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Add Feature Flag to Disable Array Preallocation for Log Record Attributes in Limited Stack Environments #2055

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Add Feature Flag to Disable Array Preallocation for Log Record Attributes in Limited Stack Environments #2055

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3cc915f
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lalitb Aug 26, 2024
d33a9b0
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lalitb Aug 26, 2024
37122a8
Merge branch 'main' into feature-no-stack-preallocated-array
cijothomas Aug 26, 2024
8ef994b
add changelog, and change featre flag name
lalitb Aug 26, 2024
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1 change: 1 addition & 0 deletions opentelemetry-sdk/Cargo.toml
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Expand Up @@ -51,6 +51,7 @@ testing = ["opentelemetry/testing", "trace", "metrics", "logs", "rt-async-std",
rt-tokio = ["tokio", "tokio-stream"]
rt-tokio-current-thread = ["tokio", "tokio-stream"]
rt-async-std = ["async-std"]
no-preallocate-attributes-array = []
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Alternate suggestion:
disable_stack_log_attributes

"Preallocate" is potentially misleading, we can pre-allocate in heap as well.

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please also add a changelog entry for this. There is a general lacking of documentaion for each of the feature flags, but that is something we need to work on independent of this PR.


[[bench]]
name = "context"
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14 changes: 14 additions & 0 deletions opentelemetry-sdk/src/logs/record.rs
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Expand Up @@ -8,15 +8,29 @@ use std::{borrow::Cow, time::SystemTime};

// According to a Go-specific study mentioned on https://go.dev/blog/slog,
// up to 5 attributes is the most common case.
#[cfg(not(feature = "no-preallocate-attributes-array"))]
const PREALLOCATED_ATTRIBUTE_CAPACITY: usize = 5;
#[cfg(feature = "no-preallocate-attributes-array")]
const PREALLOCATED_ATTRIBUTE_CAPACITY: usize = 0;
#[cfg(feature = "no-preallocate-attributes-array")]
const OVERFLOW_ATTRIBUTE_CAPACITY: usize = 5;

/// Represents a collection of log record attributes with a predefined capacity.
///
/// This type uses `GrowableArray` to store key-value pairs of log attributes, where each attribute is an `Option<(Key, AnyValue)>`.
/// The initial attributes are allocated in a fixed-size array of capacity `PREALLOCATED_ATTRIBUTE_CAPACITY`.
/// If more attributes are added beyond this capacity, additional storage is handled by dynamically growing a vector.
#[cfg(not(feature = "no-preallocate-attributes-array"))]
pub(crate) type LogRecordAttributes =
GrowableArray<Option<(Key, AnyValue)>, PREALLOCATED_ATTRIBUTE_CAPACITY>;
/// When the `no-preallocate-attributes-array` feature flag is enabled, we don't use array allocation.
/// Instead, the vector part of `GrowableArray` is used, and OVERFLOW_ATTRIBUTE_CAPACITY allocation occurs when the first entry is added.
#[cfg(feature = "no-preallocate-attributes-array")]
pub(crate) type LogRecordAttributes = GrowableArray<
Option<(Key, AnyValue)>,
PREALLOCATED_ATTRIBUTE_CAPACITY,
OVERFLOW_ATTRIBUTE_CAPACITY,
>;

#[derive(Debug, Default, Clone, PartialEq)]
#[non_exhaustive]
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