mod_cluster/mod_proxy error "ajp_ilink_receive() can't receive header" happening on cping/cpong with EAP 7

Issue

• Applications not accessible through webservers. We're getting 503 responses:

Service Temporarily Unavailable
  The server is temporarily unable to service your request due to maintenance downtime or capacity problems. Please try again later.

• Some server instances stop in an unexpected way.
• Error messages seen in Apache log related to ajp.
• The following mod_cluster errors are seen in the httpd error log:

[error] (70007)The timeout specified has expired: ajp_ilink_receive() can't receive header
...
[error] (104)Connection reset by peer: ajp_ilink_receive() can't receive header
[error] ajp_handle_cping_cpong: ajp_ilink_receive failed

• We are frequently receiving the below error on our apache webservers.

[error] (70007)The timeout specified has expired: ajp_cping_cpong: apr_socket_recv failed.

• Connectivity issue on EWS.
• mod_cluster dropping connections to JBoss.
• JBOSS applications were not reachable through Apache Web Servers.It seems that the threads between Apache Servers and JBOSS servers are exhausted causing an '503 Service temporarily unavailable' error.