seed the rng

Cargo.toml

@@ -1,15 +1,15 @@
 [package]
-name = "cron-with-randomness"
-version = "0.0.2"
+name = "cron-within-interval"
+version = "0.1.0"
 edition = "2021"
 
 [dependencies]
-anyhow = "1.0.75"
-chrono = "0.4.31"
-cron = "0.12.0"
-lazy_static = "1.4.0"
-rand = "0.8.5"
-regex = "1.10.2"
+anyhow = "1.0"
+chrono = "0.4"
+cron = "0.12"
+lazy_static = "1.5"
+rand = "0.8"
+regex = "1.10"
 
 [dev-dependencies]
-simple_accumulator = "0.5.0"
+simple_accumulator = "0.7.0"

src/lib.rs

@@ -1,8 +1,10 @@
-//! cron-with-randomness
+//! cron-within-interval
 //!
 //! Extended cron shorthands that support sampling from given interval. In addition to standard
 //! expression supported by excellent crate cron, we support following type of expressions.
 //!
+//! The random number is seeded so you always get the same sequence.
+//!
 //! - `@daily{h=9-17}` means run once between 9am and 5pm chosen randomly.  
 //! - `@daily{h=9-12,h=15-20}` means run once between 9am and 12pm or between 3pm and 8pm.
 //!
@@ -21,6 +23,9 @@ use cron::Schedule;
 use rand::{seq::SliceRandom, Rng};
 use regex::Regex;
 
+/// Global seed fro rngs.
+const SEED: u64 = 1443;
+
 lazy_static::lazy_static! {
     static ref RE: Regex = Regex::new(
         r"(?x)
@@ -107,7 +112,7 @@ impl CronWithRandomness {
     where
         Z: chrono::TimeZone,
     {
-        let mut rng = rand::thread_rng();
+        let mut rng = rand::StdRng::seed_from_u64(SEED);
         let mut result_datetime = datetime.clone();
 
         // pick a random minute. We have to reduce one hour from the hour range after this.
@@ -155,7 +160,7 @@ impl FromStr for Interval {
 impl Interval {
     /// Generate a random value between the interval
     fn random(&self) -> i16 {
-        let mut rng = rand::thread_rng();
+        let mut rng = rand::StdRng::seed_from_u64(SEED);
         // high is exclusive
         rng.gen_range(self.0..self.1)
     }