Avrora
[](https://hex.pm/packages/avrora) [](https://hexdocs.pm/avrora) [](https://travis-ci.org/Strech/avrora)Getting Started
This library supports convenient encoding and decoding of Avro messages.
It can read the Avro schema from local files or the Confluent® Schema Registry, caching data in memory for performance.
It supports reading and writing data Kafka wire format prefix and from Object Container Files formats.
Many thanks to the AvroTurf Ruby gem for inspiration.
Add Avrora to your project
Add Avrora to mix.exs
as a dependency:
def deps do
[
{:avrora, "~> 0.7"}
]
end
Configuration
Configure the library in config/config.exs
:
config :avrora,
registry_url: "http://localhost:8081",
schemas_path: Path.expand("./priv/schemas")
names_cache_ttl: :timer.minutes(5)
registry_url
- URL for the Confluent Schema Registry, defaultnil
schemas_path
- Base path for locally stored schema files, default./priv/schemas
names_cache_ttl
- Time in ms to cache schemas in memory, default 300_000.
Set names_cache_ttl
to :infinity
to cache forever. This is safe when
schemas are resolved in the Schema Registry by numeric id or versioned name, as
it is unique. If the schema is resolved by name, then someone may update the
schema, so the TTL ensures that it will be reloaded to use the latest version.
Start cache process
Avrora uses an in-memory cache to speed up schema lookup.
Add it to your supervision tree:
children = [
Avrora
]
Supervisor.start_link(children, strategy: :one_for_one)
Or start the cache process manually:
{:ok, pid} = Avrora.start_link()
Usage
The primary way to use the library is via the Avrora.encode/2
and
Avrora.decode/2
functions. These functions load the Avro schema for you.
If registry_url
is defined, they first search the Schema Registry, falling
back to local files. If the schema is then found locally but not in the
registry, they will register the schema.
These examples assume you have a Payment
schema stored in the file
priv/schemas/io/confluent/Payment.avsc
:
{
"type": "record",
"name": "Payment",
"namespace": "io.confluent",
"fields": [
{
"name": "id",
"type": "string"
},
{
"name": "amount",
"type": "double"
}
]
}
When running interactively, first make sure the cache is started:
{:ok, pid} = Avrora.start_link()
encode/2
To encode a Payment
message:
{:ok, pid} = Avrora.start_link()
message = %{"id" => "tx-1", "amount" => 15.99}
{:ok, encoded} = Avrora.encode(message, schema_name: "io.confluent.Payment")
<<79, 98, 106, 1, 3, 204, 2, 20, 97, 118, 114, 111, 46, 99, 111, 100, 101, 99,
8, 110, 117, 108, 108, 22, 97, 118, 114, 111, 46, 115, 99, 104, 101, 109, 97,
144, 2, 123, 34, 110, 97, 109, 101, 115, 112, 97, 99, 101, 34, 58, 34, 105,
111, 46, 99, 111, 110, 102, 108, 117, 101, 110, 116, 34, 44, 34, 110, 97, 109,
101, 34, 58, 34, 80, 97, 121, 109, 101, 110, 116, 34, 44, 34, 116, 121, 112,
101, 34, 58, 34, 114, 101, 99, 111, 114, 100, 34, 44, 34, 102, 105, 101, 108,
100, 115, 34, 58, 91, 123, 34, 110, 97, 109, 101, 34, 58, 34, 105, 100, 34,
44, 34, 116, 121, 112, 101, 34, 58, 34, 115, 116, 114, 105, 110, 103, 34, 125,
44, 123, 34, 110, 97, 109, 101, 34, 58, 34, 97, 109, 111, 117, 110, 116, 34,
44, 34, 116, 121, 112, 101, 34, 58, 34, 100, 111, 117, 98, 108, 101, 34, 125,
93, 125, 0, 138, 124, 66, 49, 157, 51, 242, 3, 33, 52, 161, 147, 221, 174,
114, 48, 2, 26, 8, 116, 120, 45, 49, 123, 20, 174, 71, 225, 250, 47, 64, 138,
124, 66, 49, 157, 51, 242, 3, 33, 52, 161, 147, 221, 174, 114, 48>>
The :format
argument controls output format:
:plain
- Just return Avro binary data, with no header or embedded schema:ocf
- Use Object Container File format, embedding the full schema with the data:registry
- Write data with Confluent Schema Registry Wire Format, which prefixes the data with the schema id:guess
- Use:registry
if possible, otherwise use:ocf
(default)
{:ok, pid} = Avrora.start_link()
message = %{"id" => "tx-1", "amount" => 15.99}
{:ok, encoded} = Avrora.encode(message, schema_name: "io.confluent.Payment", format: :plain)
<<8, 116, 120, 45, 49, 123, 20, 174, 71, 225, 250, 47, 64>>
decode/2
Decode Payment
message using the specified schema:
{:ok, pid} = Avrora.start_link()
message = <<8, 116, 120, 45, 49, 123, 20, 174, 71, 225, 250, 47, 64>>
{:ok, decoded} = Avrora.decode(message, schema_name: "io.confluent.Payment")
%{"id" => "tx-1", "amount" => 15.99}
decode/1
Decode a message, auto-detecting the schema using magic bytes. It first tries resolving the schema using the integer id in the wire format header.
Next it tries reading using the Object Container Files embedded schema.
NOTE: Messages encoded with OCF are wrapped in a List.
{:ok, pid} = Avrora.start_link()
message =
<<79, 98, 106, 1, 3, 204, 2, 20, 97, 118, 114, 111, 46, 99, 111, 100, 101, 99,
8, 110, 117, 108, 108, 22, 97, 118, 114, 111, 46, 115, 99, 104, 101, 109, 97,
144, 2, 123, 34, 110, 97, 109, 101, 115, 112, 97, 99, 101, 34, 58, 34, 105,
111, 46, 99, 111, 110, 102, 108, 117, 101, 110, 116, 34, 44, 34, 110, 97, 109,
101, 34, 58, 34, 80, 97, 121, 109, 101, 110, 116, 34, 44, 34, 116, 121, 112,
101, 34, 58, 34, 114, 101, 99, 111, 114, 100, 34, 44, 34, 102, 105, 101, 108,
100, 115, 34, 58, 91, 123, 34, 110, 97, 109, 101, 34, 58, 34, 105, 100, 34, 44,
34, 116, 121, 112, 101, 34, 58, 34, 115, 116, 114, 105, 110, 103, 34, 125, 44,
123, 34, 110, 97, 109, 101, 34, 58, 34, 97, 109, 111, 117, 110, 116, 34, 44,
34, 116, 121, 112, 101, 34, 58, 34, 100, 111, 117, 98, 108, 101, 34, 125, 93,
125, 0, 84, 229, 97, 195, 95, 74, 85, 204, 143, 132, 4, 241, 94, 197, 178, 106,
2, 26, 8, 116, 120, 45, 49, 123, 20, 174, 71, 225, 250, 47, 64, 84, 229, 97,
195, 95, 74, 85, 204, 143, 132, 4, 241, 94, 197, 178, 106>>
{:ok, decoded} = Avrora.decode(message)
[%{"id" => "tx-1", "amount" => 15.99}]