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Add hot reload support for configuration
Reloads the configuration when it has been changed, and recreates all collectors and observers. If an error occurs during reload, Duck will continue to use the old configuration, but write an error to the console output. Closes #53
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| Original file line number | Diff line number | Diff line change |
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@@ -3,5 +3,5 @@ | |
| **/*.rs.bk | ||
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| # Configuration | ||
| config.json | ||
| /config.json | ||
| data/ | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,168 @@ | ||
| use std::fs; | ||
| use std::path::PathBuf; | ||
| use std::sync::{Arc, Mutex}; | ||
| use std::time::SystemTime; | ||
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| use crate::config::{Configuration, ConfigurationLoader}; | ||
| use crate::utils::text::VariableProvider; | ||
| use crate::DuckResult; | ||
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| /////////////////////////////////////////////////////////// | ||
| // Configuration loader | ||
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| #[derive(Clone)] | ||
| pub struct JsonConfigurationLoader<'a> { | ||
| path: PathBuf, | ||
| reader: &'a dyn FileReader, | ||
| modified: Arc<Mutex<u64>>, | ||
| } | ||
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| impl<'a> JsonConfigurationLoader<'a> { | ||
| pub fn create(path: PathBuf) -> Self { | ||
| JsonConfigurationLoader::new(path, &DefaultFileReader {}) | ||
| } | ||
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| fn new(path: PathBuf, reader: &'a dyn FileReader) -> Self { | ||
| JsonConfigurationLoader { | ||
| path, | ||
| reader, | ||
| modified: Arc::new(Mutex::new(0)), | ||
| } | ||
| } | ||
| } | ||
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| impl<'a> ConfigurationLoader for JsonConfigurationLoader<'a> { | ||
| fn exist(&self) -> bool { | ||
| self.path.exists() | ||
| } | ||
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| fn has_changed(&self) -> DuckResult<bool> { | ||
| let modified = self.reader.modified(&self.path)?; | ||
| if *self.modified.lock().unwrap() != modified { | ||
| return Ok(true); | ||
| } | ||
| Ok(false) | ||
| } | ||
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| fn load(&self, variables: &dyn VariableProvider) -> DuckResult<Configuration> { | ||
| // Read the configuration and deserialize it | ||
| let json = self.reader.read_to_string(&self.path)?; | ||
| let config: Configuration = Configuration::from_json(variables, json)?; | ||
| // Update the modified time to the current one. | ||
| let modified = self.reader.modified(&self.path)?; | ||
| *self.modified.lock().unwrap() = modified; | ||
| Ok(config) | ||
| } | ||
| } | ||
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| /////////////////////////////////////////////////////////// | ||
| // File reader | ||
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| trait FileReader: Send + Sync { | ||
| /// Returns the content of the file as a string | ||
| fn read_to_string(&self, path: &PathBuf) -> DuckResult<String>; | ||
| /// Gets the modified time as Epoch time | ||
| fn modified(&self, path: &PathBuf) -> DuckResult<u64>; | ||
| } | ||
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| struct DefaultFileReader {} | ||
| impl FileReader for DefaultFileReader { | ||
| fn read_to_string(&self, path: &PathBuf) -> DuckResult<String> { | ||
| Ok(fs::read_to_string(path)?) | ||
| } | ||
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| fn modified(&self, path: &PathBuf) -> DuckResult<u64> { | ||
| Ok(fs::metadata(path)? | ||
| .modified()? | ||
| .duration_since(SystemTime::UNIX_EPOCH)? | ||
| .as_secs()) | ||
| } | ||
| } | ||
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| /////////////////////////////////////////////////////////// | ||
| // Tests | ||
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| #[cfg(test)] | ||
| mod tests { | ||
| use super::*; | ||
| use crate::utils::text::TestVariableProvider; | ||
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| struct FakeFileReader { | ||
| json: String, | ||
| modified: Arc<Mutex<u64>>, | ||
| } | ||
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| impl FakeFileReader { | ||
| fn new<T: Into<String>>(json: T, modified: u64) -> Self { | ||
| Self { | ||
| json: json.into(), | ||
| modified: Arc::new(Mutex::new(modified)), | ||
| } | ||
| } | ||
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| pub fn inc_modified(&self) { | ||
| let mut modified = self.modified.lock().unwrap(); | ||
| *modified = *modified + 1; | ||
| } | ||
| } | ||
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| impl FileReader for FakeFileReader { | ||
| fn read_to_string(&self, _path: &PathBuf) -> DuckResult<String> { | ||
| Ok(self.json.clone()) | ||
| } | ||
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| fn modified(&self, _path: &PathBuf) -> DuckResult<u64> { | ||
| let modified = self.modified.lock().unwrap(); | ||
| Ok(*modified) | ||
| } | ||
| } | ||
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| #[test] | ||
| fn should_load_expected_configuration() { | ||
| // Given | ||
| let path = PathBuf::from("config.json"); | ||
| let reader = FakeFileReader::new(include_str!("test_data/config.json"), 1583092970); | ||
| let config = JsonConfigurationLoader::new(path, &reader); | ||
| let variables = TestVariableProvider::new(); | ||
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| // When | ||
| let config = config.load(&variables).unwrap(); | ||
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| // Then | ||
| assert_eq!(99, config.interval); | ||
| assert_eq!("Duck test server", config.title); | ||
| } | ||
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| #[test] | ||
| fn should_indicate_if_configuration_has_not_changed_since_read() { | ||
| // Given | ||
| let path = PathBuf::from("config.json"); | ||
| let reader = FakeFileReader::new(include_str!("test_data/config.json"), 1583092970); | ||
| let handle = JsonConfigurationLoader::new(path, &reader); | ||
| let variables = TestVariableProvider::new(); | ||
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| // When | ||
| handle.load(&variables).unwrap(); | ||
| let has_changed = handle.has_changed().unwrap(); | ||
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| // Then | ||
| assert!(!has_changed); | ||
| } | ||
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| #[test] | ||
| fn should_indicate_if_configuration_changed_since_read() { | ||
| // Given | ||
| let path = PathBuf::from("config.json"); | ||
| let reader = FakeFileReader::new(include_str!("test_data/config.json"), 1583092970); | ||
| let handle = JsonConfigurationLoader::new(path, &reader); | ||
| let variables = TestVariableProvider::new(); | ||
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| // When | ||
| handle.load(&variables).unwrap(); | ||
| reader.inc_modified(); | ||
| let has_changed = handle.has_changed().unwrap(); | ||
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| // Then | ||
| assert!(has_changed); | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,5 @@ | ||
| { | ||
| "interval": 99, | ||
| "title": "Duck test server", | ||
| "collectors": [ ] | ||
| } |
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