On 10/11/2017 06:09, Bernd Eckenfels wrote:
Hello,
TCP keepalive is a rather elegant mechanism to detect abandoned TCP
Connections. With increased distribution of components and inclusion
of Cloud based services I have the feeling it has become more important.
Yet it is rather clumsy to use, because in addition to actually
enabling it in the application for every generated socket it also
typically requires reconfiguration of the OS Settings, since the
Defaults like 2h (Linux) to start the detection are nowhere near a
useful short detection time.
On native applications there is therefore a trend to configure the
times on a per-connection base with the appropriate APIs. For example
a Oracle Database 12c reconfigures the TCP keepalive settings when the
sqlnet.expire_time* setting is used.
For sockets used in OpenJDK/Oracle jvm there seems to be no way to
configure per-connection Settings and there is also no global option
to turn on keep-alive for Java applications which do not contain
specific code. (This is especially a problem since there is also no OS
switch to turn this on, so solutions like pre-loaded shared libraries
have to be used, which is rather ugly)
-Djdk.net.tcpkeepalive=true ; set the keepalive option on all new
sockets, allow the API to unset it selectively
I wonder what the idea here on the list is, would this be a
interesting Addition to the socket Option API and a good System property?
I don't recall this coming up before. If it were to go ahead then it may
have some spec implications, e.g. TCP_NODELAY is specified to be false
by default in the API specs.
-Alan
