This example shows several examples of Load Balancer EIP with Apache Camel application using Spring Boot.
You can run this example using
mvn spring-boot:run
The example contains a rest endpoint to trigger various loadbalancers.
You can send 10 messages to the endpoint with:
for i in {1..10}; do curl -X POST -H "Content-Type: text/plain" -d "$i" http://localhost:8080/loadbalancer/round-robin/; done
In the application logs you will see, that the messages are distributed evenly between two defined endpoint routes:
RoundRobin: Route 1 received message 1 RoundRobin: Route 2 received message 2 RoundRobin: Route 1 received message 3 RoundRobin: Route 2 received message 4 RoundRobin: Route 1 received message 5 RoundRobin: Route 2 received message 6 RoundRobin: Route 1 received message 7 RoundRobin: Route 2 received message 8 RoundRobin: Route 1 received message 9 RoundRobin: Route 2 received message 10
A random endpoint is selected for each exchange.
You can send 10 messages to the endpoint with:
for i in {1..10}; do curl -X POST -H "Content-Type: text/plain" -d "$i" http://localhost:8080/loadbalancer/random/; done
The messages are loadbalanced randomly across two endpoints:
Random: Route 1 received message 1 Random: Route 1 received message 2 Random: Route 2 received message 3 Random: Route 1 received message 4 Random: Route 1 received message 5 Random: Route 1 received message 6 Random: Route 2 received message 7 Random: Route 1 received message 8 Random: Route 1 received message 9 Random: Route 2 received message 10
Sticky load balancing is using an Expression to calculate a correlation key to perform the sticky load balancing; like jsessionid in the web or JMSXGroupID in JMS.
The header used in this example is called correlation-key, so sending the same value over multiple requests will cause the message to be routed to the same endpoint.
First send a header value abc
for i in {1..3}; do curl -X POST -H "Content-Type: text/plain" -H "correlation-key: abc" -d "Foo" http://localhost:8080/loadbalancer/sticky/; done
Sticky: Route 1 received message Foo Sticky: Route 1 received message Foo Sticky: Route 1 received message Foo
A different header value def will cause using a different route:
for i in {1..4}; do curl -X POST -H "Content-Type: text/plain" -H "correlation-key: def" -d "Bar" http://localhost:8080/loadbalancer/sticky/; done
Sticky: Route 2 received message Bar Sticky: Route 2 received message Bar Sticky: Route 2 received message Bar Sticky: Route 2 received message Bar
Changing the value back to abc will use the same route as previously:
for i in {1..2}; do curl -X POST -H "Content-Type: text/plain" -H "correlation-key: abc" -d "Baz" http://localhost:8080/loadbalancer/sticky/; done
Sticky: Route 1 received message Baz Sticky: Route 1 received message Baz
Sends the message to all destinations (like JMS Topics).
for i in {1..3}; do curl -X POST -H "Content-Type: text/plain" -d "$i" http://localhost:8080/loadbalancer/topic/; done
Topic: Route 1 received message 1 Topic: Route 2 received message 1 Topic: Route 1 received message 2 Topic: Route 2 received message 2 Topic: Route 1 received message 3 Topic: Route 2 received message 3
In case of failures the exchange will be tried on the next endpoint. In this example the first endpoint always throws an exception.
curl -X POST -H "Content-Type: text/plain" -d "Success" http://localhost:8080/loadbalancer/failover/
Failover: Endpoint 1 received message Success Failover: Endpoint 1 throws an exception to simulate processing error ... Failover: Endpoint 2 received message Success
The weighted load balancing policy allows you to specify a processing load distribution ratio for each server with respect to the others. In addition to the weight, endpoint selection is then further refined using round-robin distribution based on weight. This example defines the weight as 3,1 so when sending a total of 4 messages, 3 will go to the first endpoint and one will go to the second.
for i in {1..4}; do curl -X POST -H "Content-Type: text/plain" -d "$i" http://localhost:8080/loadbalancer/weighted/; done
Weighted: Route 1 received message 1 Weighted: Route 2 received message 2 Weighted: Route 1 received message 3 Weighted: Route 1 received message 4
If you hit any problem using Camel or have some feedback, then please let us know.
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The Camel riders!