Addressing feedback:

* Use explicit returns if there's a return somewhere else in the function.

* Return an error if a log group couldn't be created.

* Make failure to set a retention policy a warning message (was already not
  a hard error).

* Map `SdkError` to service errors to remove some nested `match` statements.

src/drivers/cloudwatch.rs

@@ -2,6 +2,7 @@ use crate::types::{LogDriver, Message};
 use anyhow::Result;
 use async_trait::async_trait;
 use aws_sdk_cloudwatchlogs::{
+    error::SdkError,
     operation::{
         create_log_group::CreateLogGroupError, create_log_stream::CreateLogStreamError,
         put_log_events::PutLogEventsError,
@@ -33,34 +34,36 @@ impl CloudWatchDriver {
             .set_log_group_name(Some(group_name.to_owned()))
             .send()
             .await
+            .map_err(SdkError::into_service_error)
         {
             Ok(_) => {
-                info!("created log group: {}", group_name);
+                info!(?group_name, "created log group");
+            }
+            Err(CreateLogGroupError::ResourceAlreadyExistsException(_)) => {
+                info!(?group_name, "log group already exists");
+            }
+            Err(e) => {
+                error!(?group_name, "failed to create log group: {e:?}");
+                return Err(e.into());
             }
-            Err(e) => match e.into_service_error() {
-                CreateLogGroupError::ResourceAlreadyExistsException(_) => {}
-                inner_err => {
-                    error!(?group_name, "failed to create log group: {:?}", inner_err);
-                }
-            },
         }
 
         self.groups.insert(group_name.to_owned());
-        match self
+        if let Err(e) = self
             .client
             .put_retention_policy()
             .log_group_name(group_name)
             .retention_in_days(90)
             .send()
             .await
+            .map_err(SdkError::into_service_error)
         {
-            Ok(_) => {}
-            Err(e) => {
-                error!(?group_name, "failed to set retention policy: {:?}", e);
-            }
+            warn!(?group_name, "failed to set retention policy: {:?}", e);
         }
-        Ok(())
+
+        return Ok(());
     }
+
     async fn create_stream(&mut self, group_name: &str, stream_name: &str) -> Result<()> {
         match self
             .client
@@ -69,28 +72,29 @@ impl CloudWatchDriver {
             .set_log_stream_name(Some(stream_name.to_owned()))
             .send()
             .await
+            .map_err(SdkError::into_service_error)
         {
             Ok(_) => {
                 info!("created log stream: {}", stream_name);
             }
-            Err(e) => match e.into_service_error() {
-                CreateLogStreamError::ResourceAlreadyExistsException(_) => {
-                    info!("caching log stream: {} (other node created)", stream_name);
-                }
-                inner_err => {
-                    error!(
-                        ?group_name,
-                        ?stream_name,
-                        "failed to create log stream: {:?}",
-                        inner_err
-                    );
-                    return Err(inner_err.into());
-                }
-            },
+
+            Err(CreateLogStreamError::ResourceAlreadyExistsException(_)) => {
+                info!("caching log stream: {} (other node created)", stream_name);
+            }
+
+            Err(e) => {
+                error!(
+                    ?group_name,
+                    ?stream_name,
+                    "failed to create log stream: {e:?}",
+                );
+                return Err(e.into());
+            }
         }
         self.streams.insert(stream_name.to_owned());
-        Ok(())
+        return Ok(());
     }
+
     async fn check_or_create_group(&mut self, group_name: &str) -> Result<()> {
         if !self.groups.contains(group_name) {
             self.create_group(group_name).await?;