Add systemd ulimit override function and set an override for NOFILE

This sets our default ulimit NOFILE to 2048, which is double what we
set things like mysql'd max_connections to.

Change-Id: I5126bed1e6b9f8c64db00eae4151ac61e47b1bf8

functions

@@ -720,6 +720,22 @@ function enable_kernel_bridge_firewall {
 }
 
 
+# Set a systemd system override
+#
+# This sets a system-side override in system.conf. A per-service
+# override would be /etc/systemd/system/${service}.service/override.conf
+function set_systemd_override {
+    local key="$1"
+    local value="$2"
+
+    local sysconf="/etc/systemd/system.conf"
+    iniset -sudo "${sysconf}" "Manager" "$key" "$value"
+    echo "Set systemd system override for ${key}=${value}"
+
+    sudo systemctl daemon-reload
+}
+
+
 # Restore xtrace
 $_XTRACE_FUNCTIONS
 

stack.sh

@@ -765,6 +765,9 @@ install_infra
 # Phase: pre-install
 run_phase stack pre-install
 
+# NOTE(danms): Set global limits before installing anything
+set_systemd_override DefaultLimitNOFILE ${ULIMIT_NOFILE}
+
 install_rpc_backend
 restart_rpc_backend
 

stackrc

@@ -925,6 +925,9 @@ fi
 # ``LOGDIR`` is always set at this point so it is not useful as a 'enable' for service logs
 # ``SCREEN_LOGDIR`` may be set, it is useful to enable the compat symlinks
 
+# System-wide ulimit file descriptors override
+ULIMIT_NOFILE=${ULIMIT_NOFILE:-2048}
+
 # Local variables:
 # mode: shell-script
 # End: