Cluster channels support "channelSendOptions" which is specified as an integer value, bitwise-ORd from the individual bits which make-up the various options. The default value is 8 for the DeltaManager which means "asynchronous". It would be nice if the configuration could use human-readable options like "async" instead of "8". These are the channel send options available: SEND_OPTIONS_ASYNCHRONOUS SEND_OPTIONS_BYTE_MESSAGE SEND_OPTIONS_MULTICAST SEND_OPTIONS_SECURE SEND_OPTIONS_SYNCHRONIZED_ACK SEND_OPTIONS_UDP SEND_OPTIONS_USE_ACK They could be specified as human-readable strings e.g. channelSendOptions="async,multicast" instead of channelSendOptions="72" which would make the configuration much easier to both read and write. For backward compatibility, the integer values should also be acceptable.
Please see https://github.com/apache/tomcat/pull/56 as a WIP. Especially given the fact that this is my first PR I would need more feedback.
*** Bug 61128 has been marked as a duplicate of this bug. ***
Fixed in r1799462, r1799464, and r1799466 (the latter being cleanup for an inadvertently-committed change to the build script). Will be in Tomcat 9.0.0.M23 and later. Back-ports likely forthcoming to Tomcat 8.5.x and Tomcat 8.0.x.