enhancement(kubernetes_logs source): Expose oldest_first (#18376)

* enhancement(kubernetes_logs source): Expose `oldest_first`

In response to #18088 (comment)

Might close: #18088

Signed-off-by: Jesse Szwedko <[email protected]>

* Improve descirptions

Signed-off-by: Jesse Szwedko <[email protected]>

---------

Signed-off-by: Jesse Szwedko <[email protected]>

src/sources/file.rs

@@ -205,7 +205,11 @@ pub struct FileConfig {
     #[serde(default)]
     pub multiline: Option<MultilineConfig>,
 
-    /// An approximate limit on the amount of data read from a single file at a given time.
+    /// Max amount of bytes to read from a single file before switching over to the next file.
+    /// **Note:** This does not apply when `oldest_first` is `true.
+    ///
+    /// This allows distributing the reads more or less evenly across
+    /// the files.
     #[serde(default = "default_max_read_bytes")]
     #[configurable(metadata(docs::type_unit = "bytes"))]
     pub max_read_bytes: usize,

src/sources/kubernetes_logs/mod.rs

@@ -163,14 +163,18 @@ pub struct Config {
     #[configurable(metadata(docs::human_name = "Ignore Files Older Than"))]
     ignore_older_secs: Option<u64>,
 
-    /// Max amount of bytes to read from a single file before switching over
-    /// to the next file.
+    /// Max amount of bytes to read from a single file before switching over to the next file.
+    /// **Note:** This does not apply when `oldest_first` is `true.
     ///
     /// This allows distributing the reads more or less evenly across
     /// the files.
     #[configurable(metadata(docs::type_unit = "bytes"))]
     max_read_bytes: usize,
 
+    /// Instead of balancing read capacity fairly across all watched files, prioritize draining the oldest files before moving on to read data from younger files.
+    #[serde(default = "default_oldest_first")]
+    pub oldest_first: bool,
+
     /// The maximum number of bytes a line can contain before being discarded.
     ///
     /// This protects against malformed lines or tailing incorrect files.
@@ -264,6 +268,7 @@ impl Default for Config {
             read_from: default_read_from(),
             ignore_older_secs: None,
             max_read_bytes: default_max_read_bytes(),
+            oldest_first: default_oldest_first(),
             max_line_bytes: default_max_line_bytes(),
             fingerprint_lines: default_fingerprint_lines(),
             glob_minimum_cooldown_ms: default_glob_minimum_cooldown_ms(),
@@ -516,6 +521,7 @@ struct Source {
     read_from: ReadFrom,
     ignore_older_secs: Option<u64>,
     max_read_bytes: usize,
+    oldest_first: bool,
     max_line_bytes: usize,
     fingerprint_lines: usize,
     glob_minimum_cooldown: Duration,
@@ -593,6 +599,7 @@ impl Source {
             read_from: ReadFrom::from(config.read_from),
             ignore_older_secs: config.ignore_older_secs,
             max_read_bytes: config.max_read_bytes,
+            oldest_first: config.oldest_first,
             max_line_bytes: config.max_line_bytes,
             fingerprint_lines: config.fingerprint_lines,
             glob_minimum_cooldown,
@@ -624,6 +631,7 @@ impl Source {
             read_from,
             ignore_older_secs,
             max_read_bytes,
+            oldest_first,
             max_line_bytes,
             fingerprint_lines,
             glob_minimum_cooldown,
@@ -763,9 +771,7 @@ impl Source {
                 max_line_length: max_line_bytes,
                 ignore_not_found: true,
             },
-            // We'd like to consume rotated pod log files first to release our file handle and let
-            // the space be reclaimed
-            oldest_first: true,
+            oldest_first,
             // We do not remove the log files, `kubelet` is responsible for it.
             remove_after: None,
             // The standard emitter.
@@ -944,6 +950,12 @@ const fn default_max_read_bytes() -> usize {
     2048
 }
 
+// We'd like to consume rotated pod log files first to release our file handle and let
+// the space be reclaimed
+const fn default_oldest_first() -> bool {
+    true
+}
+
 const fn default_max_line_bytes() -> usize {
     // NOTE: The below comment documents an incorrect assumption, see
     // https://github.com/vectordotdev/vector/issues/6967

website/cue/reference/components/sources/base/file.cue

@@ -228,8 +228,14 @@ base: components: sources: file: configuration: {
 		}
 	}
 	max_read_bytes: {
-		description: "An approximate limit on the amount of data read from a single file at a given time."
-		required:    false
+		description: """
+			Max amount of bytes to read from a single file before switching over to the next file.
+			**Note:** This does not apply when `oldest_first` is `true.
+
+			This allows distributing the reads more or less evenly across
+			the files.
+			"""
+		required: false
 		type: uint: {
 			default: 2048
 			unit:    "bytes"

website/cue/reference/components/sources/base/kubernetes_logs.cue

@@ -165,8 +165,8 @@ base: components: sources: kubernetes_logs: configuration: {
 	}
 	max_read_bytes: {
 		description: """
-			Max amount of bytes to read from a single file before switching over
-			to the next file.
+			Max amount of bytes to read from a single file before switching over to the next file.
+			**Note:** This does not apply when `oldest_first` is `true.
 
 			This allows distributing the reads more or less evenly across
 			the files.
@@ -209,6 +209,11 @@ base: components: sources: kubernetes_logs: configuration: {
 			}
 		}
 	}
+	oldest_first: {
+		description: "Instead of balancing read capacity fairly across all watched files, prioritize draining the oldest files before moving on to read data from younger files."
+		required:    false
+		type: bool: default: true
+	}
 	pod_annotation_fields: {
 		description: "Configuration for how the events are enriched with Pod metadata."
 		required:    false