BUILD/MINOR: ci: cancel duplicate pipelines on forked project

gitlab is not good in detecting duplicate pipelines,
so this is ensuring that we do not run duplicate jobs
for same merge request, but still allows running
if you do not open merge request

Author: oktalz

.gitlab-ci.yml

@@ -1,4 +1,5 @@
 stages:
+  - bots
   - diff
   - lint
   - unit-tests
@@ -13,6 +14,18 @@ variables:
   DOCKER_DRIVER: overlay2
   GO_VERSION: "1.24"
   DOCKER_VERSION: "27.0"
+pipelines-check:
+  stage: bots
+  needs: []
+  image:
+    name: $CI_REGISTRY_GO/docker:$DOCKER_VERSION-go$GO_VERSION
+    entrypoint: [ "" ]
+  rules:
+    - if: $CI_PIPELINE_SOURCE == 'merge_request_event'
+  tags:
+    - go
+  script:
+    - go run cmd/gitlab-mr-pipelines/main.go
 diff:
   stage: diff
   rules:

cmd/gitlab-mr-pipelines/main.go

@@ -0,0 +1,141 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"strconv"
+	"strings"
+)
+
+//nolint:forbidigo
+func main() {
+	// Check if we are in a merge request context
+	mrIID := os.Getenv("CI_MERGE_REQUEST_IID")
+	if mrIID == "" {
+		fmt.Println("Not a merge request. Exiting.")
+		os.Exit(0)
+	}
+
+	// Get necessary environment variables
+	gitlabAPIURL := os.Getenv("CI_API_V4_URL")
+	projectID := os.Getenv("CI_PROJECT_ID")
+	sourceProjectID := os.Getenv("CI_MERGE_REQUEST_SOURCE_PROJECT_ID")
+	gitlabToken := os.Getenv("GITLAB_TOKEN")
+
+	if gitlabAPIURL == "" || projectID == "" || sourceProjectID == "" {
+		fmt.Println("Missing required GitLab CI/CD environment variables.")
+		os.Exit(1)
+	}
+
+	if gitlabToken == "" {
+		fmt.Print("GitLab token not found in environment variable.\n")
+		os.Exit(1)
+	}
+
+	// 1. Get all old pipelines for this Merge Request
+	pipelinesToCancel, err := getOldMergeRequestPipelines(gitlabAPIURL, projectID, mrIID, gitlabToken)
+	if err != nil {
+		fmt.Printf("Error getting merge request pipelines: %v\n", err)
+		os.Exit(1)
+	}
+
+	if len(pipelinesToCancel) == 0 {
+		fmt.Println("No old, running pipelines found for this merge request.")
+		os.Exit(0)
+	}
+
+	fmt.Printf("Found %d old pipelines to cancel.\n", len(pipelinesToCancel))
+
+	// 2. Cancel all found pipelines
+	for _, p := range pipelinesToCancel {
+		fmt.Printf("Canceling pipeline ID %d on project ID %d\n", p.ID, p.ProjectID)
+		err = cancelPipeline(gitlabAPIURL, strconv.Itoa(p.ProjectID), p.ID, gitlabToken)
+		if err != nil {
+			// Log error but continue trying to cancel others
+			fmt.Printf("Failed to cancel pipeline %d: %v\n", p.ID, err)
+		} else {
+			fmt.Printf("Successfully requested cancellation for pipeline %d\n", p.ID)
+		}
+	}
+}
+
+type pipelineInfo struct {
+	ID        int    `json:"id"`
+	ProjectID int    `json:"project_id"`
+	Status    string `json:"status"`
+}
+
+func getOldMergeRequestPipelines(apiURL, projectID, mrIID, token string) ([]pipelineInfo, error) {
+	// Get the current pipeline ID to avoid canceling ourselves
+	currentPipelineIDStr := os.Getenv("CI_PIPELINE_ID")
+	var currentPipelineID int
+	if currentPipelineIDStr != "" {
+		// a non-integer value will result in 0, which is fine since pipeline IDs are positive
+		currentPipelineID, _ = strconv.Atoi(currentPipelineIDStr)
+	}
+
+	url := fmt.Sprintf("%s/projects/%s/merge_requests/%s/pipelines", apiURL, projectID, mrIID)
+	req, err := http.NewRequest("GET", url, nil) //nolint:noctx,usestdlibvars
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set("PRIVATE-TOKEN", token) //nolint:canonicalheader
+
+	client := &http.Client{}
+	resp, err := client.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		body, _ := io.ReadAll(resp.Body)
+		return nil, fmt.Errorf("failed to list merge request pipelines: status %d, body: %s", resp.StatusCode, string(body))
+	}
+
+	var pipelines []pipelineInfo
+	if err := json.NewDecoder(resp.Body).Decode(&pipelines); err != nil {
+		return nil, err
+	}
+
+	var pipelinesToCancel []pipelineInfo
+	for _, p := range pipelines {
+		// Cancel pipelines that are running or pending, and are not the current pipeline
+		if (p.Status == "running" || p.Status == "pending") && p.ID != currentPipelineID {
+			pipelinesToCancel = append(pipelinesToCancel, p)
+		}
+	}
+
+	return pipelinesToCancel, nil
+}
+
+func cancelPipeline(apiURL, projectID string, pipelineID int, token string) error {
+	url := fmt.Sprintf("%s/projects/%s/pipelines/%d/cancel", apiURL, projectID, pipelineID)
+	req, err := http.NewRequest("POST", url, nil) //nolint:noctx,usestdlibvars
+	if err != nil {
+		return err
+	}
+	req.Header.Set("PRIVATE-TOKEN", token) //nolint:canonicalheader
+
+	client := &http.Client{}
+	resp, err := client.Do(req)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		body, _ := io.ReadAll(resp.Body)
+		// It's possible the pipeline is already finished.
+		if strings.Contains(string(body), "Cannot cancel a pipeline that is not pending or running") {
+			fmt.Println("Pipeline already finished, nothing to do.") //nolint:forbidigo
+			return nil
+		}
+		return fmt.Errorf("failed to cancel pipeline: status %d, body: %s", resp.StatusCode, string(body))
+	}
+
+	return nil
+}