Develop Reference

How to connect Apache Ignite Thin Client to Apache Ignite Cluster?

I have a running Ignite cluster and I use AWS S3 for node discovery:
TcpDiscoveryS3IpFinder ipFinder = new TcpDiscoveryS3IpFinder();
BasicAWSCredentials awsCredentials =
new BasicAWSCredentials(igniteAccessKey, igniteSecretAccessKey);
ipFinder.setAwsCredentials(awsCredentials);
ipFinder.setBucketName(igniteBucketName);
ipFinder.setBucketEndpoint("s3.eu-central-1.amazonaws.com");
TcpDiscoverySpi spi = new TcpDiscoverySpi();
spi.setIpFinder(ipFinder);
IgniteConfiguration cfg = new IgniteConfiguration();
cfg.setClientMode(true);
cfg.setDiscoverySpi(spi);
Ignition.start(cfg);
It works very well and I can connect to this cluster using Apache Ignite Client nodes.
But what about Apache Ignite Thin Client? Thin client uses ClientConfiguration class (instead of IgniteConfiguration) that requires a list of IP addresses of cluster nodes. AFAIK one can only hardcode that list of IP addresses. From official documentation:
ClientConfiguration cfg = new ClientConfiguration().setAddresses("127.0.0.1:10800");
try (IgniteClient client = Ignition.startClient(cfg)) {
ClientCache<Integer, String> cache = client.cache("myCache");
// Get data from the cache
}
So I have questions:
How should I handle situations when a list of IP addresses change?
Is there any way to use node discovery for Thin clients?

You can use domain names as well as IP addresses. But you can't use node discovery with thin clients.

server failover with Quarkus Reactive MySQL Clients / io.vertx.mysqlclient

Does io.vertx.mysqlclient support server failover as it can be set up with MySQL Connector/J?
My application is based on quarkus using io.vertx.mutiny.mysqlclient.MySQLPool which in turn is based on io.vertx.mysqlclient. If there is support for server failover in that stack, how can it be set up? I did not find any hints in the documentation and code.

No it doesn't support failover.
You could create two clients and then use Munity failover methods to get the same effect:
MySQLPool client1 = ...
MySQLPool client2 = ...
private Uni<List<Data>> query(MySQLPool client) {
// Use client param to send queries to the database
}
Uni<List<Data>> results = query(client1)
.onFailure().recoverWithUni(() -> query(client2));

How to set Eureka URL from code at client application startup

We need to set Eureka server URL at client application from startup code, but it seems there is no way how to do it.
We have a mechanism how to discover Eureka server on network by UDP multicast broadcasting. Server sends response back to the client with information about IP address and port where Eureka server is running. But we don't know how to set this URL in Eureka client application from code. It seems the only way how to set Eureka server URL is the property eureka.client.serviceUrl.defaultZone in application.property file.
// Server - start a new thread with UDP packet detection and reply mechanism
LocationService.listenAndReplyToEurekaClients(thisServerPort);
// Server - application start
SpringApplication.run(EurekaServerApplication.class, args);
// Client - send UDP packet and receive reply with Eureka server IP and port
Response response = LocationService.findEurekaServerAddress(5, 3, TimeUnit.SECONDS);
var hostProtocol = "http";
var eurekaUrl = new URL(
hostProtocol,
response.getEurekaAddress(),
response.getEurekaPort(),"").toString();
We would like to set this eurekaURL to the client before it starts registering to Eureka server.

In this case, we can do following things-
Extend EurekaClientConfigBean and override getEurekaServerServiceUrls method. Method returns a List of String which is nothing but list of all the URLS, of eureka instances. You need to set the URL here from your response which has IP and port.
Later create the discovery client using- DiscoveryClient(ApplicationInfoManager applicationInfoManager, EurekaClientConfig config). (Its going to be a Bean for sure).
That should work.
You can create ApplicationInfoManager as-
ApplicationInfoManager applicationInfoManager =
initializeApplicationInfoManager(webAppInstanceConfig);
Where WebAppInstanceConfig is-
class WebAppInstanceConfig extends MyDataCenterInstanceConfig {// Override all the needed properties from MyDataCenterInstanceConfig}

Asynchronous Thrift Java Client over UNIX Domain Socket

I have an application consisting of a Java Thrift Asynchronous client communicating with a Python/Twisted Thrift Asynchronous server over TCP using the loopback interface (localhost).
I want to use a UNIX domain socket instead of a TCP socket for increased throughput, but I cannot find a suitable Asynchronous (Non-blocking) UNIX Domain Socket implementation for Java to use with Thrift.
I had this Python/Twisted TCP Thrift server:
handler = ThriftServiceHandler(am)
processor = ThriftServiceHandler.Processor(handler)
pfactory = TBinaryProtocol.TBinaryProtocolFactory()
reactor.listenTCP(PORT, TTwisted.ThriftServerFactory(processor, pfactory), interface="127.0.0.1")
And I managed to create an Asynchronous UNIX Domain Socket Thrift server with:
handler = ThriftServiceHandler(am)
processor = ThriftServiceHandler.Processor(handler)
pfactory = TBinaryProtocol.TBinaryProtocolFactory()
reactor.listenUNIX("thrift.sock", TTwisted.ThriftServerFactory(processor, pfactory))
Currently I have this Java client:
clientManager = new TAsyncClientManager();
factory = new TBinaryProtocol.Factory();
socket = new TNonblockingSocket("127.0.0.1", thriftConstants.PORT);
client = new ThriftService.AsyncClient(this.factory, this.clientManager, this.socket);
But I am missing how to do the Java Client implementation. I looked at using https://github.com/jnr/jnr-unixsocket and https://github.com/kohlschutter/junixsocket, but I couldn't get them to work with Thrift's Java AsyncClient. Any help would be appreciated.
I am using the latest version of Thrift (0.9.2).

Multi-threaded connection manager with Jersey Apache Client 4

I have a Jersey client up and running, using the Apache Client 4 library, like this:
private Client createClient() {
ApacheHttpClient4Config cc = new DefaultApacheHttpClient4Config();
// boring stuff here
return ApacheHttpClient4.create(cc);
}
But this by default uses a BasicClientConnManager, which doesn't allow multi-threaded connections.
The ApacheHttpClient4Config Javadoc says that I need to set the PROPERTY_CONNECTION_MANAGER to a ThreadSafeClientConnManager instance if I want multi-threaded operation. I can do this, and it works OK:
private Client createClient() {
ApacheHttpClient4Config cc = new DefaultApacheHttpClient4Config();
cc.getProperties().put(ApacheHttpClient4Config.PROPERTY_CONNECTION_MANAGER,
new ThreadSafeClientConnManager());
// boring stuff here
return ApacheHttpClient4.create(cc);
}
But ThreadSafeClientConnManager is deprecated. This is annoying.
The more modern version is PoolingHttpClientConnectionManager. Unfortunately, though, the ApacheHttpClient4.create() method requires the connection manager to be an implementation of ClientConnectionManager (itself deprecated), and PoolingHttpClientConnectionManager doesn't implement that interface. So if I try to use it, my connection manager gets ignored and we're back to a BasicClientConnManager.
How can I end up with a thread-safe client without using anything that's deprecated?

You can create the client as follows (see https://github.com/phillbarber/connection-leak-test/blob/master/src/test/java/com/github/phillbarber/connectionleak/IntegrationTestThatExaminesConnectionPoolBeforeAndAfterRun.java#L30-L33):
client = new ApacheHttpClient4(new ApacheHttpClient4Handler(HttpClients.custom()
.setConnectionManager(new PoolingHttpClientConnectionManager())
.build(), null, false));