diff options
| -rw-r--r-- | src/main.rs | 29 |
1 files changed, 21 insertions, 8 deletions
diff --git a/src/main.rs b/src/main.rs index 29a71974b89b..b8eeb6b9fb5c 100644 --- a/src/main.rs +++ b/src/main.rs @@ -1,4 +1,4 @@ -// Copyright (C) 2018 Aprila Bank ASA (contact: vincent@aprila.no) +// Copyright (C) 2018 Vincent Ambo <mail@tazj.in> // // journaldriver is free software: you can redistribute it and/or // modify it under the terms of the GNU General Public License as @@ -49,7 +49,7 @@ use chrono::prelude::*; use failure::ResultExt; use serde_json::{from_str, Value}; use std::env; -use std::fs::{self, File}; +use std::fs::{self, File, rename}; use std::io::{self, Read, ErrorKind, Write}; use std::mem; use std::path::PathBuf; @@ -105,9 +105,16 @@ lazy_static! { /// Path to the file in which journaldriver should persist its /// cursor state. - static ref POSITION_FILE: PathBuf = env::var("CURSOR_POSITION_FILE") + static ref CURSOR_FILE: PathBuf = env::var("CURSOR_POSITION_FILE") .unwrap_or("/var/lib/journaldriver/cursor.pos".into()) .into(); + + /// Path to the temporary file used for cursor position writes. + static ref CURSOR_TMP_FILE: PathBuf = { + let mut tmp_path = CURSOR_FILE.clone(); + tmp_path.set_extension("pos.tmp"); + tmp_path + }; } /// Convenience helper for retrieving values from the metadata server. @@ -482,10 +489,16 @@ fn receiver_loop(mut journal: Journal) -> Result<()> { } } -/// Writes the current cursor into `/var/journaldriver/cursor.pos`. +/// Writes the current cursor into `/var/journaldriver/cursor.pos`. To +/// avoid issues with journaldriver being terminated while the cursor +/// is still being written, this will first write the cursor into a +/// temporary file and then move it. fn persist_cursor(cursor: String) -> Result<()> { - let mut file = File::create(&*POSITION_FILE)?; - write!(file, "{}", cursor).map_err(Into::into) + let mut file = File::create(&*CURSOR_TMP_FILE)?; + write!(file, "{}", cursor).context("Failed to write cursor file")?; + rename(&*CURSOR_TMP_FILE, &*CURSOR_FILE) + .context("Failed to move cursor file") + .map_err(Into::into) } /// Flushes all drained records to Stackdriver. Any Stackdriver @@ -564,7 +577,7 @@ fn write_entries(token: &Token, request: Value) -> Result<()> { fn initial_cursor() -> Result<JournalSeek> { let read_result: io::Result<String> = (|| { let mut contents = String::new(); - let mut file = File::open(&*POSITION_FILE)?; + let mut file = File::open(&*CURSOR_FILE)?; file.read_to_string(&mut contents)?; Ok(contents.trim().into()) })(); @@ -586,7 +599,7 @@ fn main () { // If the cursor file does not yet exist, the directory structure // leading up to it should be created: - let cursor_position_dir = POSITION_FILE.parent() + let cursor_position_dir = CURSOR_FILE.parent() .expect("Invalid cursor position file path"); fs::create_dir_all(cursor_position_dir) |