engine: allow timely timeline initialization

This fixes a bug where the the timeline was initialized before one
had the opportunity to set timeline.enabled

src/core/app.lua

@@ -46,6 +46,7 @@ function timeline ()
       timeline_log = timeline_mod.new("events.timeline")
       timeline_mod.rate(timeline_log, 9) -- initially log events with rate >= 9
       events = timeline_mod.load_events(timeline_log, "core.engine")
+      packet.initialize_events()
    end
    return timeline_log
 end
@@ -267,6 +268,8 @@ end
 
 -- Return the configuration actions needed to migrate from old config to new.
 function compute_config_actions (old, new)
+   timeline() -- Ensure timeline is created and initialized
+
    local actions = {}
 
    -- First determine the links that are going away and remove them.
@@ -333,6 +336,8 @@ end
 
 -- Update the active app network by applying the necessary actions.
 function apply_config_actions (actions)
+   timeline() -- Ensure timeline is created and initialized
+
    -- Table of functions that execute config actions
    local ops = {}
    -- As an efficiency hack, some apps rely on the fact that we add

src/core/packet.lua

@@ -116,7 +116,9 @@ function initialize (max_packets)
       shm.unlink("engine/packets.freelist")
    end
    packets_fl = freelist_create("engine/packets.freelist", max_packets)
-
+end
+
+function initialize_events ()
    if not events then
       events = timeline.load_events(engine.timeline(), "core.packet")
    end

src/lib/ptree/worker.lua

@@ -15,7 +15,7 @@ local channel      = require("lib.ptree.channel")
 local action_codec = require("lib.ptree.action_codec")
 local ptree_alarms = require("lib.ptree.alarms")
 local timeline     = require("core.timeline")
-local events       = timeline.load_events(engine.timeline(), "core.engine")
+local events
 
 local Worker = {}
 
@@ -105,7 +105,9 @@ function Worker:main ()
 
    if not engine.auditlog_enabled then engine.enable_auditlog() end
 
-   engine.timeline()
+   if not events then 
+      events = timeline.load_events(engine.timeline(), "core.engine")
+   end
 
    engine.enable_tick()