From: Petr Špaček <petr.spacek@nic.cz>
Date: Wed, 14 Oct 2020 09:08:43 +0000 (+0200)
Subject: map: rework result handling
X-Git-Tag: v5.2.0~6^2~21
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cdeaddc910b241772444cb8bf318d6aebd8a9c4c;p=thirdparty%2Fknot-resolver.git

map: rework result handling

map() command on leader instance now:
- detects call errors on followers
- detects unsupported number of return values
- detects unsupported data types which cannot be serialized
- keeps nil return values (signaled by table counter "n")

Fixes: #662
---

diff --git a/daemon/lua/sandbox.lua.in b/daemon/lua/sandbox.lua.in
index 60c71ac7d..1b0632e20 100644
--- a/daemon/lua/sandbox.lua.in
+++ b/daemon/lua/sandbox.lua.in
@@ -2,6 +2,8 @@
 
 local debug = require('debug')
 local ffi = require('ffi')
+local kluautil = require('kluautil')
+local krprint = require("krprint")
 
 -- Units
 kB = 1024
@@ -650,21 +652,43 @@ end
 
 -- Global commands for map()
 
-local krprint = require("krprint")
+-- must be public because it is called from eval_cmd()
+-- when map() commands are read from control socket
+function _map_luaobj_call_wrapper(cmd)
+	local func = eval_cmd_compile(cmd, true)
+	local ret = kluautil.kr_table_pack(xpcall(func, debug.traceback))
+	local ok, serial = pcall(krprint.serialize_lua, ret, 'error')
+	if not ok then
+		return krprint.serialize_lua(
+			kluautil.kr_table_pack(false, "returned values cannot be serialized: "
+				.. serial))
+	else
+		return serial
+	end
+end
+
 function map(cmd, format)
 	local socket = require('cqueues.socket')
-	local kluautil = require('kluautil')
 	local bit = require("bit")
 	local local_sockets = {}
 	local results = {}
 
-	format = format or 'luaobj'
 	if (type(cmd) ~= 'string') then
 		panic('map() command must be a string') end
 	if (#cmd <= 0) then
 		panic('map() command must be non-empty') end
+	-- syntax check on input command to detect typos early
+	local chunk, err = eval_cmd_compile(cmd, false)
+	if not chunk then
+		panic('failure when compiling map() command: %s', err)
+	end
+
+	format = format or 'luaobj'
 	if (format ~= 'luaobj' and format ~= 'strings') then
 		panic('map() output format must be luaobj or strings') end
+	if format == 'luaobj' then
+		cmd = '_map_luaobj_call_wrapper([=====[' .. cmd .. ']=====])'
+	end
 
 	-- find out control socket paths
 	for _,v in pairs(net.list()) do
@@ -678,55 +702,72 @@ function map(cmd, format)
 			worker.control_path)
 	end
 
-	-- validate input command to detect typos early
-	local chunk, err = eval_cmd_compile(cmd, false)
-	if not chunk then
-		panic('failure when compiling map() command: %s', err)
-	end
-
+	local result_count = 0
 	-- finally execute it on all instances
-	for _,file in ipairs(filetab) do
+	for _, file in ipairs(filetab) do
 		local local_exec = false
-		for _,lsoc in ipairs(local_sockets) do
+		for _, lsoc in ipairs(local_sockets) do
 			if file == lsoc then
 				local_exec = true
 			end
 		end
+		local path = worker.control_path..file
+		local path_name = (local_exec and 'this instance') or path
+		if verbose() then
+			log('executing map() on %s: command %s', path_name, cmd)
+		end
 
+		local ret
 		if local_exec then
-			local ret = eval_cmd(cmd, format == 'luaobj')
-			-- crop to a single return value similarly to original map()
-			table.insert(results, ret)
+			ret = eval_cmd(cmd)
 		else
-			local s = socket.connect({ path = worker.control_path..file })
+			local s = socket.connect({ path = path })
 			s:setmode('bn', 'bn')
 			local status, err = pcall(s.connect, s)
 			if not status then
-				print(err)
+				log('map() error while connecting to control socket %s: '
+					.. '%s (ignoring this socket)', path, err)
+				goto continue
 			else
 				s:write('__binary\n')
-				recv = s:read(2)
-				if format == 'luaobj' then
-					s:write('require("krprint").serialize_lua('..cmd..')\n')
-				else
-					s:write(cmd..'\n')
-				end
-				local recv = s:read(4)
+				local recv = s:read(2)
+				assert(recv == '> ', 'map() protocol error, undefined state')
+				s:write(cmd..'\n')
+				recv = s:read(4)
 				local len = tonumber(recv:byte(1))
 				for i=2,4 do
 					len = bit.bor(bit.lshift(len, 8), tonumber(recv:byte(i)))
 				end
-				recv = s:read(len)
-				if format == 'strings' then
-					table.insert(results, recv)
-				else
-					table.insert(results, krprint.deserialize_lua(recv))
-				end
-
+				ret = s:read(len)
 				s:close()
 			end
 		end
+		result_count = result_count + 1
+		if format == 'luaobj' then
+			ret = krprint.deserialize_lua(ret)
+			-- ret is now table with xpcall results
+			assert(type(ret) == 'table', 'map() protocol error, '
+				.. 'table with results not retured by follower')
+			if (ret.n ~= 2) then
+				panic('unexpected number of return values in map() response: '
+					.. 'only single return value is allowed, '
+					.. 'use kluautil.kr_table_pack() helper')
+			end
+			local ok, retval = ret[1], ret[2]
+			if ok == false then
+				panic('error when executing map() command on control socket %s: '
+					.. '%s. command execution state is now undefined!',
+					path, retval)
+			end
+			-- drop wrapper table and return only the actual return value
+			ret = retval
+		else
+			assert(type(ret) == 'string', 'map() protocol error, '
+				.. 'string not retured by follower')
+		end
+		results[result_count] = ret
+		::continue::
 	end
-
+	results.n = result_count
 	return results
 end