Add log-injection example

- Remove ngx.var
- config.service is not required anymore

kong/plugins/ddtrace/handler.lua

@@ -86,14 +86,13 @@ end
 local function expose_tracing_variables(span)
  -- Expose traceID and parentID for other plugin to consume and also set an NGINX variable
  -- that can be use for in `log_format` directive for correlation with logs.
- -- NOTE: kong.ctx has the same lifetime as the current request.
  local trace_id = btohex(span.trace_id.high or 0, 16) .. btohex(span.trace_id.low, 16)
  local span_id = btohex(span.span_id, 16)
 
- kong.ctx.shared.datadog_sdk_trace_id = trace_id
- kong.ctx.shared.datadog_sdk_span_id = span_id
- ngx.var.datadog_sdk_trace_id = trace_id
- ngx.var.datadog_sdk_span_id = span_id
+ -- NOTE: kong.ctx has the same lifetime as the current request.
+ local kong_shared = kong.ctx.shared
+ kong_shared.datadog_sdk_trace_id = trace_id
+ kong_shared.datadog_sdk_span_id = span_id
 end
 
 -- adds the proxy span to the datadog context, unless it already exists

kong/plugins/ddtrace/schema.lua

@@ -118,7 +118,7 @@ return {
  config = {
  type = "record",
  fields = {
- { service_name = { type = "string", required = true } },
+ { service_name = { type = "string" } },
  { environment = { type = "string" } },
  -- priority of values for agent address details are resolved in new_trace_agent_writer
  { agent_host = typedefs.host({}) },