fix for invalid parquet issue (#829)

Detect the 0 sized parquet,
log the error and delete the parquet and retain the 
grouped arrow files. The arrow files will be converted 
to parquet in the next sync cycle (every 60 secs)

server/src/storage/staging.rs

@@ -255,34 +255,36 @@ pub fn convert_disk_files_to_parquet(
                 custom_partition_fields.insert(custom_partition_field.to_string(), index);
             }
         }
-        let parquet_file = fs::File::create(&parquet_path).map_err(|_| MoveDataError::Create)?;
         let props = parquet_writer_props(
             time_partition.clone(),
             index_time_partition,
             custom_partition_fields,
         )
         .build();
-
         schemas.push(merged_schema.clone());
         let schema = Arc::new(merged_schema);
-        let mut writer = ArrowWriter::try_new(parquet_file, schema.clone(), Some(props))?;
+        let parquet_file = fs::File::create(&parquet_path).map_err(|_| MoveDataError::Create)?;
+        let mut writer = ArrowWriter::try_new(&parquet_file, schema.clone(), Some(props))?;
         for ref record in record_reader.merged_iter(schema, time_partition.clone()) {
             writer.write(record)?;
         }
 
         writer.close()?;
-
-        for file in files {
-            let file_size = file.metadata().unwrap().len();
-            let file_type = file.extension().unwrap().to_str().unwrap();
-
-            if fs::remove_file(file.clone()).is_err() {
-                log::error!("Failed to delete file. Unstable state");
-                process::abort()
+        if parquet_file.metadata().unwrap().len() == 0 {
+            log::error!("Invalid parquet file detected, removing it");
+            fs::remove_file(parquet_path).unwrap();
+        } else {
+            for file in files {
+                let file_size = file.metadata().unwrap().len();
+                let file_type = file.extension().unwrap().to_str().unwrap();
+                if fs::remove_file(file.clone()).is_err() {
+                    log::error!("Failed to delete file. Unstable state");
+                    process::abort()
+                }
+                metrics::STORAGE_SIZE
+                    .with_label_values(&["staging", stream, file_type])
+                    .sub(file_size as i64);
             }
-            metrics::STORAGE_SIZE
-                .with_label_values(&["staging", stream, file_type])
-                .sub(file_size as i64);
         }
     }