Implements facility to reuse plugin ids

scripts/lua/modules/plugins_consts_utils.lua

@@ -0,0 +1,206 @@
+--
+-- (C) 2013-20 - ntop.org
+--
+
+local plugins_consts_utils = {}
+local dirs = ntop.getDirs()
+
+-- ##############################################
+
+local AVAILABLE_CONSTS = {
+   flow = {
+      min_id = 0, max_id = 63, reuse_ids = true,
+   },
+   alert = {
+      min_id = 0, max_id = 255, reuse_ids = false
+   }
+}
+
+-- ##############################################
+
+local id_requests = {
+   flow = {},
+   alert = {}
+}
+
+-- ##############################################
+
+local function assigned_ids_hname(const_type)
+   return string.format("ntopng.prefs.plugins_consts_utils.assigned_ids.const_type_%s", const_type)
+end
+
+-- ##############################################
+
+local function assigned_id_key(const_type, const_key)
+   return string.format("ntopng.prefs.plugins_consts_utils.assigned_ids.const_type_%s.const_key_%s", const_type, const_key)
+end
+
+-- ##############################################
+
+local function get_assigned_ids(const_type)
+   local hname = assigned_ids_hname(const_type)
+   local assigned_ids = ntop.getHashAllCache(hname) or {}
+   local cur_id_to_key = {}
+   local cur_key_to_id = {}
+
+   for const_id, const_key in pairs(assigned_ids) do
+      local const_id_n = tonumber(const_id)
+
+      if const_id_n < AVAILABLE_CONSTS[const_type]["min_id"] or const_id_n > AVAILABLE_CONSTS[const_type]["max_id"] then
+	 traceError(TRACE_ERROR, TRACE_CONSOLE, string.format("Ignoring id %i outside boundaries for '%s'", const_id_n, const_type))
+      else
+	 cur_id_to_key[const_id_n] = const_key
+	 cur_key_to_id[const_key] = const_id_n
+      end
+   end
+
+   return cur_id_to_key, cur_key_to_id
+end
+
+-- ##############################################
+
+local function commit_new_ids(const_type, new_ids)
+   local hname = assigned_ids_hname(const_type)
+
+   for const_key, const_id in pairs(new_ids) do
+      local const_id_s = string.format("%i", const_id)
+
+      -- Attempt to lookup for the id in the cache. Attempting to commit a new id to an existing
+      -- it, causes the old key to be reused the new key. This is used for example when reusing ids
+      local existing = ntop.getHashCache(hname, const_id)
+      if not isEmptyString(existing) then
+	 traceError(TRACE_NORMAL, TRACE_CONSOLE, string.format("Reusing id %i '%s' to '%s'", const_id, existing, const_key))
+	 ntop.delHashCache(hname, const_id_s)
+
+	 local existing_kname = assigned_id_key(const_type, existing)
+	 ntop.delCache(existing_kname)
+      end
+
+      -- Now it's time to set the new id, both in the hash table...
+      ntop.setHashCache(hname, const_id, const_key)
+
+      -- ... and as a single key
+      local kname = assigned_id_key(const_type, const_key)
+      ntop.setPref(kname, const_id_s)
+   end
+end
+
+-- ##############################################
+
+function plugins_consts_utils.clear_id_requests(const_type)
+   id_requests[const_type] = {}
+end
+
+-- ##############################################
+
+function plugins_consts_utils.request_id(const_type, const_key)
+   if not AVAILABLE_CONSTS[const_type] then
+      traceError(TRACE_ERROR, TRACE_CONSOLE, string.format("Unknown const type '%s'", const_type))
+      return
+   end
+
+   id_requests[const_type][#id_requests[const_type] + 1] = const_key
+end
+
+-- ##############################################
+
+function plugins_consts_utils.assign_requested_ids(const_type)
+   if not AVAILABLE_CONSTS[const_type] then
+      traceError(TRACE_ERROR, TRACE_CONSOLE, string.format("Unknown const type '%s'", const_type))
+      return
+   end
+
+   local cur_id_to_key, cur_key_to_id = get_assigned_ids(const_type)
+   local available_ids = {}
+   local used_ids = {}
+   local new_ids = {}
+   local found_ids = {}
+   local deferred_requests = {}
+   local reused_ids = {}
+
+   -- Prepare used and available ids by iterating the current existing ids (i.e., those
+   -- that have already been assigned)
+   for i = AVAILABLE_CONSTS[const_type]["min_id"], AVAILABLE_CONSTS[const_type]["max_id"] do
+      if cur_id_to_key[i] then
+	 used_ids[#used_ids + 1] = i
+      else
+	 available_ids[#available_ids + 1] = i
+      end
+   end
+
+   for _, req in ipairs(id_requests[const_type]) do
+      if cur_key_to_id[req] then
+	 -- Id found: already assigned, nothing to do
+	 found_ids[#found_ids + 1] = cur_key_to_id[req]
+      elseif #available_ids > 0 then
+	 -- At least an id is available in the pool of available ids
+	 new_ids[req] = table.remove(available_ids, 1)
+      elseif AVAILABLE_CONSTS[const_type]["reuse_ids"] then
+	 -- No ids available but reuse of old ids is enabled
+	 deferred_requests[#deferred_requests + 1] = req
+      else
+	 -- No ids available and reuse not allowed, unable to assign.
+	 traceError(TRACE_ERROR, TRACE_CONSOLE, string.format("Unable to assign an id to '%s' for const type '%s'. No more ids available", req, const_type))
+      end
+   end
+
+   commit_new_ids(const_type, new_ids)
+
+   if #deferred_requests > 0 then
+      for _, used_id in ipairs(used_ids) do
+	 local used_id_found = false
+
+	 for _, found_id in ipairs(found_ids) do
+	    if used_id == found_id then
+	       -- Used id found during this run, cannot reuse it
+	       used_id_found = true
+	       break
+	    end
+	 end
+
+	 if not used_id_found then
+	    -- This id is used but not found so it means no plugin is using it (during this run) and it can be reused
+	    reused_ids[table.remove(deferred_requests, 1)] = used_id
+	 end
+
+	 if #deferred_requests == 0 then
+	    -- No more work to do
+	    break
+	 end
+      end
+
+      commit_new_ids(const_type, reused_ids)
+
+      if #deferred_requests > 0 then
+	 for _, req in ipairs(deferred_requests) do
+	    traceError(TRACE_ERROR, TRACE_CONSOLE, string.format("Unable to reuse any id for '%s' with const type '%s'.", req, const_type))
+	 end
+      end
+   end
+end
+
+-- ##############################################
+
+function plugins_consts_utils.get_assigned_id(const_type, const_key)
+   if not AVAILABLE_CONSTS[const_type] then
+      traceError(TRACE_ERROR, TRACE_CONSOLE, string.format("Unknown const type '%s'", const_type))
+      return
+   end
+
+   -- Avoid reading the whole hash, just read the single key to re-use also ntopng internal caching mechanism
+   local kname = assigned_id_key(const_type, const_key)
+   local assigned_id = tonumber(ntop.getPref(kname))
+
+   -- Make sure the index is within the configured bounds
+   if assigned_id then
+      if assigned_id < AVAILABLE_CONSTS[const_type]["min_id"] or assigned_id > AVAILABLE_CONSTS[const_type]["max_id"] then
+	 traceError(TRACE_ERROR, TRACE_CONSOLE, string.format("Ignoring id %i outside boundaries for '%s'", assigned_id, const_type))
+	 -- Clear it as it should have that value
+	 assigned_id = nil
+      end
+   end
+
+   return assigned_id
+end
+
+return plugins_consts_utils