Add function for calculating the size limit of log volumes

Author: siegfriedweber

CHANGELOG.md

@@ -4,6 +4,12 @@ All notable changes to this project will be documented in this file.
 
 ## [Unreleased]
 
+### Added
+
+- Add a function for calculating the size limit of log volumes ([#621]).
+
+[#621]: https://github.com/stackabletech/operator-rs/pull/621
+
 ## [0.43.0] - 2023-07-06
 
 ### Added

src/product_logging/framework.rs

@@ -2,11 +2,15 @@
 
 use std::cmp;
 
-use k8s_openapi::api::core::v1::ResourceRequirements;
-
 use crate::{
-    builder::ContainerBuilder, commons::product_image_selection::ResolvedProductImage,
-    k8s_openapi::api::core::v1::Container, kube::Resource, role_utils::RoleGroupRef,
+    builder::ContainerBuilder,
+    commons::product_image_selection::ResolvedProductImage,
+    k8s_openapi::{
+        api::core::v1::{Container, ResourceRequirements},
+        apimachinery::pkg::api::resource::Quantity,
+    },
+    kube::Resource,
+    role_utils::RoleGroupRef,
 };
 
 use super::spec::{
@@ -26,6 +30,50 @@ const SHUTDOWN_FILE: &str = "shutdown";
 /// File name of the Vector config file
 pub const VECTOR_CONFIG_FILE: &str = "vector.toml";
 
+/// Calculate the size limit for the log volume.
+///
+/// The size limit must be much larger than the sum of the given maximum log file sizes for the
+/// following reasons:
+/// - The log file rollover occurs when the log file exceeds the maximum log file size. Depending
+///   on the size of the last log entries, the file can be several kilobytes larger than defined.
+/// - The actual disk usage depends on the block size of the file system.
+/// - OpenShift sometimes reserves more than twice the amount of blocks than needed. For instance,
+///   a ZooKeeper log file with 4,127,151 bytes occupied 4,032 blocks. Then log entries were written
+///   and the actual file size increased to 4,132,477 bytes which occupied 8,128 blocks.
+///
+/// # Example
+///
+/// ```
+/// use stackable_operator::{
+///     builder::{
+///         PodBuilder,
+///         meta::ObjectMetaBuilder,
+///     },
+/// };
+/// # use stackable_operator::product_logging::framework::calculate_log_volume_size_limit;
+///
+/// pub const MAX_INIT_CONTAINER_LOG_FILES_SIZE_IN_MIB: u32 = 1;
+/// pub const MAX_MAIN_CONTAINER_LOG_FILES_SIZE_IN_MIB: u32 = 10;
+///
+/// PodBuilder::new()
+///     .metadata(ObjectMetaBuilder::default().build())
+///     .add_empty_dir_volume(
+///         "log",
+///         Some(product_logging::framework::calculate_log_volume_size_limit(
+///             &[
+///                 MAX_INIT_CONTAINER_LOG_FILES_SIZE_IN_MIB,
+///                 MAX_MAIN_CONTAINER_LOG_FILES_SIZE_IN_MIB,
+///             ],
+///         )),
+///     )
+///     .build()
+///     .unwrap();
+/// ```
+pub fn calculate_log_volume_size_limit(max_log_files_size_in_mib: &[u32]) -> Quantity {
+    let log_volume_size_limit_in_mib = max_log_files_size_in_mib.iter().sum::<u32>() * 3;
+    Quantity(format!("{log_volume_size_limit_in_mib}Mi"))
+}
+
 /// Create a Bash command which filters stdout and stderr according to the given log configuration
 /// and additionally stores the output in log files
 ///