Development console

The development server prints a boxed banner once at boot and one aligned line per request. The banner and the log are designed to be scanned — methods and status codes are colored, slow requests are highlighted, and everything adapts to the terminal.

Boot banner#

On altair server the console shows:

╭──────────────────────────────────────────────╮
│                Altair v0.2.2                 │
├──────────────────────────────────────────────┤
│ Environment   Development                    │
│ Address       http://localhost:3000          │
│ PID           15244                          │
│ Routes        5                              │
│ Middleware    6                              │
│ Crystal       1.21.0                         │
│ Started in    12.3ms                         │
╰──────────────────────────────────────────────╯

The banner is printed to STDOUT outside the log stream. Address shows localhost when the server binds to 0.0.0.0. Started in measures the time from Application#start to the banner.

Request log#

Each request logs one line through config.logger (Log.for("altair")):

17:33:04  GET      /                     200    0.1ms
17:33:05  POST     /posts                201    1.2ms
17:33:06  DELETE   /posts/4              204    0.2ms

Columns are aligned (method.ljust(7), path.ljust(22), status.rjust(3)), so the output scans as a table. Long paths are truncated with a leading ellipsis (…/very/long/path).

Colors#

Methods and status codes are colored by family when the terminal supports it:

• Methods: GET green, POST blue, PUT yellow, PATCH magenta, DELETE red, OPTIONS cyan
• Status: 2xx green, 3xx blue, 4xx yellow, 5xx red

Colors auto-detect STDOUT.tty? and respect NO_COLOR=1 and TERM=dumb. Force them on or off:

class Blog < Altair::Application
  config.logger_colors = true  # nil = auto, true/false = forced
end

Slow requests#

Requests slower than config.slow_request_threshold (default 20.milliseconds) are highlighted in yellow and suffixed with [SLOW]:

17:33:04  GET      /dashboard            200  124.3ms [SLOW]

Tune or disable the threshold:

config.slow_request_threshold = 50.milliseconds

Set it to 0.milliseconds to highlight every request, or to a large value to never highlight.

Timestamps and counter#

config.logger_timestamps = true       # HH:MM:SS prefix (default true)
config.logger_request_counter = true  # #0001 prefix (default false)
config.logger_compact = true          # compact single-line without alignment

Compact mode logs GET / 200 0.1ms without timestamps or padding — useful when piping to a file.

Request ID#

When the RequestId middleware assigns an identifier, it is appended:

17:33:04  GET      /posts                200    0.8ms (abc-123)

The same identifier is echoed back in the X-Request-Id response header.

Error output#

On unhandled exceptions (500) the console logs a highlighted block to STDERR via config.logger.error:

──────────────────────────────────────────────────

500 Internal Server Error

Route
GET /users/42

Controller
UsersController#show

Exception
NilAssertionError

Message
User not found

Location
src/controllers/users.cr:42

──────────────────────────────────────────────────

The HTML error page is still rendered in the browser when config.debug is true; the console block makes the same information visible without switching context.

Configuration reference#

Swap config.logger for a Log with an IO::Memory backend in specs to capture and assert on the output.