协议扩展 - 用例

    function client.on_data(ctxt, payload)
        --
        -- code to parse payload.data into protocol message comes here
        --
        -- sending the message to lb
        ns.send(ctxt.output, "EOM", {data = message})
    end -- client.on_data

    function server.on_data(ctxt, payload)
        --
        -- code to parse payload.data into protocol message comes here
        --
        -- sending the message to client
        ns.send(ctxt.output, "EOM", {data = message})

    end -- server.on_data
<!--NeedCopy-->

        -- send the message to lb




        -- user_token is set to do LB based on clientID




        ns.send(ctxt.output, "EOM", {data = message,

                                 user_token = token_info})
<!--NeedCopy-->

-- send the data so far to lb

-- user_session is set to clientID as well (it will be used to persist session)

ns.send(ctxt.output, “DATA”, {data = data, user_session = clientID})
<!--NeedCopy-->

        -- send the data so far to lb
        ns.send(ctxt.output, "DATA", {data = data,
                                       user_token = clientID})
        -- pipe the subsequent traffic to the lb - to bypass the client on_data handler
        ns.pipe(ctxt.input, ctxt.output)
<!--NeedCopy-->

    local lb_map = {
       ["client1*"] = "lb_1",
       ["client2*"] = "lb_2",
       ["client3*"] = "lb_3",
       ["client4*"] = "lb_4"
    }

    -- map the clientID to the corresponding LB vserver and connect to it
    for client_pattern, lbname in pairs(lb_map) do
       local match_idx = string.find(clientID, client_pattern)
       if (match_idx == 1) then
      lb_ctxt = ctxt:lb_connect(lbname)
      if (lb_ctxt == nil) then
         error("Failed to connect to LB vserver: " .. lbname)
      end
      break
       end
    end
    if (lb_ctxt == nil) then
    -- If lb context is NULL, the user can raise an error or send data to default LB
       error("Failed to map LB vserver for client: " .. clientID)
    end
-- send the data so far to lb
ns.send(lb_ctxt, "DATA", {data = data}
<!--NeedCopy-->

data:replace(offset, length, new_string)
data:insert(offset, new_string)
data:delete(offset, length)
data:gsub(pattern, replace [,n]))

-- Get the offset of the pattern, we want to replace
   local old_pattern = “pattern to repalace”
local old_pattern_length = old_pattern:len()
   local pat_off, pat_end = data:find(old_pattern)
   -- pattern is not present
if (not pat_off) then
    goto send_data
   end
  -- If the data we want to modify is not completely present, then
  -- wait for more data
  if (not pat_end) then
        ctxt:hold(data)
        data = nil
     goto done
  end
data:replace(pat_off, old_pattern_length, “new pattern”)
::send_data::
ns.send(ctxt.output, “EOM”, {data = data})
::done::

data:insert(5, “pattern to insert”)

-- Get the offset of the pattern, after or before which we want to insert
   local pattern = “pattern after/before which we need to insert”
local pattern_length = pattern:len()
   local pat_off, pat_end = data:find(pattern)
-- pattern is not present
   if (not pat_off) then
    goto send_data
   end
  -- If the pattern after which we want to insert is not
  -- completely present, then wait for more data
  if (not pat_end) then
        ctxt:hold(data)
        data = nil
     goto done
  end
-- Insert after the pattern
data:insert(pat_end + 1, “pattern to insert”)
   -- Insert before the pattern
data:insert(pat_off, “pattern to insert”)
::send_data::
    ns.send(ctxt.output, “EOM”, {data = data})
::done::

-- Get the offset of the pattern, we want to delete
   local delete_pattern = “pattern to delete”
local delete_pattern_length = delete_pattern:len()
   local pat_off, pat_end = data:find(old_pattern)
   -- pattern is not present
if (not pat_off) then
          goto send_data
   end
  -- If the data we want to delete is not completely present,
  -- then wait for more data
  if (not pat_end) then
        ctxt:hold(data)
        data = nil
    goto done
  end
data:delete(pat_off, delete_pattern_length)
::send_data::
ns.send(ctxt.output, “EOM”, {data = data})
::done::

    -- Replace all the instances of the pattern with the new string
data:gsub(“old pattern”, “new string”)
-- Replace only 2 instances of “old pattern”
data:gsub(“old pattern”, “new string”, 2)
-- Insert new_string before all instances of “http”
data:gsub(“input data”, “(http)”, “new_string%1”)
-- Insert new_string after all instances of “http”
data:gsub(“input data”, “(http)”, “%1new_string”)
-- Insert new_string before only 2 instances of “http”
data:gsub(“input data”, “(http)”, “new_string%1”, 2)

    -- If the input packet is not MQTT CONNECT type, then
-- send some error response to the client.
function client.on_data(ctxt, payload)
    local data = payload.data
    local offset = 1
    local msg_type = 0
    local error_response = “Missing MQTT Connect packet.”
    byte = data:byte(offset)
msg_type = bit32.rshift(byte, 4)
if (msg_type ~= 1) then
-- Send the error response
   ns.send(ctxt.client, “DATA”, {data = error_response})
-- Since error response has been sent, so now close the connection
    ctxt:close()
end

-- After sending request, send some log message to the server.
function client.on_data(ctxt, payload)
local data = payload.data
local log_message = “client id : “..data:sub(3, 7)..” user name : “ data:sub(9, 15)
-- Send the request we get from the client to backend server
ns.send(ctxt.output, “DATA”, {data = data})
After sending the request, also send the log message
ns.send(ctxt.output, “DATA”, {data = log_message”})
end

-- If the HTTP response status message is “Not Found”,
-- then send another request to the server.
function server.on_data(ctxt, payload)
    local data = payload.data
    local request “GET /default.html HTTP/1.1\r\n\r\n”ss
    local start, end = data:find(“Not Found”)
    if (start) then
    -- Send the another request to server
        ns.send(ctxt.server, “DATA”, {data = request})
end

-- Send a request to the next processing context
-- on the connection establishment.
function client.init(ctxt)
   local request “PROXY TCP4” + ctxt.client.ip.src.to_s + “ “ + ctxt.client.ip.dst.to_s + “ “ + ctxt.client.tcp.srcport + “ “ +     ctxt.client.tcp.dstport
-- Send the another request to server
   ns.send(ctxt.output, “DATA”, {data = request})
  end