//! # Goose
//! 
//! Have you ever been attacked by a goose?
//! 
//! Goose is a load testing tool based on [Locust](https://locust.io/).
//! User behavior is defined with standard Rust code.
//! 
//! Goose load tests are built by creating an application with Cargo,
//! and declaring a dependency on the Goose library.
//! 
//! Goose uses the `reqwest::blocking` API to provide a convenient HTTP
//! client. (Async support is on the roadmap, also provided through the
//! `reqwest` library.)
//! 
//! ## Creating and running a Goose load test
//! 
//! ### Creating a simple Goose load test
//! 
//! First create a new empty cargo application, for example:
//! 
//! ```bash
//! $ mkdir loadtest
//! $ cd loadtest/
//! $ cargo init
//!      Created binary (application) package
//! ```
//! 
//! Add Goose as a dependency in `Cargo.toml`:
//! 
//! ```toml
//! [dependencies]
//! goose = "0.4"
//! ```
//! 
//! Add the following boilerplate use declarations at the top of your `src/main.rs`:
//! 
//! ```rust
//! use goose::{goose_init, goose_launch};
//! use goose::goose::{GooseTaskSets, GooseTaskSet, GooseClient, GooseTask};
//! ```
//! 
//! Below your `main` funcation (which currently is the default `Hello, world!`), add
//! one or more load test functions. The names of these functions are arbitrary, but it is
//! recommended you use self-documenting names. Each load test function must accept a mutable
//! GooseClient pointer. For example:
//! 
//! ```rust
//! fn loadtest_foo(client: &mut GooseClient) {
//!   let _response = client.get("/path/to/foo");
//! }   
//! ```
//! 
//! In the above example, we're using the GooseClient helper method `get` to load a path
//! on the website we are load testing. This helper creates a Reqwest request builder, and
//! uses it to build and execute a request for the above path. If you want access to the
//! request builder object, you can instead use the `goose_get` helper, for example to
//! set a timout on this specific request:
//! 
//! ```rust
//! use std::time;
//! 
//! fn loadtest_bar(client: &mut GooseClient) {
//!   let three_seconds = time::Duration::from_secs(3);
//!   let request_builder = client.goose_get("/path/to/bar");
//!   let _response = client.goose_send(request_builder.timeout(three_seconds));
//! }   
//! ```
//! 
//! We pass the `request_builder` object to `goose_send` which builds and executes it, also
//! collecting useful statistics which can be viewed with the `--print-stats` flag.
//! 
//! Once all our tasks are created, we edit the main function to initialize goose and register
//! the tasks. In this very simple example we only have two tasks to register, but in a real
//! load test you can have any number of task sets with any number of individual tasks.
//! 
//! ```goose
//! fn main() {
//!   // Initialize Goose.
//!   let goose_state = goose_init();
//! 
//!   // Initialize a single object to hold all our task sets.
//!   let mut goose_task_sets = GooseTaskSets::new();
//! 
//!   // Create and configure our first task set.
//!   let mut loadtest_tasks = GooseTaskSet::new("LoadtestTasks")
//!     // Apply random sleep after each task runs.
//!     .set_wait_time(0, 3);
//! 
//!   // Register the foo task, assigning it a weight of 10.
//!   loadtest_tasks.register_task(GooseTask::new().set_weight(10).set_function(loadtest_foo));
//!   // Register the bar task, assigning it a weight of 2 (so it runs 1/5 as
//!   // often as bar). Apply a task name which shows up in statistics.
//!   loadtest_tasks.register_task(GooseTask::named("bar").set_weight(2).set_function(loadtest_bar));
//! 
//!   // Register our task set.
//!   goose_task_sets.register_taskset(loadtest_tasks);
//! 
//!   // With all task sets and tasks registered, launch the load test.
//!   goose_launch(goose_state, goose_task_sets);
//! }
//! ```
//! 
//! Goose now spins up a configurable number of clients, each simulating a user on your
//! website. Thanks to Reqwest, each user maintains its own client state, handling cookies
//! and more so your "users" can log in, fill out forms, and more, as real users on your
//! sites would do.
//! 
//! ### Running the Goose load test
//! 
//! Attempts to run our example will result in an error, as we have not yet defined the
//! host against which this loadtest should be run. We intentionally do not hard code the
//! host in the individual tasks, as this allows us to run the test against different
//! environments, such as local and staging.
//! 
//! ```bash
//! $ cargo run --release -- 
//!    Compiling loadtest v0.1.0 (~/loadtest)
//!     Finished release [optimized] target(s) in 1.52s
//!      Running `target/release/loadtest`
//! 05:33:06 [ERROR] Host must be defined globally or per-TaskSet. No host defined for LoadtestTasks.
//! ```
//! Pass in the `-h` flag to see all available run-time options. For now, we'll use a few
//! options to customize our load test.
//! 
//! ```bash
//! $ cargo run --release -- --host http://apache.fosciana --print-stats -t 30s -v
//! ```
//! 
//! The first option we specified is `--host`, and in this case I'm telling Goose to run the load test
//! against an 8-core VM on my local network. The `--print-stats` flag configures Goose to collect
//! statistics as the load test runs, printing running statistics during the test and final summary
//! statistics when finished. The `-t 30s` option tells Goose to end the load test after 30 seconds
//! (for real load tests you'll certainly want to run it longer, you can use `m` to specify minutes
//! and `h` to specify hours. For example, `-t 1h30m` would run the load test for 1 hour 30 minutes).
//! Finally, the `-v` flag tells goose to display INFO and higher level logs to stdout, giving more
//! insight into what is happening. (Additional `-v` flags will result in considerably more debug
//! output, and are not recommended for running actual load tests; they're only useful if you're
//! trying to debugging Goose itself.)
//! 
//! 
//! ```bash
//!    Finished release [optimized] target(s) in 0.05s
//!     Running `target/release/loadtest --host 'http://apache.fosciana' --print-stats -t 30s -v`
//! 05:56:30 [ INFO] Output verbosity level: INFO
//! 05:56:30 [ INFO] Logfile verbosity level: INFO
//! 05:56:30 [ INFO] Writing to log file: goose.log

//! ```
//! 
//! By default Goose will write a log file with INFO and higher level logs into the same directory
//! as you run the test from.
//! 
//! ```bash
//! 05:56:30 [ INFO] run_time = 30
//! 05:56:30 [ INFO] concurrent clients defaulted to 8 (number of CPUs)
//! 05:56:30 [ INFO] hatch_rate defaulted to 8 (number of CPUs)
//! ```
//! 
//! Goose will default to launching 1 client per available CPU core, and will launch them all in
//! one second. You can change how many clients are launched with the `-c` option, and you can
//! change how many clients are launched per second with the `-r` option. For example, `-c 30 -r 2`
//! would launch 30 clients over 15 seconds.
//! 
//! ```bash
//! 05:56:30 [ INFO] global host configured: http://apache.fosciana
//! 05:56:30 [ INFO] launching client 1 from LoadtestTasks...
//! 05:56:30 [ INFO] launching client 2 from LoadtestTasks...
//! 05:56:30 [ INFO] launching client 3 from LoadtestTasks...
//! 05:56:30 [ INFO] launching client 4 from LoadtestTasks...
//! 05:56:30 [ INFO] launching client 5 from LoadtestTasks...
//! 05:56:30 [ INFO] launching client 6 from LoadtestTasks...
//! 05:56:30 [ INFO] launching client 7 from LoadtestTasks...
//! 05:56:31 [ INFO] launching client 8 from LoadtestTasks...
//! 05:56:31 [ INFO] launched 8 clients...
//! ```
//! 
//! Each client is launched in its own thread with its own client state. Goose is able to make
//! very efficient use of server resources.
//! 
//! ```bash
//! 05:56:46 [ INFO] printing running statistics after 15 seconds...
//! ------------------------------------------------------------------------------ 
//!  Name                    | # reqs         | # fails        | req/s  | fail/s
//!  ----------------------------------------------------------------------------- 
//!  GET /path/to/foo        | 15,795         | 0 (0%)         | 1,053  | 0    
//!  GET bar                 | 3,161          | 0 (0%)         | 210    | 0    
//!  ------------------------+----------------+----------------+--------+--------- 
//!  Aggregated              | 18,956         | 0 (0%)         | 1,263  | 0    
//! ------------------------------------------------------------------------------
//! ```
//! 
//! When printing statistics, by default will display running values approximately
//! every 15 seconds. Running statistics are broken into two tables. The first, above,
//! shows how many requests have been made, how many of them failed (non-200 response),
//! and the corresponding per-second rates.
//! 
//! Note that Goose respected the per-task weights we sent, and `foo` (with a weight of
//! 10) is being loaded five times as often as `bar` (with a weight of 2). Also notice
//! that because we didn't name the `foo` task by default we see the URL loaded in the
//! statistics, whereas we did name the `bar` task so we see the name in the statistics.
//! 
//! ```bash
//!  Name                    | Avg (ms)   | Min        | Max        | Mean      
//!  ----------------------------------------------------------------------------- 
//!  GET /path/to/foo        | 0.67       | 0.31       | 13.51      | 0.53      
//!  GET bar                 | 0.60       | 0.33       | 13.42      | 0.53      
//!  ------------------------+------------+------------+------------+------------- 
//!  Aggregated              | 0.66       | 0.31       | 13.51      | 0.56      
//! ```
//! 
//! The second table in running statistics provides details on respone times. In our
//! example (which is running over wifi from my development lapopt), on average each
//! page is returning within `0.66` milliseconds. The quickest page response was for 
//! `foo` within `0.31` milliseconds. The slowest page response was also for `foo` within
//! `13.51` milliseconds.
//! 
//! 
//! ```bash
//! 05:37:10 [ INFO] stopping after 30 seconds...
//! 05:37:10 [ INFO] waiting for clients to exit
//! ```
//! 
//! Our example only runs for 30 seconds, so we only see running statistics once. Once
//! the test is complete, we get more detail in the final summary. The first two tables
//! are the same as what we saw earlier, however now they include all statistics for the
//! entire load test:
//! 
//! ```bash
//! ------------------------------------------------------------------------------ 
//!  Name                    | # reqs         | # fails        | req/s  | fail/s
//!  ----------------------------------------------------------------------------- 
//!  GET bar                 | 6,050          | 0 (0%)         | 201    | 0    
//!  GET /path/to/foo        | 30,257         | 0 (0%)         | 1,008  | 0    
//!  ------------------------+----------------+----------------+--------+---------- 
//!  Aggregated              | 36,307         | 0 (0%)         | 1,210  | 0    
//! -------------------------------------------------------------------------------
//!  Name                    | Avg (ms)   | Min        | Max        | Mean      
//!  ----------------------------------------------------------------------------- 
//!  GET bar                 | 0.66       | 0.32       | 108.87     | 0.53      
//!  GET /path/to/foo        | 0.68       | 0.31       | 109.50     | 0.53      
//!  ------------------------+------------+------------+------------+------------- 
//!  Aggregated              | 0.67       | 0.31       | 109.50     | 0.50      
//! -------------------------------------------------------------------------------
//! ```
//! 
//! The ratio between `foo` and `bar` remained 5:2 as expected. As the test ran,
//! however, we saw some slower page loads, with the slowest again `foo` this time
//! at `109.50` milliseconds.
//! 
//! ```bash
//! Slowest page load within specified percentile of requests (in ms):
//! ------------------------------------------------------------------------------
//! Name                    | 50%    | 75%    | 98%    | 99%    | 99.9%  | 99.99%
//! ----------------------------------------------------------------------------- 
//! GET bar                 | 0.53   | 0.66   | 2.17   | 5.37   | 18.72  | 123.16
//! GET /path/to/foo        | 0.53   | 0.66   | 2.65   | 10.60  | 18.00  | 107.32
//! ------------------------+------------+------------+------------+------------- 
//! Aggregated              | 0.53   | 0.66   | 2.37   | 6.45   | 18.32  | 108.18
//! ```
//! 
//! A new table shows additional information, breaking down response-time by
//! percentile. This shows that the slowest page loads only happened in the
//! slowest .001% of page loads, so were very much an edge case. 99.9% of the time
//! page loads happened in less than 20 milliseconds.


#[macro_use]
extern crate log;

//#[macro_use]
//extern crate goose_codegen;

extern crate structopt;

pub mod goose;

mod client;
mod stats;
mod util;

use std::collections::{BTreeMap, HashMap};
use std::f32;
use std::fs::File;
use std::path::PathBuf;
use std::sync::{Arc, mpsc};
use std::sync::atomic::{AtomicBool, Ordering};
use std::{thread, time};

use rand::thread_rng;
use rand::seq::SliceRandom;
use simplelog::*;
use structopt::StructOpt;
use url::Url;

use goose::{GooseTaskSets, GooseTaskSet, GooseTask, GooseClient, GooseClientMode, GooseClientCommand, GooseRequest};

/// Global state for Goose loadtest.
#[derive(Debug, Clone)]
pub struct GooseState {
    configuration: Configuration,
    number_of_cpus: usize,
    run_time: usize,
    clients: usize,
    active_clients: usize,
}
/// Goose global state is initialized by calling GooseState::new(configuration).
impl GooseState {
    fn new(configuration: Configuration) -> GooseState {
        GooseState {
            configuration: configuration,
            number_of_cpus: num_cpus::get(),
            run_time: 0,
            clients: 0,
            active_clients: 0,
        }
    }
}

/// Configuration options available when launching a Goose loadtest.
#[derive(StructOpt, Debug, Clone)]
#[structopt(name = "client")]
pub struct Configuration {
    /// Host to load test in the following format: http://10.21.32.33
    #[structopt(short = "H", long, required=false, default_value="")]
    host: String,

    ///// Rust module file to import, e.g. '../other.rs'.
    //#[structopt(short = "f", long, default_value="goosefile")]
    //goosefile: String,

    /// Number of concurrent Goose users (defaults to available CPUs).
    #[structopt(short, long)]
    clients: Option<usize>,

    /// How many users to spawn per second (defaults to available CPUs).
    #[structopt(short = "r", long)]
    hatch_rate: Option<usize>,

    /// Stop after the specified amount of time, e.g. (300s, 20m, 3h, 1h30m, etc.).
    #[structopt(short = "t", long, required=false, default_value="")]
    run_time: String,

    /// Prints stats in the console
    #[structopt(long)]
    print_stats: bool,

    /// Includes status code counts in console stats
    #[structopt(long)]
    status_codes: bool,

    /// Only prints summary stats
    #[structopt(long)]
    only_summary: bool,

    /// Resets statistics once hatching has been completed
    #[structopt(long)]
    reset_stats: bool,

    /// Shows list of all possible Goose tasks and exits
    #[structopt(short, long)]
    list: bool,

    //// Number of seconds to wait for a simulated user to complete any executing task before exiting. Default is to terminate immediately.
    //#[structopt(short, long, required=false, default_value="0")]
    //stop_timeout: usize,

    // The number of occurrences of the `v/verbose` flag
    /// Debug level (-v, -vv, -vvv, etc.)
    #[structopt(short = "v", long, parse(from_occurrences))]
    verbose: u8,

    // The number of occurrences of the `g/log-level` flag
    /// Log level (-g, -gg, -ggg, etc.)
    #[structopt(short = "g", long, parse(from_occurrences))]
    log_level: u8,

    #[structopt(long, default_value="goose.log")]
    log_file: String,
}

/// Allocate a vector of weighted GooseClient
fn weight_task_set_clients(task_sets: &GooseTaskSets, clients: usize, state: &GooseState) -> Vec<GooseClient> {
    trace!("weight_task_set_clients");

    let mut u: usize = 0;
    let mut v: usize;
    for task_set in &task_sets.task_sets {
        if u == 0 {
            u = task_set.weight;
        }
        else {
            v = task_set.weight;
            trace!("calculating greatest common denominator of {} and {}", u, v);
            u = util::gcd(u, v);
            trace!("inner gcd: {}", u);
        }
    }
    // 'u' will always be the greatest common divisor
    debug!("gcd: {}", u);

    // Build a weighted lists of task sets (identified by index)
    let mut weighted_task_sets = Vec::new();
    for (index, task_set) in task_sets.task_sets.iter().enumerate() {
        // divide by greatest common divisor so vector is as short as possible
        let weight = task_set.weight / u;
        trace!("{}: {} has weight of {} (reduced with gcd to {})", index, task_set.name, task_set.weight, weight);
        let mut weighted_sets = vec![index; weight];
        weighted_task_sets.append(&mut weighted_sets);
    }
    // Shuffle the weighted list of task sets
    weighted_task_sets.shuffle(&mut thread_rng());

    // Allocate a state for each client that will be spawned.
    let mut weighted_clients = Vec::new();
    let mut client_count = 0;
    let config = state.configuration.clone();
    loop {
        for task_sets_index in &weighted_task_sets {
            let task_set_host = task_sets.task_sets[*task_sets_index].host.clone();
            weighted_clients.push(GooseClient::new(
                task_sets.task_sets[*task_sets_index].task_sets_index,
                task_set_host,
                task_sets.task_sets[*task_sets_index].min_wait,
                task_sets.task_sets[*task_sets_index].max_wait,
                &config
            ));
            client_count += 1;
            if client_count >= clients {
                trace!("created {} weighted_clients", client_count);
                return weighted_clients;
            }
        }
    }
}

/// Returns a sequenced bucket of weighted usize pointers to Goose Tasks
fn weight_tasks(task_set: &GooseTaskSet) -> (Vec<Vec<usize>>, Vec<Vec<usize>>, Vec<Vec<usize>>) {
    trace!("weight_tasks for {}", task_set.name);

    // A BTreeMap of Vectors allows us to group and sort tasks per sequence value.
    let mut sequenced_tasks: BTreeMap <usize, Vec<GooseTask>> = BTreeMap::new();
    let mut sequenced_on_start_tasks: BTreeMap <usize, Vec<GooseTask>> = BTreeMap::new();
    let mut sequenced_on_stop_tasks: BTreeMap <usize, Vec<GooseTask>> = BTreeMap::new();
    let mut unsequenced_tasks: Vec<GooseTask> = Vec::new();
    let mut unsequenced_on_start_tasks: Vec<GooseTask> = Vec::new();
    let mut unsequenced_on_stop_tasks: Vec<GooseTask> = Vec::new();
    let mut u: usize = 0;
    let mut v: usize;
    // Handle ordering of tasks.
    for task in &task_set.tasks {
        if task.sequence > 0 {
            if task.on_start {
                if let Some(sequence) = sequenced_on_start_tasks.get_mut(&task.sequence) {
                    // This is another task with this order value.
                    sequence.push(task.clone());
                }
                else {
                    // This is the first task with this order value.
                    sequenced_on_start_tasks.insert(task.sequence, vec![task.clone()]);
                }
            }
            // Allow a task to be both on_start and on_stop.
            if task.on_stop {
                if let Some(sequence) = sequenced_on_stop_tasks.get_mut(&task.sequence) {
                    // This is another task with this order value.
                    sequence.push(task.clone());
                }
                else {
                    // This is the first task with this order value.
                    sequenced_on_stop_tasks.insert(task.sequence, vec![task.clone()]);
                }
            }
            if !task.on_start && !task.on_stop {
                if let Some(sequence) = sequenced_tasks.get_mut(&task.sequence) {
                    // This is another task with this order value.
                    sequence.push(task.clone());
                }
                else {
                    // This is the first task with this order value.
                    sequenced_tasks.insert(task.sequence, vec![task.clone()]);
                }
            }
        }
        else {
            if task.on_start {
                unsequenced_on_start_tasks.push(task.clone());
            }
            if task.on_stop {
                unsequenced_on_stop_tasks.push(task.clone());
            }
            if !task.on_start && !task.on_stop {
                unsequenced_tasks.push(task.clone());
            }
        }
        // Look for lowest common divisor amongst all tasks of any weight.
        if u == 0 {
            u = task.weight;
        }
        else {
            v = task.weight;
            trace!("calculating greatest common denominator of {} and {}", u, v);
            u = util::gcd(u, v);
            trace!("inner gcd: {}", u);
        }
    }
    // 'u' will always be the greatest common divisor
    debug!("gcd: {}", u);

    // Apply weight to sequenced tasks.
    let mut weighted_tasks: Vec<Vec<usize>> = Vec::new();
    for (_sequence, tasks) in sequenced_tasks.iter() {
        let mut sequence_weighted_tasks = Vec::new();
        for task in tasks {
            // divide by greatest common divisor so bucket is as small as possible
            let weight = task.weight / u;
            trace!("{}: {} has weight of {} (reduced with gcd to {})", task.tasks_index, task.name, task.weight, weight);
            let mut tasks = vec![task.tasks_index; weight];
            sequence_weighted_tasks.append(&mut tasks);
        }
        weighted_tasks.push(sequence_weighted_tasks);
    }
    // Apply weight to unsequenced tasks.
    trace!("created weighted_tasks: {:?}", weighted_tasks);
    let mut weighted_unsequenced_tasks = Vec::new();
    for task in unsequenced_tasks {
        // divide by greatest common divisor so bucket is as small as possible
        let weight = task.weight / u;
        trace!("{}: {} has weight of {} (reduced with gcd to {})", task.tasks_index, task.name, task.weight, weight);
        let mut tasks = vec![task.tasks_index; weight];
        weighted_unsequenced_tasks.append(&mut tasks);
    }
    // Unsequenced tasks come lost.
    weighted_tasks.push(weighted_unsequenced_tasks);

    // Apply weight to on_start sequenced tasks.
    let mut weighted_on_start_tasks: Vec<Vec<usize>> = Vec::new();
    for (_sequence, tasks) in sequenced_on_start_tasks.iter() {
        let mut sequence_on_start_weighted_tasks = Vec::new();
        for task in tasks {
            // divide by greatest common divisor so bucket is as small as possible
            let weight = task.weight / u;
            trace!("{}: {} has weight of {} (reduced with gcd to {})", task.tasks_index, task.name, task.weight, weight);
            let mut tasks = vec![task.tasks_index; weight];
            sequence_on_start_weighted_tasks.append(&mut tasks);
        }
        weighted_on_start_tasks.push(sequence_on_start_weighted_tasks);
    }
    // Apply weight to unsequenced on_start tasks.
    trace!("created weighted_on_start_tasks: {:?}", weighted_tasks);
    let mut weighted_on_start_unsequenced_tasks = Vec::new();
    for task in unsequenced_on_start_tasks {
        // divide by greatest common divisor so bucket is as small as possible
        let weight = task.weight / u;
        trace!("{}: {} has weight of {} (reduced with gcd to {})", task.tasks_index, task.name, task.weight, weight);
        let mut tasks = vec![task.tasks_index; weight];
        weighted_on_start_unsequenced_tasks.append(&mut tasks);
    }
    // Unsequenced tasks come lost.
    weighted_on_start_tasks.push(weighted_on_start_unsequenced_tasks);

    // Apply weight to on_stop sequenced tasks.
    let mut weighted_on_stop_tasks: Vec<Vec<usize>> = Vec::new();
    for (_sequence, tasks) in sequenced_on_stop_tasks.iter() {
        let mut sequence_on_stop_weighted_tasks = Vec::new();
        for task in tasks {
            // divide by greatest common divisor so bucket is as small as possible
            let weight = task.weight / u;
            trace!("{}: {} has weight of {} (reduced with gcd to {})", task.tasks_index, task.name, task.weight, weight);
            let mut tasks = vec![task.tasks_index; weight];
            sequence_on_stop_weighted_tasks.append(&mut tasks);
        }
        weighted_on_stop_tasks.push(sequence_on_stop_weighted_tasks);
    }
    // Apply weight to unsequenced on_stop tasks.
    trace!("created weighted_on_stop_tasks: {:?}", weighted_tasks);
    let mut weighted_on_stop_unsequenced_tasks = Vec::new();
    for task in unsequenced_on_stop_tasks {
        // divide by greatest common divisor so bucket is as small as possible
        let weight = task.weight / u;
        trace!("{}: {} has weight of {} (reduced with gcd to {})", task.tasks_index, task.name, task.weight, weight);
        let mut tasks = vec![task.tasks_index; weight];
        weighted_on_stop_unsequenced_tasks.append(&mut tasks);
    }
    // Unsequenced tasks come last.
    weighted_on_stop_tasks.push(weighted_on_stop_unsequenced_tasks);

    (weighted_on_start_tasks, weighted_tasks, weighted_on_stop_tasks)
}

fn is_valid_host(host: &str) -> bool {
    match Url::parse(host) {
        Ok(_) => true,
        Err(e) => {
            error!("invalid host '{}': {}", host, e);
            std::process::exit(1);
        }
    }
}

/// If run_time was specified, detect when it's time to shut down
fn timer_expired(started: time::Instant, run_time: usize) -> bool {
    if run_time > 0 && started.elapsed().as_secs() >= run_time as u64 {
        true
    }
    else {
        false
    }
}

/// Merge per-client-statistics from client thread into global parent statistics
fn merge_from_client(
    parent_request: &GooseRequest,
    client_request: &GooseRequest,
    config: &Configuration,
) -> GooseRequest {
    // Make a mutable copy where we can merge things
    let mut merged_request = parent_request.clone();
    merged_request.response_times.extend_from_slice(&client_request.response_times);
    merged_request.success_count += &client_request.success_count;
    merged_request.fail_count += &client_request.fail_count;
    // Only accrue overhead of merging status_code_counts if we're going to display the results
    if config.status_codes {
        for (status_code, count) in &client_request.status_code_counts {
            let new_count;
            // Add client count into global count
            if let Some(existing_status_code_count) = merged_request.status_code_counts.get(&status_code) {
                new_count = *existing_status_code_count + *count;
            }
            // No global count exists yet, so start with client count
            else {
                new_count = *count;
            }
            merged_request.status_code_counts.insert(*status_code, new_count);
        }
    }
    merged_request
}

pub fn goose_init() -> GooseState {
    let mut goose_state = GooseState::new(Configuration::from_args());

    // Allow optionally controlling debug output level
    let debug_level;
    match goose_state.configuration.verbose {
        0 => debug_level = LevelFilter::Warn,
        1 => debug_level = LevelFilter::Info,
        2 => debug_level = LevelFilter::Debug,
        _ => debug_level = LevelFilter::Trace,
    }

    // Allow optionally controlling log level
    let log_level;
    match goose_state.configuration.log_level {
        0 => log_level = LevelFilter::Info,
        1 => log_level = LevelFilter::Debug,
        _ => log_level = LevelFilter::Trace,
    }

    let log_file = PathBuf::from(&goose_state.configuration.log_file);

    CombinedLogger::init(vec![
        TermLogger::new(
            debug_level,
            Config::default(),
            TerminalMode::Mixed).unwrap(),
        WriteLogger::new(
            log_level,
            Config::default(),
            File::create(&log_file).unwrap(),
        )]).unwrap();
    info!("Output verbosity level: {}", debug_level);
    info!("Logfile verbosity level: {}", log_level);
    info!("Writing to log file: {}", log_file.display());

    // Don't allow overhead of collecting status codes unless we're printing statistics.
    if goose_state.configuration.status_codes && !goose_state.configuration.print_stats {
        error!("You must enable --print-stats to enable --status-codes.");
        std::process::exit(1);
    }

    // Don't allow overhead of collecting statistics unless we're printing them.
    if goose_state.configuration.only_summary && !goose_state.configuration.print_stats {
        error!("You must enable --print-stats to enable --only-summary.");
        std::process::exit(1);
    }

    // Configure maximum run time if specified, otherwise run until canceled.
    if goose_state.configuration.run_time != "" {
        goose_state.run_time = util::parse_timespan(&goose_state.configuration.run_time);
    }
    else {
        goose_state.run_time = 0;
    }
    info!("run_time = {}", goose_state.run_time);

    // Configure number of client threads to launch, default to the number of CPU cores available.
    goose_state.clients = match goose_state.configuration.clients {
        Some(c) => {
            if c == 0 {
                error!("At least 1 client is required.");
                std::process::exit(1);
            }
            else {
                c
            }
        }
        None => {
            let c = goose_state.number_of_cpus;
            info!("concurrent clients defaulted to {} (number of CPUs)", c);
            c
        }
    };
    debug!("clients = {}", goose_state.clients);

    goose_state
}

pub fn goose_launch(mut goose_state: GooseState, mut goose_task_sets: GooseTaskSets) {
    // At least one task set is required.
    if goose_task_sets.task_sets.len() <= 0 {
        error!("No task sets defined in goosefile.");
        std::process::exit(1);
    }

    if goose_state.configuration.list {
        // Display task sets and tasks, then exit.
        println!("Available tasks:");
        for task_set in goose_task_sets.task_sets {
            println!(" - {} (weight: {})", task_set.name, task_set.weight);
            for task in task_set.tasks {
                println!("    o {} (weight: {})", task.name, task.weight);
            }
        }
        std::process::exit(0);
    }

    // Configure number of client threads to launch per second, default to the number of CPU cores available.
    let hatch_rate = match goose_state.configuration.hatch_rate {
        Some(h) => {
            if h == 0 {
                error!("The hatch_rate must be greater than 0, and generally should be no more than 100 * NUM_CORES.");
                std::process::exit(1);
            }
            else {
                h
            }
        }
        None => {
            let h = goose_state.number_of_cpus;
            info!("hatch_rate defaulted to {} (number of CPUs)", h);
            h
        }
    };
    debug!("hatch_rate = {}", hatch_rate);

    // Confirm there's either a global host, or each task set has a host defined.
    if goose_state.configuration.host.len() == 0 {
        for task_set in &goose_task_sets.task_sets {
            match &task_set.host {
                Some(h) => {
                    if is_valid_host(h) {
                        info!("host for {} configured: {}", task_set.name, h);
                    }
                }
                None => {
                    error!("Host must be defined globally or per-TaskSet. No host defined for {}.", task_set.name);
                    std::process::exit(1);
                }
            }
        }
    }
    else {
        if is_valid_host(&goose_state.configuration.host) {
            info!("global host configured: {}", goose_state.configuration.host);
        }
    }

    // Apply weights to tasks in each task set.
    for task_set in &mut goose_task_sets.task_sets {
        let (weighted_on_start_tasks, weighted_tasks, weighted_on_stop_tasks) = weight_tasks(&task_set);
        task_set.weighted_on_start_tasks = weighted_on_start_tasks;
        task_set.weighted_tasks = weighted_tasks;
        task_set.weighted_on_stop_tasks = weighted_on_stop_tasks;
        debug!("weighted {} on_start: {:?} tasks: {:?} on_stop: {:?}", task_set.name, task_set.weighted_on_start_tasks, task_set.weighted_tasks, task_set.weighted_on_stop_tasks);
    }

    // Allocate a state for each of the clients we are about to start.
    goose_task_sets.weighted_clients = weight_task_set_clients(&goose_task_sets, goose_state.clients, &goose_state);

    // Our load test is officially starting.
    let mut started = time::Instant::now();
    // Spawn clients at hatch_rate per second, or one every 1 / hatch_rate fraction of a second.
    let sleep_float = 1.0 / hatch_rate as f32;
    let sleep_duration = time::Duration::from_secs_f32(sleep_float);
    // Collect client threads in a vector for when we want to stop them later.
    let mut clients = vec![];
    // Collect client thread channels in a vector so we can talk to the client threads.
    let mut client_channels = vec![];
    // Create a single channel allowing all Goose child threads to sync state back to parent
    let (all_threads_sender, parent_receiver): (mpsc::Sender<GooseClient>, mpsc::Receiver<GooseClient>) = mpsc::channel();
    // Spawn clients, each with their own weighted task_set.
    for mut thread_client in goose_task_sets.weighted_clients.clone() {
        // Stop launching threads if the run_timer has expired.
        if timer_expired(started, goose_state.run_time) {
            break;
        }

        // Copy weighted tasks and weighted on start tasks into the client thread.
        thread_client.weighted_tasks = goose_task_sets.task_sets[thread_client.task_sets_index].weighted_tasks.clone();
        thread_client.weighted_on_start_tasks = goose_task_sets.task_sets[thread_client.task_sets_index].weighted_on_start_tasks.clone();
        thread_client.weighted_on_stop_tasks = goose_task_sets.task_sets[thread_client.task_sets_index].weighted_on_stop_tasks.clone();
        // Remember which task group this client is using.
        thread_client.weighted_clients_index = goose_state.active_clients;

        // Create a per-thread channel allowing parent thread to control child threads.
        let (parent_sender, thread_receiver): (mpsc::Sender<GooseClientCommand>, mpsc::Receiver<GooseClientCommand>) = mpsc::channel();
        client_channels.push(parent_sender);

        // We can only launch tasks if the task list is non-empty
        if thread_client.weighted_tasks.len() > 0 {
            // Copy the client-to-parent sender channel, used by all threads.
            let thread_sender = all_threads_sender.clone();

            // Hatching a new Goose client.
            thread_client.set_mode(GooseClientMode::HATCHING);
            // Notify parent that our run mode has changed to Hatching.
            thread_sender.send(thread_client.clone()).unwrap();

            // Copy the appropriate task_set into the thread.
            let thread_task_set = goose_task_sets.task_sets[thread_client.task_sets_index].clone();

            // We number threads from 1 as they're human-visible (in the logs), whereas active_clients starts at 0.
            let thread_number = goose_state.active_clients + 1;

            // Launch a new client.
            let client = thread::spawn(move || {
                 client::client_main(thread_number, thread_task_set, thread_client, thread_receiver, thread_sender)
            });

            clients.push(client);
            goose_state.active_clients += 1;
            debug!("sleeping {:?} milliseconds...", sleep_duration);
            thread::sleep(sleep_duration);
        }
    }
    // Restart the timer now that all threads are launched.
    started = time::Instant::now();
    info!("launched {} clients...", goose_state.active_clients);

    // Ensure we have request statistics when we're displaying running statistics.
    if goose_state.configuration.print_stats && !goose_state.configuration.only_summary {
        for (index, send_to_client) in client_channels.iter().enumerate() {
            send_to_client.send(GooseClientCommand::SYNC).unwrap();
            debug!("telling client {} to sync stats", index);
        }
    }

    // Track whether or not we've (optionally) reset the statistics after all clients started.
    let mut statistics_reset: bool = false;

    // Catch ctrl-c to allow clean shutdown to display statistics.
    let canceled = Arc::new(AtomicBool::new(false));
    let caught_ctrlc = canceled.clone();
    ctrlc::set_handler(move || {
        if caught_ctrlc.load(Ordering::SeqCst) {
            // We caught a second ctrl-c, exit early
            error!("caught another ctrl-c, exiting immediately...");
            std::process::exit(1);
        }
        else {
            warn!("caught ctrl-c, stopping...");
            caught_ctrlc.store(true, Ordering::SeqCst);
        }
    }).expect("Failed to set Ctrl-C signal handler.");

    // Determine when to display running statistics (if enabled).
    let mut statistics_timer = time::Instant::now();
    let mut display_running_statistics = false;

    // Move into a local variable, actual run_time may be less due to SIGINT (ctrl-c).
    let mut run_time = goose_state.run_time;
    loop {
        // When displaying running statistics, sync data from client threads first.
        if goose_state.configuration.print_stats {
            // Synchronize statistics from client threads into parent.
            if timer_expired(statistics_timer, 15) {
                statistics_timer = time::Instant::now();
                for (index, send_to_client) in client_channels.iter().enumerate() {
                    send_to_client.send(GooseClientCommand::SYNC).unwrap();
                    debug!("telling client {} to sync stats", index);
                }
                if !goose_state.configuration.only_summary {
                    display_running_statistics = true;
                    // Give client threads time to send statstics.
                    let pause = time::Duration::from_millis(100);
                    thread::sleep(pause);
                }
            }

            // Load messages from client threads until the receiver queue is empty.
            let mut message = parent_receiver.try_recv();
            while message.is_ok() {
                // Messages contain per-client statistics: merge them into the global statistics.
                let unwrapped_message = message.unwrap();
                let weighted_clients_index = unwrapped_message.weighted_clients_index;
                goose_task_sets.weighted_clients[weighted_clients_index].weighted_bucket = unwrapped_message.weighted_bucket;
                goose_task_sets.weighted_clients[weighted_clients_index].weighted_bucket_position = unwrapped_message.weighted_bucket_position;
                goose_task_sets.weighted_clients[weighted_clients_index].mode = unwrapped_message.mode;
                // If our local copy of the task set doesn't have tasks, clone them from the remote thread
                if goose_task_sets.weighted_clients[weighted_clients_index].weighted_tasks.len() == 0 {
                    goose_task_sets.weighted_clients[weighted_clients_index].weighted_clients_index = unwrapped_message.weighted_clients_index;
                    goose_task_sets.weighted_clients[weighted_clients_index].weighted_tasks = unwrapped_message.weighted_tasks.clone();
                }
                // Syncronize client requests
                for (request_key, request) in unwrapped_message.requests {
                    trace!("request_key: {}", request_key);
                    let merged_request;
                    if let Some(parent_request) = goose_task_sets.weighted_clients[weighted_clients_index].requests.get(&request_key) {
                        merged_request = merge_from_client(parent_request, &request, &goose_state.configuration);
                    }
                    else {
                        // First time seeing this request, simply insert it.
                        merged_request = request.clone();
                    }
                    goose_task_sets.weighted_clients[weighted_clients_index].requests.insert(request_key.to_string(), merged_request);
                }
                message = parent_receiver.try_recv();
            }

            // Flush statistics collected prior to all client threads running
            if goose_state.configuration.reset_stats && !statistics_reset {
                info!("statistics reset...");
                for (client_index, client) in goose_task_sets.weighted_clients.clone().iter().enumerate() {
                    let mut reset_client = client.clone();
                    // Start again with an empty requests hashmap.
                    reset_client.requests = HashMap::new();
                    goose_task_sets.weighted_clients[client_index] = reset_client;
                }
                statistics_reset = true;
            }
        }

        if timer_expired(started, run_time) || canceled.load(Ordering::SeqCst) {
            run_time = started.elapsed().as_secs() as usize;
            info!("stopping after {} seconds...", run_time);
            for (index, send_to_client) in client_channels.iter().enumerate() {
                send_to_client.send(GooseClientCommand::EXIT).unwrap();
                debug!("telling client {} to sync stats", index);
            }
            info!("waiting for clients to exit");
            for client in clients {
                let _ = client.join();
            }
            debug!("all clients exited");

            // If we're printing statistics, collect the final messages received from clients
            if goose_state.configuration.print_stats {
                let mut message = parent_receiver.try_recv();
                while message.is_ok() {
                    let unwrapped_message = message.unwrap();
                    let weighted_clients_index = unwrapped_message.weighted_clients_index;
                    goose_task_sets.weighted_clients[weighted_clients_index].mode = unwrapped_message.mode;
                    // Syncronize client requests
                    for (request_key, request) in unwrapped_message.requests {
                        trace!("request_key: {}", request_key);
                        let merged_request;
                        if let Some(parent_request) = goose_task_sets.weighted_clients[weighted_clients_index].requests.get(&request_key) {
                            merged_request = merge_from_client(parent_request, &request, &goose_state.configuration);
                        }
                        else {
                            // First time seeing this request, simply insert it.
                            merged_request = request.clone();
                        }
                        goose_task_sets.weighted_clients[weighted_clients_index].requests.insert(request_key.to_string(), merged_request);
                    }
                    message = parent_receiver.try_recv();
                }
            }

            // All clients are done, exit out of loop for final cleanup.
            break;
        }

        // If enabled, display running statistics after sync
        if display_running_statistics {
            display_running_statistics = false;
            stats::print_running_stats(&goose_state.configuration, &goose_task_sets, started.elapsed().as_secs() as usize);
        }

        let one_second = time::Duration::from_secs(1);
        thread::sleep(one_second);
    }

    if goose_state.configuration.print_stats {
        stats::print_final_stats(&goose_state.configuration, &goose_task_sets, started.elapsed().as_secs() as usize);
    }
}