Add support for multiple column names to be passed in the message

field of an alert

Fixes #564

Author: nitisht

server/src/alerts/mod.rs

@@ -135,40 +135,39 @@ pub struct Message {
 
 impl Message {
     // checks if message (with a column name) is valid (i.e. the column name is present in the schema)
-    pub fn valid(&self, schema: &Schema, column: Option<&str>) -> bool {
-        if let Some(col) = column {
-            return get_field(&schema.fields, col).is_some();
-        }
-        true
+    pub fn valid(&self, schema: &Schema, column: &str) -> bool {
+        return get_field(&schema.fields, column).is_some();
     }
 
-    pub fn extract_column_name(&self) -> Option<&str> {
+    pub fn extract_column_names(&self) -> Option<Vec<&str>> {
         let re = Regex::new(r"\{(.*?)\}").unwrap();
         let tokens: Vec<&str> = re
             .captures_iter(self.message.as_str())
             .map(|cap| cap.get(1).unwrap().as_str())
             .collect();
-        // the message can have either no column name ({column_name} not present) or one column name
-        // return Some only if there is exactly one column name present
-        if tokens.len() == 1 {
-            return Some(tokens[0]);
+        // the message can have either no column name ({column_name} not present) or any number of {column_name} present
+        // return None if there is no column name present in the message
+        if tokens.is_empty() {
+            return None;
         }
-        None
+        Some(tokens)
     }
 
-    // returns the message with the column name replaced with the value of the column
+    // returns the message with the column name(s) replaced with the value of the column
     fn get(&self, event: RecordBatch) -> String {
-        if let Some(column) = self.extract_column_name() {
-            if let Some(value) = event.column_by_name(column) {
-                let arr = cast(value, &DataType::Utf8).unwrap();
-                let value = as_string_array(&arr).value(0);
+        let mut replace_message = self.message.clone();
+        if let Some(columns) = self.extract_column_names() {
+            for column in columns {
+                if let Some(value) = event.column_by_name(column) {
+                    let arr = cast(value, &DataType::Utf8).unwrap();
+                    let value = as_string_array(&arr).value(0);
 
-                return self
-                    .message
-                    .replace(&format!("{{{column}}}"), value.to_string().as_str());
+                    replace_message = replace_message
+                        .replace(&format!("{{{column}}}"), value.to_string().as_str());
+                }
             }
         }
-        self.message.clone()
+        replace_message
     }
 }
 

server/src/handlers/http/logstream.rs

@@ -154,17 +154,19 @@ pub async fn put_alert(
 
     let schema = STREAM_INFO.schema(&stream_name)?;
     for alert in &alerts.alerts {
-        let column = alert.message.extract_column_name();
-        let is_valid = alert.message.valid(&schema, column);
-        if !is_valid {
-            let col = column.unwrap_or("");
-            return Err(StreamError::InvalidAlertMessage(
-                alert.name.to_owned(),
-                col.to_string(),
-            ));
-        }
-        if !alert.rule.valid_for_schema(&schema) {
-            return Err(StreamError::InvalidAlert(alert.name.to_owned()));
+        if let Some(columns) = alert.message.extract_column_names() {
+            for column in columns {
+                let is_valid = alert.message.valid(&schema, column);
+                if !is_valid {
+                    return Err(StreamError::InvalidAlertMessage(
+                        alert.name.to_owned(),
+                        column.to_string(),
+                    ));
+                }
+                if !alert.rule.valid_for_schema(&schema) {
+                    return Err(StreamError::InvalidAlert(alert.name.to_owned()));
+                }
+            }
         }
     }