| % Licensed under the Apache License, Version 2.0 (the "License"); you may not |
| % use this file except in compliance with the License. You may obtain a copy of |
| % the License at |
| % |
| % http://www.apache.org/licenses/LICENSE-2.0 |
| % |
| % Unless required by applicable law or agreed to in writing, software |
| % distributed under the License is distributed on an "AS IS" BASIS, WITHOUT |
| % WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the |
| % License for the specific language governing permissions and limitations under |
| % the License. |
| |
| -module(rexi_monitor). |
| -export([start/1, stop/1]). |
| |
| |
| %% @doc spawn_links a process which monitors the supplied list of items and |
| %% returns the process ID. If a monitored process exits, the caller will |
| %% receive a {rexi_DOWN, MonitoringPid, DeadPid, Reason} message. |
| -spec start([pid() | atom() | {atom(),node()}]) -> pid(). |
| start(Procs) -> |
| Parent = self(), |
| Nodes = [node() | nodes()], |
| {Mon, Skip} = lists:partition(fun(P) -> should_monitor(P, Nodes) end, |
| Procs), |
| spawn_link(fun() -> |
| [notify_parent(Parent, P, noconnect) || P <- Skip], |
| [erlang:monitor(process, P) || P <- Mon], |
| wait_monitors(Parent) |
| end). |
| |
| %% @doc Cleanly shut down the monitoring process and flush all rexi_DOWN |
| %% messages from our mailbox. |
| -spec stop(pid()) -> ok. |
| stop(MonitoringPid) -> |
| MonitoringPid ! {self(), shutdown}, |
| flush_down_messages(). |
| |
| %% internal functions %% |
| |
| notify_parent(Parent, Pid, Reason) -> |
| couch_stats:increment_counter([rexi, down]), |
| erlang:send(Parent, {rexi_DOWN, self(), Pid, Reason}). |
| |
| should_monitor(Pid, Nodes) when is_pid(Pid) -> |
| lists:member(node(Pid), Nodes); |
| should_monitor({_, Node}, Nodes) -> |
| lists:member(Node, Nodes). |
| |
| wait_monitors(Parent) -> |
| receive |
| {'DOWN', _, process, Pid, Reason} -> |
| notify_parent(Parent, Pid, Reason), |
| wait_monitors(Parent); |
| {Parent, shutdown} -> |
| ok |
| end. |
| |
| flush_down_messages() -> |
| receive {rexi_DOWN, _, _, _} -> |
| flush_down_messages() |
| after 0 -> |
| ok |
| end. |