How to get the time when Kong Gateway sends a request to upstream and receives a response

Kong handles requests in phases: the access phase ends just before the request is sent to upstream, and the log phase begins just after the full response is received.

• Send time: Obtainable at the end of the access phase. The Post-Function plugin runs after all other plugins, so it can capture this timestamp.
• Receive time: Obtainable at the beginning of the log phase. The Pre-Function plugin runs before all other plugins in the log phase, so it can capture this timestamp.

To implement this:

1. Set the following parameter for Kong Gateway to use the socket package in the Pre-Function/Post-Function plugins:

   untrusted_lua_sandbox_requires = socket

   Copied!

   If you run Kong in a container, set the following env var instead:

   KONG_UNTRUSTED_LUA_SANDBOX_REQUIRES = socket

   Copied!

2. Enable the Post-Function plugin on the target Route/Service object to log the send time:

   plugins:
   - name: post-function
     config:
       access:
       - |-
         local socket = require "socket"
         local s_time = socket.gettime()*1000
         kong.log('sending time(ms): ', s_time)
     enabled: true

   Copied!

3. Enable the Pre-Function plugin on the target Route/Service object to log receive time:

   plugins:
   - name: pre-function
     config:
       log:
       - |-
         local socket = require "socket"
         local r_time = socket.gettime()*1000
         kong.log('receiving time(ms): ', r_time)
     enabled: true

   Copied!

4. Send a request to Kong Gateway again, and you will see the following times (ms) in the Kong Gateway error log:

• The time when Kong Gateway sends a request to upstream
• The time Kong Gateway gets the whole response from upstream