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overhaul error messages

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Inspired by the poor error message here:
https://github.com/scottlamb/moonfire-nvr/issues/107#issuecomment-777587727

*   print the friendlier Display version of the error rather than Debug.
    Eg, "EROFS: Read-only filesystem" rather than "Sys(EROFS)". Do this
    everywhere: on command exit, on syncer retries, and on stream
    retries.
*   print the most immediate problem and additional lines for each
    cause.
*   print the backtrace or an advertisement for RUST_BACKTRACE=1 if it's
    unavailable.
*   also mention RUST_BACKTRACE=1 in the troubleshooting guide.
*   add context in various places, including pathnames. There are surely
    many places more it'd be helpful, but this is a start.
*   allow subcommands to return failure without an Error.
    In particular, "moonfire-nvr check" does its own error printing
    because it wants to print all the errors it finds. Printing "see
    earlier errors" with a meaningless stack trace seems like it'd just
    confuse. But I also want to get rid of the misleading "Success" at
    the end and 0 return to the OS.
This commit is contained in:
Scott Lamb
2021-02-11 10:45:56 -08:00
parent ff1615a0b4
commit 9a5957d5ef
19 changed files with 101 additions and 55 deletions
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27
server/db/dir.rs
View File

@@ -151,7 +151,7 @@ pub(crate) fn read_meta(dir: &Fd) -> Result<schema::DirMeta, Error> {
}
let data = &data[pos..pos+len as usize];
let mut s = protobuf::CodedInputStream::from_bytes(&data);
meta.merge_from(&mut s).map_err(|e| e.context("Unable to parse metadata proto: {}"))?;
meta.merge_from(&mut s).map_err(|e| e.context("Unable to parse metadata proto"))?;
Ok(meta)
}
@@ -164,17 +164,18 @@ pub(crate) fn write_meta(dirfd: RawFd, meta: &schema::DirMeta) -> Result<(), Err
}
data.resize(FIXED_DIR_META_LEN, 0); // pad to required length.
let mut f = crate::fs::openat(dirfd, cstr!("meta"), OFlag::O_CREAT | OFlag::O_WRONLY,
Mode::S_IRUSR | Mode::S_IWUSR)?;
let stat = f.metadata()?;
Mode::S_IRUSR | Mode::S_IWUSR)
.map_err(|e| e.context("Unable to open meta file"))?;
let stat = f.metadata().map_err(|e| e.context("Unable to stat meta file"))?;
if stat.len() == 0 {
// Need to sync not only the data but also the file metadata and dirent.
f.write_all(&data)?;
f.sync_all()?;
nix::unistd::fsync(dirfd)?;
f.write_all(&data).map_err(|e| e.context("Unable to write to meta file"))?;
f.sync_all().map_err(|e| e.context("Unable to sync meta file"))?;
nix::unistd::fsync(dirfd).map_err(|e| e.context("Unable to sync dir"))?;
} else if stat.len() == FIXED_DIR_META_LEN as u64 {
// Just syncing the data will suffice; existing metadata and dirent are fine.
f.write_all(&data)?;
f.sync_data()?;
f.write_all(&data).map_err(|e| e.context("Unable to write to meta file"))?;
f.sync_data().map_err(|e| e.context("Unable to sync meta file"))?;
} else {
bail!("Existing meta file is {}-byte; expected {}", stat.len(), FIXED_DIR_META_LEN);
}
@@ -194,8 +195,8 @@ impl SampleFileDir {
FlockArg::LockExclusiveNonblock
} else {
FlockArg::LockSharedNonblock
})?;
let dir_meta = read_meta(&s.fd)?;
}).map_err(|e| e.context(format!("unable to lock dir {}", path)))?;
let dir_meta = read_meta(&s.fd).map_err(|e| e.context("unable to read meta file"))?;
if !SampleFileDir::consistent(db_meta, &dir_meta) {
let serialized =
db_meta.write_length_delimited_to_bytes().expect("proto3->vec is infallible");
@@ -230,7 +231,8 @@ impl SampleFileDir {
pub(crate) fn create(path: &str, db_meta: &schema::DirMeta)
-> Result<Arc<SampleFileDir>, Error> {
let s = SampleFileDir::open_self(path, true)?;
s.fd.lock(FlockArg::LockExclusiveNonblock)?;
s.fd.lock(FlockArg::LockExclusiveNonblock)
.map_err(|e| e.context(format!("unable to lock dir {}", path)))?;
let old_meta = read_meta(&s.fd)?;
// Verify metadata. We only care that it hasn't been completely opened.
@@ -265,8 +267,7 @@ impl SampleFileDir {
}
fn open_self(path: &str, create: bool) -> Result<Arc<SampleFileDir>, Error> {
let fd = Fd::open(path, create)
.map_err(|e| format_err!("unable to open sample file dir {}: {}", path, e))?;
let fd = Fd::open(path, create)?;
Ok(Arc::new(SampleFileDir {
fd,
}))