Enable overwriting ingest pipelines by default. (elastic#2273)

Enable `apm-server.register.ingest.pipeline.overwrite` by default,
as described in `apm-server.yml`.

fixes elastic#2272

beater/config.go

@@ -166,7 +166,7 @@ func (c *pipelineConfig) isEnabled() bool {
 }
 
 func (c *pipelineConfig) shouldOverwrite() bool {
-	return c != nil && (c.Overwrite != nil && *c.Overwrite)
+	return c != nil && (c.Overwrite == nil || *c.Overwrite)
 }
 
 func (c *rumConfig) memoizedSmapMapper() (sourcemap.Mapper, error) {

beater/config_test.go

@@ -290,7 +290,7 @@ func TestPipeline(t *testing.T) {
 		enabled, overwrite bool
 	}{
 		{c: nil, enabled: false, overwrite: false},
-		{c: &pipelineConfig{}, enabled: false, overwrite: false},
+		{c: &pipelineConfig{}, enabled: false, overwrite: true}, //default values
 		{c: &pipelineConfig{Enabled: &falsy, Overwrite: &truthy},
 			enabled: false, overwrite: true},
 		{c: &pipelineConfig{Enabled: &truthy, Overwrite: &falsy},

changelogs/7.2.asciidoc

@@ -13,6 +13,7 @@ https://github.com/elastic/apm-server/compare/v7.1.0\...v7.2.0[View commits]
 [float]
 ==== Bug fixes
 - Require client authentication by default when `apm-server.ssl.enabled` is true {pull}2224[2224].
+- Set `apm-server.register.ingest.pipeline.overwrite` to true by default {pull}2273[2273].
 
 [float]
 ==== Added

tests/system/test_pipelines.py

@@ -60,9 +60,9 @@ def test_setup_pipelines(self):
 
 
 class PipelineRegisterTest(ElasticTest):
+    # pipeline.overwrite should be enabled by default.
     config_overrides = {
         "register_pipeline_enabled": "true",
-        "register_pipeline_overwrite": "true"
     }
 
     @unittest.skipUnless(INTEGRATION_TESTS, "integration test")