[exporter/elasticsearch] deprecate 'dedot' config (#33780)

**Description:**

Deprecate `exporter/elasticsearch`'s "dedot" configuration. In a future
release we will remove this configuration, and always dedot ECS mode,
never for raw/none modes.

**Link to tracking Issue:**


#33772

**Testing:**

N/A

**Documentation:**

Updated the README.

.chloggen/elasticsearch-deprecate-dedot.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: deprecation
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: exporter/elasticsearch
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Deprecate the "dedot" configuration.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [33772]
+
+# (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: dedot has been deprecated, and will always be enabled in ECS mode and disabled for other modes in future
+
+# 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/README.md

@@ -131,8 +131,9 @@ behaviours, which may be configured throug the following settings:
     Try to find and remove duplicate fields/attributes from events before publishing
     to Elasticsearch. Some structured logging libraries can produce duplicate fields
     (for example zap). Elasticsearch will reject documents that have duplicate fields.
-  - `dedot` (default=true): When enabled attributes with `.` will be split into
-    proper json objects.
+  - `dedot` (default=true; DEPRECATED, in future dedotting will always be enabled
+    for ECS mode, and never for other modes): When enabled attributes with `.`
+    will be split into proper json objects.
 
 #### ECS mapping mode
 

exporter/elasticsearchexporter/config.go

@@ -164,6 +164,9 @@ type MappingsSettings struct {
 	// as Elasticsearch will reject documents with duplicate JSON object keys.
 	Dedup bool `mapstructure:"dedup"`
 
+	// Deprecated: [v0.104.0] dedotting will always be applied for ECS mode
+	// in future, and never for other modes. Elasticsearch's "dot_expander"
+	// Ingest processor may be used as an alternative for non-ECS modes.
 	Dedot bool `mapstructure:"dedot"`
 }
 
@@ -319,4 +322,7 @@ func logConfigDeprecationWarnings(cfg *Config, logger *zap.Logger) {
 	if !cfg.Mapping.Dedup {
 		logger.Warn("dedup has been deprecated, and will always be enabled in future")
 	}
+	if cfg.Mapping.Dedot && cfg.MappingMode() != MappingECS || !cfg.Mapping.Dedot && cfg.MappingMode() == MappingECS {
+		logger.Warn("dedot has been deprecated: in the future, dedotting will always be performed in ECS mode only")
+	}
 }

exporter/elasticsearchexporter/factory_test.go

@@ -102,6 +102,7 @@ func TestFactory_DedupDeprecated(t *testing.T) {
 	cfg := withDefaultConfig(func(cfg *Config) {
 		cfg.Endpoint = "http://testing.invalid:9200"
 		cfg.Mapping.Dedup = false
+		cfg.Mapping.Dedot = false // avoid dedot warnings
 	})
 
 	loggerCore, logObserver := observer.New(zap.WarnLevel)
@@ -126,3 +127,42 @@ func TestFactory_DedupDeprecated(t *testing.T) {
 	assert.Equal(t, "dedup has been deprecated, and will always be enabled in future", records[1].Message)
 	assert.Equal(t, "dedup has been deprecated, and will always be enabled in future", records[2].Message)
 }
+
+func TestFactory_DedotDeprecated(t *testing.T) {
+	loggerCore, logObserver := observer.New(zap.WarnLevel)
+	set := exportertest.NewNopSettings()
+	set.Logger = zap.New(loggerCore)
+
+	cfgNoDedotECS := withDefaultConfig(func(cfg *Config) {
+		cfg.Endpoint = "http://testing.invalid:9200"
+		cfg.Mapping.Dedot = false
+		cfg.Mapping.Mode = "ecs"
+	})
+
+	cfgDedotRaw := withDefaultConfig(func(cfg *Config) {
+		cfg.Endpoint = "http://testing.invalid:9200"
+		cfg.Mapping.Dedot = true
+		cfg.Mapping.Mode = "raw"
+	})
+
+	for _, cfg := range []*Config{cfgNoDedotECS, cfgDedotRaw} {
+		factory := NewFactory()
+		logsExporter, err := factory.CreateLogsExporter(context.Background(), set, cfg)
+		require.NoError(t, err)
+		require.NoError(t, logsExporter.Shutdown(context.Background()))
+
+		tracesExporter, err := factory.CreateTracesExporter(context.Background(), set, cfg)
+		require.NoError(t, err)
+		require.NoError(t, tracesExporter.Shutdown(context.Background()))
+
+		metricsExporter, err := factory.CreateMetricsExporter(context.Background(), set, cfg)
+		require.NoError(t, err)
+		require.NoError(t, metricsExporter.Shutdown(context.Background()))
+	}
+
+	records := logObserver.AllUntimed()
+	assert.Len(t, records, 6)
+	for _, record := range records {
+		assert.Equal(t, "dedot has been deprecated: in the future, dedotting will always be performed in ECS mode only", record.Message)
+	}
+}