Reporter.File

Reporting to a file.

This reporter logs debugging information about completed requests to a file or stdout (in that case, pass in `devstdout` as the file to log to).

Every line this reporter logs is a JSON string. This 'structured logging' output is optimized for external logging platforms that display these logs in a pretty UI.

This logger supports sampling of successful requests, to help save money when sending logs to external services.

Documentation

report :: Handler -> Text -> TracingSpan -> IO ()

Log tracing information for a request to a file. Tracing information contains nested spans but will appear flattend in the log. Each tracing span will appear on its own line in the log, ordered by its start date.

Example usage:

settings <- File.decode
handler <- File.handler settings
File.report handler "request-id" span

data Handler

Contextual information this reporter needs to do its work. You can create one using handler.

handler :: Settings -> IO Handler

Create a Handler for a specified set of Settings. Do this once when your application starts and reuse the Handler you get.

cleanup :: Handler -> IO ()

Clean up your handler after you're done with it. Call this before your application shuts down.

data Settings

Configuration settings for this reporter. A value of this type can be read from the environment using the decoder function.

decoder :: Decoder Settings

Read Settings from environment variables. Default variables will be used in case no environment variable is set for an option.

logFile :: Settings -> FilePath

The file to log too. On unix systems you can set this to devstdout in order to log to stdout.

environment variable

LOG_FILE

default value

app.log

appName :: Settings -> Text

The name of this application. This will be attached to all logs.

environment variable

LOG_ROOT_NAMESPACE

default value

your-application-name-here

appEnvironment :: Settings -> Text

The environment this application is running in. This will be attached to all logs.

environment variable

ENVIRONMENT

default value

development

fractionOfSuccessRequestsLogged :: Settings -> Float

The fraction of requests that should be logged. Set to 1 if you want to log everything, and a lower value to save money.

environment variable

FRACTION_OF_SUCCESS_REQUESTS_LOGGED

default value

1