feature: add custom retention periods for data (#892)

* feature: add custom retention periods for data

* docs: update changelog

* docs: update docs

11 files changed, 120 insertions, 60 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index c2635ebe..b5b11afe 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -32,6 +32,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - [#868](https://github.com/ClementTsang/bottom/pull/868): Make temperature widget sortable.
 - [#870](https://github.com/ClementTsang/bottom/pull/870): Make disk widget sortable.
 - [#881](https://github.com/ClementTsang/bottom/pull/881): Add pasting to the search bar.
+- [#892](https://github.com/ClementTsang/bottom/pull/892): Add custom retention periods for data.
 
 ## [0.6.8] - 2022-02-01
 
diff --git a/Cargo.lock b/Cargo.lock
index b497b1cf..8b50515b 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -224,6 +224,8 @@ dependencies = [
  "futures-timer",
  "fxhash",
  "heim",
+ "humantime",
+ "humantime-serde",
  "indexmap",
  "itertools",
  "kstring",
@@ -890,6 +892,22 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7f24254aa9a54b5c858eaee2f5bccdb46aaf0e486a595ed5fd8f86ba55232a70"
 
 [[package]]
+name = "humantime"
+version = "2.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9a3a5bfb195931eeb336b2a7b4d761daec841b97f947d34394601737a7bba5e4"
+
+[[package]]
+name = "humantime-serde"
+version = "1.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "57a3db5ea5923d99402c94e9feb261dc5ee9b4efa158b0315f788cf549cc200c"
+dependencies = [
+ "humantime",
+ "serde",
+]
+
+[[package]]
 name = "ident_case"
 version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
diff --git a/Cargo.toml b/Cargo.toml
index 72f1ed0e..bc9dd6b3 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -73,6 +73,8 @@ flume = "0.10.14"
 futures = "0.3.21"
 futures-timer = "3.0.2"
 fxhash = "0.2.1"
+humantime = "2.1.0"
+humantime-serde = "1.1.1"
 indexmap = "1.8.1"
 itertools = "0.10.3"
 kstring = { version = "2.0.0", features = ["arc"] }
diff --git a/docs/content/configuration/command-line-flags.md b/docs/content/configuration/command-line-flags.md
index 3247c482..febf2068 100644
--- a/docs/content/configuration/command-line-flags.md
+++ b/docs/content/configuration/command-line-flags.md
@@ -44,3 +44,4 @@ The following flags can be provided to bottom in the command line to change the
 | `-V, --version`                       | Prints version information.                                    |
 | `-W, --whole_word`                    | Enables whole-word matching by default.                        |
 | `--enable_gpu_memory`                 | Enable collecting and displaying GPU memory usage.             |
+| `--retention`                         | How much data is stored at once in terms of time.              |
diff --git a/docs/content/configuration/config-file/flags.md b/docs/content/configuration/config-file/flags.md
index 93c71379..5aa218ca 100644
--- a/docs/content/configuration/config-file/flags.md
+++ b/docs/content/configuration/config-file/flags.md
@@ -37,3 +37,4 @@ Most of the [command line flags](../../command-line-flags) have config file equi
 | `network_use_bytes`          | Boolean                                                                                        | Displays the network widget using bytes.                       |
 | `network_use_log`            | Boolean                                                                                        | Displays the network widget with a log scale.                  |
 | `enable_gpu_memory`          | Boolean                                                                                        | Shows the GPU memory widget.                                   |
+| `retention`                  | String (human readable time, such as "10m", "1h", etc.)                                        | How much data is stored at once in terms of time.              |
diff --git a/sample_configs/default_config.toml b/sample_configs/default_config.toml
index 74b30da3..7ead3315 100644
--- a/sample_configs/default_config.toml
+++ b/sample_configs/default_config.toml
@@ -71,6 +71,8 @@
 #disable_advanced_kill = false
 # Shows GPU(s) memory
 #enable_gpu_memory = false
+# How much data is stored at once in terms of time.
+#retention = "10m"
 
 # These are all the components that support custom theming.  Note that colour support
 # will depend on terminal support.
diff --git a/src/app.rs b/src/app.rs
index 3669bfa9..ee8b3ee6 100644
--- a/src/app.rs
+++ b/src/app.rs
@@ -72,6 +72,7 @@ pub struct AppConfigFields {
     pub network_unit_type: DataUnit,
     pub network_scale_type: AxisScaling,
     pub network_use_binary_prefix: bool,
+    pub retention_ms: u64,
 }
 
 /// For filtering out information
@@ -2186,16 +2187,16 @@ impl App {
                 {
                     let new_time = cpu_widget_state.current_display_time
                         + self.app_config_fields.time_interval;
-                    if new_time <= constants::STALE_MAX_MILLISECONDS {
+                    if new_time <= self.app_config_fields.retention_ms {
                         cpu_widget_state.current_display_time = new_time;
                         self.cpu_state.force_update = Some(self.current_widget.widget_id);
                         if self.app_config_fields.autohide_time {
                             cpu_widget_state.autohide_timer = Some(Instant::now());
                         }
                     } else if cpu_widget_state.current_display_time
-                        != constants::STALE_MAX_MILLISECONDS
+                        != self.app_config_fields.retention_ms
                     {
-                        cpu_widget_state.current_display_time = constants::STALE_MAX_MILLISECONDS;
+                        cpu_widget_state.current_display_time = self.app_config_fields.retention_ms;
                         self.cpu_state.force_update = Some(self.current_widget.widget_id);
                         if self.app_config_fields.autohide_time {
                             cpu_widget_state.autohide_timer = Some(Instant::now());
@@ -2211,16 +2212,16 @@ impl App {
                 {
                     let new_time = mem_widget_state.current_display_time
                         + self.app_config_fields.time_interval;
-                    if new_time <= constants::STALE_MAX_MILLISECONDS {
+                    if new_time <= self.app_config_fields.retention_ms {
                         mem_widget_state.current_display_time = new_time;
                         self.mem_state.force_update = Some(self.current_widget.widget_id);
                         if self.app_config_fields.autohide_time {
                             mem_widget_state.autohide_timer = Some(Instant::now());
                         }
                     } else if mem_widget_state.current_display_time
-                        != constants::STALE_MAX_MILLISECONDS
+                        != self.app_config_fields.retention_ms
                     {
-                        mem_widget_state.current_display_time = constants::STALE_MAX_MILLISECONDS;
+                        mem_widget_state.current_display_time = self.app_config_fields.retention_ms;
                         self.mem_state.force_update = Some(self.current_widget.widget_id);
                         if self.app_config_fields.autohide_time {
                             mem_widget_state.autohide_timer = Some(Instant::now());
@@ -2236,16 +2237,16 @@ impl App {
                 {
                     let new_time = net_widget_state.current_display_time
                         + self.app_config_fields.time_interval;
-                    if new_time <= constants::STALE_MAX_MILLISECONDS {
+                    if new_time <= self.app_config_fields.retention_ms {
                         net_widget_state.current_display_time = new_time;
                         self.net_state.force_update = Some(self.current_widget.widget_id);
                         if self.app_config_fields.autohide_time {
                             net_widget_state.autohide_timer = Some(Instant::now());
                         }
                     } else if net_widget_state.current_display_time
-                        != constants::STALE_MAX_MILLISECONDS
+                        != self.app_config_fields.retention_ms
                     {
-                        net_widget_state.current_display_time = constants::STALE_MAX_MILLISECONDS;
+                        net_widget_state.current_display_time = self.app_config_fields.retention_ms;
                         self.net_state.force_update = Some(self.current_widget.widget_id);
                         if self.app_config_fields.autohide_time {
                             net_widget_state.autohide_timer = Some(Instant::now());
diff --git a/src/bin/main.rs b/src/bin/main.rs
index a1fdcbc1..2130ecb3 100644
--- a/src/bin/main.rs
+++ b/src/bin/main.rs
@@ -85,12 +85,12 @@ fn main() -> Result<()> {
         let lock = thread_termination_lock.clone();
         let cvar = thread_termination_cvar.clone();
         let cleaning_sender = sender.clone();
-        const OFFSET_WAIT_TIME: u64 = constants::STALE_MAX_MILLISECONDS + 60000;
+        let offset_wait_time = app.app_config_fields.retention_ms + 60000;
         thread::spawn(move || {
             loop {
                 let result = cvar.wait_timeout(
                     lock.lock().unwrap(),
-                    Duration::from_millis(OFFSET_WAIT_TIME),
+                    Duration::from_millis(offset_wait_time),
                 );
                 if let Ok(result) = result {
                     if *(result.0) {
@@ -271,7 +271,7 @@ fn main() -> Result<()> {
                 }
                 BottomEvent::Clean => {
                     app.data_collection
-                        .clean_data(constants::STALE_MAX_MILLISECONDS);
+                        .clean_data(app.app_config_fields.retention_ms);
                 }
             }
         }
diff --git a/src/clap.rs b/src/clap.rs
index b26c4c6a..043b79b3 100644
--- a/src/clap.rs
+++ b/src/clap.rs
@@ -348,6 +348,13 @@ use CPU (3) as the default instead.
             "Displays the network widget with binary prefixes (i.e. kibibits, mebibits) rather than a decimal prefix (i.e. kilobits, megabits). Defaults to decimal prefixes.",
         );
 
+    let retention = Arg::new("retention")
+        .long("retention")
+        .takes_value(true)
+        .value_name("time")
+        .help("The timespan of data kept.")
+        .long_help("How much data is stored at once in terms of time. Takes in human-readable time spans (e.g. 10m, 1h), with a minimum of 1 minute. Note higher values will take up more memory. Defaults to 10 minutes.");
+
     #[allow(unused_mut)]
     let mut app = Command::new(crate_name!())
         .version(crate_version!())
@@ -391,7 +398,8 @@ use CPU (3) as the default instead.
         .arg(network_use_binary_prefix)
         .arg(current_usage)
         .arg(use_old_network_legend)
-        .arg(whole_word);
+        .arg(whole_word)
+        .arg(retention);
 
     #[cfg(feature = "battery")]
     {
diff --git a/src/constants.rs b/src/constants.rs
index 6c8c9546..4cdb1369 100644
--- a/src/constants.rs
+++ b/src/constants.rs
@@ -5,9 +5,6 @@ use crate::options::ConfigColours;
 // Default widget ID
 pub const DEFAULT_WIDGET_ID: u64 = 56709;
 
-// How long to store data.
-pub const STALE_MAX_MILLISECONDS: u64 = 600 * 1000; // Keep 10 minutes of data.
-
 // How much data is SHOWN
 pub const DEFAULT_TIME_MILLISECONDS: u64 = 60 * 1000; // Defaults to 1 min.
 pub const STALE_MIN_MILLISECONDS: u64 = 30 * 1000; // Lowest is 30 seconds
@@ -549,6 +546,8 @@ pub const CONFIG_TEXT: &str = r##"# This is a default config file for bottom.  A
 #disable_advanced_kill = false
 # Shows GPU(s) memory
 #enable_gpu_memory = false
+# How much data is stored at once in terms of time.
+#retention = "10m"
 
 # These are all the components that support custom theming.  Note that colour support
 # will depend on terminal support.
diff --git a/src/options.rs b/src/options.rs
index cc8b57f3..22491468 100644
--- a/src/options.rs
+++ b/src/options.rs
@@ -3,9 +3,10 @@ use std::{
     collections::{HashMap, HashSet},
     convert::TryInto,
     str::FromStr,
-    time::Instant,
+    time::{Duration, Instant},
 };
 
+use clap::ArgMatches;
 use layout_options::*;
 use regex::Regex;
 use serde::{Deserialize, Serialize};
@@ -88,6 +89,9 @@ pub struct ConfigFlags {
     pub network_use_log: Option<bool>,
     pub network_use_binary_prefix: Option<bool>,
     pub enable_gpu_memory: Option<bool>,
+    #[serde(with = "humantime_serde")]
+    #[serde(default)]
+    pub retention: Option<Duration>,
 }
 
 #[derive(Clone, Default, Debug, Deserialize, Serialize)]
@@ -168,13 +172,16 @@ pub struct IgnoreList {
 }
 
 pub fn build_app(
-    matches: &clap::ArgMatches, config: &mut Config, widget_layout: &BottomLayout,
+    matches: &ArgMatches, config: &mut Config, widget_layout: &BottomLayout,
     default_widget_id: u64, default_widget_type_option: &Option<BottomWidgetType>,
     colours: &CanvasColours,
 ) -> Result<App> {
     use BottomWidgetType::*;
+
+    let retention_ms =
+        get_retention_ms(matches, config).context("Update `retention` in your config file.")?;
     let autohide_time = get_autohide_time(matches, config);
-    let default_time_value = get_default_time_value(matches, config)
+    let default_time_value = get_default_time_value(matches, config, retention_ms)
         .context("Update 'default_time_value' in your config file.")?;
     let use_basic_mode = get_use_basic_mode(matches, config);
 
@@ -224,7 +231,7 @@ pub fn build_app(
         use_current_cpu_total: get_use_current_cpu_total(matches, config),
         use_basic_mode,
         default_time_value,
-        time_interval: get_time_interval(matches, config)
+        time_interval: get_time_interval(matches, config, retention_ms)
             .context("Update 'time_delta' in your config file.")?,
         hide_time: get_hide_time(matches, config),
         autohide_time,
@@ -241,6 +248,7 @@ pub fn build_app(
         network_scale_type,
         network_unit_type,
         network_use_binary_prefix,
+        retention_ms,
     };
 
     for row in &widget_layout.rows {
@@ -422,7 +430,7 @@ pub fn build_app(
 }
 
 pub fn get_widget_layout(
-    matches: &clap::ArgMatches, config: &Config,
+    matches: &ArgMatches, config: &Config,
 ) -> error::Result<(BottomLayout, u64, Option<BottomWidgetType>)> {
     let left_legend = get_use_left_legend(matches, config);
     let (default_widget_type, mut default_widget_count) =
@@ -486,9 +494,7 @@ pub fn get_widget_layout(
     Ok((bottom_layout, default_widget_id, default_widget_type))
 }
 
-fn get_update_rate_in_milliseconds(
-    matches: &clap::ArgMatches, config: &Config,
-) -> error::Result<u64> {
+fn get_update_rate_in_milliseconds(matches: &ArgMatches, config: &Config) -> error::Result<u64> {
     let update_rate_in_milliseconds = if let Some(update_rate) = matches.value_of("rate") {
         update_rate.parse::<u64>().map_err(|_| {
             BottomError::ConfigError(
@@ -515,7 +521,7 @@ fn get_update_rate_in_milliseconds(
 }
 
 fn get_temperature(
-    matches: &clap::ArgMatches, config: &Config,
+    matches: &ArgMatches, config: &Config,
 ) -> error::Result<data_harvester::temperature::TemperatureType> {
     if matches.is_present("fahrenheit") {
         return Ok(data_harvester::temperature::TemperatureType::Fahrenheit);
@@ -541,7 +547,7 @@ fn get_temperature(
 }
 
 /// Yes, this function gets whether to show average CPU (true) or not (false)
-fn get_show_average_cpu(matches: &clap::ArgMatches, config: &Config) -> bool {
+fn get_show_average_cpu(matches: &ArgMatches, config: &Config) -> bool {
     if matches.is_present("hide_avg_cpu") {
         return false;
     } else if let Some(flags) = &config.flags {
@@ -553,7 +559,7 @@ fn get_show_average_cpu(matches: &clap::ArgMatches, config: &Config) -> bool {
     true
 }
 
-fn get_use_dot(matches: &clap::ArgMatches, config: &Config) -> bool {
+fn get_use_dot(matches: &ArgMatches, config: &Config) -> bool {
     if matches.is_present("dot_marker") {
         return true;
     } else if let Some(flags) = &config.flags {
@@ -564,7 +570,7 @@ fn get_use_dot(matches: &clap::ArgMatches, config: &Config) -> bool {
     false
 }
 
-fn get_use_left_legend(matches: &clap::ArgMatches, config: &Config) -> bool {
+fn get_use_left_legend(matches: &ArgMatches, config: &Config) -> bool {
     if matches.is_present("left_legend") {
         return true;
     } else if let Some(flags) = &config.flags {
@@ -576,7 +582,7 @@ fn get_use_left_legend(matches: &clap::ArgMatches, config: &Config) -> bool {
     false
 }
 
-fn get_use_current_cpu_total(matches: &clap::ArgMatches, config: &Config) -> bool {
+fn get_use_current_cpu_total(matches: &ArgMatches, config: &Config) -> bool {
     if matches.is_present("current_usage") {
         return true;
     } else if let Some(flags) = &config.flags {
@@ -588,7 +594,7 @@ fn get_use_current_cpu_total(matches: &clap::ArgMatches, config: &Config) -> boo
     false
 }
 
-fn get_use_basic_mode(matches: &clap::ArgMatches, config: &Config) -> bool {
+fn get_use_basic_mode(matches: &ArgMatches, config: &Config) -> bool {
     if matches.is_present("basic") {
         return true;
     } else if let Some(flags) = &config.flags {
@@ -600,7 +606,10 @@ fn get_use_basic_mode(matches: &clap::ArgMatches, config: &Config) -> bool {
     false
 }
 
-fn get_default_time_value(matches: &clap::ArgMatches, config: &Config) -> error::Result<u64> {
+/// FIXME: Let this accept human times.
+fn get_default_time_value(
+    matches: &ArgMatches, config: &Config, retention_ms: u64,
+) -> error::Result<u64> {
     let default_time = if let Some(default_time_value) = matches.value_of("default_time_value") {
         default_time_value.parse::<u64>().map_err(|_| {
             BottomError::ConfigError(
@@ -621,17 +630,19 @@ fn get_default_time_value(matches: &clap::ArgMatches, config: &Config) -> error:
         return Err(BottomError::ConfigError(
             "set your default value to be at least 30000 milliseconds.".to_string(),
         ));
-    } else if default_time > STALE_MAX_MILLISECONDS {
+    } else if default_time > retention_ms {
         return Err(BottomError::ConfigError(format!(
             "set your default value to be at most {} milliseconds.",
-            STALE_MAX_MILLISECONDS
+            retention_ms
         )));
     }
 
     Ok(default_time)
 }
 
-fn get_time_interval(matches: &clap::ArgMatches, config: &Config) -> error::Result<u64> {
+fn get_time_interval(
+    matches: &ArgMatches, config: &Config, retention_ms: u64,
+) -> error::Result<u64> {
     let time_interval = if let Some(time_interval) = matches.value_of("time_delta") {
         time_interval.parse::<u64>().map_err(|_| {
             BottomError::ConfigError(
@@ -652,17 +663,17 @@ fn get_time_interval(matches: &clap::ArgMatches, config: &Config) -> error::Resu
         return Err(BottomError::ConfigError(
             "set your time delta to be at least 1000 milliseconds.".to_string(),
         ));
-    } else if time_interval > STALE_MAX_MILLISECONDS {
+    } else if time_interval > retention_ms {
         return Err(BottomError::ConfigError(format!(
             "set your time delta to be at most {} milliseconds.",
-            STALE_MAX_MILLISECONDS
+            retention_ms
         )));
     }
 
     Ok(time_interval)
 }
 
-pub fn get_app_grouping(matches: &clap::ArgMatches, config: &Config) -> bool {
+pub fn get_app_grouping(matches: &ArgMatches, config: &Config) -> bool {
     if matches.is_present("group") {
         return true;
     } else if let Some(flags) = &config.flags {
@@ -673,7 +684,7 @@ pub fn get_app_grouping(matches: &clap::ArgMatches, config: &Config) -> bool {
     false
 }
 
-pub fn get_app_case_sensitive(matches: &clap::ArgMatches, config: &Config) -> bool {
+pub fn get_app_case_sensitive(matches: &ArgMatches, config: &Config) -> bool {
     if matches.is_present("case_sensitive") {
         return true;
     } else if let Some(flags) = &config.flags {
@@ -684,7 +695,7 @@ pub fn get_app_case_sensitive(matches: &clap::ArgMatches, config: &Config) -> bo
     false
 }
 
-pub fn get_app_match_whole_word(matches: &clap::ArgMatches, config: &Config) -> bool {
+pub fn get_app_match_whole_word(matches: &ArgMatches, config: &Config) -> bool {
     if matches.is_present("whole_word") {
         return true;
     } else if let Some(flags) = &config.flags {
@@ -695,7 +706,7 @@ pub fn get_app_match_whole_word(matches: &clap::ArgMatches, config: &Config) ->
     false
 }
 
-pub fn get_app_use_regex(matches: &clap::ArgMatches, config: &Config) -> bool {
+pub fn get_app_use_regex(matches: &ArgMatches, config: &Config) -> bool {
     if matches.is_present("regex") {
         return true;
     } else if let Some(flags) = &config.flags {
@@ -706,7 +717,7 @@ pub fn get_app_use_regex(matches: &clap::ArgMatches, config: &Config) -> bool {
     false
 }
 
-fn get_hide_time(matches: &clap::ArgMatches, config: &Config) -> bool {
+fn get_hide_time(matches: &ArgMatches, config: &Config) -> bool {
     if matches.is_present("hide_time") {
         return true;
     } else if let Some(flags) = &config.flags {
@@ -717,7 +728,7 @@ fn get_hide_time(matches: &clap::ArgMatches, config: &Config) -> bool {
     false
 }
 
-fn get_autohide_time(matches: &clap::ArgMatches, config: &Config) -> bool {
+fn get_autohide_time(matches: &ArgMatches, config: &Config) -> bool {
     if matches.is_present("autohide_time") {
         return true;
     } else if let Some(flags) = &config.flags {
@@ -730,7 +741,7 @@ fn get_autohide_time(matches: &clap::ArgMatches, config: &Config) -> bool {
 }
 
 fn get_default_widget_and_count(
-    matches: &clap::ArgMatches, config: &Config,
+    matches: &ArgMatches, config: &Config,
 ) -> error::Result<(Option<BottomWidgetType>, u64)> {
     let widget_type = if let Some(widget_type) = matches.value_of("default_widget_type") {
         let parsed_widget = widget_type.parse::<BottomWidgetType>()?;
@@ -779,7 +790,7 @@ fn get_default_widget_and_count(
     }
 }
 
-fn get_disable_click(matches: &clap::ArgMatches, config: &Config) -> bool {
+fn get_disable_click(matches: &ArgMatches, config: &Config) -> bool {
     if matches.is_present("disable_click") {
         return true;
     } else if let Some(flags) = &config.flags {
@@ -790,7 +801,7 @@ fn get_disable_click(matches: &clap::ArgMatches, config: &Config) -> bool {
     false
 }
 
-fn get_use_old_network_legend(matches: &clap::ArgMatches, config: &Config) -> bool {
+fn get_use_old_network_legend(matches: &ArgMatches, config: &Config) -> bool {
     if matches.is_present("use_old_network_legend") {
         return true;
     } else if let Some(flags) = &config.flags {
@@ -801,7 +812,7 @@ fn get_use_old_network_legend(matches: &clap::ArgMatches, config: &Config) -> bo
     false
 }
 
-fn get_hide_table_gap(matches: &clap::ArgMatches, config: &Config) -> bool {
+fn get_hide_table_gap(matches: &ArgMatches, config: &Config) -> bool {
     if matches.is_present("hide_table_gap") {
         return true;
     } else if let Some(flags) = &config.flags {
@@ -812,7 +823,7 @@ fn get_hide_table_gap(matches: &clap::ArgMatches, config: &Config) -> bool {
     false
 }
 
-fn get_use_battery(matches: &clap::ArgMatches, config: &Config) -> bool {
+fn get_use_battery(matches: &ArgMatches, config: &Config) -> bool {
     if cfg!(feature = "battery") {
         if matches.is_present("battery") {
             return true;
@@ -825,7 +836,7 @@ fn get_use_battery(matches: &clap::ArgMatches, config: &Config) -> bool {
     false
 }
 
-fn get_enable_gpu_memory(matches: &clap::ArgMatches, config: &Config) -> bool {
+fn get_enable_gpu_memory(matches: &ArgMatches, config: &Config) -> bool {
     if cfg!(feature = "gpu") {
         if matches.is_present("enable_gpu_memory") {
             return true;
@@ -839,7 +850,7 @@ fn get_enable_gpu_memory(matches: &clap::ArgMatches, config: &Config) -> bool {
 }
 
 #[allow(dead_code)]
-fn get_no_write(matches: &clap::ArgMatches, config: &Config) -> bool {
+fn get_no_write(matches: &ArgMatches, config: &Config) -> bool {
     if matches.is_present("no_write") {
         return true;
     } else if let Some(flags) = &config.flags {
@@ -887,9 +898,7 @@ fn get_ignore_list(ignore_list: &Option<IgnoreList>) -> error::Result<Option<Fil
     }
 }
 
-pub fn get_color_scheme(
-    matches: &clap::ArgMatches, config: &Config,
-) -> error::Result<ColourScheme> {
+pub fn get_color_scheme(matches: &ArgMatches, config: &Config) -> error::Result<ColourScheme> {
     if let Some(color) = matches.value_of("color") {
         // Highest priority is always command line flags...
         return ColourScheme::from_str(color);
@@ -914,7 +923,7 @@ pub fn get_color_scheme(
     Ok(ColourScheme::Default)
 }
 
-fn get_mem_as_value(matches: &clap::ArgMatches, config: &Config) -> bool {
+fn get_mem_as_value(matches: &ArgMatches, config: &Config) -> bool {
     if matches.is_present("mem_as_value") {
         return true;
     } else if let Some(flags) = &config.flags {
@@ -925,7 +934,7 @@ fn get_mem_as_value(matches: &clap::ArgMatches, config: &Config) -> bool {
     false
 }
 
-fn get_is_default_tree(matches: &clap::ArgMatches, config: &Config) -> bool {
+fn get_is_default_tree(matches: &ArgMatches, config: &Config) -> bool {
     if matches.is_present("tree") {
         return true;
     } else if let Some(flags) = &config.flags {
@@ -936,7 +945,7 @@ fn get_is_default_tree(matches: &clap::ArgMatches, config: &Config) -> bool {
     false
 }
 
-fn get_show_table_scroll_position(matches: &clap::ArgMatches, config: &Config) -> bool {
+fn get_show_table_scroll_position(matches: &ArgMatches, config: &Config) -> bool {
     if matches.is_present("show_table_scroll_position") {
         return true;
     } else if let Some(flags) = &config.flags {
@@ -947,7 +956,7 @@ fn get_show_table_scroll_position(matches: &clap::ArgMatches, config: &Config) -
     false
 }
 
-fn get_is_default_process_command(matches: &clap::ArgMatches, config: &Config) -> bool {
+fn get_is_default_process_command(matches: &ArgMatches, config: &Config) -> bool {
     if matches.is_present("process_command") {
         return true;
     } else if let Some(flags) = &config.flags {
@@ -958,7 +967,7 @@ fn get_is_default_process_command(matches: &clap::ArgMatches, config: &Config) -
     false
 }
 
-fn get_is_advanced_kill_disabled(matches: &clap::ArgMatches, config: &Config) -> bool {
+fn get_is_advanced_kill_disabled(matches: &ArgMatches, config: &Config) -> bool {
     if matches.is_present("disable_advanced_kill") {
         return true;
     } else if let Some(flags) = &config.flags {
@@ -969,7 +978,7 @@ fn get_is_advanced_kill_disabled(matches: &clap::ArgMatches, config: &Config) ->
     false
 }
 
-fn get_network_unit_type(matches: &clap::ArgMatches, config: &Config) -> DataUnit {
+fn get_network_unit_type(matches: &ArgMatches, config: &Config) -> DataUnit {
     if matches.is_present("network_use_bytes") {
         return DataUnit::Byte;
     } else if let Some(flags) = &config.flags {
@@ -983,7 +992,7 @@ fn get_network_unit_type(matches: &clap::ArgMatches, config: &Config) -> DataUni
     DataUnit::Bit
 }
 
-fn get_network_scale_type(matches: &clap::ArgMatches, config: &Config) -> AxisScaling {
+fn get_network_scale_type(matches: &ArgMatches, config: &Config) -> AxisScaling {
     if matches.is_present("network_use_log") {
         return AxisScaling::Log;
     } else if let Some(flags) = &config.flags {
@@ -997,7 +1006,7 @@ fn get_network_scale_type(matches: &clap::ArgMatches, config: &Config) -> AxisSc
     AxisScaling::Linear
 }
 
-fn get_network_use_binary_prefix(matches: &clap::ArgMatches, config: &Config) -> bool {
+fn get_network_use_binary_prefix(matches: &ArgMatches, config: &Config) -> bool {
     if matches.is_present("network_use_binary_prefix") {
         return true;
     } else if let Some(flags) = &config.flags {
@@ -1007,3 +1016,21 @@ fn get_network_use_binary_prefix(matches: &clap::ArgMatches, config: &Config) ->
     }
     false
 }
+
+fn get_retention_ms(matches: &ArgMatches, config: &Config) -> error::Result<u64> {
+    const DEFAULT_RETENTION_MS: u64 = 600 * 1000; // Keep 10 minutes of data.
+
+    if let Some(retention) = matches.value_of("retention") {
+        humantime::parse_duration(retention)
+            .map(|dur| dur.as_millis() as u64)
+            .map_err(|err| BottomError::ConfigError(format!("invalid retention duration: {err:?}")))
+    } else if let Some(flags) = &config.flags {
+        if let Some(retention) = flags.retention {
+            Ok(retention.as_millis() as u64)
+        } else {
+            Ok(DEFAULT_RETENTION_MS)
+        }
+    } else {
+        Ok(DEFAULT_RETENTION_MS)
+    }
+}