Update README

Signed-off-by: Bogdan Drutu <bogdandrutu@gmail.com>

exporter/stackdriverexporter/README.md

@@ -12,14 +12,20 @@ The following configuration options are supported:
 - `number_of_workers` (optional): NumberOfWorkers sets the number of go rountines that send requests. The minimum number of workers is 1.
 - `resource_mappings` (optional): ResourceMapping defines mapping of resources from source (OpenCensus) to target (Stackdriver).
   - `label_mappings` (optional): Optional flag signals whether we can proceed with transformation if a label is missing in the resource.
+- `retry_on_failure` (optional): Configuration for how to handle retries when sending data to Google Cloud fails.
+  - `enabled` (default = true)
+  - `initial_interval` (default = 5s): Time to wait after the first failure before retrying; ignored if `enabled` is `false`
+  - `max_interval` (default = 30s): Is the upper bound on backoff; ignored if `enabled` is `false`
+  - `max_elapsed_time` (default = 120s): Is the maximum amount of time spent trying to send a batch; ignored if `enabled` is `false`
+- `sending_queue` (optional): Configuration for how to buffer traces before sending.
+  - `enabled` (default = true)
+  - `num_consumers` (default = 10): Number of consumers that dequeue batches; ignored if `enabled` is `false`
+  - `queue_size` (default = 5000): Maximum number of batches kept in memory before data; ignored if `enabled` is `false`;
+    User should calculate this as `num_seconds * requests_per_second` where:
+    - `num_seconds` is the number of seconds to buffer in case of a backend outage
+    - `requests_per_second` is the average number of requests per seconds.
 
-Additional configuration for the trace exporter:
-
-- `trace.bundle_delay_threshold` (optional): Starting from the time that the first span is added to a bundle, once this delay has passed, handle the bundle. If not set, uses the exporter default.
-- `trace.bundle_count_threshold` (optional): Once a bundle has this many spans, handle the bundle. Since only one span at a time is added to a bundle, no bundle will exceed this threshold, so it also serves as a limit. If not set, uses the exporter default.
-- `trace.bundle_byte_threshold` (optional): Once the number of bytes in current bundle reaches this threshold, handle the bundle. This triggers handling, but does not cap the total size of a bundle. If not set, uses the exporter default.
-- `trace.bundle_byte_limit` (optional): The maximum size of a bundle, in bytes. Zero means unlimited.
-- `trace.buffer_max_bytes` (optional): The maximum number of bytes that the Bundler will keep in memory before returning ErrOverflow. If not set, uses the exporter default.
+Note: These `retry_on_failure` and `sending_queue` are provided (and documented) by the [Exporter Helper](https://github.com/open-telemetry/opentelemetry-collector/tree/main/exporter/exporterhelper#configuration)
 
 Additional configuration for the metric exporter:
 
@@ -48,12 +54,15 @@ exporters:
           - source_key: source.label1
             target_key: target_label_1
 
-    trace:
-      bundle_delay_threshold: 2s
-      bundle_count_threshold: 50
-      bundle_byte_threshold: 15e3
-      bundle_byte_limit: 0
-      buffer_max_bytes: 8e6
+    retry_on_failure:
+      enabled: true
+      initial_interval: 5s
+      max_interval: 30s
+      max_elapsed_time: 120s
+    sending_queue:
+      enabled: true
+      num_consumers: 2
+      queue_size: 50
 
     metric:
       prefix: prefix
@@ -70,3 +79,23 @@ following proxy environment variables:
 
 If set at Collector start time then exporters, regardless of protocol,
 will or will not proxy traffic as defined by these environment variables.
+
+
+# Recommendations
+
+It is recommended to always run a [batch processor](https://github.com/open-telemetry/opentelemetry-collector/tree/main/processor/batchprocessor)
+and [memory limiter](https://github.com/open-telemetry/opentelemetry-collector/tree/main/processor/memorylimiter) for tracing pipelines to ensure
+optimal network usage and avoiding memory overruns.  You may also want to run an additional
+[sampler](https://github.com/open-telemetry/opentelemetry-collector/tree/main/processor/probabilisticsamplerprocessor), depending on your needs.
+
+
+# Deprecatations
+
+The previous trace configuration (v0.21.0) has been deprecated in favor of the common configuration options available in OpenTelemetry. These will cause a failure to start
+and should be migrated:
+
+- `trace.bundle_delay_threshold` (optional): Use `batch` processor instead ([docs](https://github.com/open-telemetry/opentelemetry-collector/tree/main/processor/batchprocessor)).
+- `trace.bundle_count_threshold` (optional): Use `batch` processor instead ([docs](https://github.com/open-telemetry/opentelemetry-collector/tree/main/processor/batchprocessor)).
+- `trace.bundle_byte_threshold` (optional): Use `memorylimiter` processor instead ([docs](https://github.com/open-telemetry/opentelemetry-collector/tree/main/processor/memorylimiter))
+- `trace.bundle_byte_limit` (optional): Use `memorylimiter` processor instead ([docs](https://github.com/open-telemetry/opentelemetry-collector/tree/main/processor/memorylimiter))
+- `trace.buffer_max_bytes` (optional): Use `memorylimiter` processor instead ([docs](https://github.com/open-telemetry/opentelemetry-collector/tree/main/processor/memorylimiter))