feat(pods): add optional tail parameter to pod logs retrieval (#335)

* feat(pods): add tailLines parameter to pod logs retrieval with default 256 lines

Signed-off-by: iamsudip <sudip.maji@harness.io>

* address review comments

Signed-off-by: iamsudip <sudip.maji@harness.io>

* test(pods): add tailLines parameter to pod logs retrieval with default 256 lines

Signed-off-by: Marc Nuri <marc@marcnuri.com>

---------

Signed-off-by: iamsudip <sudip.maji@harness.io>
Signed-off-by: Marc Nuri <marc@marcnuri.com>
Co-authored-by: Marc Nuri <marc@marcnuri.com>

README.md

@@ -261,6 +261,7 @@ The following sets of tools are available (all on by default):
   - `name` (`string`) **(required)** - Name of the Pod to get the logs from
   - `namespace` (`string`) - Namespace to get the Pod logs from
   - `previous` (`boolean`) - Return previous terminated container logs (Optional)
+  - `tail` (`number`) - Number of lines to retrieve from the end of the logs (Optional, default: 100)
 
 - **pods_run** - Run a Kubernetes Pod in the current or provided namespace with the provided container image and optional name
   - `image` (`string`) **(required)** - Container Image to run in the Pod

pkg/kubernetes/pods.go

@@ -17,10 +17,14 @@ import (
 	"k8s.io/client-go/tools/remotecommand"
 	"k8s.io/metrics/pkg/apis/metrics"
 	metricsv1beta1api "k8s.io/metrics/pkg/apis/metrics/v1beta1"
+	"k8s.io/utils/ptr"
 
 	"github.com/containers/kubernetes-mcp-server/pkg/version"
 )
 
+// Default number of lines to retrieve from the end of the logs
+const DefaultTailLines = int64(100)
+
 type PodsTopOptions struct {
 	metav1.ListOptions
 	AllNamespaces bool
@@ -92,17 +96,26 @@ func (k *Kubernetes) PodsDelete(ctx context.Context, namespace, name string) (st
 		k.ResourcesDelete(ctx, &schema.GroupVersionKind{Group: "", Version: "v1", Kind: "Pod"}, namespace, name)
 }
 
-func (k *Kubernetes) PodsLog(ctx context.Context, namespace, name, container string, previous bool) (string, error) {
-	tailLines := int64(256)
+func (k *Kubernetes) PodsLog(ctx context.Context, namespace, name, container string, previous bool, tail int64) (string, error) {
 	pods, err := k.manager.accessControlClientSet.Pods(k.NamespaceOrDefault(namespace))
 	if err != nil {
 		return "", err
 	}
-	req := pods.GetLogs(name, &v1.PodLogOptions{
-		TailLines: &tailLines,
+
+	logOptions := &v1.PodLogOptions{
 		Container: container,
 		Previous:  previous,
-	})
+	}
+
+	// Only set tailLines if a value is provided (non-zero)
+	if tail > 0 {
+		logOptions.TailLines = &tail
+	} else {
+		// Default to DefaultTailLines lines when not specified
+		logOptions.TailLines = ptr.To(DefaultTailLines)
+	}
+
+	req := pods.GetLogs(name, logOptions)
 	res := req.Do(ctx)
 	if res.Error() != nil {
 		return "", res.Error()

pkg/mcp/pods_test.go

@@ -756,6 +756,41 @@ func TestPodsLog(t *testing.T) {
 				return
 			}
 		})
+
+		// Test with tail parameter
+		podsTailLines, err := c.callTool("pods_log", map[string]interface{}{
+			"namespace": "ns-1",
+			"name":      "a-pod-in-ns-1",
+			"tail":      50,
+		})
+		t.Run("pods_log with tail=50 returns pod log", func(t *testing.T) {
+			if err != nil {
+				t.Fatalf("call tool failed %v", err)
+				return
+			}
+			if podsTailLines.IsError {
+				t.Fatalf("call tool failed")
+				return
+			}
+		})
+
+		// Test with invalid tail parameter
+		podsInvalidTailLines, _ := c.callTool("pods_log", map[string]interface{}{
+			"namespace": "ns-1",
+			"name":      "a-pod-in-ns-1",
+			"tail":      "invalid",
+		})
+		t.Run("pods_log with invalid tail returns error", func(t *testing.T) {
+			if !podsInvalidTailLines.IsError {
+				t.Fatalf("call tool should fail")
+				return
+			}
+			expectedErrorMsg := "failed to parse tail parameter: expected integer"
+			if errMsg := podsInvalidTailLines.Content[0].(mcp.TextContent).Text; !strings.Contains(errMsg, expectedErrorMsg) {
+				t.Fatalf("unexpected error message, expected to contain '%s', got '%s'", expectedErrorMsg, errMsg)
+				return
+			}
+		})
 	})
 }
 

pkg/mcp/testdata/toolsets-core-tools.json

@@ -202,6 +202,12 @@
         "previous": {
           "description": "Return previous terminated container logs (Optional)",
           "type": "boolean"
+        },
+        "tail": {
+          "default": 100,
+          "description": "Number of lines to retrieve from the end of the logs (Optional, default: 100)",
+          "minimum": 0,
+          "type": "integer"
         }
       },
       "required": [

pkg/mcp/testdata/toolsets-full-tools-openshift.json

@@ -308,6 +308,12 @@
         "previous": {
           "description": "Return previous terminated container logs (Optional)",
           "type": "boolean"
+        },
+        "tail": {
+          "default": 100,
+          "description": "Number of lines to retrieve from the end of the logs (Optional, default: 100)",
+          "minimum": 0,
+          "type": "integer"
         }
       },
       "required": [

pkg/mcp/testdata/toolsets-full-tools.json

@@ -308,6 +308,12 @@
         "previous": {
           "description": "Return previous terminated container logs (Optional)",
           "type": "boolean"
+        },
+        "tail": {
+          "default": 100,
+          "description": "Number of lines to retrieve from the end of the logs (Optional, default: 100)",
+          "minimum": 0,
+          "type": "integer"
         }
       },
       "required": [

pkg/toolsets/core/pods.go

@@ -201,6 +201,12 @@ func initPods() []api.ServerTool {
 						Type:        "string",
 						Description: "Name of the Pod container to get the logs from (Optional)",
 					},
+					"tail": {
+						Type:        "integer",
+						Description: "Number of lines to retrieve from the end of the logs (Optional, default: 100)",
+						Default:     api.ToRawMessage(kubernetes.DefaultTailLines),
+						Minimum:     ptr.To(float64(0)),
+					},
 					"previous": {
 						Type:        "boolean",
 						Description: "Return previous terminated container logs (Optional)",
@@ -396,7 +402,24 @@ func podsLog(params api.ToolHandlerParams) (*api.ToolCallResult, error) {
 	if previous != nil {
 		previousBool = previous.(bool)
 	}
-	ret, err := params.PodsLog(params, ns.(string), name.(string), container.(string), previousBool)
+	// Extract tailLines parameter
+	tail := params.GetArguments()["tail"]
+	var tailInt int64
+	if tail != nil {
+		// Convert to int64 - safely handle both float64 (JSON number) and int types
+		switch v := tail.(type) {
+		case float64:
+			tailInt = int64(v)
+		case int:
+			tailInt = int64(v)
+		case int64:
+			tailInt = v
+		default:
+			return api.NewToolCallResult("", fmt.Errorf("failed to parse tail parameter: expected integer, got %T", tail)), nil
+		}
+	}
+
+	ret, err := params.PodsLog(params.Context, ns.(string), name.(string), container.(string), previousBool, tailInt)
 	if err != nil {
 		return api.NewToolCallResult("", fmt.Errorf("failed to get pod %s log in namespace %s: %v", name, ns, err)), nil
 	} else if ret == "" {