# Elixir Client for Apache Pulsar
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> [!TIP]
> Using [Broadway](https://github.com/dashbitco/broadway)? Check out the companion project: [off_broadway_pulsar](https://github.com/efcasado/off_broadway_pulsar).
An Elixir client for [Apache Pulsar](https://pulsar.apache.org/).
## Installation
Add `:pulsar_elixir` to your dependencies in `mix.exs`:
```elixir
def deps do
[
{:pulsar, "~> 2.4.0", hex: :pulsar_elixir}
]
end
```
## Quick Start
Assuming you have Pulsar running on `localhost:6650` and that you have implemented a basic
consumer like the one below:
```elixir
defmodule MyPulsarConsumer do
use Pulsar.Consumer.Callback
def handle_message(message, state) do
IO.puts("Received: #{message.payload}")
{:ok, state}
end
end
```
You can start producing and consuming messages with the following configuration:
```elixir
config :pulsar,
host: "pulsar://localhost:6650",
consumers: [
my_consumer: [
topic: "persistent://my-tenant/my-namespace/my-topic",
subscription_name: "my-subscription",
callback_module: MyPulsarConsumer
]
],
producers: [
my_producer: [
topic: "persistent://my-tenant/my-namespace/my-topic"
]
]
```
Sending a message using the configured producer can be done as follows:
```elixir
Pulsar.send(:my_producer, "Hello, Pulsar!")
```
By default, brokers, consumers and producers are started within the scope of the
`:default` client, but you can also configure multiple clients (which may come in
handy if you need to connect to multiple clusters).
```elixir
clients: [
client_1: [
host: "pulsar://host.cluster1.com:6650"
],
client_2: [
host: "pulsar://host.cluster2.com:6650"
]
]
```
Then, you can specify the client in the consumer or producer configuration using
the `client` key, eg. `client: :client_1`.
```elixir
producers: [
my_producer_1: [
client: :client_1
topic: "persistent://my-tenant/my-namespace/my-topic"
]
]
```
If your Pulsar cluster requires authentication, you can configure it in the client
using the `auth` key:
```elixir
auth: [
type: Pulsar.Auth.OAuth2,
opts: [
client_id: "<YOUR-OAUTH2-CLIENT-ID>",
client_secret: "<YOUR-OAUTH2-CLIENT-SECRET>",
site: "<YOUR-OAUTH2-ISSUER-URL>",
audience: "<YOUR-OAUTH2-AUDIENCE>"
]
]
```
## Testing
> [!IMPORTANT]
> Do not forget to add the following line to your `/etc/hosts` file before running the tests:
>
> ```
> 127.0.0.1 broker1 broker2
> ```
To run the tests, run the following command:
```
mix test
```
If you want to run only a subset of tests, specify the file including the tests you want to run
```
mix test test/integration/consumer_test.exs
```
You can also run individual tests by passing the line number where they are defined
```
mix test test/integration/consumer_test.exs:43
```
The `examples` directory includes a number of examples that demonstrate the use of the Pulsar client.
For example:
```
mix run --no-start examples/bingo.exs
```
## Features
The full feature matrix for Apache Pulsar can be found [here](https://pulsar.apache.org/client-feature-matrix/).
| Component | Feature | Supported |
|-----------|------------------------------------|-----------|
| Client | TLS encryption | ✅ |
| Client | Authentication | ⚠️ |
| Client | Transaction | ❌ |
| Client | Statistics | ❌ |
| Producer | Sync send | ✅ |
| Producer | Async send | ❌ |
| Producer | Batching | ❌ |
| Producer | Chunking | ✅ |
| Producer | Compression | ✅ |
| Producer | Schema | ❌ |
| Producer | Partitioned topics | ✅ |
| Producer | Access modes | ✅ |
| Consumer | ACK | ✅ |
| Consumer | Batch-index ACK | ✅ |
| Consumer | NACK | ✅ |
| Consumer | NACK back-off | ❌ |
| Consumer | Batching | ✅ |
| Consumer | Partitioned topics | ✅ |
| Consumer | Chunking | ✅ |
| Consumer | Seek | ✅ |
| Consumer | Subscription types | ✅ |
| Consumer | Subscription modes | ✅ |
| Consumer | Retry letter topic | ❌ |
| Consumer | Dead letter topic | ✅ |
| Consumer | Compression | ✅ |
| Consumer | Compaction | ❌ |
| Consumer | Schema | ❌ |
| Consumer | Configurable flow control settings | ✅ |
| Reader | | ❌ |
| TableView | | ❌ |
