Added max value length per span attribute (#634)

Author: mamunto

Sources/OpenTelemetrySdk/Trace/RecordEventsReadableSpan.swift

@@ -46,6 +46,8 @@ public class RecordEventsReadableSpan: ReadableSpan {
     public private(set) var totalRecordedLinks: Int
     /// Max number of attributes per span.
     public private(set) var maxNumberOfAttributes: Int
+    /// Max value length of attribute per span.
+    public private(set) var maxValueLengthPerSpanAttribute: Int
     /// Max number of attributes per event.
     public private(set) var maxNumberOfAttributesPerEvent: Int
 
@@ -140,6 +142,7 @@ public class RecordEventsReadableSpan: ReadableSpan {
         events = ArrayWithCapacity<SpanData.Event>(capacity: spanLimits.eventCountLimit)
         maxNumberOfAttributes = spanLimits.attributeCountLimit
         maxNumberOfAttributesPerEvent = spanLimits.attributePerEventCountLimit
+        maxValueLengthPerSpanAttribute = spanLimits.attributeValueLengthLimit
     }
 
     /// Creates and starts a span with the given configuration.
@@ -253,7 +256,13 @@ public class RecordEventsReadableSpan: ReadableSpan {
             if attributes[key] == nil, totalAttributeCount > maxNumberOfAttributes {
                 return
             }
-            attributes[key] = value
+            /// Process only `string` type value
+            if case .string(let value) = value {
+                let formattedValue = value.count > maxValueLengthPerSpanAttribute ? String(value.prefix(maxValueLengthPerSpanAttribute)) : value
+                attributes[key] = AttributeValue(formattedValue)
+            } else {
+                attributes[key] = value
+            }
         }
     }
 

Sources/OpenTelemetrySdk/Trace/SpanLimits.swift

@@ -21,6 +21,9 @@ public struct SpanLimits: Equatable {
     public private(set) var attributePerEventCountLimit: Int = 128
     /// the global default max number of attributes per Link.
     public private(set) var attributePerLinkCountLimit: Int = 128
+    /// the global default attributes value max length
+    public private(set) var attributeValueLengthLimit: Int = Int.max
+    
     /// Returns the defaultSpanLimits.
     public init() {}
 
@@ -30,6 +33,12 @@ public struct SpanLimits: Equatable {
         return spanLimits
     }
 
+    @discardableResult public func settingAttributeValueLengthLimit(_ number: UInt) -> Self {
+        var spanLimits = self
+        spanLimits.attributeValueLengthLimit = number > 0 ? Int(number) : 0
+        return spanLimits
+    }
+
     @discardableResult public func settingEventCountLimit(_ number: UInt) -> Self {
         var spanLimits = self
         spanLimits.eventCountLimit = number > 0 ? Int(number) : 0
@@ -56,6 +65,7 @@ public struct SpanLimits: Equatable {
 
     public static func == (lhs: SpanLimits, rhs: SpanLimits) -> Bool {
         return lhs.attributeCountLimit == rhs.attributeCountLimit &&
+            lhs.attributeValueLengthLimit == rhs.attributeValueLengthLimit &&
             lhs.eventCountLimit == rhs.eventCountLimit &&
             lhs.linkCountLimit == rhs.linkCountLimit &&
             lhs.attributePerEventCountLimit == rhs.attributePerEventCountLimit &&

Tests/OpenTelemetrySdkTests/Trace/RecordEventsReadableSpanTests.swift

@@ -417,6 +417,21 @@ class RecordEventsReadableSpanTest: XCTestCase {
         XCTAssertEqual(spanData.totalAttributeCount, 2 * maxNumberOfAttributes)
     }
 
+    func testAttributesValueLength() {
+        let maxValueLength = 8
+        let spanLimits = SpanLimits().settingAttributeValueLengthLimit(UInt(maxValueLength))
+        let span = createTestSpan(config: spanLimits)
+        span.setAttribute(key: "max_value_length", value: .string("this is a big text that is longer than \(maxValueLength) characters"))
+        span.end()
+        let spanData = span.toSpanData()
+        if case .string(let value) = spanData.attributes["max_value_length"] {
+            XCTAssertEqual(span.maxValueLengthPerSpanAttribute, maxValueLength)
+            XCTAssertEqual(value, "this is ")
+        } else {
+            XCTFail()
+        }
+    }
+    
     func testDroppingAndAddingAttributes() {
         let maxNumberOfAttributes = 8
         let spanLimits = SpanLimits().settingAttributeCountLimit(UInt(maxNumberOfAttributes))