Instream

InfluxDB driver for Elixir

Warning

This module is experimental at the moment and may change unexpectedly.

Tested influxdb version: 0.10.0 (see .travis.yml to be sure)

Setup

Add Instream as a dependency to your mix.exs file:

defp deps do
  [ { :instream, "~> 0.10" } ]
end

You should also update your applications to include all necessary projects:

def application do
  [ applications: [ :instream ] ]
end

Testing

To run the tests you need to have the http-authentication enabled.

Using the statements from the .travis.yml you can generate all necessary users for the tests with their proper privileges.

Usage

Connections

Defining a connection requires defining a module:

defmodule MyApp.MyConnection do
  use Instream.Connection, otp_app: :my_app
end

The :otp_app name and the name of the module can be freely chosen. They only need to be linked to an entry in your config.exs:

config :my_app, MyApp.MyConnection,
  hosts:  [ "localhost" ],
  pool:   [ max_overflow: 0, size: 1 ],
  port:   8086,
  scheme: "http",
  writer: Instream.Writer.Line

Note: While you can define as many hosts as you please only the first one will be used. This is subject to change.

You now have a connection definition you can hook into your supervision tree:

Supervisor.start_link(
  [ MyApp.MyConnection.child_spec ],
  strategy: :one_for_one
)

Default Connection Values

Only the hosts key is mandatory for a connection configuration. The following values will be used as defaults if no other value is set:

config :my_app, MyApp.MyConnection,
  pool:   [ max_overflow: 10, size: 5 ],
  port:   8086,
  scheme: "http",
  writer: Instream.Writer.Line

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

Authentication

To connect to an influxdb instance with http_auth enabled you have to configure your credentials:

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

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

Writer Configuration

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, MyApp.MyConnection,
  hosts: [ "localhost" ],
  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.

Ping

To validate a connection you can send ping requests to the server:

Instream.Connection.ping()

The response will be :pong on success or :error on any failure.

Queries

Every query can be executed asynchronously by passing [async: true] to MyApp.MyConnection.execute(). The result will then always be an immediate :ok without waiting for the query to be actually executed.

Administrative Queries

Managing Databases:

# create "my_database"
"my_database"
|> Instream.Cluster.Database.create()
|> MyApp.MyConnection.execute()

# drop "my_database"
"my_database"
|> Instream.Cluster.Database.drop()
|> MyApp.MyConnection.execute()

Managing Retention Policies:

# create "my_rp" retention policy
# argument order: policy, database, duration, replication, default
Instream.Cluster.RetentionPolicy.create(
  "my_rp", "my_database", "1h", 3, true
)
|> MyApp.MyConnection.execute()

# drop "my_rp" retention policy
Instream.Cluster.RetentionPolicy.drop("my_rp", "my_database")
|> MyApp.MyConnection.execute()

Data Queries

Please see the point “Series Definitions” on how to write data to your InfluxDB database.

Reading data:

# passing database to execute/1
"SELECT * FROM some_measurement"
|> MyApp.MyConnection.query(database: "my_database")

# defining database in the query
"SELECT * FROM \"my_database\".\"default\".\"some_measurement\""
|> MyApp.MyConnection.query()

# passing precision (= epoch) for query results
"SELECT * FROM some_measurement"
|> MyApp.MyConnection.query(precision: :minutes)

Query Builder

Experimental definition! Will change often and unexpected! (or may disappear…)

Using the query builder you can avoid writing your select statements by hand:

import Instream.Query.Builder

# SELECT one, or, more, fields FROM some_measurement
from(MySeries)
|> select([ "one", "or", "more", "fields" ])
|> MyApp.MyConnection.query()

# SELECT * FROM some_measurement WHERE binary = 'foo' AND numeric = 42
from("some_measurement")
|> where(%{ binary: "foo", numeric: 42 })
|> MyApp.MyConnection.query()

Series Definitions

If you do not want to define the raw maps for writing data you can pre-define a series for later usage:

defmodule MySeries do
  use Instream.Series

  series do
    database    "my_database"
    measurement "my_measurement"

    tag :bar
    tag :foo

    field :value
  end
end

Default Values

You can include a default value for tags in your series definition:

series do
  tag :host, default: "www"

  field :value, default: 100
end

These values will be pre-assigned when using the data struct. All fields or tags without a default value will be set to nil.

Writing Series Points

You can then use this module to assemble a data point (one at a time) for writing:

data = %MySeries{}
data = %{ data | fields: %{ data.fields | value: 17 }}
data = %{ data | tags:   %{ data.tags   | bar: "bar", foo: "foo" }}

And then write one or many at once:

data
|> MyApp.MyConnection.write()

# write the point asynchronously
data
|> MyApp.MyConnection.write(async: true)

# write multiple points at once
[ point_1, point_2, point_3 ]
|> MyApp.MyConnection.write()

If you want to pass an explicit timestamp to the database you can use the key :timestamp:

data = %MySeries{}
data = %{ data | timestamp: 1439587926000000000 }

The timestamp is (by default) expected to be a nanosecond unix timestamp. To use a different precision (for all points in this write operation!) you can change this value by modifying your write call:

data = %MySeries{}
data = %{ data | timestamp: 1439587926 }

data
|> MyApp.MyConnection.write([ async: true, precision: :seconds ])

Supported precision types are:

• :hours
• :minutes
• :seconds
• :milli_seconds
• :micro_seconds
• :nano_seconds

Please be aware that the UDP protocol writer does not support custom timestamp precisions. All UDP timestamps are implicitly expected to already be at nanosecond precision.

License

Apache License, Version 2.0