feat(opentelemetry):set variable resource attributes

kong/plugins/opentelemetry/handler.lua

@@ -1,6 +1,7 @@
 
 local otel_traces = require "kong.plugins.opentelemetry.traces"
 local otel_logs = require "kong.plugins.opentelemetry.logs"
+local otel_utils = require "kong.plugins.opentelemetry.utils"
 local dynamic_hook = require "kong.dynamic_hook"
 local o11y_logs = require "kong.observability.logs"
 local kong_meta = require "kong.meta"
@@ -42,6 +43,11 @@ end
 
 
 function OpenTelemetryHandler:log(conf)
+  -- Read resource attributes variable
+  if conf.resource_attributes then
+    conf["compiled_resource_attributes"] = otel_utils.read_resource_attributes(conf.resource_attributes)
+  end
+
   -- Traces
   if conf.traces_endpoint then
     otel_traces.log(conf)

kong/plugins/opentelemetry/logs.lua

@@ -21,7 +21,11 @@ local prepare_logs = otlp.prepare_logs
 
 local function http_export_logs(conf, logs_batch)
   local headers = get_headers(conf.headers)
-  local payload = encode_logs(logs_batch, conf.resource_attributes)
+  local resource_attributes = conf.resource_attributes
+  if conf.compiled_resource_attributes then
+    resource_attributes = conf.compiled_resource_attributes
+  end
+  local payload = encode_logs(spans, resource_attributes)
 
   local ok, err = http_export_request({
     connect_timeout = conf.connect_timeout,

kong/plugins/opentelemetry/schema.lua

@@ -1,5 +1,10 @@
 local typedefs = require "kong.db.schema.typedefs"
 local Schema = require "kong.db.schema"
+local pl_template = require "pl.template"
+
+local compile_opts = {
+  escape = "\xff", -- disable '#' as a valid template escape
+}
 
 local function custom_validator(attributes)
   for _, v in pairs(attributes) do
@@ -14,6 +19,12 @@ local function custom_validator(attributes)
     if vtype == "string" and #v == 0 then
       return nil, "required field missing"
     end
+    local status, res, err = pcall(pl_template.compile, v, compile_opts)
+    if not status or err then
+      return false, "value '" .. v ..
+              "' is not in supported format, error:" ..
+              (status and res or err)
+    end
   end
 
   return true

kong/plugins/opentelemetry/traces.lua

@@ -122,7 +122,11 @@ end
 
 local function http_export_traces(conf, spans)
   local headers = get_headers(conf.headers)
-  local payload = encode_traces(spans, conf.resource_attributes)
+  local resource_attributes = conf.resource_attributes
+  if conf.compiled_resource_attributes then
+    resource_attributes = conf.compiled_resource_attributes
+  end
+  local payload = encode_traces(spans, resource_attributes)
 
   local ok, err = http_export_request({
     connect_timeout = conf.connect_timeout,

kong/plugins/opentelemetry/utils.lua

@@ -1,9 +1,17 @@
 local http = require "resty.http"
 local clone = require "table.clone"
-
+local sandbox = require "kong.tools.sandbox"
+local deep_copy = require("kong.tools.table").deep_copy
+local pl_template = require "pl.template"
+local lua_enabled = sandbox.configuration.enabled
+local sandbox_enabled = sandbox.configuration.sandbox_enabled
+local get_request_headers = kong.request.get_headers
+local get_uri_args = kong.request.get_query
+local rawset = rawset
+local str_find = string.find
 local tostring = tostring
 local null = ngx.null
-
+local EMPTY = require("kong.tools.table").EMPTY
 
 local CONTENT_TYPE_HEADER_NAME = "Content-Type"
 local DEFAULT_CONTENT_TYPE_HEADER = "application/x-protobuf"
@@ -13,6 +21,7 @@ local DEFAULT_HEADERS = {
 
 local _log_prefix = "[otel] "
 
+
 local function http_export_request(conf, pb_data, headers)
   local httpc = http.new()
   httpc:set_timeouts(conf.connect_timeout, conf.send_timeout, conf.read_timeout)
@@ -48,8 +57,118 @@ local function get_headers(conf_headers)
 end
 
 
+local compile_opts = {
+  escape = "\xff", -- disable '#' as a valid template escape
+}
+
+local template_cache = setmetatable( {}, { __mode = "k" })
+
+
+local function param_value(source_template, resource_attributes, template_env)
+  if not source_template or source_template == "" then
+    return nil
+  end
+
+  if not lua_enabled then
+    -- Detect expressions in the source template
+    local expr = str_find(source_template, "%$%(.*%)")
+    if expr then
+      return nil, "loading of untrusted Lua code disabled because " ..
+                  "'untrusted_lua' config option is set to 'off'"
+    end
+    -- Lua is disabled, no need to render the template
+    return source_template
+  end
+
+  -- find compiled templates for this plugin-configuration array
+  local compiled_templates = template_cache[resource_attributes]
+  if not compiled_templates then
+    compiled_templates = {}
+    -- store it by `resource_attributes` which is part of the plugin `conf` table
+    -- it will be GC'ed at the same time as `conf` and hence invalidate the
+    -- compiled templates here as well as the cache-table has weak-keys
+    template_cache[resource_attributes] = compiled_templates
+  end
+
+  -- Find or compile the specific template
+  local compiled_template = compiled_templates[source_template]
+  if not compiled_template then
+    compiled_template = assert(pl_template.compile(source_template, compile_opts))
+    compiled_templates[source_template] = compiled_template
+  end
+
+  return compiled_template:render(template_env)
+end
+
+local function read_resource_attributes(resource_attributes)
+  if not resource_attributes then
+    return EMPTY
+  end
+  local __meta_environment = {
+    __index = function(self, key)
+      local lazy_loaders = {
+        headers = function(self)
+          return get_request_headers() or EMPTY
+        end,
+        query_params = function(self)
+          return get_uri_args() or EMPTY
+        end,
+        uri_captures = function(self)
+          return (ngx.ctx.router_matches or EMPTY).uri_captures or EMPTY
+        end,
+        shared = function(self)
+          return ((kong or EMPTY).ctx or EMPTY).shared or EMPTY
+        end,
+      }
+      local loader = lazy_loaders[key]
+      if not loader then
+        if lua_enabled and not sandbox_enabled then
+          return _G[key]
+        end
+        return
+      end
+      -- set the result on the table to not load again
+      local value = loader()
+      rawset(self, key, value)
+      return value
+    end,
+    __newindex = function(self)
+      error("This environment is read-only.")
+    end,
+  }
+
+  local template_env = {}
+  if lua_enabled and sandbox_enabled then
+    -- load the sandbox environment to be used to render the template
+    template_env = deep_copy(sandbox.configuration.environment)
+    -- here we can optionally add functions to expose to the sandbox, eg:
+    -- tostring = tostring,
+    -- because headers may contain array elements such as duplicated headers
+    -- type is a useful function in these cases. See issue #25.
+    template_env.type = type
+  end
+  setmetatable(template_env, __meta_environment)
+  local compiled_resource_attributes = {}
+  for current_name, current_value in pairs(resource_attributes) do
+    local res, err = param_value(current_value, resource_attributes, template_env)
+    if err then
+      ngx_log(ngx_DEBUG, _log_prefix, "failed to render the template " ..
+            current_value .. ", error:" .. err)
+      return nil
+    end
+
+    if res then
+      compiled_resource_attributes[current_name] = res
+    end
+  end
+  return compiled_resource_attributes
+end
+
+
+
 return {
   http_export_request = http_export_request,
   get_headers = get_headers,
   _log_prefix = _log_prefix,
+  read_resource_attributes = read_resource_attributes,
 }