[pbs-devel] [PATCH proxmox-backup v3 3/9] config: add JobState helper

[Dominik Csapak <d.csapak@proxmox.com>]

this is intended to be a generic helper to (de)serialize job states
(e.g., sync, verify, and so on)

writes a json file into '/var/lib/proxmox-backup/jobstates/TYPE-ID.json'

the api creates the directory with the correct permissions, like
the rrd directory

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
---
 src/bin/proxmox-backup-api.rs |   1 +
 src/config.rs                 |   1 +
 src/config/jobstate.rs        | 258 ++++++++++++++++++++++++++++++++++
 3 files changed, 260 insertions(+)
 create mode 100644 src/config/jobstate.rs

diff --git a/src/bin/proxmox-backup-api.rs b/src/bin/proxmox-backup-api.rs
index 9dde46c0..ea306cf0 100644
--- a/src/bin/proxmox-backup-api.rs
+++ b/src/bin/proxmox-backup-api.rs
@@ -37,6 +37,7 @@ async fn run() -> Result<(), Error> {
     config::update_self_signed_cert(false)?;
 
     proxmox_backup::rrd::create_rrdb_dir()?;
+    proxmox_backup::config::jobstate::create_jobstate_dir()?;
 
     if let Err(err) = generate_auth_key() {
         bail!("unable to generate auth key - {}", err);
diff --git a/src/config.rs b/src/config.rs
index 2aeccaec..c2ac6da1 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -18,6 +18,7 @@ use crate::buildcfg;
 pub mod acl;
 pub mod cached_user_info;
 pub mod datastore;
+pub mod jobstate;
 pub mod network;
 pub mod remote;
 pub mod sync;
diff --git a/src/config/jobstate.rs b/src/config/jobstate.rs
new file mode 100644
index 00000000..45672cea
--- /dev/null
+++ b/src/config/jobstate.rs
@@ -0,0 +1,258 @@
+//! Generic JobState handling
+//!
+//! A 'Job' can have 3 states
+//!  - Created, when a schedule was created but never executed
+//!  - Started, when a job is running right now
+//!  - Finished, when a job was running in the past
+//!
+//! and is identified by 2 values: jobtype and jobname (e.g. 'syncjob' and 'myfirstsyncjob')
+//!
+//! This module Provides 2 helper structs to handle those coniditons
+//! 'Job' which handles locking and writing to a file
+//! 'JobState' which is the actual state
+//!
+//! an example usage would be
+//! ```no_run
+//! # use anyhow::{bail, Error};
+//! # use proxmox_backup::server::TaskState;
+//! # use proxmox_backup::config::jobstate::*;
+//! # fn some_code() -> TaskState { TaskState::OK }
+//! # fn code() -> Result<(), Error> {
+//! // locks the correct file under /var/lib
+//! // or fails if someone else holds the lock
+//! let mut job = match Job::new("jobtype", "jobname") {
+//!     Ok(job) => job,
+//!     Err(err) => bail!("could not lock jobstate"),
+//! };
+//!
+//! // job holds the lock
+//! match job.load() {
+//!     Ok(()) => {},
+//!     Err(err) => bail!("could not load state {}", err),
+//! }
+//!
+//! // now the job is loaded;
+//! job.start("someupid")?;
+//! // do something
+//! let task_state = some_code();
+//! job.finish(task_state)?;
+//!
+//! // release the lock
+//! drop(job);
+//! # Ok(())
+//! # }
+//!
+//! ```
+use std::fs::File;
+use std::path::{Path, PathBuf};
+use std::time::Duration;
+
+use serde::{Serialize, Deserialize};
+use anyhow::{bail, Error, format_err};
+use proxmox::tools::fs::{file_read_optional_string, replace_file, create_path, CreateOptions, open_file_locked};
+
+use crate::tools::epoch_now_u64;
+use crate::server::{TaskState, UPID, worker_is_active_local, upid_read_status};
+
+#[serde(rename_all="kebab-case")]
+#[derive(Serialize,Deserialize)]
+/// Represents the State of a specific Job
+pub enum JobState {
+    /// A job was created at 'time', but never started/finished
+    Created { time: i64 },
+    /// The Job was last started in 'upid',
+    Started { upid: String },
+    /// The Job was last started in 'upid', which finished with 'state' at 'endtime'
+    Finished { upid: String, endtime: i64, state: TaskState }
+}
+
+/// Represents a Job and holds the correct lock
+pub struct Job {
+    jobtype: String,
+    jobname: String,
+    /// The State of the job
+    pub state: JobState,
+    _lock: File,
+}
+
+const JOB_STATE_BASEDIR: &str = "/var/lib/proxmox-backup/jobstates";
+
+/// Create jobstate stat dir with correct permission
+pub fn create_jobstate_dir() -> Result<(), Error> {
+    let backup_user = crate::backup::backup_user()?;
+    let opts = CreateOptions::new()
+        .owner(backup_user.uid)
+        .group(backup_user.gid);
+
+    create_path(JOB_STATE_BASEDIR, None, Some(opts))
+        .map_err(|err: Error| format_err!("unable to create rrdb stat dir - {}", err))?;
+
+    Ok(())
+}
+
+fn get_path(jobtype: &str, jobname: &str) -> PathBuf {
+    let mut path = PathBuf::from(JOB_STATE_BASEDIR);
+    path.push(format!("{}-{}.json", jobtype, jobname));
+    path
+}
+
+fn get_lock<P>(path: P) -> Result<File, Error>
+where
+    P: AsRef<Path>
+{
+    let mut path = path.as_ref().to_path_buf();
+    path.set_extension("lck");
+    open_file_locked(path, Duration::new(10, 0))
+}
+
+/// Removes the statefile of a job, this is useful if we delete a job
+pub fn remove_state_file(jobtype: &str, jobname: &str) -> Result<(), Error> {
+    let path = get_path(jobtype, jobname);
+    let _lock = get_lock(&path)?;
+    std::fs::remove_file(&path).map_err(|err|
+        format_err!("cannot remove statefile for {} - {}: {}", jobtype, jobname, err)
+    )
+}
+
+/// Returns the last run time of a job by reading the statefile
+/// Note that this is not locked
+pub fn last_run_time(jobtype: &str, jobname: &str) -> Result<i64, Error> {
+    match JobState::load(jobtype, jobname)? {
+        JobState::Created { time } => Ok(time),
+        JobState::Started { upid } | JobState::Finished { upid, .. } => {
+            let upid: UPID = upid.parse().map_err(|err|
+                format_err!("could not parse upid from state: {}", err)
+            )?;
+            Ok(upid.starttime)
+        }
+    }
+}
+
+impl JobState {
+    /// Loads and deserializes the jobstate from type and name.
+    /// When the loaded state indicates a started UPID,
+    /// we go and check if it has already stopped, and
+    /// returning the correct state.
+    ///
+    /// This does not update the state in the file.
+    pub fn load(jobtype: &str, jobname: &str) -> Result<Self, Error> {
+        if let Some(state) = file_read_optional_string(get_path(jobtype, jobname))? {
+            match serde_json::from_str(&state)? {
+                JobState::Started { upid } => {
+                    let parsed: UPID = upid.parse()
+                        .map_err(|err| format_err!("error parsing upid: {}", err))?;
+
+                    if !worker_is_active_local(&parsed) {
+                        let (endtime, state) = upid_read_status(&parsed)
+                            .map_err(|err| format_err!("error reading upid log status: {}", err))?;
+
+                        Ok(JobState::Finished {
+                            upid,
+                            endtime,
+                            state
+                        })
+                    } else {
+                        Ok(JobState::Started { upid })
+                    }
+                }
+                other => Ok(other),
+            }
+        } else {
+            Ok(JobState::Created {
+                time: epoch_now_u64()? as i64
+            })
+        }
+    }
+}
+
+impl Job {
+    /// Creates a new instance of a job with the correct lock held
+    /// (will be hold until the job is dropped again).
+    ///
+    /// This does not load the state from the file, to do that,
+    /// 'load' must be called
+    pub fn new(jobtype: &str, jobname: &str) -> Result<Self, Error> {
+        let path = get_path(jobtype, jobname);
+
+        let _lock = get_lock(&path)?;
+
+        Ok(Self{
+            jobtype: jobtype.to_string(),
+            jobname: jobname.to_string(),
+            state: JobState::Created {
+                time: epoch_now_u64()? as i64
+            },
+            _lock,
+        })
+    }
+
+    /// Loads the state from the statefile if it exists.
+    /// If not, it gets created. Updates 'Started' State to 'Finished'
+    /// if we detect the UPID already stopped
+    pub fn load(&mut self) -> Result<(), Error> {
+        self.state = JobState::load(&self.jobtype, &self.jobname)?;
+
+        if let Err(err) = self.write_state() {
+            bail!("could not write statefile: {}", err);
+        }
+
+        Ok(())
+    }
+
+    /// Start the job and update the statefile accordingly
+    /// Fails if the job was already started
+    pub fn start(&mut self, upid: &str) -> Result<(), Error> {
+        match self.state {
+            JobState::Started { .. } => {
+                bail!("cannot start job that is started!");
+            }
+            _ => {}
+        }
+
+        self.state = JobState::Started{
+            upid: upid.to_string(),
+        };
+
+        self.write_state()
+    }
+
+    /// Finish the job and update the statefile accordingly with the given taskstate
+    /// Fails if the job was not yet started
+    pub fn finish(&mut self, state: TaskState) -> Result<(), Error> {
+        let upid = match &self.state {
+            JobState::Created { .. } => bail!("cannot finish when not started"),
+            JobState::Started { upid } => upid,
+            JobState::Finished { upid, .. } => upid,
+        }.to_string();
+
+        let endtime: i64 = epoch_now_u64()? as i64;
+
+        self.state = JobState::Finished {
+            upid,
+            endtime,
+            state,
+        };
+
+        self.write_state()
+    }
+
+    fn write_state(&mut self) -> Result<(), Error> {
+        let serialized = serde_json::to_string(&self.state)?;
+        let path = get_path(&self.jobtype, &self.jobname);
+
+        let backup_user = crate::backup::backup_user()?;
+        let mode = nix::sys::stat::Mode::from_bits_truncate(0o0644);
+        // set the correct owner/group/permissions while saving file
+        // owner(rw) = backup, group(r)= backup
+        let options = CreateOptions::new()
+            .perm(mode)
+            .owner(backup_user.uid)
+            .group(backup_user.gid);
+
+        replace_file(
+            path,
+            serialized.as_bytes(),
+            options,
+        )
+    }
+}
-- 
2.20.1