Modulewai-log-0.4.0.1Haskell2010

Network.Wai.Log

A simple logging middleware for WAI applications that supports the 'log-*' family of packages: https://hackage.haskell.org/package/log-base

When logging to stdout using defaultOptions, the output looks like this:

2020-10-27 12:30:23 INFO eid-server: Request received {
  "url": "/api/v1/transaction/new",
  "body_length": "KnownLength 136",
  "method": "POST",
  "user_agent": "curl/7.68.0",
  "request_id": "f2c89425-9ec4-4cd2-ae56-4bab23681fce",
  "remote_host": "127.0.0.1:34694"
}
2020-10-27 12:30:23 INFO eid-server: Sending response {
  "request_id": "f2c89425-9ec4-4cd2-ae56-4bab23681fce"
}
2020-10-27 12:30:23 INFO eid-server: Request complete {
  "response_body": null,
  "url": "/api/v1/transaction/new",
  "method": "POST",
  "status": {
    "code": 400,
    "message": "Bad Request"
  },
  "time": {
    "process": 2.97493e-3,
    "full": 3.159565e-3
  },
  "request_id": "f2c89425-9ec4-4cd2-ae56-4bab23681fce"
}

3 types
7 values

Packagewai-log-0.4.0.1
Exports10
LanguageHaskell2010
LicenceBSD-3-Clause
SourceLog.hs

Create a Middleware

2 declarations

valuemkLogMiddleware :: MonadLog m => m (LogMiddleware UUID)

Create a LogMiddleware using defaultOptions

Use mkLogMiddlewareWith for custom Options

valuemkLogMiddlewareWith

:: (MonadLog m, ToJSON id)
=> Options id
-> m (LogMiddleware id)

Create a LogMiddleware using the supplied Options

Type

typetype LogMiddleware id = (id -> Application) -> Application

The classic wai Middleware type is Application -> Application, but that does not work when you want to pass logging context down to the Application.

Instead we pass an id to the Application, containing the request_id, so it can be logged in the application's context.

Options

datadata Options id

Logging options

Logging response body involves extracting it from Response via IO operations, therefore the logBody option takes Request, Status and ResponseHeaders as arguments to decide whether the IO operations of body extraction have to be performed. The resulting Maybe function is the constructor of a loggable Value from the body bytestring builder.

Constructors

Options
- logLevel :: LogLevel
- logRequest :: id -> Request -> [Pair]
- logResponse :: id -> Request -> Response -> Value -> ResponseTime -> [Pair]
- logBody :: Maybe (Request -> Status -> ResponseHeaders -> Maybe (Builder -> Value))
  An optional constructor of the response body log value.
- logGetRequestId :: Request -> IO id
  A function for getting the request id

datadata ResponseTime

Timing data

Constructors

ResponseTime
- processing :: NominalDiffTime
  Time between request received and application finished processing request
- full :: NominalDiffTime
  Time between request received and response sent

valuedefaultOptions :: Options UUID

Default Options

{ logLevel = LogInfo
, logRequest = defaultLogRequest
, logResponse = defaultLogResponse
, logGetRequestId = 'const nextRandom'
}

valuedefaultLogRequest :: ToJSON id => id -> Request -> [Pair]

Logs the following request values:

request_uuid
method
url path
remote host
user agent
body-length

valuedefaultLogResponse

:: ToJSON id
=> id
-> Request
-> Response
-> Value
-> ResponseTime
-> [Pair]

Logs the following values:

request_id
request method
request url path
response_body details provided as Value
status code
status message
time full
time processing

Time is in seconds as that is how NominalDiffTime is treated by default

valuemkOpaqueDefaultOptions :: ToJSON id => (Request -> IO id) -> Options id

Build a default Options record for an opaque id given a function for retrieving an id.

Helpers

valuelogRequestId :: (MonadLog m, ToJSON id) => id -> m a -> m a

Helper to consistently log the request id in your application by adding request_id field to log's localData