Bump to cernan 0.7.5

This release contains fixes for the overlong holding of file
descriptors in a couple of spots inside of cernan:

  * 07d3fad :: drop unused structures after cernan boot
  * de747e1 :: drop deleted files from polling in file source

The first change allows hopper to drop file descriptors opened
as a part of cernan startup. The second change allows the file source
to drop file descriptors as soon as the files are marked deleted.
Previously we assumed that this could be avoided on the expectation
of applications creating a new logfile. This assumption was not
valid.

Signed-off-by: Brian L. Troutwine <blt@postmates.com>

Cargo.toml

@@ -7,7 +7,7 @@ license = "MIT"
 name = "cernan"
 readme = "README.md"
 repository = "https://github.com/postmates/cernan"
-version = "0.7.5-pre"
+version = "0.7.5"
 
 [[bin]]
 name = "cernan"

src/source/file/file_server.rs

@@ -118,28 +118,21 @@ impl Source for FileServer {
             // line polling
             for (path, mut watcher) in fp_map.drain() {
                 let mut lines_read: usize = 0;
-                loop {
-                    match watcher.read_line(&mut buffer) {
-                        Ok(sz) => {
-                            if sz > 0 {
-                                lines_read += 1;
-                                lines.push(
-                                    metric::LogLine::new(
-                                        path.to_str().expect("not a valid path"),
-                                        &buffer,
-                                    ).overlay_tags_from_map(&self.tags),
-                                );
-                                buffer.clear();
-                            } else {
-                                break;
-                            }
-                            if lines_read > self.max_lines_read {
-                                break;
-                            }
-                        }
-                        _ => {
-                            break;
-                        }
+                while let Ok(sz) = watcher.read_line(&mut buffer) {
+                    if sz > 0 {
+                        lines_read += 1;
+                        lines.push(
+                            metric::LogLine::new(
+                                path.to_str().expect("not a valid path"),
+                                &buffer,
+                            ).overlay_tags_from_map(&self.tags),
+                        );
+                        buffer.clear();
+                    } else {
+                        break;
+                    }
+                    if lines_read > self.max_lines_read {
+                        break;
                     }
                 }
                 report_full_telemetry(

src/source/file/file_watcher.rs

@@ -96,10 +96,8 @@ impl FileWatcher {
     /// up to some maximum but unspecified amount of time. `read_line` will open
     /// a new file handler at need, transparently to the caller.
     pub fn read_line(&mut self, mut buffer: &mut String) -> io::Result<usize> {
-        if self.reopen {
-            if self.file_id() != self.file_id {
-                self.open_at_start();
-            }
+        if self.reopen && self.file_id() != self.file_id {
+            self.open_at_start();
         }
         if let Some(ref mut reader) = self.reader {
             // match here on error, if metadata doesn't match up open_at_start
@@ -115,11 +113,8 @@ impl FileWatcher {
                     Ok(buffer.len())
                 }
                 Err(e) => {
-                    match e.kind() {
-                        io::ErrorKind::NotFound => {
-                            self.reopen = true;
-                        }
-                        _ => {}
+                    if let io::ErrorKind::NotFound = e.kind() {
+                        self.reopen = true;
                     }
                     Err(e)
                 }