[feat][broker]:Support broker configuration for BookKeeper client TCP keep-alive options (apache#25580)

Signed-off-by: xiaolongran <xiaolongran@tencent.com>

Author: wolfstudy

conf/broker.conf

@@ -1256,6 +1256,28 @@ managedLedgerDefaultAckQuorum=2
 # the BookkeeperPackagesStorage bookkeeper client), except the distributed log bookkeeper client.
 # The dlog bookkeeper client is configured in the functions worker configuration file.
 
+# TCP keep-alive settings for the BookKeeper client connections from the broker to bookies.
+# These options were introduced in BookKeeper 4.17.3 (see apache/bookkeeper#4683) and are
+# forwarded to the BookKeeper client via the generic "bookkeeper_" prefix mechanism above.
+# A value of -1 (BookKeeper default) defers to the operating system's TCP keep-alive settings.
+# Uncomment and adjust to enable finer-grained keep-alive probing from the broker.
+#
+# Note: TCP keep-alive is a two-sided mechanism. Tuning these on the broker (BookKeeper
+# client) side only affects connections initiated by the broker. To complete the picture
+# you should also tune the bookie node's OS-level keep-alive settings via sysctl, e.g.
+# net.ipv4.tcp_keepalive_time / tcp_keepalive_intvl / tcp_keepalive_probes, since the
+# BookKeeper server (bookie) currently does not expose application-level keep-alive knobs.
+
+# Idle time (in seconds) before the first TCP keep-alive probe is sent on an otherwise idle
+# BookKeeper client connection.
+#bookkeeper_tcpKeepIdle=300
+# Interval (in seconds) between subsequent TCP keep-alive probes when no acknowledgement is
+# received from the bookie.
+#bookkeeper_tcpKeepIntvl=60
+# Number of unacknowledged TCP keep-alive probes before the connection is considered dead
+# and closed.
+#bookkeeper_tcpKeepCnt=5
+
 # How frequently to flush the cursor positions that were accumulated due to rate limiting. (seconds).
 # Default is 60 seconds
 managedLedgerCursorPositionFlushSeconds=60