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journald: Don't prefix message_id field to make use of Journal Message Catalogs easier #3111

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journald: Don't prefix message_id field to make use of Journal Message Catalogs easier #3111

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12 changes: 7 additions & 5 deletions tracing-journald/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -53,6 +53,8 @@ mod memfd;
#[cfg(target_os = "linux")]
mod socket;

static FIELDS_NOT_PREFIXED: [&str; 2] = ["message", "message_id"];

/// Sends events and their fields to journald
///
/// [journald conventions] for structured field names differ from typical tracing idioms, and journald
Expand All @@ -74,8 +76,8 @@ mod socket;
/// For events recorded inside spans, an additional `SPAN_NAME` field is emitted with the name of
/// each of the event's parent spans.
///
/// User-defined fields other than the event `message` field have a prefix applied by default to
/// prevent collision with standard fields.
/// User-defined fields other than the event `message` and `message_id` fields have a prefix applied
/// by default to prevent collision with standard fields.
///
/// [journald conventions]: https://www.freedesktop.org/software/systemd/man/systemd.journal-fields.html
pub struct Layer {
Expand Down Expand Up @@ -123,7 +125,7 @@ impl Layer {
}

/// Sets the prefix to apply to names of user-defined fields other than the event `message`
/// field. Defaults to `Some("F")`.
/// and `message_id` fields. Defaults to `Some("F")`.
pub fn with_field_prefix(mut self, x: Option<String>) -> Self {
self.field_prefix = x;
self
Expand Down Expand Up @@ -349,8 +351,8 @@ impl<'a> EventVisitor<'a> {

fn put_prefix(&mut self, field: &Field) {
if let Some(prefix) = self.prefix {
if field.name() != "message" {
// message maps to the standard MESSAGE field so don't prefix it
if !FIELDS_NOT_PREFIXED.contains(&field.name()) {
// message maps to the standard MESSAGE or MESSAGE_ID field so don't prefix it
self.buf.extend_from_slice(prefix.as_bytes());
self.buf.push(b'_');
}
Expand Down
68 changes: 54 additions & 14 deletions tracing-journald/tests/journal.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -118,14 +118,19 @@ fn retry<T, E>(f: impl Fn() -> Result<T, E>) -> Result<T, E> {
/// Additionally filter by the `_PID` field with the PID of this
/// test process, to make sure this method only reads journal entries
/// created by this test process.
fn read_from_journal(test_name: &str) -> Vec<HashMap<String, Field>> {
fn read_from_journal(test_name: &str, prefix: Option<&str>) -> Vec<HashMap<String, Field>> {
let prefix = if let Some(prefix) = prefix {
format!("{prefix}_")
} else {
String::new()
};
let stdout = String::from_utf8(
Command::new("journalctl")
// We pass --all to circumvent journalctl's default limit of 4096 bytes for field values
.args(["--user", "--output=json", "--all"])
// Filter by the PID of the current test process
.arg(format!("_PID={}", std::process::id()))
.arg(format!("TEST_NAME={}", test_name))
.arg(dbg!(format!("{prefix}TEST_NAME={test_name}")))
.output()
.unwrap()
.stdout,
Expand All @@ -142,9 +147,12 @@ fn read_from_journal(test_name: &str) -> Vec<HashMap<String, Field>> {
///
/// Try to read lines for `testname` from journal, and `retry()` if the wasn't
/// _exactly_ one matching line.
fn retry_read_one_line_from_journal(testname: &str) -> HashMap<String, Field> {
fn retry_read_one_line_from_journal(
testname: &str,
prefix: Option<&str>,
) -> HashMap<String, Field> {
retry(|| {
let mut messages = read_from_journal(testname);
let mut messages = read_from_journal(testname, prefix);
if messages.len() == 1 {
Ok(messages.pop().unwrap())
} else {
Expand All @@ -162,7 +170,7 @@ fn simple_message() {
with_journald(|| {
info!(test.name = "simple_message", "Hello World");

let message = retry_read_one_line_from_journal("simple_message");
let message = retry_read_one_line_from_journal("simple_message", None);
assert_eq!(message["MESSAGE"], "Hello World");
assert_eq!(message["PRIORITY"], "5");
});
Expand All @@ -173,7 +181,7 @@ fn multiline_message() {
with_journald(|| {
warn!(test.name = "multiline_message", "Hello\nMultiline\nWorld");

let message = retry_read_one_line_from_journal("multiline_message");
let message = retry_read_one_line_from_journal("multiline_message", None);
assert_eq!(message["MESSAGE"], "Hello\nMultiline\nWorld");
assert_eq!(message["PRIORITY"], "4");
});
Expand All @@ -187,7 +195,7 @@ fn multiline_message_trailing_newline() {
"A trailing newline\n"
);

let message = retry_read_one_line_from_journal("multiline_message_trailing_newline");
let message = retry_read_one_line_from_journal("multiline_message_trailing_newline", None);
assert_eq!(message["MESSAGE"], "A trailing newline\n");
assert_eq!(message["PRIORITY"], "3");
});
Expand All @@ -198,7 +206,7 @@ fn internal_null_byte() {
with_journald(|| {
debug!(test.name = "internal_null_byte", "An internal\x00byte");

let message = retry_read_one_line_from_journal("internal_null_byte");
let message = retry_read_one_line_from_journal("internal_null_byte", None);
assert_eq!(message["MESSAGE"], b"An internal\x00byte"[..]);
assert_eq!(message["PRIORITY"], "6");
});
Expand All @@ -210,7 +218,7 @@ fn large_message() {
with_journald(|| {
debug!(test.name = "large_message", "Message: {}", large_string);

let message = retry_read_one_line_from_journal("large_message");
let message = retry_read_one_line_from_journal("large_message", None);
assert_eq!(
message["MESSAGE"],
format!("Message: {}", large_string).as_str()
Expand All @@ -228,7 +236,7 @@ fn simple_metadata() {
with_journald_layer(sub, || {
info!(test.name = "simple_metadata", "Hello World");

let message = retry_read_one_line_from_journal("simple_metadata");
let message = retry_read_one_line_from_journal("simple_metadata", None);
assert_eq!(message["MESSAGE"], "Hello World");
assert_eq!(message["PRIORITY"], "5");
assert_eq!(message["TARGET"], "journal");
Expand All @@ -248,7 +256,7 @@ fn journal_fields() {
with_journald_layer(sub, || {
info!(test.name = "journal_fields", "Hello World");

let message = retry_read_one_line_from_journal("journal_fields");
let message = retry_read_one_line_from_journal("journal_fields", None);
assert_eq!(message["MESSAGE"], "Hello World");
assert_eq!(message["PRIORITY"], "5");
assert_eq!(message["TARGET"], "journal");
Expand All @@ -268,7 +276,7 @@ fn span_metadata() {

info!(test.name = "span_metadata", "Hello World");

let message = retry_read_one_line_from_journal("span_metadata");
let message = retry_read_one_line_from_journal("span_metadata", None);
assert_eq!(message["MESSAGE"], "Hello World");
assert_eq!(message["PRIORITY"], "5");
assert_eq!(message["TARGET"], "journal");
Expand All @@ -294,7 +302,7 @@ fn multiple_spans_metadata() {

info!(test.name = "multiple_spans_metadata", "Hello World");

let message = retry_read_one_line_from_journal("multiple_spans_metadata");
let message = retry_read_one_line_from_journal("multiple_spans_metadata", None);
assert_eq!(message["MESSAGE"], "Hello World");
assert_eq!(message["PRIORITY"], "5");
assert_eq!(message["TARGET"], "journal");
Expand Down Expand Up @@ -324,10 +332,42 @@ fn spans_field_collision() {
"Hello World"
);

let message = retry_read_one_line_from_journal("spans_field_collision");
let message = retry_read_one_line_from_journal("spans_field_collision", None);
assert_eq!(message["MESSAGE"], "Hello World");
assert_eq!(message["SPAN_NAME"], vec!["span1", "span2"]);

assert_eq!(message["SPAN_FIELD"], vec!["foo1", "foo2", "foo3"]);
});
}

#[test]
fn prefix_custom_fields() {
let layer = Layer::new()
.unwrap()
.with_field_prefix(Some("PRE".to_string()));
with_journald_layer(layer, || {
info!(bar = "foo", test.name = "prefix_test", "Hello World");

let message = retry_read_one_line_from_journal("prefix_test", Some("PRE"));
assert_eq!(message["MESSAGE"], "Hello World");
assert_eq!(message["PRE_BAR"], "foo");
});
}

#[test]
fn do_not_prefix_field_message_id() {
let layer = Layer::new()
.unwrap()
.with_field_prefix(Some("PRE".to_string()));
with_journald_layer(layer, || {
info!(
message_id = "68228769143b4a0a946f9ad3bca57b20",
test.name = "no_prefix_test",
"Hello World"
);

let message = retry_read_one_line_from_journal("no_prefix_test", Some("PRE"));
assert_eq!(message["MESSAGE"], "Hello World");
assert_eq!(message["MESSAGE_ID"], "68228769143b4a0a946f9ad3bca57b20");
});
}