fix: avoid breaking changes

Author: jcmfernandes

internal/core/bootstrap.go

@@ -1,14 +1,37 @@
 package core
 
 import (
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
 	"os"
 
 	"github.com/google/uuid"
 	"github.com/shirou/gopsutil/v4/process"
 	"github.com/testcontainers/testcontainers-go/internal/config"
 )
 
-// sessionID returns a unique session ID for the current test session.
+// sessionID returns a unique session ID for the current test session. Because each Go package
+// will be run in a separate process, we need a way to identify the current test session.
+// By test session, we mean:
+//   - a single "go test" invocation (including flags)
+//   - a single "go test ./..." invocation (including flags)
+//   - the execution of a single test or a set of tests using the IDE
+//
+// As a consequence, with the sole goal of aggregating test execution across multiple
+// packages, this function will use the parent process ID (pid) of the current process
+// and its creation date, to use it to generate a unique session ID. We are using the parent pid because
+// the current process will be a child process of:
+//   - the process that is running the tests, e.g.: "go test";
+//   - the process that is running the application in development mode, e.g. "go run main.go -tags dev";
+//   - the process that is running the tests in the IDE, e.g.: "go test ./...".
+//
+// Finally, we will hash the combination of the "testcontainers-go:" string with the parent pid
+// and the creation date of that parent process to generate a unique session ID.
+//
+// This sessionID will be used to:
+//   - identify the test session, aggregating the test execution of multiple packages in the same test session.
+//   - tag the containers created by testcontainers-go, adding a label to the container with the session ID.
 var sessionID string
 
 // projectPath returns the current working directory of the parent test process running Testcontainers for Go.
@@ -20,17 +43,18 @@ var projectPath string
 // we need a way to identify the current test process, in the form of a UUID
 var processID string
 
+const sessionIDPlaceholder = "testcontainers-go:%d:%d"
+
 func init() {
 	cfg := config.Read()
 	if cfg.SessionID != "" {
 		sessionID = cfg.SessionID
-	} else {
-		sessionID = uuid.New().String()
 	}
 
 	processID = uuid.New().String()
 
 	parentPid := os.Getppid()
+	var createTime int64
 	fallbackCwd, err := os.Getwd()
 	if err != nil {
 		// very unlikely to fail, but if it does, we will use a temp dir
@@ -39,6 +63,9 @@ func init() {
 
 	processes, err := process.Processes()
 	if err != nil {
+		if sessionID == "" {
+			sessionID = uuid.New().String()
+		}
 		projectPath = fallbackCwd
 		return
 	}
@@ -54,8 +81,28 @@ func init() {
 		}
 		projectPath = cwd
 
+		t, err := p.CreateTime()
+		if err != nil {
+			if sessionID == "" {
+				sessionID = uuid.New().String()
+			}
+			return
+		}
+
+		createTime = t
 		break
 	}
+
+	if sessionID == "" {
+		hasher := sha256.New()
+		_, err = fmt.Fprintf(hasher, sessionIDPlaceholder, parentPid, createTime)
+		if err != nil {
+			sessionID = uuid.New().String()
+			return
+		}
+
+		sessionID = hex.EncodeToString(hasher.Sum(nil))
+	}
 }
 
 func ProcessID() string {