[exporter/elasticsearch] Fix CloudID parsing to correctly handle Elastic Cloud IDs when sent with multiple dollar sign separators (#44325)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description

The CloudID decoder was incorrectly using `strings.Cut()`, which only
splits at the first delimiter, resulting in malformed URLs when the
decoded CloudID contained multiple `$` separators. Changed to use
`strings.Split()` to match the reference implementation from the
[go-elasticsearch](https://github.com/elastic/go-elasticsearch/blob/4739f334675880df102135bcca6104c8c63b59db/elasticsearch.go#L474)
library.

<!-- Issue number (e.g. #1234) or full URL to issue, if applicable. -->
#### Link to tracking issue
Fixes #44306

<!--Describe what testing was performed and which tests were added.-->
#### Testing

Added tests to validate this behaviour and the expected output.

Signed-off-by: Paulo Dias <[email protected]>

Author: paulojmdias

.chloggen/fix_44306.yaml

@@ -0,0 +1,30 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: "bug_fix"
+
+# The name of the component, or a single word describing the area of concern, (e.g. receiver/filelog)
+component: exporter/elasticsearch
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Fix CloudID parsing to correctly handle Elastic Cloud IDs when sent with multiple dollar sign separators
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [44306]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext: |
+  The CloudID decoder was incorrectly using `strings.Cut()` which only splits on the first delimiter,
+  causing malformed URLs when the decoded CloudID contained multiple `$` separators. Changed to use
+  `strings.Split()` to match the reference implementation from go-elasticsearch library.
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [user]

exporter/elasticsearchexporter/config.go

@@ -483,11 +483,11 @@ func parseCloudID(input string) (*url.URL, error) {
 		return nil, err
 	}
 
-	before, after, ok := strings.Cut(string(decoded), "$")
-	if !ok {
+	parts := strings.Split(string(decoded), "$")
+	if len(parts) < 2 {
 		return nil, fmt.Errorf("invalid decoded CloudID %q", string(decoded))
 	}
-	return url.Parse(fmt.Sprintf("https://%s.%s", after, before))
+	return url.Parse(fmt.Sprintf("https://%s.%s", parts[1], parts[0]))
 }
 
 func handleDeprecatedConfig(cfg *Config, logger *zap.Logger) {

exporter/elasticsearchexporter/config_test.go

@@ -555,6 +555,49 @@ func TestConfig_Validate_Environment(t *testing.T) {
 	})
 }
 
+func TestParseCloudID(t *testing.T) {
+	tests := map[string]struct {
+		input       string
+		expectedURL string
+		expectError bool
+	}{
+		"valid cloudid with multiple dollar signs": {
+			input:       "foo:YmFyLmNsb3VkLmVzLmlvJGFiYzEyMyRkZWY0NTY=",
+			expectedURL: "https://abc123.bar.cloud.es.io",
+			expectError: false,
+		},
+		"valid cloudid with two parts": {
+			input:       "test:ZG9tYWluLmNvbSRlcy1pZA==",
+			expectedURL: "https://es-id.domain.com",
+			expectError: false,
+		},
+		"missing colon": {
+			input:       "invalid",
+			expectError: true,
+		},
+		"invalid base64": {
+			input:       "test:!!!invalid!!!",
+			expectError: true,
+		},
+		"missing dollar sign": {
+			input:       "test:YWJj",
+			expectError: true,
+		},
+	}
+
+	for name, tt := range tests {
+		t.Run(name, func(t *testing.T) {
+			url, err := parseCloudID(tt.input)
+			if tt.expectError {
+				assert.Error(t, err)
+			} else {
+				require.NoError(t, err)
+				assert.Equal(t, tt.expectedURL, url.String())
+			}
+		})
+	}
+}
+
 func withDefaultConfig(fns ...func(*Config)) *Config {
 	cfg := createDefaultConfig().(*Config)
 	for _, fn := range fns {