Settings View Source Snap (Snap v0.9.0)

Snap is split into a few key modules:

• Snap.Cluster - clusters are wrappers around the Elasticsearch HTTP API. We use these to perform low-level HTTP requests.

• Snap.Indexes - a convenience wrapper around the Elasticsearch indexes APIs, allowing the creation, deleting and aliasing of indexes, along with hotswap functionality to bulk load documents into an aliased index, switching to it atomically.

• Snap.Document - a convenience wrapper around the Document APIs, allowing the creating, updating and deleting individual documents.

• Snap.Search - for performing searches

• Snap.Multi - for performing multiple searches in a single query

• Snap.Bulk - a convenience wrapper around bulk operations, using Stream to stream actions (such as Snap.Bulk.Action.Create) to be performed against the Snap.Cluster.

Additionally, there are other supporting modules:

• Snap.HTTPClient - defines how to send HTTP requests. Comes with a built in adapter for Finch (Snap.HTTPClient.Adapters.Finch)

• Snap.Auth - defines how an HTTP request is modified to include authentication headers. Snap.Auth.Plain implements HTTP Basic Auth.

• Snap.Cluster.Namespace - for isolating cluster and processes to work on separate indexes

Set up

Snap.Cluster is a wrapped around an Elasticsearch cluster. We can define it like so:

defmodule MyApp.Cluster do
  use Snap.Cluster, otp_app: :my_app
end

The configuration for the cluster can be defined in your config:

config :my_app, MyApp.Cluster,
  url: "http://localhost:9200",
  username: "username",
  password: "password"

Or you can load it dynamically by implementing Snap.Cluster.init/1.

Each cluster defines start_link/1 which must be invoked before using the cluster and optionally accepts an explicit config. It creates the supervision tree, including the connection pool.

Include it in your application:

def start(_type, _args) do
  children = [
    {MyApp.Cluster, []}
  ]

  opts = [strategy: :one_for_one, name: MyApp.Supervisor]
  Supervisor.start_link(children, opts)
end

Config

The following configuration options are supported:

• url - the URL of the Elasticsearch HTTP endpoint (required)
• username - the username used to access the cluster
• password - the password used to access the cluster
• auth - the auth module used to configure the HTTP authentication headers (defaults to Snap.Auth.Plain)
• http_client_adapter - the adapter that will be used to send HTTP requests. Check Snap.HTTPClient for more information. (defaults to Snap.HTTPClient.Adapters.Finch)
• telemetry_prefix - the prefix of the telemetry events (defaults to [:my_app, :snap])
• index_namespace - see Snap.Cluster.Namespace for details (defaults to nil)

Telemetry

Snap supports sending Telemetry events on each HTTP request. It sends one event per query, of the name [:my_app, :snap, :request].

The telemetry event has the following measurements:

• response_time - how long the request took to return
• decode_time - how long the response took to decode into a map or exception
• total_time - how long everything took in total

In addition, the metadata contains a map of:

• method - the HTTP method used
• path - the path requested
• port - the port requested
• host - the host requested
• headers - a list of the headers sent
• body - the body sent
• result - the result returned to the user

Testing

See Snap.Test for details.