feature(otel-collector): ordered processors list

charts/sourcegraph/CHANGELOG.md

@@ -8,6 +8,7 @@ Use `**BREAKING**:` to denote a breaking change
 
 ## Unreleased
 
+- Added support for ordering trace processors via `openTelemetry.gateway.config.traces.tracePipelineProcessors`, falling back to processors ordered by name when unset
 - Removed the unused executor controller `/data` PersistentVolumeClaim from the Kubernetes-native executor chart (`sourcegraph-executor/k8s`), along with the now-orphaned `storageClass` and `executor.storageSize` values and the vestigial `EXECUTOR_KUBERNETES_PERSISTENCE_VOLUME_NAME` env var. Since single-job-pod became the only k8s execution mode, job pods use their own ephemeral `emptyDir` volume and the controller writes nothing to `/data`.
 - Removed the non-functional `executor.replicas` value from the Kubernetes-native executor chart; the controller is a singleton (it pins Job pods to its own node), so `replicas > 1` never worked.
 - Added support for overriding `replicaCount` per dedicated `worker` replica via `worker.replicas[].replicaCount`, falling back to `worker.replicaCount` when unset

charts/sourcegraph/README.md

@@ -228,6 +228,7 @@ In addition to the documented values, all services also support the following va
 | openTelemetry.gateway.config.traces.exporters | object | `{}` | Define where traces should be exported to. Read how to configure different backends in the [OpenTelemetry documentation](https://opentelemetry.io/docs/collector/configuration/#exporters) |
 | openTelemetry.gateway.config.traces.exportersTlsSecretName | string | `""` | Define the name of a preexisting secret containing TLS certificates for exporters, which will be mounted under "/tls". Read more about TLS configuration of exporters in the [OpenTelemetry Collector documentation](https://github.com/open-telemetry/opentelemetry-collector/blob/main/config/configtls/README.md) |
 | openTelemetry.gateway.config.traces.processors | object | `{}` | Define trace processors. Read how to configure sampling in the [OpenTelemetry documentation](https://docs.sourcegraph.com/admin/observability/opentelemetry#sampling-traces) |
+| openTelemetry.gateway.config.traces.tracePipelineProcessors | list | `[]` | Define the order in which processors are applied in the traces pipeline. When set, this takes precedence over the iteration order of `processors` (which cannot be relied on to preserve insertion order). Must contain exactly the same processor names as the keys of `processors`. |
 | openTelemetry.gateway.containerSecurityContext.allowPrivilegeEscalation | bool | `false` |  |
 | openTelemetry.gateway.containerSecurityContext.runAsGroup | int | `101` |  |
 | openTelemetry.gateway.containerSecurityContext.runAsUser | int | `100` |  |

charts/sourcegraph/templates/otel-collector/otel-collector.ConfigMap.yaml

@@ -44,9 +44,15 @@ data:
             - otlp
           {{- if .Values.openTelemetry.gateway.config.traces.processors }}
           processors:
+            {{- if .Values.openTelemetry.gateway.config.traces.tracePipelineProcessors }}
+            {{- range .Values.openTelemetry.gateway.config.traces.tracePipelineProcessors }}
+            - {{ . }}
+            {{- end }}
+            {{- else }}
             {{- range $key, $val := .Values.openTelemetry.gateway.config.traces.processors }}
             - {{ $key }}
             {{- end }}
+            {{- end }}
           {{- end }}
           exporters:
             {{- range $key, $val := .Values.openTelemetry.gateway.config.traces.exporters }}

charts/sourcegraph/tests/otelCollectorProcessors_test.yaml

@@ -0,0 +1,72 @@
+---
+suite: otelCollectorProcessors
+templates:
+  - otel-collector/otel-collector.ConfigMap.yaml
+set:
+  openTelemetry:
+    gateway:
+      config:
+        traces:
+          exporters:
+            otlp:
+              endpoint: "otlp.service.com:443"
+tests:
+  - it: should not render a processors section when none are configured
+    asserts:
+      - notMatchRegex:
+          path: data["config.yaml"]
+          pattern: "processors:"
+  - it: should order pipeline processors by map key when tracePipelineProcessors is not set
+    set:
+      openTelemetry:
+        gateway:
+          config:
+            traces:
+              processors:
+                memory_limiter:
+                  check_interval: 1s
+                batch:
+                  timeout: 1s
+    asserts:
+      - matchRegex:
+          path: data["config.yaml"]
+          pattern: "processors:\\s*\\n\\s*- batch\\s*\\n\\s*- memory_limiter"
+  - it: should order pipeline processors using tracePipelineProcessors when set
+    set:
+      openTelemetry:
+        gateway:
+          config:
+            traces:
+              processors:
+                memory_limiter:
+                  check_interval: 1s
+                batch:
+                  timeout: 1s
+              tracePipelineProcessors:
+                - memory_limiter
+                - batch
+    asserts:
+      - matchRegex:
+          path: data["config.yaml"]
+          pattern: "processors:\\s*\\n\\s*- memory_limiter\\s*\\n\\s*- batch"
+  - it: should still define processor configs regardless of ordering source
+    set:
+      openTelemetry:
+        gateway:
+          config:
+            traces:
+              processors:
+                memory_limiter:
+                  check_interval: 1s
+                batch:
+                  timeout: 1s
+              tracePipelineProcessors:
+                - memory_limiter
+                - batch
+    asserts:
+      - matchRegex:
+          path: data["config.yaml"]
+          pattern: "check_interval: 1s"
+      - matchRegex:
+          path: data["config.yaml"]
+          pattern: "timeout: 1s"

charts/sourcegraph/values.yaml

@@ -665,6 +665,11 @@ openTelemetry:
         # -- Define trace processors.
         # Read how to configure sampling in the [OpenTelemetry documentation](https://docs.sourcegraph.com/admin/observability/opentelemetry#sampling-traces)
         processors: {}
+        # -- Define the order in which processors are applied in the traces pipeline. When set, this
+        # takes precedence over the iteration order of `processors` (which cannot be relied on to
+        # preserve insertion order). Must contain exactly the same processor names as the keys of
+        # `processors`.
+        tracePipelineProcessors: []
         # -- Define where traces should be exported to.
         # Read how to configure different backends in the [OpenTelemetry documentation](https://opentelemetry.io/docs/collector/configuration/#exporters)
         exporters: {}