Shinyproxy: [Bug Report] AJAX error 503 (Service Unavailable) in ShinyProxy (version 2.3.0)

In the new release version (2.3.0) of ShinyProxy, all the Apps that use DT with server processing mode will break. The browser complains Ajax errors while browsers programmer tool says "jquery.min.js:4 POST http://myip/app_direct/retire/session/cbc7bf01da3a023b6db378384c240836/dataobj/shiny_table?w=&nonce=22377961e7fd2317 503 (Service Unavailable)"

alert box as bellowings:
myip 顯示
DataTables warning: table id = DataTables_Table_0 - Ajax error. For more information about this error, please see http://datatables.net/tn/7

like https://github.com/openanalytics/shinyproxy/issues/140

my enviornment:
OS: Ubuntu Ubuntu 18.04.3 LTS
authentication: keycloak 7.0.0
ReverseProxy: Nginx
Example-shiny-App:

library(shiny)
library(DT)

ui <- fluidPage(DT::dataTableOutput('tbl'))
server <- function(input, output, session) {
output$tbl <- DT::renderDataTable(data.frame(Col_1=c(1:10), Col_2=c(11:20)))
}
shinyApp(ui, server)

Exact the same machine (docker,shinyproxy,nginx setting) with simple auth or ldap in application.yml is running without any trouble.

shinyproxy.log as belowings:
2019-08-28 11:46:21.991 INFO 14337 --- [XNIO-2 task-3] e.o.containerproxy.service.UserService : User logged in [user: test1]
2019-08-28 11:46:25.142 INFO 14337 --- [XNIO-2 task-6] c.s.docker.client.DefaultDockerClient : Starting container with Id: f24f391a707d19228f5e97da1e7f8e271230760e91bee2898f454b0bddd0f15a
2019-08-28 11:46:28.068 INFO 14337 --- [XNIO-2 task-6] e.o.containerproxy.service.ProxyService : Proxy activated [user: test1] [spec: retire] [id: 4199b4a8-60dd-43e7-ad8e-0bfac025cc76]
2019-08-28 11:46:28.828 ERROR 14337 --- [XNIO-2 I/O-3] io.undertow.proxy : UT005028: Proxy request to /proxy_endpoint/4199b4a8-60dd-43e7-ad8e-0bfac025cc76/session/4fba467e8b4976c85ad4be80ee538d7d/dataobj/shiny_table failed

io.undertow.server.TruncatedResponseException: null
at io.undertow.client.http.HttpRequestConduit.truncateWrites(HttpRequestConduit.java:711) ~[undertow-core-1.4.22.Final.jar!/:1.4.22.Final]
at io.undertow.conduits.AbstractFixedLengthStreamSinkConduit.terminateWrites(AbstractFixedLengthStreamSinkConduit.java:256) ~[undertow-core-1.4.22.Final.jar!/:1.4.22.Final]
at org.xnio.conduits.ConduitStreamSinkChannel.shutdownWrites(ConduitStreamSinkChannel.java:178) ~[xnio-api-3.3.8.Final.jar!/:3.3.8.Final]
at io.undertow.channels.DetachableStreamSinkChannel.shutdownWrites(DetachableStreamSinkChannel.java:79) ~[undertow-core-1.4.22.Final.jar!/:1.4.22.Final]
at io.undertow.server.handlers.proxy.ProxyHandler$HTTPTrailerChannelListener.handleEvent(ProxyHandler.java:754) ~[undertow-core-1.4.22.Final.jar!/:1.4.22.Final]
at io.undertow.server.handlers.proxy.ProxyHandler$ProxyAction$1.completed(ProxyHandler.java:646) [undertow-core-1.4.22.Final.jar!/:1.4.22.Final]
at io.undertow.server.handlers.proxy.ProxyHandler$ProxyAction$1.completed(ProxyHandler.java:561) [undertow-core-1.4.22.Final.jar!/:1.4.22.Final]
at io.undertow.client.http.HttpClientExchange.invokeReadReadyCallback(HttpClientExchange.java:212) [undertow-core-1.4.22.Final.jar!/:1.4.22.Final]
at io.undertow.client.http.HttpClientConnection.initiateRequest(HttpClientConnection.java:410) [undertow-core-1.4.22.Final.jar!/:1.4.22.Final]
at io.undertow.client.http.HttpClientConnection.sendRequest(HttpClientConnection.java:343) [undertow-core-1.4.22.Final.jar!/:1.4.22.Final]
at io.undertow.server.handlers.proxy.ProxyHandler$ProxyAction.run(ProxyHandler.java:561) [undertow-core-1.4.22.Final.jar!/:1.4.22.Final]
at io.undertow.util.SameThreadExecutor.execute(SameThreadExecutor.java:35) [undertow-core-1.4.22.Final.jar!/:1.4.22.Final]
at io.undertow.server.HttpServerExchange.dispatch(HttpServerExchange.java:815) [undertow-core-1.4.22.Final.jar!/:1.4.22.Final]
at io.undertow.server.handlers.proxy.ProxyHandler$ProxyClientHandler.completed(ProxyHandler.java:316) [undertow-core-1.4.22.Final.jar!/:1.4.22.Final]
at io.undertow.server.handlers.proxy.ProxyHandler$ProxyClientHandler.completed(ProxyHandler.java:290) [undertow-core-1.4.22.Final.jar!/:1.4.22.Final]
at io.undertow.server.handlers.proxy.ProxyConnectionPool.connectionReady(ProxyConnectionPool.java:338) [undertow-core-1.4.22.Final.jar!/:1.4.22.Final]
at io.undertow.server.handlers.proxy.ProxyConnectionPool.connect(ProxyConnectionPool.java:525) [undertow-core-1.4.22.Final.jar!/:1.4.22.Final]
at io.undertow.server.handlers.proxy.LoadBalancingProxyClient.getConnection(LoadBalancingProxyClient.java:301) [undertow-core-1.4.22.Final.jar!/:1.4.22.Final]
at eu.openanalytics.containerproxy.util.ProxyMappingManager$1.getConnection(ProxyMappingManager.java:88) [containerproxy-0.8.3.jar!/:0.8.3]
at io.undertow.server.handlers.proxy.ProxyHandler$ProxyClientHandler.run(ProxyHandler.java:310) [undertow-core-1.4.22.Final.jar!/:1.4.22.Final]
at org.xnio.nio.WorkerThread.safeRun(WorkerThread.java:582) [xnio-nio-3.3.8.Final.jar!/:3.3.8.Final]
at org.xnio.nio.WorkerThread.run(WorkerThread.java:466) [xnio-nio-3.3.8.Final.jar!/:3.3.8.Final]