View Source Instream.Connection.Config (Instream v2.0.0)

Configuration helper module.


How To Configure

There are multiple ways to configure a connection:

  • Application Configuration: config files
  • Runtime/Startup Configuration: functions modifying the application configuration
  • Inline Configuration: values known at compile time

All three can be mixed as required.


Application Configuration

If you know all configuration values before starting your application you can use config files (e.g. config.exs, release.exs and/or runtime.exs) to set up your connection(s):

config :my_app, MyConnection,
  database: "my_default_database",
  host: "",
  port: 8086


Runtime/Startup Configuration

An alternative to config files is using an initializer function that will be called every time your connection is started (or restarted) in your supervision tree:

config :my_app, MyConnection,
  init: {MyInitModule, :my_init_fun}

config :my_app, MyOtherConnection,
  init: {MyInitModule, :my_init_fun, [:extra, :args]}

defmodule MyInitModule do
  @spec my_init_fun(module) :: :ok
  def my_init_fun(conn), do: my_init_fun(conn, :extra, :args)

  @spec my_init_fun(module, atom, atom) :: :ok
  def my_init_fun(conn, :extra, :args) do
    config =
        host: "",
        port: 64210

    Application.put_env(:my_app, conn, config)

When the connection is started the function will be called with the connection module as the first argument.

The function is expected to always return :ok.


Inline Configuration

In some environments it is sufficient to define the configuration in the connection module itself, for example during tests:

defmodule MyConnection do
  use Instream.Connection,
    config: [
      host: "",
      port: 8086

These values will be overwritten by and/or merged with the application environment values (if available) when the configuration is accessed.


Configuration Defaults

The following values will be used as defaults if no other value is set:

config :my_app, MyConnection,
  version: :v1,
  host: "localhost",
  port: 8086,
  scheme: "http",
  http_client: Instream.HTTPClient.Hackney,
  loggers: [{Instream.Log.DefaultLogger, :log, []}],
  writer: Instream.Writer.Line,
  json_decoder: {Jason, :decode!, [[keys: :atoms]]},
  json_encoder: {Jason, :encode!, []}

This also means that per default the connection uses no authentication.


InfluxDB Version

By default (version: :v1) the communication will be done with the expectation of an InfluxDB 1.x server responding. If you are communicating with an InfluxDB 2.x server please configure version: :v2.

Any methods not supported by your configured version will respond with a special error tuple {:error, :version_mismatch} when called.


HTTP Client

Internally all requests are done using the configured :http_client.



Default for not otherwise configured HTTP Client is :hackney.

The configuration key :http_opts is directly passed to the client process. Parts of it are also used internally by :hackney to control more generic behaviour (request pool to be used and its configuration).

Please see :hackney.request/5 for a complete list of available options.

Setting the :http_opts key when calling a connection method allows usage of per-call options. The options are merged with the connection options and then passed on.

Unix Socket Connections

Some InfluxDB versions allow connecting via a unix socket. These sockets have native support in :hackney with the appropriate configuration:

config :my_app, MyConnection,
  scheme: "http+unix",
  host: URI.encode_www_form("/path/to/influxdb.sock")

Please be aware that you need to encode the socket path yourself.


JSON Library

By default the library used for encoding/decoding JSON is Jason. For the time :instream directly depends on it to ensure it is available.

If you want to use another library you can switch it:

config :my_app, MyConnection,
  json_decoder: MyJSONLibrary,
  json_encoder: MyJSONLibrary

config :my_app, MyConnection,
  json_decoder: {MyJSONLibrary, :decode_argless},
  json_encoder: {MyJSONLibrary, :decode_argless}

config :my_app, MyConnection,
  json_decoder: {MyJSONLibrary, :decode_it, [[keys: :atoms]]},
  json_encoder: {MyJSONLibrary, :decode_it, []}

If you configure only a module name it will be called as module.decode!(binary) and module.encode!(map). When using a more complete {m, f} or {m, f, args} configuration the data to decode/encode will passed as the first argument with your configured extra arguments following.



To connect to an InfluxDB instance with HTTP authentication enabled you have to configure your credentials:

config :my_app, MyConnection,
  auth: [method: :basic, username: "root", password: "root"]

config :my_app, MyConnection,
  auth: [method: :token, token: "Ln0quM0YVQcJilrp"]

For method you can choose between header authentication using :basic (InfluxDB v1) or :token (InfluxDB v2), or query parameters using :query (InfluxDB v1). If nothing or an invalid value is given the connection will be made using :basic authentication.


Point Writer

If you are using the regular line protocol writer Instream.Writer.Line you are done without having anything to configure. It is used by default and connects to the port you have configured for connection.

To write points over UDP you can adjust your configuration:

config :my_app, MyConnection,
  port_udp: 8089,
  writer: Instream.Writer.UDP

The connection will then write using UDP and connecting to the port :port_udp. All non-write queries will be send to the regular :port you have configured.



All queries are (by default) logged using Logger.debug/1 via the default logging module Instream.Log.DefaultLogger. To customize logging you have to alter the configuration of your connection:

config :my_app, MyConnection,
  loggers: [
    {FirstLogger, :log_fun, []},
    {SecondLogger, :log_fun, [:additional, :args]}

This configuration replaces the default logging module.

Configuration is given as a tuple of {module, function, arguments}. The log entry will be inserted as the first argument of the method call. It will be one of Instream.Log.PingEntry, Instream.Log.QueryEntry, Instream.Log.StatusEntry or Instream.Log.WriteEntry, depending on what type of request should be logged.

In addition to query specific information every entry carries metadata around:

  • :query_time: milliseconds it took to send request and receive the response
  • :response_status: status code or 0 if not applicable/available

When using the default logger you should re-configure :logger to be able to get them printed:

config :logger, :console,
  format: "

$time $metadata[$level] $message ",

  metadata: [:application, :pid, :query_time, :response_status]

To prevent a query from being logged you can pass an option: false)
MyConnection.query(query, log: false)

Link to this section Summary


Returns the configuration for a connection.

Link to this section Functions

Link to this function

get(otp_app, conn, key, defaults)

View Source
@spec get(
  otp_app :: atom(),
  conn :: module(),
  key :: nil | atom(),
  defaults :: Keyword.t()
) :: term()

Returns the configuration for a connection.

The configuration will be merged with global defaults and the defaults passed to the lookup function. The latter are usually the inline defaults from the connection module (conn).

If an otp_app is passed it will be used to fetch configuration values from the application environment.

Priority for configuration lookup (first found is returned):

  1. Application configuration
  2. Inline configuration
  3. Global defaults