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https://github.com/rlopzc/logger_exporter

Export your logs to the service of your choice.
https://github.com/rlopzc/logger_exporter

elixir elixir-phoenix heroku logger logger-backend logging

Last synced: 9 days ago
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Export your logs to the service of your choice.

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# LoggerExporter

Export your logs to the service of your choice.

I created this library because I wanted to export logs to a different service in
Heroku. There is no simple way to export your logs.

## Supported exporters:
- Loki
- Mezmo (LogDNA)

Implement your own exporter using `LoggerExporter.Exporters.Exporter` behaviour.

## Supported formatters:
- Basic. By default, it will read your logger `:console` format configuration.
Example:
```elixir
config :logger, :console, format: "$time $message"
```
Defaults to `$time $metadata[$level] $message`

Implement your own formatter using `LoggerExporter.Formatters.Formatter` behaviour.

## Plug Logger

A plug for logging request information. It will log the method, path, params,
status and duration.

You can add it to your MyApp.Endpoint:
```elixir
# Log level defaults to :info
plug LoggerExporter.Loggers.Plug

# Dynamic log
plug LoggerExporter.Loggers.Plug, log: {__MODULE__, :log_level, []}

# Disables logging for routes like /health_check
def log_level(%{path_info: ["health_check"]}), do: false
def log_level(_), do: :info
```

## Installation

Add `logger_exporter` to your list of dependencies in `mix.exs`:

```elixir
def deps do
[
{:logger_exporter, "~> 0.4.0"}
]
end
```

## Configuration

By default, the timestamp sent for each log to the external service is in UTC: `System.os_time(:nanosecond)`

| option | description | default |
|------------------|---------------------------------------------------------------------------------------------------------------|--------------------------------------------|
| level | The logger level to report. | `:info` |
| formatter | Allows the selection of a formatter implementation. | `LoggerExporter.Formatters.BasicFormatter` |
| metadata | Metadata to log. | `[]` |
| exporter | Allows selection of a exporter implementation. | `LoggerExporter.Exporters.LokiExporter` |
| host | The host of the service without the path. The path is inferred by the exporter. | No default. Required |
| app_name | The name of the app to use as label. | No default. Required |
| environment_name | The name of the app to use as label. | No default. Required |
| http_client | Allows the selection of the HTTP client. | `LoggerExporter.HttpClient.ReqClient` |
| send_to_http | If set to false, the library will not make any actual API calls. This is useful for test or dev environments. | `true` |
| http_auth | See below for configuration | No default |

### HTPP Auth

Supported authentication methods:
- Basic
- Bearer
- Custom

| auth | examples | result |
| -------- | ------------------------------------------ | ------------------------------------------------ |
| basic | `{:basic, "user", "pxIsldPlwty"}` | `"Authorization: Basic CshL2XlkX57cww=="` |
| bearer | `{:bearer, "WmRUuBOnTjDwP6jo3bno"}` | `"Authorization: Bearer WmRUuBOnTjDwP6jo3bno"` |
| custom | `{:header, "apiKey", "dAWRQQkZCc2A=="}` | `"apiKey: dAWRQQkZCc2A=="` |

## Usage in Phoenix

1. Add the following to deps section of your mix.exs: `{:logger_exporter, "~> 0.4.0"}`
and then `mix deps.get`

2. Add `LoggerExporter.Backend` to your logger's backends configuration

```
config :logger,
backends: [:console, LoggerExporter.Backend]
```

3. Add config related to the exporter and other fields.
ie. for `LokiExporter`

```elixir
config :logger, LoggerExporter,
host: "http://localhost:3100",
app_name: "my_app",
environment_name: config_env(),
http_auth: {:basic, System.fetch_env!("LOKI_USER"), System.fetch_env!("LOKI_PASSWORD")},
metadata: [:request_id]
```

4. Start the LoggerExporter GenServer in the supervised children list.
In `application.ex` add to the children list:

```elixir
children [
...
LoggerExporter
]
```
5. (Optional) Add custom Plug logger.
In `MyApp.Endpoint` add the plug after `Plug.Parsers`.
If you see duplicate logs, remove `Plug.Telemetry` from your endpoint.

```elixir
plug Plug.Parsers,
...

plug LoggerExporter.Loggers.Plug
```

## JSON Formatter Example

If you want to log in JSON format, you can use the formatter of another library:
[logger_json](https://github.com/Nebo15/logger_json)

You need to implement the following formatter using the `LoggerExporter.Formatters.Formatter` behaviour.

```elixir
defmodule MyFormatter do
@behaviour LoggerExporter.Formatters.Formatter

alias LoggerJSON.Formatters.BasicLogger

@impl true
def format_event(level, msg, ts, md, md_keys) do
BasicLogger.format_event(level, msg, ts, md, md_keys, [])
|> Jason.encode!()
end
end
```

Then, configure it like this:
```elixir
config :logger, LoggerExporter,
formatter: MyFormatter
```

Tada! You have JSON logs!

## Telemetry

Telemetry integration for logging and error reporting.

There is a default logger for you to attach. It logs when the `status` is `:error`

In your `application.ex`

```elixir
:ok = LoggerExporter.Telemetry.attach_default_logger()
```

### HTTP Post batch events

LoggerExporter emits the following events for processing each batch (sending it through http)

- `[:logger_exporter, :batch, :start]` -- starting to process the events
- `[:logger_exporter, :batch, :stop]` -- after the events is processed
- `[:logger_exporter, :batch, :exception]` -- after the events are processed

The following chart shows which metadata you can expect for each event:

| event | measures | metadata |
| ------------ | -------------- | --------- |
| `:start` | `:system_time` | `:events` |
| `:stop` | `:duration` | `:events, :status, :response` |
| `:exception` | `:duration` | `:events, :kind, :reason, :stacktrace` |

Metadata
* `:events` - the list of `LoggerExporter.Event` processed.
* `:status` - either `:ok` or `:error`.
* `:response` - information of the response.