When using new websocket remoting capability, we are seeing following error in node log after node is successfuly connected:

Inbound agent connected from 192.168.0.207 Remoting version: 4.0.1 This is a Unix agent ERROR: Failed to monitor for Free Temp Space java.util.concurrent.TimeoutException at hudson.remoting.Request$1.get(Request.java:316) at hudson.remoting.Request$1.get(Request.java:240) at hudson.remoting.FutureAdapter.get(FutureAdapter.java:59) at hudson.node_monitors.AbstractAsyncNodeMonitorDescriptor.monitorDetailed(AbstractAsyncNodeMonitorDescriptor.java:114) at hudson.node_monitors.AbstractAsyncNodeMonitorDescriptor.monitor(AbstractAsyncNodeMonitorDescriptor.java:78) at hudson.node_monitors.AbstractNodeMonitorDescriptor$Record.run(AbstractNodeMonitorDescriptor.java:306) ERROR: Failed to monitor for Free Disk Space java.util.concurrent.TimeoutException at hudson.remoting.Request$1.get(Request.java:316) at hudson.remoting.Request$1.get(Request.java:240) at hudson.remoting.FutureAdapter.get(FutureAdapter.java:59) at hudson.node_monitors.AbstractAsyncNodeMonitorDescriptor.monitorDetailed(AbstractAsyncNodeMonitorDescriptor.java:114) at hudson.node_monitors.AbstractAsyncNodeMonitorDescriptor.monitor(AbstractAsyncNodeMonitorDescriptor.java:78) at hudson.node_monitors.AbstractNodeMonitorDescriptor$Record.run(AbstractNodeMonitorDescriptor.java:306)

Our setup is nginx proxy with OAuth2 and allowed locations without authentication:

{{ location ~ (/jnlpJars/.*)$ {}}
  proxy_pass http://localhost:8080$1;
  access_by_lua return;
  proxy_set_header Host $host;
  proxy_set_header X-Real-IP $remote_addr;
  proxy_max_temp_file_size 0;
{{ }}}
{{ location ~ (/generic-webhook-trigger/?)$ {}}
  proxy_pass http://localhost:8080$1;
  access_by_lua return;
  proxy_set_header Host $host;
  proxy_set_header X-Real-IP $remote_addr;
  proxy_max_temp_file_size 0;
{{ }}}
{{ location ~ (/wsagents/.*)$ {}}
  proxy_pass http://localhost:8080$1;
  access_by_lua return;
  proxy_http_version 1.1;
  proxy_set_header Upgrade $http_upgrade;
  proxy_set_header Connection "Upgrade";
  proxy_set_header Host $host;
  proxy_set_header X-Real-IP $remote_addr;
  proxy_max_temp_file_size 0;
{{ }}}
{{ location ~ (/wsecho/?)$ {}}
  proxy_pass http://localhost:8080$1;
  access_by_lua return;
  proxy_http_version 1.1;
  proxy_set_header Upgrade $http_upgrade;
  proxy_set_header Connection "Upgrade";
  proxy_set_header Host $host;
  proxy_set_header X-Real-IP $remote_addr;
  proxy_max_temp_file_size 0;
{{ }}}

our jenkins-slave.jnlp:

<jnlp codebase="https://ourjenkins.tld/computer/blr-jenkins-slave-01/" spec="1.0+"><information><title>Agent for blr-jenkins-slave-01</title><vendor>Jenkins project</vendor><homepage href="https://jenkins-ci.org/"></homepage></information><security><all-permissions></all-permissions></security><resources><j2se version="1.8+"></j2se><jar href="https://ourjenkins.tld/jnlpJars/remoting.jar"></jar></resources><application-desc main-class="hudson.remoting.jnlp.Main"><argument>oursecretkey</argument><argument>jenkins-slave-01</argument><argument>-webSocket</argument><argument>-workDir</argument><argument>/var/lib/jenkins</argument><argument>-internalDir</argument><argument>remoting</argument><argument>-url</argument><argument>https://ourjenkins.tld/</argument></application-desc></jnlp>