Basic alarms channel mechanism

src/apps/config/alarm_codec.lua

@@ -2,6 +2,8 @@
 
 module(...,package.seeall)
 
+local S = require("syscall")
+local channel = require("apps.config.channel")
 local ffi = require("ffi")
 
 local alarm_names = { 'raise_alarm', 'clear_alarm' }
@@ -81,6 +83,36 @@ function decode(buf, len)
    return { name, assert(alarms[name], name)(codec) }
 end
 
+---
+
+local alarms_channel
+
+function get_channel()
+   if alarms_channel then return alarms_channel end
+   local name = '/'..S.getpid()..'/alarms-follower-channel'
+   local success, value = pcall(channel.open, name)
+   if success then
+      alarms_channel = value
+   end
+   return alarms_channel
+end
+
+function raise_alarm (key, args)
+   local channel = get_channel()
+   if channel then
+      local buf, len = encode({'raise_alarm', {key, args}})
+      channel:put_message(buf, len)
+   end
+end
+
+function clear_alarm (key)
+   local channel = get_channel()
+   if channel then
+      local buf, len = encode({'clear_alarm', {key, args}})
+      channel:put_message(buf, len)
+   end
+end
+
 function selftest ()
    print('selftest: apps.config.alarm_codec')
    local lib = require("core.lib")

src/apps/config/follower.lua

@@ -23,6 +23,7 @@ function Follower:new (conf)
    ret.period = 1/conf.Hz
    ret.next_time = app.now()
    ret.channel = channel.create('config-follower-channel', 1e6)
+   ret.alarms_channel = channel.create('alarms-follower-channel', 1e6)
    ret.pending_actions = {}
    return ret
 end

src/apps/config/leader.lua

@@ -17,8 +17,10 @@ local app = require("core.app")
 local shm = require("core.shm")
 local app_graph = require("core.config")
 local action_codec = require("apps.config.action_codec")
+local alarm_codec = require("apps.config.alarm_codec")
 local support = require("apps.config.support")
 local channel = require("apps.config.channel")
+local alarms = require("lib.yang.alarms")
 
 Leader = {
    config = {
@@ -723,6 +725,40 @@ function Leader:pull ()
    self.next_time = app.now() + self.period
    self:handle_calls_from_peers()
    self:send_messages_to_followers()
+   self:receive_alarms_from_followers()
+end
+
+function Leader:receive_alarms_from_followers ()
+   for _,follower in ipairs(self.followers) do
+      self:receive_alarms_from_follower(follower)
+   end
+end
+
+function Leader:receive_alarms_from_follower (follower)
+   if not follower.alarms_channel then
+      local name = '/'..tostring(follower.pid)..'/alarms-follower-channel'
+      local success, channel = pcall(channel.open, name)
+      if not success then return end
+      follower.alarms_channel = channel
+   end
+   local channel = follower.alarms_channel
+   while true do
+      local buf, len = channel:peek_message()
+      if not buf then break end
+      local alarm = alarm_codec.decode(buf, len)
+      self:handle_alarm(follower, alarm)
+      channel:discard_message(len)
+   end
+end
+
+function Leader:handle_alarm (follower, alarm)
+   local fn, args = unpack(alarm)
+   if fn == 'raise_alarm' then
+      alarms.raise_alarm(unpack(args))
+   end
+   if fn == 'clear_alarm' then
+      alarms.clear_alarm(unpack(args))
+   end
 end
 
 function Leader:stop ()

src/lib/yang/alarms.lua

@@ -0,0 +1,7 @@
+module(..., package.seeall)
+
+function raise_alarm (key, args)
+   print('raise_alarm')
+   print('key: '..key)
+   print('args: '..args)
+end