[Exporter.OTLP] Disk persistance - handle malformed files names (#7108)

Co-authored-by: Martin Costello <martin@martincostello.com>

Author: Kielek

src/OpenTelemetry.Exporter.OpenTelemetryProtocol/CHANGELOG.md

@@ -7,6 +7,10 @@ Notes](../../RELEASENOTES.md).
 
 ## Unreleased
 
+* Fixed an issue in persistent storage cleanup where malformed `.blob`, `.tmp`,
+  or `.lock` filenames could throw and interrupt maintenance.
+  ([#7108](https://github.com/open-telemetry/opentelemetry-dotnet/pull/7108))
+
 * **Breaking change:** Fixed an insecure disk retry default. Disk retry now
   requires `OTEL_DOTNET_EXPERIMENTAL_OTLP_DISK_RETRY_DIRECTORY_PATH` when
   `OTEL_DOTNET_EXPERIMENTAL_OTLP_RETRY=disk` is configured. The exporter no

src/OpenTelemetry.Exporter.OpenTelemetryProtocol/PersistentStorage/PersistentStorageHelper.cs

@@ -40,7 +40,13 @@ internal static bool RemoveExpiredLease(DateTime leaseDeadline, string filePath)
             var fileDateTime = GetDateTimeFromLeaseName(filePath);
             if (fileDateTime < leaseDeadline)
             {
-                var newFilePath = filePath.Substring(0, filePath.LastIndexOf('@'));
+                var atSignIndex = filePath.LastIndexOf('@');
+                if (atSignIndex == -1)
+                {
+                    return false;
+                }
+
+                var newFilePath = filePath.Substring(0, atSignIndex);
                 try
                 {
                     File.Move(filePath, newFilePath);
@@ -132,7 +138,13 @@ internal static string CreateSubdirectory(string path)
     internal static DateTime GetDateTimeFromBlobName(string filePath)
     {
         var fileName = GetFileNameWithoutExtension(filePath);
-        var timestamp = fileName.Substring(0, fileName.LastIndexOf('-'));
+        var dashIndex = fileName.LastIndexOf('-');
+        if (dashIndex == -1)
+        {
+            return DateTime.SpecifyKind(DateTime.MinValue, DateTimeKind.Utc);
+        }
+
+        var timestamp = fileName.Substring(0, dashIndex);
 
         return Parse(timestamp);
     }

test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/PersistentStorage/PersistentStorageHelperTests.cs

@@ -49,6 +49,7 @@ public void GetDateTimeFromBlobName_WithDifferentPathFormats_ReturnsCorrectDateT
     [InlineData("invalid-format.blob")]
     [InlineData("2024-01-15T14:30:25Z-abc123.blob")]
     [InlineData("abc-def.blob")]
+    [InlineData("invalidformat.blob")]
     public void GetDateTimeFromBlobName_InvalidFormat_ReturnsDateTimeMinValue(string filePath)
     {
         var result = PersistentStorageHelper.GetDateTimeFromBlobName(filePath);
@@ -217,4 +218,14 @@ public void GetDateTimeFromLeaseName_ConsistentResults_ForMultipleCalls(string f
         Assert.Equal(result1a, result1b);
         Assert.NotEqual(result1a, result2);
     }
+
+    [Fact]
+    public void RemoveExpiredLease_WithoutLeaseDelimiter_ReturnsFalse()
+    {
+        var leaseDeadline = DateTime.UtcNow;
+
+        var result = PersistentStorageHelper.RemoveExpiredLease(leaseDeadline, "invalid-format.lock");
+
+        Assert.False(result);
+    }
 }