This was discussed with@chemicL inmicrometer-metrics/micrometer#5472

Currently,DefaultWebClient executesExchangeFilterFunction as the reactive pipeline is assembled during subscription. This means that if imperative code is executed in a filter function, it won't be aware of the current observation through the local scope.

For example, when automatic context propagation is enabled for Reactor operators, the logger MDC will not know about the current traceId/spanId.

ExchangeFilterFunctionassertionFilter = (request,chain) -> {logger.info("This log will not contain the traceId information");returnchain.exchange(request);};

We should defer the execution of filter functions to fix that limitation.