[GitHub] [apisix] tokers commented on a diff in pull request #7822: feat: Add ability to inject headers via prefix to otel traces

[GitBox <gi...@apache.org>]

tokers commented on code in PR #7822:
URL: https://github.com/apache/apisix/pull/7822#discussion_r961484339


##########
apisix/plugins/opentelemetry.lua:
##########
@@ -273,6 +280,25 @@ local function create_tracer_obj(conf)
 end
 
 
+local function inject_attributes(attributes, wanted_attributes, source)
+    for _, key in ipairs(wanted_attributes) do
+        local is_key_a_match = #key >= 2 and key:sub(-1, -1) == "*"
+        local prefix = key:sub(0, -2)

Review Comment:
   We can only calculate the `prefix` only if `is_key_a_match` is `true` since it will generate a new string object. What about re-organizing the code to:
   
   ```lua
   local is_prefix_key = #key >= 2 and key:byte(-1, -1) == str_byte("*")
   
   if is_prefix_key then
       local prefix = key:sub(0, -2)
       for possible_key, value in pairs(source) do
           if core.string.has_prefix(possible_key, prefix) then
               core.table.insert(attributes, attr.string(possible_key, value))
           end
       end
   else
   
       local val = source[key]
       if val then
           core.table.insert(attributes, attr.string(key, val))
       end
   end
   ```
   
   Note it's just a pseudo code.



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