Netcetera | 19
    20. 20. Station resolver module (1) - The Wemlin Hub Station resolver module does station resolving with help of the reference stations list The reference station list contains all CH stations listed in the “Stationsnamen Fahrplan und Antragsformular für Mutationen“ http://www.bav.admin.ch/dokumentation/publikationen/00475/01497/index.html - We use the reference station list primarily to match references to stations in incoming data (HAFAS, VDV, GTFS) to known stations for which we fully control the names, have the coordinates and other meta-data that can be associated with them. - The list is well defined JSON file that lists - attributes of the stations (full name, local name, place, coordinates, agency etc) - their respective referenceId - a set of rules that may be used to match the station in incoming data - connection areas Netcetera | 20
    21. 21. Station Resolver (2) - I Every station is resolved by a set of rules: - General rules Station specific rules General rules - station id (optimal) - station similarity – we use Apache Lucene for search of name similarity in combination with coordinates distance tolerance - Station specific rules - matchByRegex – when the station has different id from the one we have, but also the name we get is slightly different Example: Bahnhof, Esslingen: Esslingen Bhf, Esslingen Bhf., Esslingen etc Netcetera | 21
    22. 22. Cache - we don’t use a DB: - all data is time bounded i.e. all data we keep is temporary (daily) - our choice was an in-memory cache - very simple java maps cache - no third party cache libraries are involved - the cache is easy to browse via the cache browser component - few implementations available: - - standard cache browser forwarding cache browser lazy loading cache browser all cache browsers can define filters Netcetera | 22
    23. 23. REST - all data that is in the cache is available via the REST api - there are two versions of the api available: - legacy api (V0): wemlin clients still operate with this one - V2 api according to the new transport.opendata.ch specification – some of the customers started using it - both apis support pretty much the same things: - locations listings – cities, stations - lines listing – all lines that operate within a network - trips – for a given period of time - departures – with realtime prognosis Netcetera | 23
    24. 24. Microkernel architectural style Illustration Netcetera | 24
    25. 25. Wemlin Hub - Blue-Green deployment - Requirement: ensure zero downtime of the system. - Decision: blue-green deployment - two identical production environments - the reverse proxy before the machines resolves to one of them depending on which one is configured active - test on the “idle” server before go-live - switch proxy to the tested instance – the other one is now “idle” - Advantages: - ensure zero downtime of the system - easy rollback if anything goes wrong Netcetera | 25
    26. 26. Wemlin Hub today - currently 4 customers (all in Switzerland) - they cover nearly 40% of the transport in all Switzerland including Liechtenstein - 17 agencies, 14 with realtime data - daily processing load - around 33’000 trips, 571’000 stops - 2’500 projections per second in peak hours (in the moment, not the actual capacity of the system) - offline transport data conversion - contract with Google for Switzerland - we convert the Swiss yearly transport schedule (over 400 agencies, ~1GB data) to GTFS (Google Transit Feed Specification) format for Google Maps usage - conversion takes ~20min Netcetera | 26
    27. 27. Contact Goran Cvetkoski, senior software engineer, Netcetera goran.cvetkoski@netcetera.com Ognen Ivanovski, chief architect, Netcetera ognen.ivanovski@netcetera.com Netcetera | 27
    28. 28. Q&A? Netcetera | 28

    ×