I deal with the topic of reactive programming.
I use WebFlux and R2dbc to access the database.
I am developing a small backend for a chat app.
So I have some questions on the subject and I would be very happy about suggestions and improvements.
This is service class
#Service
public class MessageService implements IMessageService {
UnicastProcessor<Message> hotProcessor = UnicastProcessor.create();
private final FluxSink<Message> fluxSink = hotProcessor.sink(FluxSink.OverflowStrategy.LATEST);
private final Flux<Message> hotFlux = hotProcessor.publish().autoConnect();
#Autowired
private MessageRepository messageRepository;
public Flux<Message> findAll() {
return this.messageRepository.findAll();
}
public Mono<Message> create(Message nachricht) {
this.fluxSink.next(nachricht);
return this.messageRepository.save(nachricht);
}
// how can I persist messages and to arrange a chat room.
public Flux<Message> finAllMessagesByChatroomId(Long id) {
return hotFlux.filter(m->m.getId().intValue() == id.intValue());
}
}
When should I use UnicastProcessor when DirectProcessor.
Update:
a little correction
public Flux<Message> finAllMessagesByChatroomId(Long id) {
return hotFlux.filter(m->m.getRoom_id == id);
}
But how can I get all the Messages from the database and add it to fluxSink?
Related
I'm novice in reactive programming and now i trying to rewrite my test spring boot web application on reactive stack(web flux, reactor, reactive mongo).
My app it is simple library with 3 type of entities: Book, Genre, Author;
Book has a link on Genre and Author. In my old app without reactive stack when i tried to remove Genre or Author which linked with some Book, i handled it moment in onBeforeDelete method which was overrided in my class which extending from AbstractMongoEventListener.
It is look like this:
#Component
public class CascadeAuthorOrGenreDeleteMongoEventListener extends AbstractMongoEventListener<Object> {
#Autowired
private BookRepository bookRepository;
#Autowired
private AuthorRepository authorRepository;
#Autowired
private GenreRepository genreRepository;
#Override
public void onBeforeDelete(BeforeDeleteEvent<Object> event) {
if (Objects.equals(event.getCollectionName(), "genre") || Objects.equals(event.getCollectionName(), "author")) {
String id = String.valueOf(event.getSource().get("_id"));
Optional<Genre> genre = genreRepository.findById(id);
Optional<Author> author = authorRepository.findById(id);
if (genre.isPresent()) {
if (bookRepository.findFirstByGenre(genre.get()) != null) {
throw new RuntimeException("Genre has related books");
}
}
if (author.isPresent()) {
if (bookRepository.findFirstByAuthor(author.get()) != null) {
throw new RuntimeException("Author has related books");
}
}
}
}
}
Now i trying to write the same code on reactive stack, I have already written some code example, but i'm not sure that is it correctly, maybe can i do it better with using reactive functions? I can't figure out with it by myself.
Here my example:
#Component
public class CascadeAuthorOrGenreDeleteMongoEventListener extends AbstractMongoEventListener<Object> {
#Autowired
private BookRepository bookRepository;
#Autowired
private AuthorRepository authorRepository;
#Autowired
private GenreRepository genreRepository;
#Override
public void onBeforeDelete(BeforeDeleteEvent<Object> event) {
if (Objects.equals(event.getCollectionName(), "genre") || Objects.equals(event.getCollectionName(), "author")) {
String id = String.valueOf(event.getSource().get("_id"));
genreRepository.findById(id)
.zipWith(authorRepository.findById(id))
.flatMap(tuple -> {
final Genre genre = tuple.getT1();
final Author author = tuple.getT2();
return bookRepository.findFirstByAuthor(author)
.switchIfEmpty(Mono.fromCallable(Book::new))
.zipWith(bookRepository.findFirstByGenre(genre)
.switchIfEmpty(Mono.fromCallable(Book::new)));
}).subscribe(tuple -> {
final Book bookByAuthor = tuple.getT1();
final Book bookByGenre = tuple.getT2();
if (bookByAuthor.getId() != null) {
throw new RuntimeException("Author has related books");
}
if (bookByGenre.getId() != null) {
throw new RuntimeException("Genre has related books");
}
});
}
}
}
Is it correct or exist way to do it better?
The application is based on the following stack:
Quarkus 1.5.0
Extensions: vertx-web, reactive-pgclient
The complete codes is here.
I created a Router by #Observes Router.
#ApplicationScoped
public class RoutesObserver {
#Inject PostsHandlers handlers;
public void route(#Observes Router router) {
router.get("/posts").produces("application/json").handler(handlers::getAll);
router.post("/posts").consumes("application/json").handler(handlers::save);
router.get("/posts/:id").produces("application/json").handler(handlers::get);
router.put("/posts/:id").consumes("application/json").handler(handlers::update);
router.delete("/posts/:id").handler(handlers::delete);
router.get("/hello").handler(rc -> rc.response().end("Hello from my route"));
}
}
And extracted the handlers into a standalone bean.
#ApplicationScoped
class PostsHandlers {
private static final Logger LOGGER = Logger.getLogger(PostsHandlers.class.getSimpleName());
PostRepository posts;
ObjectMapper objectMapper;
#Inject
public PostsHandlers(PostRepository posts, ObjectMapper objectMapper) {
this.posts = posts;
this.objectMapper = objectMapper;
}
public void getAll(RoutingContext rc) {
this.posts.findAll().thenAccept(
data -> rc.response()
.write(toJson(data))
.end()
);
}
//... other methods.
}
And the PostRepository used the Java 8 CompletionStage API.
#ApplicationScoped
public class PostRepository {
private static final Logger LOGGER = LoggerFactory.getLogger(PostRepository.class);
private final PgPool client;
#Inject
public PostRepository(PgPool _client) {
this.client = _client;
}
public CompletionStage<List<Post>> findAll() {
return client.query("SELECT * FROM posts ORDER BY id ASC")
.execute()
.thenApply(rs -> StreamSupport.stream(rs.spliterator(), false)
.map(this::from)
.collect(Collectors.toList())
);
}
And when I ran this application and tried to access the /posts. It is frozen and no response printed.
When using the write method, you need to set (beforehand) the content-length header.
There are a several approaches to handle this:
You can use .end(toJson(data)) instead of write(...).end() - it will computed the length automatically
You can use .putHeader("transfer-encoding", "chunked") and you write(...).end() - if you plan to retrieve multiple results, it's interesting as it writes each chunk to the client one by one, avoiding sending a large payload in one go
you can set the content-length as in:
String result = toJson(data);
rc.response()
.putHeader("content-length", Long.toString(result.length()))
.write(result)
.end();
How can we create a multi-tenant application in spring webflux using Mongodb-reactive repository?
I cannot find any complete resources on the web for reactive applications. all the resources available are for non-reactive applications.
UPDATE:
In a non-reactive application, we used to store contextual data in ThreadLocal but this cannot be done with reactive applications as there is thread switching. There is a way to store contextual info in reactor Context inside a WebFilter, But I don't how get hold of that data in ReactiveMongoDatabaseFactory class.
Thanks.
I was able to Implement Multi-Tenancy in Spring Reactive application using mangodb. Main classes responsible for realizing were: Custom MongoDbFactory class, WebFilter class (instead of Servlet Filter) for capturing tenant info and a ThreadLocal class for storing tenant info. Flow is very simple:
Capture Tenant related info from the request in WebFilter and set it in ThreadLocal. Here I am sending Tenant info using header: X-Tenant
Implement Custom MondoDbFactory class and override getMongoDatabase() method to return database based on current tenant available in ThreadLocal class.
Source code is:
CurrentTenantHolder.java
package com.jazasoft.demo;
public class CurrentTenantHolder {
private static final ThreadLocal<String> currentTenant = new InheritableThreadLocal<>();
public static String get() {
return currentTenant.get();
}
public static void set(String tenant) {
currentTenant.set(tenant);
}
public static String remove() {
synchronized (currentTenant) {
String tenant = currentTenant.get();
currentTenant.remove();
return tenant;
}
}
}
TenantContextWebFilter.java
package com.example.demo;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.stereotype.Component;
import org.springframework.web.server.ServerWebExchange;
import org.springframework.web.server.WebFilter;
import org.springframework.web.server.WebFilterChain;
import reactor.core.publisher.Mono;
#Component
public class TenantContextWebFilter implements WebFilter {
public static final String TENANT_HTTP_HEADER = "X-Tenant";
#Override
public Mono<Void> filter(ServerWebExchange exchange, WebFilterChain chain) {
ServerHttpRequest request = exchange.getRequest();
if (request.getHeaders().containsKey(TENANT_HTTP_HEADER)) {
String tenant = request.getHeaders().getFirst(TENANT_HTTP_HEADER);
CurrentTenantHolder.set(tenant);
}
return chain.filter(exchange).doOnSuccessOrError((Void v, Throwable throwable) -> CurrentTenantHolder.remove());
}
}
MultiTenantMongoDbFactory.java
package com.example.demo;
import com.mongodb.reactivestreams.client.MongoClient;
import com.mongodb.reactivestreams.client.MongoDatabase;
import org.springframework.dao.DataAccessException;
import org.springframework.data.mongodb.core.SimpleReactiveMongoDatabaseFactory;
public class MultiTenantMongoDbFactory extends SimpleReactiveMongoDatabaseFactory {
private final String defaultDatabase;
public MultiTenantMongoDbFactory(MongoClient mongoClient, String databaseName) {
super(mongoClient, databaseName);
this.defaultDatabase = databaseName;
}
#Override
public MongoDatabase getMongoDatabase() throws DataAccessException {
final String tlName = CurrentTenantHolder.get();
final String dbToUse = (tlName != null ? tlName : this.defaultDatabase);
return super.getMongoDatabase(dbToUse);
}
}
MongoDbConfig.java
package com.example.demo;
import com.mongodb.reactivestreams.client.MongoClient;
import com.mongodb.reactivestreams.client.MongoClients;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.mongodb.core.ReactiveMongoClientFactoryBean;
import org.springframework.data.mongodb.core.ReactiveMongoTemplate;
#Configuration
public class MongoDbConfig {
#Bean
public ReactiveMongoTemplate reactiveMongoTemplate(MultiTenantMongoDbFactory multiTenantMongoDbFactory) {
return new ReactiveMongoTemplate(multiTenantMongoDbFactory);
}
#Bean
public MultiTenantMongoDbFactory multiTenantMangoDbFactory(MongoClient mongoClient) {
return new MultiTenantMongoDbFactory(mongoClient, "test1");
}
#Bean
public ReactiveMongoClientFactoryBean mongoClient() {
ReactiveMongoClientFactoryBean clientFactory = new ReactiveMongoClientFactoryBean();
clientFactory.setHost("localhost");
return clientFactory;
}
}
UPDATE:
In reactive-stream we cannot store contextual information in ThreadLocal any more as the request is not tied to a single thread, So, This is not the correct solution.
However, Contextual information can be stored reactor Context in WebFilter like this. chain.filter(exchange).subscriberContext(context -> context.put("tenant", tenant));. Problem is how do get hold of this contextual info in ReactiveMongoDatabaseFactory implementation class.
Here is my very rough working solution for Spring WebFlux - they have since updated the ReactiveMongoDatabaseFactory - getMongoDatabase to return a Mono
Create web filter
public class TenantContextFilter implements WebFilter {
private static final Logger LOGGER = LoggerFactory.getLogger(TenantContextFilter.class);
#Override
public Mono<Void> filter(ServerWebExchange swe, WebFilterChain wfc) {
ServerHttpRequest request = swe.getRequest();
HttpHeaders headers = request.getHeaders();
if(headers.getFirst("X-TENANT-ID") == null){
LOGGER.info(String.format("Missing X-TENANT-ID header"));
throw new ResponseStatusException(HttpStatus.UNAUTHORIZED);
}
String tenantId = headers.getFirst("X-TENANT-ID");
LOGGER.info(String.format("Processing request with tenant identifier [%s]", tenantId));
return wfc.filter(swe)
.contextWrite(TenantContextHolder.setTenantId(tenantId));
}
}
Create class to get context (credit to somewhere I found this)
public class TenantContextHolder {
public static final String TENANT_ID = TenantContextHolder.class.getName() + ".TENANT_ID";
public static Context setTenantId(String id) {
return Context.of(TENANT_ID, Mono.just(id));
}
public static Mono<String> getTenantId() {
return Mono.deferContextual(contextView -> {
if (contextView.hasKey(TENANT_ID)) {
return contextView.get(TENANT_ID);
}
return Mono.empty();
}
);
}
public static Function<Context, Context> clearContext() {
return (context) -> context.delete(TENANT_ID);
}
}
My spring security setup (all requests allowed for testing)
#EnableWebFluxSecurity
#EnableReactiveMethodSecurity
public class SecurityConfig {
#Bean
public SecurityWebFilterChain WebFilterChain(ServerHttpSecurity http) {
return http
.formLogin(it -> it.disable())
.cors(it -> it.disable()) //fix this
.httpBasic(it -> it.disable())
.csrf(it -> it.disable())
.securityContextRepository(NoOpServerSecurityContextRepository.getInstance())
.authorizeExchange(it -> it.anyExchange().permitAll()) //allow anonymous
.addFilterAt(new TenantContextFilter(), SecurityWebFiltersOrder.HTTP_BASIC)
.build();
}
}
Create Tenant Mongo DB Factory
I still have some clean-up work for defaults etc...
public class MultiTenantMongoDBFactory extends SimpleReactiveMongoDatabaseFactory {
private static final Logger LOGGER = LoggerFactory.getLogger(MultiTenantMongoDBFactory.class);
private final String defaultDb;
public MultiTenantMongoDBFactory(MongoClient mongoClient, String databaseName) {
super(mongoClient, databaseName);
this.defaultDb = databaseName;
}
#Override
public Mono<MongoDatabase> getMongoDatabase() throws DataAccessException {
return TenantContextHolder.getTenantId()
.map(id -> {
LOGGER.info(String.format("Database trying to retrieved is [%s]", id));
return super.getMongoDatabase(id);
})
.flatMap(db -> {
return db;
})
.log();
}
}
Configuration Class
#Configuration
#EnableReactiveMongoAuditing
#EnableReactiveMongoRepositories(basePackages = {"com.order.repository"})
class MongoDbConfiguration {
#Bean
public ReactiveMongoDatabaseFactory reactiveMongoDatabaseFactory() {
return new MultiTenantMongoDBFactory(MongoClients.create("mongodb://user:password#localhost:27017"), "tenant_catalog");
}
#Bean
public ReactiveMongoTemplate reactiveMongoTemplate() {
ReactiveMongoTemplate template = new ReactiveMongoTemplate(reactiveMongoDatabaseFactory());
template.setWriteResultChecking(WriteResultChecking.EXCEPTION);
return template;
}
}
Entity Class
#Document(collection = "order")
//getters
//setters
Testing
Create two mongo db's with same collection, put different documents in both
In Postman I just did a get request with the "X-TENANT-ID" header and database name as the value (e.g. tenant-12343 or tenant-34383) and good to go!
Does anyone know how we can inject context into User Manager > MongoDB serStore at runtime in .net core 2.0.
We cannot do this at startup due to the context being dynamic but the UserStore is not accessible and UserManager has too many variables to new up, and it is wrong. Are there any solutions?
public class UserStore<TUser> :
IUserPasswordStore<TUser>,
IUserRoleStore<TUser>,
IUserLoginStore<TUser>,
IUserSecurityStampStore<TUser>,
IUserEmailStore<TUser>,
IUserClaimStore<TUser>,
IUserPhoneNumberStore<TUser>,
IUserTwoFactorStore<TUser>,
IUserLockoutStore<TUser>,
IQueryableUserStore<TUser>,
IUserAuthenticationTokenStore<TUser>
where TUser : IdentityUser
{
private readonly IMongoCollection<TUser> _Users;
//THIS IS WHERE WE WANT TO INJECT THE users AT RUNTIME
public UserStore(IMongoCollection<TUser> users)
{
_Users = users;
}
public virtual void Dispose()
{
// no need to dispose of anything, mongodb handles connection pooling automatically
}
public virtual async Task<IdentityResult> CreateAsync(TUser user, CancellationToken token)
{
await _Users.InsertOneAsync(user, cancellationToken: token);
return IdentityResult.Success;
}
unfortunately users is null at startup, and should be as the tenant has not been created at that point.
We have also been using the saaskit.Multitenancy and just can't find a solution.
Any help would be much appreciated.
Thanks
i think u need a generic repository to act as a wrapper for IMongoCollection then inject the repository inside controllers
public class Repository<T>
{
public IMongoCollection<T> Collection { get; private set; }
public Repository(IDbFactory dbFactory)
{
MongoClient client = new MongoClient("ur connection string");
this.Collection = client.GetDatabase("db").GetCollection<T>(typeof(T).Name);
}
public T Find(Expression<Func<T, bool>> filter)
{
return this.Collection.AsQueryable<T>().FirstOrDefault<T>(filter);
}
public async Task<T> FindAsync(Expression<Func<T, bool>> filter)
{
return await this.Collection.AsQueryable<T>().FirstOrDefaultAsync<T>(filter);
}
// here add more methods
}
then register the dependency as below inside Startup.cs
public void ConfigureServices(IServiceCollection services)
{
services.AddTransient(typeof(IRepository<>), typeof(Repository<>));
services.AddMvc();
}
finally inside controllers u inject the generic repository, also dont forget to Implement the IDisopsible in genereic repository
public class ProductController : Controller
{
private readonly IRepository<Product> _productRepository = null;
public ProductController(IRepository<Product> productRepository)
{
this._productRepository = productRepository;
}
}
HI i just want to know whether the XDCR replication is possible with spring data Couchbase. If possible how can i achieve that .please help .
My Code Sample
//configuration class
#Configuration
public class ApplicationConfig {
#Bean
public CouchbaseClient couchbaseClient() throws IOException {
return new CouchbaseClient(Arrays.asList(URI
.create("http://localhost:8091/pools")), "xxxw", "");
}
#Bean
public CouchbaseTemplate couchbaseTemplate() throws IOException {
return new CouchbaseTemplate(couchbaseClient());
}
}
#Document
public class Person {
#Field
String name;
#Id
String id;
public Person(final String personId, final String personname,
final int personIdAge, final JSONObject personData) {
this.id = personId;
this.name = personname;
this.age = personIdAge;
this.body = personData;
}
}
//main Test class
public class Test {
public static void main(String s[]) {
try {
ApplicationContext context = new AnnotationConfigApplicationContext(
ApplicationConfig.class);
CouchbaseTemplate template = context.getBean("couchbaseTemplate",
CouchbaseTemplate.class);
} catch (Exception e) {
e.printStackTrace();
}
}
How can i achieve repltcaion to elastic search index through spring data couchbase . with this sample classes ..??
Using elastic search in Couchbase is not dependent on what you client application looks like or whether or not it uses Spring. As long as you are storing data in Couchbase in JSON format things should work fine.
Setting up elastic search is more of an operations task than a development task. Take a look at the instructions at the link below and then run you application code as is. If you have configured everything properly then your data should end up in elastic search.
http://docs.couchbase.com/couchbase-elastic-search/