fix(error-log-logger): avoid sending stale error log (#4690)

apisix/plugins/error-log-logger.lua

@@ -25,7 +25,6 @@ local table = core.table
 local schema_def = core.schema
 local ngx = ngx
 local tcp = ngx.socket.tcp
-local string = string
 local tostring = tostring
 local ipairs  = ipairs
 local lrucache = core.lrucache.new({
@@ -122,12 +121,12 @@ end
 
 
 local function update_filter(value)
-    local level = log_level[string.upper(value.level)]
+    local level = log_level[value.level]
     local status, err = errlog.set_filter_level(level)
     if not status then
         return nil, "failed to set filter level by ngx.errlog, the error is :" .. err
     else
-        core.log.debug("set the filter_level to ", config.level)
+        core.log.notice("set the filter_level to ", value.level)
     end
 
     return value
@@ -149,12 +148,17 @@ local function process()
 
     end
 
+    local err_level = log_level[metadata.value.level]
     local entries = {}
     local logs = errlog.get_logs(9)
     while ( logs and #logs>0 ) do
         for i = 1, #logs, 3 do
-            table.insert(entries, logs[i + 2])
-            table.insert(entries, "\n")
+            -- There will be some stale error logs after the filter level changed.
+            -- We should avoid reporting them.
+            if logs[i] <= err_level then
+                table.insert(entries, logs[i + 2])
+                table.insert(entries, "\n")
+            end
         end
         logs = errlog.get_logs(9)
     end

t/plugin/error-log-logger.t

@@ -327,7 +327,44 @@ qr/please set the correct plugin_metadata for error-log-logger/
 
 
 
-=== TEST 10: delete the route
+=== TEST 10: avoid sending stale error log
+--- yaml_config
+apisix:
+    enable_admin: true
+    admin_key: null
+plugins:
+  - error-log-logger
+--- config
+    location /tg {
+        content_by_lua_block {
+            local core = require("apisix.core")
+            local t = require("lib.test_admin").test
+            core.log.warn("this is a warning message for test.")
+            local code, body = t('/apisix/admin/plugin_metadata/error-log-logger',
+                ngx.HTTP_PUT,
+                [[{
+                    "host": "127.0.0.1",
+                    "port": 1999,
+                    "level": "ERROR",
+                    "inactive_timeout": 1
+                }]]
+                )
+            ngx.sleep(2)
+            core.log.error("this is an error message for test.")
+        }
+    }
+--- request
+GET /tg
+--- response_body
+--- no_error_log eval
+qr/\[Server\] receive data:.*this is a warning message for test./
+--- error_log eval
+qr/\[Server\] receive data:.*this is an error message for test./
+--- wait: 5
+
+
+
+=== TEST 11: delete the route
 --- yaml_config
 apisix:
     enable_admin: true