[pbs-devel] [RFC PATCH proxmox-backup 2/2] server/worker_task: simplify task log writing

[Dominik Csapak]

instead of prerotating 1000 tasks
(which resulted in 2 writes each time an active worker was finished)
simply append finished tasks to the archive (which will be rotated)

page cache should be good enough so that we can get the task logs fast

since existing installations might have an 'index' file, we
still have to read tasks from there

Signed-off-by: Dominik Csapak <d.csapak at proxmox.com>
---
maybe there is a better way to get rid of the index file handling?
we cannot really simply append the index file to the archive in
a postinst since the old daemon may still write into it..

do we actually care? the users may lose some task information, but
no actual harm should come from lost task logs, since we use
the jobstate for the state handling and scheduling

we could also simply removing the index code from the iterator
and leave it in 'update_active_workers' so that after the next finished
active task, we move them from the index file to archive
so we lose them just temporarily....?

not sure so sending as RFC

 src/server/worker_task.rs | 39 ++++++++++++---------------------------
 1 file changed, 12 insertions(+), 27 deletions(-)

diff --git a/src/server/worker_task.rs b/src/server/worker_task.rs
index 8ef0fde7..2e873904 100644
--- a/src/server/worker_task.rs
+++ b/src/server/worker_task.rs
@@ -35,8 +35,6 @@ pub const PROXMOX_BACKUP_ACTIVE_TASK_FN: &str = concat!(PROXMOX_BACKUP_TASK_DIR_
 pub const PROXMOX_BACKUP_INDEX_TASK_FN: &str = concat!(PROXMOX_BACKUP_TASK_DIR_M!(), "/index");
 pub const PROXMOX_BACKUP_ARCHIVE_TASK_FN: &str = concat!(PROXMOX_BACKUP_TASK_DIR_M!(), "/archive");
 
-const MAX_INDEX_TASKS: usize = 1000;
-
 lazy_static! {
     static ref WORKER_TASK_LIST: Mutex<HashMap<usize, Arc<WorkerTask>>> = Mutex::new(HashMap::new());
 
@@ -363,7 +361,10 @@ fn update_active_workers(new_upid: Option<&UPID>) -> Result<(), Error> {
 
     let lock = lock_task_list_files(true)?;
 
+    // TODO remove with 2.0?
     let mut finish_list: Vec<TaskListInfo> = read_task_file_from_path(PROXMOX_BACKUP_INDEX_TASK_FN)?;
+    let had_index_file = !finish_list.is_empty();
+
     let mut active_list: Vec<TaskListInfo> = read_task_file_from_path(PROXMOX_BACKUP_ACTIVE_TASK_FN)?
         .into_iter()
         .filter_map(|info| {
@@ -412,33 +413,10 @@ fn update_active_workers(new_upid: Option<&UPID>) -> Result<(), Error> {
         }
     });
 
-
-    let start = if finish_list.len() > MAX_INDEX_TASKS {
-        finish_list.len() - MAX_INDEX_TASKS
-    } else {
-        0
-    };
-
-    let end = (start+MAX_INDEX_TASKS).min(finish_list.len());
-
-    let index_raw = if end > start {
-        render_task_list(&finish_list[start..end])
-    } else {
-        "".to_string()
-    };
-
-    replace_file(
-        PROXMOX_BACKUP_INDEX_TASK_FN,
-        index_raw.as_bytes(),
-        CreateOptions::new()
-            .owner(backup_user.uid)
-            .group(backup_user.gid),
-    )?;
-
-    if !finish_list.is_empty() && start > 0 {
+    if !finish_list.is_empty() {
         match std::fs::OpenOptions::new().append(true).create(true).open(PROXMOX_BACKUP_ARCHIVE_TASK_FN) {
             Ok(mut writer) => {
-                for info in &finish_list[0..start] {
+                for info in &finish_list {
                     writer.write_all(render_task_line(&info).as_bytes())?;
                 }
             },
@@ -448,6 +426,12 @@ fn update_active_workers(new_upid: Option<&UPID>) -> Result<(), Error> {
         nix::unistd::chown(PROXMOX_BACKUP_ARCHIVE_TASK_FN, Some(backup_user.uid), Some(backup_user.gid))?;
     }
 
+    // TODO Remove with 2.0?
+    // for compatibility, if we had an INDEX file, we do not need it anymore
+    if had_index_file {
+        let _ = nix::unistd::unlink(PROXMOX_BACKUP_INDEX_TASK_FN);
+    }
+
     drop(lock);
 
     Ok(())
@@ -518,6 +502,7 @@ enum TaskFile {
     End,
 }
 
+// TODO remove Index with 2.0?
 pub struct TaskListInfoIterator {
     list: VecDeque<TaskListInfo>,
     file: TaskFile,
-- 
2.20.1