tools: add logrotate module

this is a helper to rotate and iterate over log files
there is an iterator for open filehandles as well as
only the filename

also it has the possibilty to rotate them
for compression, zstd is used

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>

src/tools.rs

@@ -32,6 +32,7 @@ pub mod ticket;
 pub mod statistics;
 pub mod systemd;
 pub mod nom;
+pub mod logrotate;
 
 mod parallel_handler;
 pub use parallel_handler::*;

src/tools/logrotate.rs

@@ -0,0 +1,184 @@
+use std::path::{Path, PathBuf};
+use std::fs::{File, rename};
+use std::os::unix::io::FromRawFd;
+use std::io::Read;
+
+use anyhow::{bail, Error};
+use nix::unistd;
+
+use proxmox::tools::fs::{CreateOptions, make_tmp_file, replace_file};
+
+/// Used for rotating log files and iterating over them
+pub struct LogRotate {
+    base_path: PathBuf,
+    compress: bool,
+}
+
+impl LogRotate {
+    /// Creates a new instance if the path given is a valid file name
+    /// (iow. does not end with ..)
+    /// 'compress' decides if compresses files will be created on
+    /// rotation, and if it will search '.zst' files when iterating
+    pub fn new<P: AsRef<Path>>(path: P, compress: bool) -> Option<Self> {
+        if path.as_ref().file_name().is_some() {
+            Some(Self {
+                base_path: path.as_ref().to_path_buf(),
+                compress,
+            })
+        } else {
+            None
+        }
+    }
+
+    /// Returns an iterator over the logrotated file names that exist
+    pub fn file_names(&self) -> LogRotateFileNames {
+        LogRotateFileNames {
+            base_path: self.base_path.clone(),
+            count: 0,
+            compress: self.compress
+        }
+    }
+
+    /// Returns an iterator over the logrotated file handles
+    pub fn files(&self) -> LogRotateFiles {
+        LogRotateFiles {
+            file_names: self.file_names(),
+        }
+    }
+
+    /// Rotates the files up to 'max_files'
+    /// if the 'compress' option was given it will compress the newest file
+    ///
+    /// e.g. rotates
+    /// foo.2.zst => foo.3.zst
+    /// foo.1.zst => foo.2.zst
+    /// foo       => foo.1.zst
+    ///           => foo
+    pub fn rotate(&mut self, options: CreateOptions, max_files: Option<usize>) -> Result<(), Error> {
+        let mut filenames: Vec<PathBuf> = self.file_names().collect();
+        if filenames.is_empty() {
+            return Ok(()); // no file means nothing to rotate
+        }
+
+        let mut next_filename = self.base_path.clone().canonicalize()?.into_os_string();
+
+        if self.compress {
+            next_filename.push(format!(".{}.zst", filenames.len()));
+        } else {
+            next_filename.push(format!(".{}", filenames.len()));
+        }
+
+        filenames.push(PathBuf::from(next_filename));
+        let count = filenames.len();
+
+        // rotate all but the first, that we maybe have to compress
+        for i in (1..count-1).rev() {
+            rename(&filenames[i], &filenames[i+1])?;
+        }
+
+        if self.compress {
+            let mut source = File::open(&filenames[0])?;
+            let (fd, tmp_path) = make_tmp_file(&filenames[1], options.clone())?;
+            let target = unsafe { File::from_raw_fd(fd) };
+            let mut encoder = match zstd::stream::write::Encoder::new(target, 0) {
+                Ok(encoder) => encoder,
+                Err(err) => {
+                    let _ = unistd::unlink(&tmp_path);
+                    bail!("creating zstd encoder failed - {}", err);
+                }
+            };
+
+            if let Err(err) = std::io::copy(&mut source, &mut encoder) {
+                let _ = unistd::unlink(&tmp_path);
+                bail!("zstd encoding failed for file {:?} - {}", &filenames[1], err);
+            }
+
+            if let Err(err) = encoder.finish() {
+                let _ = unistd::unlink(&tmp_path);
+                bail!("zstd finish failed for file {:?} - {}", &filenames[1], err);
+            }
+
+            if let Err(err) = rename(&tmp_path, &filenames[1]) {
+                let _ = unistd::unlink(&tmp_path);
+                bail!("rename failed for file {:?} - {}", &filenames[1], err);
+            }
+
+            unistd::unlink(&filenames[0])?;
+        } else {
+            rename(&filenames[0], &filenames[1])?;
+        }
+
+        // create empty original file
+        replace_file(&filenames[0], b"", options)?;
+
+        if let Some(max_files) = max_files {
+            // delete all files > max_files
+            for file in filenames.iter().skip(max_files) {
+                if let Err(err) = unistd::unlink(file) {
+                    eprintln!("could not remove {:?}: {}", &file, err);
+                }
+            }
+        }
+
+        Ok(())
+    }
+}
+
+/// Iterator over logrotated file names
+pub struct LogRotateFileNames {
+    base_path: PathBuf,
+    count: usize,
+    compress: bool,
+}
+
+impl Iterator for LogRotateFileNames {
+    type Item = PathBuf;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.count > 0 {
+            let mut path: std::ffi::OsString = self.base_path.clone().into();
+
+            path.push(format!(".{}", self.count));
+            self.count += 1;
+
+            if Path::new(&path).is_file() {
+                Some(path.into())
+            } else if self.compress {
+                path.push(".zst");
+                if Path::new(&path).is_file() {
+                    Some(path.into())
+                } else {
+                    None
+                }
+            } else {
+                None
+            }
+        } else if self.base_path.is_file() {
+            self.count += 1;
+            Some(self.base_path.to_path_buf())
+        } else {
+            None
+        }
+    }
+}
+
+/// Iterator over logrotated files by returning a boxed reader
+pub struct LogRotateFiles {
+    file_names: LogRotateFileNames,
+}
+
+impl Iterator for LogRotateFiles {
+    type Item = Box<dyn Read + Send>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let filename = self.file_names.next()?;
+        let file = File::open(&filename).ok()?;
+
+        if filename.extension().unwrap_or(std::ffi::OsStr::new("")) == "zst" {
+            let encoder = zstd::stream::read::Decoder::new(file).ok()?;
+            return Some(Box::new(encoder));
+        }
+
+        Some(Box::new(file))
+    }
+}