provide fallback if no client configurations were defined

src/bin/consumer.rs

@@ -52,8 +52,8 @@ fn main() -> Result<()> {
     let input_topic = matches.value_of("input_topic").unwrap();
     let consumer_configs = matches
         .values_of("consumer_configs")
-        .context("consumer configs")?
-        .collect::<Vec<&str>>();
+        .and_then(|v| Some(v.collect::<Vec<&str>>()))
+        .unwrap_or(vec![]);
 
     let consumer: BaseConsumer<ConsumerCallbackLogger> = kafka::create_client(
         bootstrap_servers,

src/bin/processor.rs

@@ -135,12 +135,12 @@ fn main() -> Result<()> {
     let output_topic = matches.value_of("output_topic").context("output topic")?;
     let consumer_configs = matches
         .values_of("consumer_configs")
-        .context("consumer configs")?
-        .collect::<Vec<&str>>();
+        .and_then(|v| Some(v.collect::<Vec<&str>>()))
+        .unwrap_or(vec![]);
     let producer_configs = matches
         .values_of("producer_configs")
-        .context("producer configs")?
-        .collect::<Vec<&str>>();
+        .and_then(|v| Some(v.collect::<Vec<&str>>()))
+        .unwrap_or(vec![]);
 
     let consumer: BaseConsumer<ConsumerCallbackLogger> = kafka::create_client(
         bootstrap_servers,

src/bin/producer.rs

@@ -70,8 +70,8 @@ fn main() -> Result<()> {
     let input_file = matches.value_of("INPUT").unwrap();
     let producer_configs = matches
         .values_of("producer_configs")
-        .context("producer configs")?
-        .collect::<Vec<&str>>();
+        .and_then(|v| Some(v.collect::<Vec<&str>>()))
+        .unwrap_or(vec![]);
 
     let producer: ThreadedProducer<ProducerCallbackLogger> = kafka::create_client(
         bootstrap_servers,