refactor: Print error messages to console for cacct

* Add more e2e tests for cacct to test if error messages are properly shown

Author: mahendrapaipuri

Makefile

@@ -192,6 +192,7 @@ test-e2e: $(PROMTOOL) build pkg/collector/testdata/sys/.unpacked pkg/collector/t
 	./scripts/e2e-test.sh -s cacct-custom-format
 	./scripts/e2e-test.sh -s cacct-admin-user
 	./scripts/e2e-test.sh -s cacct-forbid-query
+	./scripts/e2e-test.sh -s cacct-invalid-config
 	./scripts/e2e-test.sh -s cacct-tsdata
 	./scripts/e2e-test.sh -s cacct-tsdata-fail
 else
@@ -278,6 +279,7 @@ test-e2e-update: build pkg/collector/testdata/sys/.unpacked pkg/collector/testda
 	./scripts/e2e-test.sh -s cacct-custom-format -u || true
 	./scripts/e2e-test.sh -s cacct-admin-user -u || true
 	./scripts/e2e-test.sh -s cacct-forbid-query -u || true
+	./scripts/e2e-test.sh -s cacct-invalid-config -u || true
 	./scripts/e2e-test.sh -s cacct-tsdata -u || true
 	./scripts/e2e-test.sh -s cacct-tsdata-fail -u || true
 else

cmd/cacct/main.go

@@ -223,6 +223,8 @@ var (
 // Custom errors.
 var (
 	errNoPerm   = errors.New("forbidden response from API server")
+	errConfig   = errors.New("unable to get cacct config")
+	errUser     = errors.New("unable to change user context")
 	errInternal = errors.New("internal server error")
 )
 
@@ -491,7 +493,7 @@ func main() {
 	// the config file can be read as the owner of this app
 	config, err := readConfig()
 	if err != nil {
-		os.Exit(checkErr(fmt.Errorf("failed to read config file: %w", err)))
+		os.Exit(checkErr(fmt.Errorf("%w: failed to read config file: %w", errConfig, err)))
 	}
 
 	// Now time to drop privileges so that rest of app will be run as regular user
@@ -503,23 +505,23 @@ func main() {
 		// Convert UID anf GID to int
 		uid, err := strconv.Atoi(currentUser.Uid)
 		if err != nil {
-			os.Exit(checkErr(fmt.Errorf("failed to get current user uid: %w", err)))
+			os.Exit(checkErr(fmt.Errorf("%w: failed to get current user uid: %w", errUser, err)))
 		}
 
 		gid, err := strconv.Atoi(currentUser.Gid)
 		if err != nil {
-			os.Exit(checkErr(fmt.Errorf("failed to get current user gid: %w", err)))
+			os.Exit(checkErr(fmt.Errorf("%w: failed to get current user gid: %w", errUser, err)))
 		}
 
 		// Set UID and GID to current user
 		err = syscall.Setuid(uid)
 		if err != nil {
-			os.Exit(checkErr(fmt.Errorf("failed to set current user uid: %w", err)))
+			os.Exit(checkErr(fmt.Errorf("%w: failed to set current user uid: %w", errUser, err)))
 		}
 
 		err = syscall.Setgid(gid)
 		if err != nil {
-			os.Exit(checkErr(fmt.Errorf("failed to set current user gid: %w", err)))
+			os.Exit(checkErr(fmt.Errorf("%w: failed to set current user gid: %w", errUser, err)))
 		}
 	}
 
@@ -799,9 +801,15 @@ func checkErr(err error) int {
 	if err != nil {
 		switch {
 		case errors.Is(err, errNoPerm):
-			fmt.Fprintln(os.Stderr, "forbidden. It is likely that the user is attempting to view statistics of others")
+			fmt.Fprintln(os.Stderr, "error: forbidden. It is likely that the user is attempting to view statistics of others")
 		case errors.Is(err, errInternal):
-			fmt.Fprintln(os.Stderr, "server did not return any data due to unknown error")
+			fmt.Fprintln(os.Stderr, "error: server did not return any data due to unknown error")
+		case errors.Is(err, errConfig):
+			fmt.Fprintln(os.Stderr, "error: "+errConfig.Error())
+		case errors.Is(err, errUser):
+			fmt.Fprintln(os.Stderr, "error: "+errUser.Error())
+		default:
+			fmt.Fprintln(os.Stderr, err.Error())
 		}
 
 		return 1

cmd/cacct/testdata/output/e2e-test-cacct-forbid-query.txt

@@ -1 +1 @@
-forbidden. It is likely that the user is attempting to view statistics of others
+error: forbidden. It is likely that the user is attempting to view statistics of others

cmd/cacct/testdata/output/e2e-test-cacct-invalid-config.txt

@@ -0,0 +1 @@
+error: unable to get cacct config

scripts/e2e-test.sh

@@ -397,6 +397,10 @@ then
   then
     desc="cacct by normal user attempt to admin query"
     fixture='cmd/cacct/testdata/output/e2e-test-cacct-forbid-query.txt'
+	elif [ "${scenario}" = "cacct-invalid-config" ]
+  then
+    desc="cacct using invalid config"
+    fixture='cmd/cacct/testdata/output/e2e-test-cacct-invalid-config.txt'
   elif [ "${scenario}" = "cacct-tsdata" ]
   then
     desc="cacct to dump time series data"
@@ -1505,6 +1509,9 @@ then
   elif [ "${scenario}" = "cacct-forbid-query" ]
   then
     ./bin/cacct --current-user=usr3 --config-path="cmd/cacct/testdata" --starttime="2022-02-20" --endtime="2022-03-20" --user=usr1,usr2 > "${fixture_output}" 2>&1 || true
+	elif [ "${scenario}" = "cacct-invalid-config" ]
+  then
+    ./bin/cacct --current-user=usr1 --config-path="nonexistant/testdata" --starttime="2022-02-20" --endtime="2022-03-20" > "${fixture_output}" 2>&1 || true
   elif [ "${scenario}" = "cacct-tsdata" ]
   then
     ./bin/cacct --current-user=usr1 --config-path="cmd/cacct/testdata" --job="147973" --ts --ts.out-dir="${tmpdir}/ts" > "${fixture_output}" 2>&1