perf: improve perf of encoding with new UTF-8 validation

This makes four changes: 1. The `EscapingScheme` and `ValidationScheme` enums are now `Copy` since they are very small and cheap to copy. They're passed by value rather than by reference. 2. The `escape_name` function now returns a `Cow` rather than a `String` to avoid allocations in many cases. 3. `escape_name` also preallocates a buffer for the escaped name rather than starting with an empty `String` and growing it, to amortize the allocations. 4. Use `is_ascii_alphabetic` and `is_ascii_digit` to check for characters that are valid in metric and label names. Based on profiles I suspect that #2 has the highest impact but haven't split these out to see how much of a difference it makes. Signed-off-by: Ben Sully <ben.sully88@gmail.com>

Author: sd2k

src/encoding.rs

@@ -770,7 +770,7 @@ impl ExemplarValueEncoder<'_> {
 
 /// Enum for determining how metric and label names will
 /// be validated.
-#[derive(Debug, PartialEq, Default, Clone)]
+#[derive(Debug, PartialEq, Default, Clone, Copy)]
 pub enum ValidationScheme {
  /// Setting that requires that metric and label names
  /// conform to the original OpenMetrics character requirements.
@@ -807,9 +807,9 @@ fn is_valid_legacy_prefix(prefix: Option<&Prefix>) -> bool {
 fn is_quoted_metric_name(
  name: &str,
  prefix: Option<&Prefix>,
- validation_scheme: &ValidationScheme,
+ validation_scheme: ValidationScheme,
 ) -> bool {
- *validation_scheme == ValidationScheme::UTF8Validation
+ validation_scheme == ValidationScheme::UTF8Validation
  && (!is_valid_legacy_metric_name(name) || !is_valid_legacy_prefix(prefix))
 }
 
@@ -818,24 +818,20 @@ fn is_valid_legacy_label_name(label_name: &str) -> bool {
  return false;
  }
  for (i, b) in label_name.chars().enumerate() {
- if !((b >= 'a' && b <= 'z')
- || (b >= 'A' && b <= 'Z')
- || b == '_'
- || (b >= '0' && b <= '9' && i > 0))
- {
+ if !(b.is_ascii_alphabetic() || b == '_' || (b.is_ascii_digit() && i > 0)) {
  return false;
  }
  }
  true
 }
 
-fn is_quoted_label_name(name: &str, validation_scheme: &ValidationScheme) -> bool {
- *validation_scheme == ValidationScheme::UTF8Validation && !is_valid_legacy_label_name(name)
+fn is_quoted_label_name(name: &str, validation_scheme: ValidationScheme) -> bool {
+ validation_scheme == ValidationScheme::UTF8Validation && !is_valid_legacy_label_name(name)
 }
 
 /// Enum for determining how metric and label names will
 /// be escaped.
-#[derive(Debug, Default, Clone)]
+#[derive(Debug, Default, Clone, Copy)]
 pub enum EscapingScheme {
  /// Replaces all legacy-invalid characters with underscores.
  #[default]
@@ -863,26 +859,30 @@ impl EscapingScheme {
  }
 }
 
-fn escape_name(name: &str, scheme: &EscapingScheme) -> String {
+fn escape_name(name: &str, scheme: EscapingScheme) -> Cow<'_, str> {
  if name.is_empty() {
- return name.to_string();
+ return name.into();
  }
- let mut escaped = String::new();
  match scheme {
- EscapingScheme::NoEscaping => return name.to_string(),
+ EscapingScheme::NoEscaping => name.into(),
+ EscapingScheme::UnderscoreEscaping | EscapingScheme::ValueEncodingEscaping
+ if is_valid_legacy_metric_name(name) =>
+ {
+ name.into()
+ }
  EscapingScheme::UnderscoreEscaping => {
- if is_valid_legacy_metric_name(name) {
- return name.to_string();
- }
+ let mut escaped = String::with_capacity(name.len());
  for (i, b) in name.chars().enumerate() {
  if is_valid_legacy_char(b, i) {
  escaped.push(b);
  } else {
  escaped.push('_');
  }
  }
+ escaped.into()
  }
  EscapingScheme::DotsEscaping => {
+ let mut escaped = String::with_capacity(name.len());
  for (i, b) in name.chars().enumerate() {
  if b == '_' {
  escaped.push_str("__");
@@ -894,11 +894,10 @@ fn escape_name(name: &str, scheme: &EscapingScheme) -> String {
  escaped.push_str("__");
  }
  }
+ escaped.into()
  }
  EscapingScheme::ValueEncodingEscaping => {
- if is_valid_legacy_metric_name(name) {
- return name.to_string();
- }
+ let mut escaped = String::with_capacity(name.len());
  escaped.push_str("U__");
  for (i, b) in name.chars().enumerate() {
  if b == '_' {
@@ -909,9 +908,9 @@ fn escape_name(name: &str, scheme: &EscapingScheme) -> String {
  write!(escaped, "_{:x}_", b as i64).unwrap();
  }
  }
+ escaped.into()
  }
  }
- escaped
 }
 
 /// Returns the escaping scheme to use based on the given header.
@@ -1120,13 +1119,13 @@ mod tests {
  ];
 
  for scenario in scenarios {
- let result = escape_name(scenario.input, &EscapingScheme::UnderscoreEscaping);
+ let result = escape_name(scenario.input, EscapingScheme::UnderscoreEscaping);
  assert_eq!(result, scenario.expected_underscores, "{}", scenario.name);
 
- let result = escape_name(scenario.input, &EscapingScheme::DotsEscaping);
+ let result = escape_name(scenario.input, EscapingScheme::DotsEscaping);
  assert_eq!(result, scenario.expected_dots, "{}", scenario.name);
 
- let result = escape_name(scenario.input, &EscapingScheme::ValueEncodingEscaping);
+ let result = escape_name(scenario.input, EscapingScheme::ValueEncodingEscaping);
  assert_eq!(result, scenario.expected_value, "{}", scenario.name);
  }
  }

src/encoding/text.rs

@@ -148,8 +148,8 @@ where
  registry.encode(
  &mut DescriptorEncoder::new(
  writer,
- &registry.name_validation_scheme(),
- &registry.escaping_scheme(),
+ registry.name_validation_scheme(),
+ registry.escaping_scheme(),
  )
  .into(),
  )
@@ -196,8 +196,8 @@ pub(crate) struct DescriptorEncoder<'a> {
  writer: &'a mut dyn Write,
  prefix: Option<&'a Prefix>,
  labels: &'a [(Cow<'static, str>, Cow<'static, str>)],
- name_validation_scheme: &'a ValidationScheme,
- escaping_scheme: &'a EscapingScheme,
+ name_validation_scheme: ValidationScheme,
+ escaping_scheme: EscapingScheme,
 }
 
 impl std::fmt::Debug for DescriptorEncoder<'_> {
@@ -207,11 +207,11 @@ impl std::fmt::Debug for DescriptorEncoder<'_> {
 }
 
 impl DescriptorEncoder<'_> {
- pub(crate) fn new<'a>(
- writer: &'a mut dyn Write,
- name_validation_scheme: &'a ValidationScheme,
- escaping_scheme: &'a EscapingScheme,
- ) -> DescriptorEncoder<'a> {
+ pub(crate) fn new(
+ writer: &'_ mut dyn Write,
+ name_validation_scheme: ValidationScheme,
+ escaping_scheme: EscapingScheme,
+ ) -> DescriptorEncoder<'_> {
  DescriptorEncoder {
  writer,
  prefix: Default::default(),
@@ -230,8 +230,8 @@ impl DescriptorEncoder<'_> {
  prefix,
  labels,
  writer: self.writer,
- name_validation_scheme: &self.name_validation_scheme,
- escaping_scheme: &self.escaping_scheme,
+ name_validation_scheme: self.name_validation_scheme,
+ escaping_scheme: self.escaping_scheme,
  }
  }
 
@@ -246,14 +246,12 @@ impl DescriptorEncoder<'_> {
  let mut escaped_prefix: Option<&Prefix> = None;
  let escaped_prefix_value: Prefix;
  if let Some(prefix) = self.prefix {
- escaped_prefix_value = Prefix::from(escape_name(prefix.as_str(), self.escaping_scheme));
+ escaped_prefix_value =
+ Prefix::from(escape_name(prefix.as_str(), self.escaping_scheme).into_owned());
  escaped_prefix = Some(&escaped_prefix_value);
  }
- let is_quoted_metric_name = is_quoted_metric_name(
- escaped_name.as_str(),
- escaped_prefix,
- self.name_validation_scheme,
- );
+ let is_quoted_metric_name =
+ is_quoted_metric_name(&escaped_name, escaped_prefix, self.name_validation_scheme);
  self.writer.write_str("# HELP ")?;
  if is_quoted_metric_name {
  self.writer.write_str("\"")?;
@@ -262,7 +260,7 @@ impl DescriptorEncoder<'_> {
  self.writer.write_str(prefix.as_str())?;
  self.writer.write_str("_")?;
  }
- self.writer.write_str(escaped_name.as_str())?;
+ self.writer.write_str(&escaped_name)?;
  if let Some(unit) = unit {
  self.writer.write_str("_")?;
  self.writer.write_str(unit.as_str())?;
@@ -282,7 +280,7 @@ impl DescriptorEncoder<'_> {
  self.writer.write_str(prefix.as_str())?;
  self.writer.write_str("_")?;
  }
- self.writer.write_str(escaped_name.as_str())?;
+ self.writer.write_str(&escaped_name)?;
  if let Some(unit) = unit {
  self.writer.write_str("_")?;
  self.writer.write_str(unit.as_str())?;
@@ -303,7 +301,7 @@ impl DescriptorEncoder<'_> {
  self.writer.write_str(prefix.as_str())?;
  self.writer.write_str("_")?;
  }
- self.writer.write_str(escaped_name.as_str())?;
+ self.writer.write_str(&escaped_name)?;
  self.writer.write_str("_")?;
  self.writer.write_str(unit.as_str())?;
  if is_quoted_metric_name {
@@ -343,8 +341,8 @@ pub(crate) struct MetricEncoder<'a> {
  unit: Option<&'a Unit>,
  const_labels: &'a [(Cow<'static, str>, Cow<'static, str>)],
  family_labels: Option<&'a dyn super::EncodeLabelSet>,
- name_validation_scheme: &'a ValidationScheme,
- escaping_scheme: &'a EscapingScheme,
+ name_validation_scheme: ValidationScheme,
+ escaping_scheme: EscapingScheme,
 }
 
 impl std::fmt::Debug for MetricEncoder<'_> {
@@ -534,14 +532,12 @@ impl MetricEncoder<'_> {
  let mut escaped_prefix: Option<&Prefix> = None;
  let escaped_prefix_value: Prefix;
  if let Some(prefix) = self.prefix {
- escaped_prefix_value = Prefix::from(escape_name(prefix.as_str(), self.escaping_scheme));
+ escaped_prefix_value =
+ Prefix::from(escape_name(prefix.as_str(), self.escaping_scheme).into_owned());
  escaped_prefix = Some(&escaped_prefix_value);
  }
- let is_quoted_metric_name = is_quoted_metric_name(
- escaped_name.as_str(),
- escaped_prefix,
- self.name_validation_scheme,
- );
+ let is_quoted_metric_name =
+ is_quoted_metric_name(&escaped_name, escaped_prefix, self.name_validation_scheme);
  if is_quoted_metric_name {
  self.writer.write_str("{")?;
  self.writer.write_str("\"")?;
@@ -550,7 +546,7 @@ impl MetricEncoder<'_> {
  self.writer.write_str(prefix.as_str())?;
  self.writer.write_str("_")?;
  }
- self.writer.write_str(escaped_name.as_str())?;
+ self.writer.write_str(&escaped_name)?;
  if let Some(unit) = self.unit {
  self.writer.write_str("_")?;
  self.writer.write_str(unit.as_str())?;
@@ -576,14 +572,12 @@ impl MetricEncoder<'_> {
  let mut escaped_prefix: Option<&Prefix> = None;
  let escaped_prefix_value: Prefix;
  if let Some(prefix) = self.prefix {
- escaped_prefix_value = Prefix::from(escape_name(prefix.as_str(), self.escaping_scheme));
+ escaped_prefix_value =
+ Prefix::from(escape_name(prefix.as_str(), self.escaping_scheme).into_owned());
  escaped_prefix = Some(&escaped_prefix_value);
  }
- let is_quoted_metric_name = is_quoted_metric_name(
- escaped_name.as_str(),
- escaped_prefix,
- self.name_validation_scheme,
- );
+ let is_quoted_metric_name =
+ is_quoted_metric_name(&escaped_name, escaped_prefix, self.name_validation_scheme);
  if self.const_labels.is_empty()
  && additional_labels.is_none()
  && self.family_labels.is_none()
@@ -750,8 +744,8 @@ impl ExemplarValueEncoder<'_> {
 pub(crate) struct LabelSetEncoder<'a> {
  writer: &'a mut dyn Write,
  first: bool,
- name_validation_scheme: &'a ValidationScheme,
- escaping_scheme: &'a EscapingScheme,
+ name_validation_scheme: ValidationScheme,
+ escaping_scheme: EscapingScheme,
 }
 
 impl std::fmt::Debug for LabelSetEncoder<'_> {
@@ -765,8 +759,8 @@ impl std::fmt::Debug for LabelSetEncoder<'_> {
 impl<'a> LabelSetEncoder<'a> {
  fn new(
  writer: &'a mut dyn Write,
- name_validation_scheme: &'a ValidationScheme,
- escaping_scheme: &'a EscapingScheme,
+ name_validation_scheme: ValidationScheme,
+ escaping_scheme: EscapingScheme,
  ) -> Self {
  Self {
  writer,
@@ -791,8 +785,8 @@ impl<'a> LabelSetEncoder<'a> {
 pub(crate) struct LabelEncoder<'a> {
  writer: &'a mut dyn Write,
  first: bool,
- name_validation_scheme: &'a ValidationScheme,
- escaping_scheme: &'a EscapingScheme,
+ name_validation_scheme: ValidationScheme,
+ escaping_scheme: EscapingScheme,
 }
 
 impl std::fmt::Debug for LabelEncoder<'_> {
@@ -818,8 +812,8 @@ impl LabelEncoder<'_> {
 
 pub(crate) struct LabelKeyEncoder<'a> {
  writer: &'a mut dyn Write,
- name_validation_scheme: &'a ValidationScheme,
- escaping_scheme: &'a EscapingScheme,
+ name_validation_scheme: ValidationScheme,
+ escaping_scheme: EscapingScheme,
 }
 
 impl std::fmt::Debug for LabelKeyEncoder<'_> {
@@ -840,12 +834,11 @@ impl<'a> LabelKeyEncoder<'a> {
 impl std::fmt::Write for LabelKeyEncoder<'_> {
  fn write_str(&mut self, s: &str) -> std::fmt::Result {
  let escaped_name = escape_name(s, self.escaping_scheme);
- let is_quoted_label_name =
- is_quoted_label_name(escaped_name.as_str(), self.name_validation_scheme);
+ let is_quoted_label_name = is_quoted_label_name(&escaped_name, self.name_validation_scheme);
  if is_quoted_label_name {
  self.writer.write_str("\"")?;
  }
- self.writer.write_str(escaped_name.as_str())?;
+ self.writer.write_str(&escaped_name)?;
  if is_quoted_label_name {
  self.writer.write_str("\"")?;
  }
@@ -1043,8 +1036,7 @@ mod tests {
 
  encode(&mut encoded, &registry).unwrap();
 
- let expected = "# HELP \"my.gauge\"\" My\ngau\nge\".\n"
- .to_owned()
+ let expected = "# HELP \"my.gauge\"\" My\ngau\nge\".\n".to_owned()
  + "# TYPE \"my.gauge\"\" gauge\n"
  + "{\"my.gauge\"\"} inf\n"
  + "# EOF\n";
@@ -1646,8 +1638,8 @@ mod tests {
  unit: None,
  const_labels: &[],
  family_labels: None,
- name_validation_scheme: &UTF8Validation,
- escaping_scheme: &NoEscaping,
+ name_validation_scheme: UTF8Validation,
+ escaping_scheme: NoEscaping,
  };
 
  encoder.encode_labels::<NoLabelSet>(None).unwrap();
@@ -1667,8 +1659,8 @@ mod tests {
  unit: None,
  const_labels: &const_labels,
  family_labels: Some(&family_labels),
- name_validation_scheme: &UTF8Validation,
- escaping_scheme: &NoEscaping,
+ name_validation_scheme: UTF8Validation,
+ escaping_scheme: NoEscaping,
  };
 
  encoder.encode_labels(Some(&additional_labels)).unwrap();
@@ -1688,12 +1680,15 @@ mod tests {
  unit: None,
  const_labels: &const_labels,
  family_labels: Some(&family_labels),
- name_validation_scheme: &UTF8Validation,
- escaping_scheme: &NoEscaping,
+ name_validation_scheme: UTF8Validation,
+ escaping_scheme: NoEscaping,
  };
 
  encoder.encode_labels(Some(&additional_labels)).unwrap();
- assert_eq!(buffer, "{\"service.name\"=\"t1\",\"whatever\\whatever\"=\"t2\",\"t*3\"=\"t3\"}");
+ assert_eq!(
+ buffer,
+ "{\"service.name\"=\"t1\",\"whatever\\whatever\"=\"t2\",\"t*3\"=\"t3\"}"
+ );
  }
 
  fn parse_with_python_client(input: String) {