MSA Spices

MSA Spices (MSA of MicroService Architecture) is a set of useful libraries that can help to automate some typical tasks when developing a microservice on Spring Boot.

Logging requests and responses

A common task is to log the content of requests and responses. Doesn't matter what is it exactly: REST controllers, database interaction methods, SOAP handlers etc. The case is similar: some parameters are incoming and some result is outgoing.

Library provides a simple way to implement logging: annotation @LogMethod. For Spring WebFlux use its sister ship annotation @LogReactiveMethod.

Reactive implementation has some limitations currently: it will not log Flux request parts, but it will do that for the responses. Currently, I recognize WebFlux implementation to be in an experimental feature, it is not tested well but seems to be working.

Configuration

You put it over some method, and it will log request params of the method and response of the method. By default, all the objects will be serialized with toString().

@LogMethod
@GetMapping("/hello/{user}")
public HelloResponse helloUser(@PathVariable String user) {
    return HelloResponse.builder()
            .name(user)
            .build();
}

The annotation has following configurable parameters:

Name	Type	Description
parameters	String[]	If empty all the params will be logged. Contains list of params that are suitable to log.
logResponse	boolean	By default, true. If false then response will not be logged. Instead it will be written <ignored>.

It can be useful to skip some params that are not suitable to log like HttpRequest or binary data. The same about response. Sometimes your answers are not applicable for logs because they can form kind of binary data etc.

This logger uses log level DEBUG. So logs will not be visible by default. If you want to activate it you can change the log level for a package of library. It is also possible to change log level dynamically while application is running with Spring Boot Actuator helper methods.

logging:
  level:
    com:
      igorivkin:
        msaspices:
          lib: DEBUG

A typical request and response will be looking like:

>>> Request 515060d3-7c4d-4749-a7de-52162615fa74, method helloUser
user="123"
<<< Response 515060d3-7c4d-4749-a7de-52162615fa74, method: helloUser
{"name":"123"}

Logger based on Slf4j so it can work with log4j2 or Logback by your choice. Just put your preferred dependency, and it should start to work with appropriate logging backend.

Rate limiting

Rate limiting is a way to restrict access to some resource in time. It allows to limit access to something, saying, with N requests per period of time. For example some kind of API allows to request it not more often than 5 times per second.

Library provides a class RateLimiter for such a purpose. It provides a simple API to use:

RateLimiter rateLimiter = RateLimiter.ofRate(5);
rateLimiter.acquire(1);
accessToSomeResourceThatShouldBeLimited();

In this example we will call accessToSomeResourceThatShouldBeLimited() not more often than 5 times per 1 second (by default it uses 1 second to restrict) but you can specify a second parameter to provide other time period in milliseconds.

For example:

RateLimiter rateLimiter = RateLimiter.ofRate(5, 2000L);

It means: 5 requests per 2 seconds.