slow-server

#!/usr/bin/env bash

############################################################################
# Starts a web server (using socat) on the given port (default 8080) which #
# returns 200 OK after waiting for n milliseconds                          #
# e.g. curl http://localhost:8080/2500 # Responds after ~2.5 seconds       #
############################################################################
# Usage:                                                                   #
#   slow-server [port]                                                     #
############################################################################
# Dependencies:                                                            #
#   socat - upgraded netcat/nc, used as a simple server                    #
#   sleep - must support fractional seconds on your system                 #
############################################################################

_slow_server() {
    # Function arguments
    local port="${1:-8080}"

    # Check for socat dependency
    if ! command -v socat >/dev/null 2>&1; then
        echo "ERROR: Missing dependency: socat" >&2
        return 1
    fi

    # Function invoked by socat below on each request
    #shellcheck disable=SC2317 # "Command appears to be unreachable. Check usage (or ignore if invoked indirectly)."
    _slow_response() {
        _is_number() {
            case "$1" in
                ''|*[!0-9]*)
                    return 1 ;; # not a number
                *)
                    return 0 ;; # is a number
            esac
        }
        local method path version
        read method path version
        local last; last="$(basename "$path")"
        printf %s "$method $path ($last)" >&2
        # Ignore other paths, return not found
        if ! _is_number "$last"; then
            echo " [ignored]" >&2 # append to previous line
            echo "HTTP/1.1 404 Not Found\r\n"
            return 0
        else
            local delay_ms="$last"
            printf '\n' >&2 # move to next line
        fi
        local seconds="$((delay_ms / 1000)).$((delay_ms % 1000))"
        sleep "$seconds"
        local response="HTTP/1.1 200 OK\r\n\r\n$last"
        echo "$response"
        echo "Done: $method $path ($delay_ms)" >&2
        unset -f _is_number
    }
    export -f _slow_response # exported for socat

    # Start simple server
    echo "Starting server at http://localhost:$port"
    socat "TCP-LISTEN:$port,fork,reuseaddr" "SYSTEM:_slow_response"
    unset -f _slow_response # unset exported function when server closes
}

_slow_server "$@"