how to log Spring 5 WebClient call

Question

I\'m trying to log a request using Spring 5 WebClient. Do you have any idea how could I achieve that?

(I\'m using Spring 5 and Spring boot 2)

The code looks

Answer 1

If you are looking to log the serialized version of the JSON in the request or response, you can create your own Json Encoder/Decoder classes that wrap the defaults and log the JSON. Specifically you would subclass the Jackson2JsonEncoder and Jackson2JsonDecoder classes and override the methods that expose the serial data.

This is explained here: https://andrew-flower.com/blog/webclient-body-logging

The approach shown above is focused mainly on non-streaming data. Doing it for streaming data might be more challenging.

It's obviously not recommended to do this in a Prod environment due to extra memory / processing required, but configuring it for development environments is useful.

Answer 2

@Matthew Buckett answer shows you how to get Netty wire logging. However, the format is not very fancy (it includes hex dump). But it can be easily customized via extending io.netty.handler.logging.LoggingHandler

public class HttpLoggingHandler extends LoggingHandler {

    @Override
    protected String format(ChannelHandlerContext ctx, String event, Object arg) {
        if (arg instanceof ByteBuf) {
            ByteBuf msg = (ByteBuf) arg;
            return msg.toString(StandardCharsets.UTF_8);
        }
        return super.format(ctx, event, arg);
    }
}

Then include it in your WebClient configuration:

HttpClient httpClient = HttpClient.create()
    .tcpConfiguration(tcpClient ->
        tcpClient.bootstrap(bootstrap ->
            BootstrapHandlers.updateLogSupport(bootstrap, new HttpLoggingHandler())));

WebClient
    .builder()
    .clientConnector(new ReactorClientHttpConnector(httpClient))
    .build()

Example:

webClient.post()
    .uri("https://postman-echo.com/post")
    .syncBody("{\"foo\" : \"bar\"}")
    .accept(MediaType.APPLICATION_JSON)
    .exchange()
    .block();

2019-09-22 18:09:21.477 DEBUG   --- [ctor-http-nio-4] c.e.w.c.e.logging.HttpLoggingHandler     : [id: 0x505be2bb] REGISTERED
2019-09-22 18:09:21.489 DEBUG   --- [ctor-http-nio-4] c.e.w.c.e.logging.HttpLoggingHandler     : [id: 0x505be2bb] CONNECT: postman-echo.com/35.170.134.160:443
2019-09-22 18:09:21.701 DEBUG   --- [ctor-http-nio-4] c.e.w.c.e.logging.HttpLoggingHandler     : [id: 0x505be2bb, L:/192.168.100.35:55356 - R:postman-echo.com/35.170.134.160:443] ACTIVE
2019-09-22 18:09:21.836 DEBUG   --- [ctor-http-nio-4] c.e.w.c.e.logging.HttpLoggingHandler     : [id: 0x505be2bb, L:/192.168.100.35:55356 - R:postman-echo.com/35.170.134.160:443] READ COMPLETE
2019-09-22 18:09:21.905 DEBUG   --- [ctor-http-nio-4] c.e.w.c.e.logging.HttpLoggingHandler     : [id: 0x505be2bb, L:/192.168.100.35:55356 - R:postman-echo.com/35.170.134.160:443] READ COMPLETE
2019-09-22 18:09:22.036 DEBUG   --- [ctor-http-nio-4] c.e.w.c.e.logging.HttpLoggingHandler     : [id: 0x505be2bb, L:/192.168.100.35:55356 - R:postman-echo.com/35.170.134.160:443] USER_EVENT: SslHandshakeCompletionEvent(SUCCESS)
2019-09-22 18:09:22.082 DEBUG   --- [ctor-http-nio-4] c.e.w.c.e.logging.HttpLoggingHandler     : POST /post HTTP/1.1
user-agent: ReactorNetty/0.8.11.RELEASE
host: postman-echo.com
Accept: application/json
Content-Type: text/plain;charset=UTF-8
content-length: 15

{"foo" : "bar"}
2019-09-22 18:09:22.083 DEBUG   --- [ctor-http-nio-4] c.e.w.c.e.logging.HttpLoggingHandler     : [id: 0x505be2bb, L:/192.168.100.35:55356 - R:postman-echo.com/35.170.134.160:443] FLUSH
2019-09-22 18:09:22.086 DEBUG   --- [ctor-http-nio-4] c.e.w.c.e.logging.HttpLoggingHandler     : [id: 0x505be2bb, L:/192.168.100.35:55356 - R:postman-echo.com/35.170.134.160:443] READ COMPLETE
2019-09-22 18:09:22.217 DEBUG   --- [ctor-http-nio-4] c.e.w.c.e.logging.HttpLoggingHandler     : HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8
Date: Sun, 22 Sep 2019 15:09:22 GMT
ETag: W/"151-Llbe8OYGC3GeZCxttuAH3BOYBKA"
Server: nginx
set-cookie: sails.sid=s%3APe39li6V8TL8FOJOzSINZRkQlZ7HFAYi.UkLZjfajJqkq9fUfF2Y8N4JOInHNW5t1XACu3fhQYSc; Path=/; HttpOnly
Vary: Accept-Encoding
Content-Length: 337
Connection: keep-alive

{"args":{},"data":"{\"foo\" : \"bar\"}","files":{},"form":{},"headers":{"x-forwarded-proto":"https","host":"postman-echo.com","content-length":"15","accept":"application/json","content-type":"text/plain;charset=UTF-8","user-agent":"ReactorNetty/0.8.11.RELEASE","x-forwarded-port":"443"},"json":null,"url":"https://postman-echo.com/post"}
2019-09-22 18:09:22.243 DEBUG   --- [ctor-http-nio-4] c.e.w.c.e.logging.HttpLoggingHandler     : [id: 0x505be2bb, L:/192.168.100.35:55356 - R:postman-echo.com/35.170.134.160:443] READ COMPLETE

If you want to suppress useless (for you) log entries like (note ACTIVE at the end):

2019-09-22 18:09:21.701 DEBUG   --- [ctor-http-nio-4] c.e.w.c.e.logging.HttpLoggingHandler     : [id: 0x505be2bb, L:/192.168.100.35:55356 - R:postman-echo.com/35.170.134.160:443] ACTIVE

You can override channelActive and others like so:

@Override
public void channelActive(ChannelHandlerContext ctx) {
    ctx.fireChannelActive();
}

The answer is based on https://www.baeldung.com/spring-log-webclient-calls

Answer 3

If you don't want to log the body, then this is really easy.

Spring Boot >= 2.1.0

Add the following to application.properties:

logging.level.org.springframework.web.reactive.function.client.ExchangeFunctions=TRACE
spring.http.log-request-details=true

The second line causes headers to be included in the log.

Spring Boot < 2.1.0

Add the following to application.properties:

logging.level.org.springframework.web.reactive.function.client.ExchangeFunctions=TRACE

Instead of the second line above, you need to declare a class like this:

@Configuration
static class LoggingCodecConfig {

    @Bean
    @Order(0)
    public CodecCustomizer loggingCodecCustomizer() {
        return (configurer) -> configurer.defaultCodecs()
                .enableLoggingRequestDetails(true);
    }

}

Courtesy of this Brian Clozel answer

Answer 4

You don't necessarily need to roll your own logger, reactor.ipc.netty.channel.ChannelOperationsHandler does it for you. Just configure your logging system for that class to log at DEBUG level:

2017-11-23 12:52:04.562 DEBUG 41449 --- [ctor-http-nio-5] r.i.n.channel.ChannelOperationsHandler   : [id: 0x9183d6da, L:/127.0.0.1:57681 - R:localhost/127.0.0.1:8000] Writing object DefaultFullHttpRequest(decodeResult: success, version: HTTP/1.1, content: UnpooledByteBufAllocator$InstrumentedUnpooledUnsafeHeapByteBuf(ridx: 0, widx: 0, cap: 0))
GET /api/v1/watch/namespaces/default/events HTTP/1.1
user-agent: ReactorNetty/0.7.1.RELEASE
host: localhost:8000
accept-encoding: gzip
Accept: application/json
content-length: 0

One way to have fewer bugs is to not write code whenever possible.

Nov 2018:

With spring-webflux:5.1.2.RELEASE, the above no longer works. Use the following instead:

logging.level.org.springframework.web.reactive.function.client.ExchangeFunctions=DEBUG
...
2018-11-06 20:58:58.181 DEBUG 20300 --- [           main] o.s.w.r.f.client.ExchangeFunctions       : [2026fbff] HTTP GET http://localhost:8080/stocks/search?symbol=AAPL
2018-11-06 20:58:58.451 DEBUG 20300 --- [ctor-http-nio-4] o.s.w.r.f.client.ExchangeFunctions       : [2026fbff] Response 400 BAD_REQUEST

To log headers or form body, set the above to TRACE level; however, that's not enough:

ExchangeStrategies exchangeStrategies = ExchangeStrategies.withDefaults();
exchangeStrategies
    .messageWriters().stream()
    .filter(LoggingCodecSupport.class::isInstance)
    .forEach(writer -> ((LoggingCodecSupport)writer).setEnableLoggingRequestDetails(true));

client = WebClient.builder()
    .exchangeStrategies(exchangeStrategies)

Mar 2019:

In response to a question in the comment that asked how to log request and response body, I don’t know if Spring has such a logger but WebClient is built on Netty, so enabling debug logging for package reactor.ipc.netty should work, along with this answer.

Answer 5

You can have netty do logging of the request/responses with by asking it todo wiretaping, if you create your Spring WebClient like this then it enables the wiretap option.

        WebClient webClient = WebClient.builder()
            .clientConnector(new ReactorClientHttpConnector(
                HttpClient.create().wiretap(true)
            ))
            .build()

and then have your logging setup:

logging.level.reactor.netty.http.client.HttpClient: DEBUG

this will log everything for the request/response (including bodies), but the format is not specific to HTTP so not very readable.

Answer 6

An update of Feb 2020 for Spring Boot 2.2.4 and Spring 5.2.3:

I did not manage to get spring.http.log-request-details=true doing its job, and current Spring WebFlux reference suggests that some coding needs be done to have headers logged, though the code example uses deprecated exchangeStrategies() method.

There is still a replacement for the deprecated method, so a compact piece of code for getting headers logged at WebClient level may look like this:

WebClient webClient = WebClient.builder()
    .codecs(configurer -> configurer.defaultCodecs().enableLoggingRequestDetails(true))
    .build();

with further

logging.level.org.springframework.web.reactive.function.client.ExchangeFunctions=TRACE

It should be noted though that not all of the headers are available (do exist) at WebFlux ExchangeFunctions level, so some more logging at Netty HttpClient level may be essential too, as per @Matthew's suggestion:

WebClient webClient = WebClient.builder()
    .clientConnector(new ReactorClientHttpConnector(
        HttpClient.create()
            .wiretap(true)))
    .build()

with further

logging.level.reactor.netty.http.client.HttpClient: DEBUG

This will get bodies logged too.