As illustrated above, I need to build a Vert.x Java app that will be an HTTP server/virtual host (TLS Http traffic, Web socket traffic) that will redirect/channel specific domain traffic to other Vert.x Java apps running on the same server, each in it's own JVM.
I have been reading for days but I remain uncertain as to how to approach all aspects of the task.
What I DO know or have experience with:
Creating an HTTP server, etc
Using a Vert.x VirtualHost handler to "handle" incoming traffic for a
specific domain
What I DO NOT know:
How do I "re-direct" a domain's traffic to another Vert.x app (this
other Vert.x app would also be running on the same server, in its own
JVM).
- Naturally this "other" Vert.x app would need to respond to HTTP
requests, etc. What Vert.x mechanisms do I employ to accomplish this
aspect of the task?
Are any of the following concepts part of the solution? I'm unfamiliar with these concepts and how they may or may not form part of the solution.:
Running each Vert.x app using -cluster option?
Vert.x Streams?
Vert.x Pumps?
There are multiple ways to let your microservices communicate with each other, the fact that all your apps are running on the same server doesn't change much, but it makes number 2.) easy to configure
1.) Rest based client - server communication
Both host and apps have a webserver
When you handle the incoming requests on the host, you simply call another app with a HttpClient
Typically all services find each others address via service discovery.
Eg: each service registers his address in a central registry then other services use this central registry to find the addresses.
Note: this maybe an overkill for you and you can just configure the addresses of the other services.
2.) You start the vertx microservices in clustered mode
the eventbus is then shared among the services
For all incoming requests you send a broadcast on the eventbus
the responsible app replies to the message
For further reading you can checkout https://vertx.io/docs/vertx-hazelcast/java/#configcluster. You start your projects with -cluster option and define the clustering in an xml configuration. I think by default it finds the services via local broadcast.
3.) You use a message broker like RabbitMq etc.
All your apps connect to a central message broker
When a new request comes in to the host, it sends a message to the message broker
The responible app then listens to the relevant messages and replies
The host receives the reply from the message broker
There are already many existing vertx clients for certain message brokers like kafka, camel, zeromq:
https://github.com/vert-x3/vertx-awesome#integration
I'm testing a consul server cluster. I am using the go client for this.
How do I enter multiple servers for the client to connect to?
Optimally it would be something like:
client, err := api.NewClient(api.DefaultConfig())
client.remotes = host_array
Is this a wrong-headed approach to using consul and the expected way for a user is to start a client node and then read the locally replicated state?
The Consul API client defaults to 127.0.0.1:8500 because there is an expectation that it will connect to a local Consul Agent running in client mode. The Consul Agent should be your "proxy" to the Consul Servers and maintain the connections with active servers so you don't have to.
https://www.consul.io/docs/internals/architecture.html
https://github.com/hashicorp/consul/issues/3689
An alternate approach could be to utilize a load balancer for a cluster of Consul Servers. Strategies for that are documented here... https://www.hashicorp.com/blog/load-balancing-strategies-for-consul
I've set up a Node-Red instance on IBM Cloud with a Socket.IO server using node-red-contrib-socketio.
I was able to subscribe to events on port 3000 on my local host fine but I'm having difficulty doing the same with the Node-Red instance on IBM Cloud.
According to my client console I seem to be able to connect but get no response using the following URL: ws://MYAPP.eu-gb.mybluemix.net/red:3000/socket.io/?EIO=3&transport=websocket Is this correct or should I be using something else like ws://MYAPP.eu-gb.mybluemix.net:3000/socket.io/?EIO=3&transport=websocket ?
Is any further configuration required in IBM Cloud to enable the connection?
If I need to authenticate within the URL I pass to the server is there a particular way that string should be structured?
Many thanks,
This will not work on Bluemix.
The Bluemix router only forwards external traffic on ports 80 and 443 (http/https) to apps.
But the app may not be actually listening on those ports (The port to listen on is passed in to the application on start up in a environment variable).
You can not just pick an arbitrary ports and listen on.
To get Kafka running, you need to set some properties in config/server.properties file. There are two settings I don't understand.
Can somebody explain the difference between listeners and advertised.listeners property?
The documentation says:
listeners: The address the socket server listens on.
and
advertised.listeners:
Hostname and port the broker will advertise to producers and consumers.
When do I have to use which setting?
listeners is what the broker will use to create server sockets.
advertised.listeners is what clients will use to connect to the brokers.
The two settings can be different if you have a "complex" network setup (with things like public and private subnets and routing in between).
Since I cannot comment yet I will post this as an "answer", adding on to M.Situations answer.
Within the same document he links there is this blurb about which listener is used by a KAFKA client (https://cwiki.apache.org/confluence/display/KAFKA/KIP-103%3A+Separation+of+Internal+and+External+traffic):
As stated previously, clients never see listener names and will make metadata requests exactly as before. The difference is that the list of endpoints they get back is restricted to the listener name of the endpoint where they made the request.
This is important as depending on what URL you use in your bootstrap.servers config that will be the URL* that the client will get back if it is mapped in advertised.listeners (do not know what the behavior is if the listener does not exist).
Also note this:
The exception is ZooKeeper-based consumers. These consumers retrieve the broker registration information directly from ZooKeeper and will choose the first listener with PLAINTEXT as the security protocol (the only security protocol they support).
As an example broker config (for all brokers in cluster):
advertised.listeners=EXTERNAL://XXXXX.compute-1.amazonaws.com:9990,INTERNAL://ip-XXXXX.ec2.internal:9993
inter.broker.listener.name=INTERNAL
listener.security.protocol.map=EXTERNAL:SSL,INTERNAL:PLAINTEXT
If the client uses XXXXX.compute-1.amazonaws.com:9990 to connect, the metadata fetch will go to that broker. However, the returning URL to use with the Group Coordinator or Leader could be 123.compute-1.amazonaws.com:9990* (a different machine!). This means that the match is done on the listener name as advertised by KIP-103 irrespective of the actual URL (node).
Since the protocol map for EXTERNAL is SSL this would force you to use an SSL keystore to connect.
If on the other hand you are within AWS lets say, you can then issue ip-XXXXX.ec2.internal:9993 and the corresponding connection would be plaintext as per the protocol map.
This is especially needed in IaaS where in my case brokers and consumers live on AWS, whereas my producer lives on a client site, thus needing different security protocols and listeners.
EDIT:
Also adding Inbound Rules is much easier now that you have different ports for different clients (brokers, producers, consumers).
EDIT2:
This article is a great in depth guide if the above is still not clear: https://rmoff.net/2018/08/02/kafka-listeners-explained/
There's so much confusion or little information in answers provided here for the question. So posting my elaborate answer for clarity.
listeners - Used by the embedded jetty web server in kafka to bind to. This jetty web server is used to provide REST API that provides the control plane for Kafka Connect workers. The hostname in this setting can be left empty if you want kafka to bind to localhost (it does by calling InetAddress.getLocalHost().getCanonicalHostName() java api)
advertised.listeners: This address is published to zookeeper by every kafka broker. If this setting is not set, then value of listeners will be used here and published to zookeeper. That's the only purpose of this setting for notifying others. Kafka Clients use the 'advertised.listeners' setting published to zookeeper (as /brokers/ids/<id>/ # endpoints) to talk to Kafka broker.
Now the question is why to have two setting? Why not a single setting? Let's say your kafka broker is sitting behind a proxy. And all the kafka clients have to talk to the proxy to reach the broker. In this case, we want kafka's embedded jetty server to bind to localhost and local port, but we can't publish this to zookeeper as clients can't use it. So kafka admin can set the setting advertised.listeners to the proxy host and port.
Also, in some of our production hosts, InetAddress.getLocalHost().getCanonicalHostName() returns empty and so listeners setting's hostname was empty which was fine for jetty to bind. But advertised.listeners was published to zookeeper as NULL:9092 since it took the same value as listeners by default. Now all the brokers tried to publish in this way to zookeeper and so brokers got the error java.lang.IllegalArgumentException: requirement failed: Configured end points null:14092 as advertised.listeners as NULL:9092 is already registered by broker 101. The fix was to change the advertised.listeners setting to have hostname in it.
Listeners are all the addresses the Kafka broker listens on (it can be more than 1 address) whereas advertised listeners are the addresses other agents (producers, consumers, or brokers) need to connect to if they want to talk to the current broker.
The 2 lists should be the same if all are running on the same machine (can connect using localhost:9092 or 127.0.0.1:9092) but if consumers, producers, or other brokers do not stay on the same machine or Docker instance, they must use different addresses (that's why we have advertised listeners). Two examples:
Saying we use Docker to run 2 Kafka instances named kafka and kafka2. kafka2 for sure cannot connect to kafka using localhost:29092. It must use kafka:9092 instead. So for kafka, listener = localhost:29092, advertised listener = kafka:9092
Producer from host machine cannot connect to kafka using kafka:9092. It must use localhost:29092 instead.
Let use the following docker-compose config to understand more about the startup process of a Kafka broker:
# config/docker-compose.yml
kafka:
image: docker.io/bitnami/kafka:3
ports:
- "29092:29092"
- "9092:9092"
environment:
- KAFKA_CFG_ZOOKEEPER_CONNECT=zookeeper:2181
- ALLOW_PLAINTEXT_LISTENER=yes
- KAFKA_CFG_LISTENER_SECURITY_PROTOCOL_MAP=CLIENT:PLAINTEXT,EXTERNAL:PLAINTEXT
- KAFKA_CFG_LISTENERS=CLIENT://:9092,EXTERNAL://:29092
- KAFKA_CFG_ADVERTISED_LISTENERS=CLIENT://kafka:9092,EXTERNAL://localhost:29092
- KAFKA_CFG_INTER_BROKER_LISTENER_NAME=CLIENT
depends_on:
- zookeeper
With this config, Docker will start 1 Kafka broker instance which listens on 2 ports:
9092 with name CLIENT
29092 with name EXTERNAL
The broker then connects to Zookeeper at zookeeper:2181 and registers its 2 addresses: kafka:9092 and localhost:29092. Also, with KAFKA_CFG_INTER_BROKER_LISTENER_NAME=CLIENT, it wants Zookeeper to tell other brokers to connect to kafka:9092 if want to talk to it.
But why need 2 ports? Read more here
References:
My notes while learning Kafka
Kafka Listeners – Explained
From this link: https://cwiki.apache.org/confluence/display/KAFKA/KIP-103%3A+Separation+of+Internal+and+External+traffic
During the 0.9.0.0 release cycle, support for multiple listeners per
broker was introduced. Each listener is associated with a security
protocol, ip/host and port. When combined with the advertised
listeners mechanism, there is a fair amount of flexibility with one
limitation: at most one listener per security protocol in each of the
two configs (listeners and advertised.listeners).
In some environments, one may want to differentiate between external
clients, internal clients and replication traffic independently of the
security protocol for cost, performance and security reasons. A few
examples that illustrate this:
Replication traffic is assigned to a separate network interface so that it does not interfere with client traffic.
External traffic goes through a proxy/load-balancer (security, flexibility) while internal traffic hits the brokers directly
(performance, cost).
Different security settings for external versus internal traffic even though the security protocol is the same (e.g. different set of
enabled SASL mechanisms, authentication servers, different keystores,
etc.)
As such, we propose that Kafka brokers should be able to define
multiple listeners for the same security protocol for binding (i.e.
listeners) and sharing (i.e. advertised.listeners) so that internal,
external and replication traffic can be separated if required.
So,
listeners - Comma-separated list of URIs we will listen on and their protocols.
Specify hostname as 0.0.0.0 to bind to all interfaces.
Leave hostname empty to bind to default interface.
Examples of legal listener lists:
PLAINTEXT://myhost:9092,TRACE://:9091
PLAINTEXT://0.0.0.0:9092, TRACE://localhost:9093
advertised.listeners - Listeners to publish to ZooKeeper for clients to use, if different than the listeners above.
In IaaS environments, this may need to be different from the interface to which the broker binds. If this is not set, the value for listeners will be used.
In elastic search i created multi-node setup.I use Java Api transport Client to communicate to Elasticsearch server.
Now i created transport client with only one IP[assume:192.129.129.12.9300]. If i request any query in single ip it communicates all nodes and returns results. What happen if it my node[192.129.129.12.9300] that i mentioned in transport Client fails. Can i communicate with other nodes. What is the optimum way configuration to use transport Client for multi node set up.
You need to activate sniff option.
See http://www.elasticsearch.org/guide/en/elasticsearch/client/java-api/current/client.html#transport-client