fix(log-serializer): do not add receive time to latencies.kong (#12795

)

changelog/unreleased/kong/log-serializer-kong-latency.yml

@@ -0,0 +1,10 @@
+message: |
+  The value of `latencies.kong` in the log serializer payload no longer includes
+  the response receive time, so it now has the same value as the
+  `X-Kong-Proxy-Latency` response header. Response receive time is recorded in
+  the new `latencies.receive` metric, so if desired, the old value can be
+  calculated as `latencies.kong + latencies.receive`. **Note:** this also
+  affects payloads from all logging plugins that use the log serializer:
+  `file-log`, `tcp-log`, `udp-log`,`http-log`, `syslog`, and `loggly`.
+type: bugfix
+scope: PDK

kong/pdk/log.lua

@@ -841,8 +841,7 @@ do
           size = to_decimal(var.bytes_sent),
         },
         latencies = {
-          kong = (ctx.KONG_PROXY_LATENCY or ctx.KONG_RESPONSE_LATENCY or 0) +
-                 (ctx.KONG_RECEIVE_TIME or 0),
+          kong = ctx.KONG_PROXY_LATENCY or ctx.KONG_RESPONSE_LATENCY or 0,
           proxy = ctx.KONG_WAITING_TIME or -1,
           request = tonumber(var.request_time) * 1000,
           receive = ctx.KONG_RECEIVE_TIME or 0,

spec/01-unit/10-log_serializer_spec.lua

@@ -21,6 +21,8 @@ describe("kong.log.serialize", function()
             },
           },
           KONG_PROXIED = true,
+          KONG_RECEIVE_TIME = 100,
+          KONG_PROXY_LATENCY = 200,
         },
         var = {
           kong_request_id = "1234",
@@ -73,10 +75,10 @@ describe("kong.log.serialize", function()
 
         -- Latencies
         assert.is_table(res.latencies)
-        assert.equal(0, res.latencies.kong)
+        assert.equal(200, res.latencies.kong)
         assert.equal(-1, res.latencies.proxy)
         assert.equal(2000, res.latencies.request)
-        assert.equal(0, res.latencies.receive)
+        assert.equal(100, res.latencies.receive)
 
         -- Request
         assert.is_table(res.request)