SynchronossPartHttpMessageReader created millions of temporary directories

[RekaDowney]

Describe the bug
I found that wheather Content-Type is multipart/form-data or application/json, SynchronossPartHttpMessageReader will create a temporal directory with prefix "synchronoss-file-upload-" every request come, and these temporal directoriese will not be cleared by docker, so now I can't execute commands such as ls in the /tmp directory.

Is it possible to postpone the execution of createTempDirectory()?

    public class SynchronossPartHttpMessageReader extends LoggingCodecSupport implements HttpMessageReader<Part> {

	private static final String FILE_STORAGE_DIRECTORY_PREFIX = "synchronoss-file-upload-";
        private Path fileStorageDirectory = createTempDirectory();

        @Override
        public Flux<Part> read(ResolvableType elementType, ReactiveHttpInputMessage message, Map<String, Object> hints) {
            return Flux.create(new SynchronossPartGenerator(message, this.fileStorageDirectory))
                    .doOnNext(part -> {
                        if (!Hints.isLoggingSuppressed(hints)) {
                            LogFormatUtils.traceDebug(logger, traceOn -> Hints.getLogPrefix(hints) + "Parsed " +
                                    (isEnableLoggingRequestDetails() ?
                                            LogFormatUtils.formatValue(part, !traceOn) :
                                            "parts '" + part.name() + "' (content masked)"));
                        }
                    });
        }

        private static Path createTempDirectory() {
            try {
                return Files.createTempDirectory(FILE_STORAGE_DIRECTORY_PREFIX);
            } catch (IOException ex) {
                throw new UncheckedIOException(ex);
            }
        }

    }

Spring Version:

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-gateway</artifactId>
            <version>2.2.8.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-web</artifactId>
            <version>5.2.15.RELEASE</version>
        </dependency>

Sample
curl -XPOST -H 'Content-Type: application/json' "https://spring-cloud-gateway/path"

[RekaDowney]

Whether frequent directory creation will cause the pod (in docker) memory increasing continuously, thereby affecting the stability of the application.
At present, I found that pod memory usage as high as 90% or more.

[spencergibb]

Closing in favor of spring-projects/spring-framework#27092