Nginx Access Log Decoder Module (DEPRECATED)

We are moving to a configuration based setup to allow for more flexible transformations. The following will produce the equivalent default behavior.

log_format = '$remote_addr - $remote_user [$time_local] "$request" $status $body_bytes_sent "$http_referer" "$http_user_agent"'

decoder_module  = {
    {"lpeg.common_log_format#build_nginx_grammar", log_format},
      time = "lpeg.heka#set_timestamp",
      Payload = "lpeg.heka#remove_payload",
      --http_user_agent = "lpeg.heka#add_normalized_user_agent",

lpeg_heka = {
    user_agent_normalized_field_name = "user_agent", -- set to override the original field name prefix
    user_agent_remove = true, -- remove the user agent field after a successful normalization

1. Decoder Configuration Table (required)

decoders_nginx_access = {
  -- The ‘log_format’ configuration directive from the nginx.conf.
  -- The $time_local or $time_iso8601 variable is converted to the number of
  -- nanosecond  since the Unix epoch and used to set the Timestamp on the message.
  log_format = '$remote_addr - $remote_user [$time_local] "$request" $status $body_bytes_sent "$http_referer" "$http_user_agent"',

  -- Transform the http_user_agent into user_agent_browser, user_agent_version, user_agent_os.
  user_agent_transform = false, -- default

  -- Always preserve the http_user_agent value if transform is enabled.
  user_agent_keep = false, -- default

  -- Only preserve the http_user_agent value if transform is enabled and fails.
  user_agent_conditional = false, -- default

  -- Always preserve the original log line in the message payload.
  payload_keep = false, -- default

2. Functions

2.1. decode

Decode and inject the resulting message


  • data (string) - Nginx access log line
  • default_headers (table/nil/none) - Heka message table containing the default header values to use, if they are not populated by the decoder. If 'Fields' is specified it should be in the hashed based format see: In the case of multiple decoders this may be the message from the previous input/decoding step.
  • mutable (bool/nil/none) - Flag indicating if the decoder can modify the default_headers/msg structure in place or if it has to be copied first.


  • err (nil, string) or throws an error on invalid data or an inject message failure
    • nil - if the decode was successful
    • string - error message if the decode failed (e.g. no match)

source code: access.lua

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