Limit number of caches

This commit adds a configuration to limit the number of caches the
tool will create.

The default value is 10.

Fixes #4

readyset_proxysql_scheduler.cnf

@@ -10,4 +10,5 @@ source_hostgroup = 11
 readyset_hostgroup = 99
 warmup_time = 60
 lock_file = '/tmp/readyset_scheduler.lock'
-operation_mode=all
+operation_mode="All"
+number_of_queries=10

src/config.rs

@@ -48,6 +48,7 @@ pub struct Config {
     pub warmup_time: Option<u16>,
     pub lock_file: Option<String>,
     pub operation_mode: Option<OperationMode>,
+    pub number_of_queries: u16,
 }
 
 pub fn read_config_file(path: &str) -> Result<String, std::io::Error> {

src/queries.rs

@@ -6,6 +6,17 @@ use crate::{
     messages,
 };
 
+const MIRROR_QUERY_TOKEN: &str = "Mirror by readyset scheduler at";
+const DESTINATION_QUERY_TOKEN: &str = "Added by readyset scheduler at";
+
+/// This function is used to find queries that are not cached in ReadySet and are not in the mysql_query_rules table.
+///
+/// # Arguments
+/// * `conn` - A mutable reference to a pooled connection to ProxySQL.
+/// * `config` - A reference to the configuration struct.
+///
+/// # Returns
+/// A vector of tuples containing the digest_text, digest, and schema name of the queries that are not cached in ReadySet and are not in the mysql_query_rules table.
 pub fn find_queries_to_cache(
     conn: &mut PooledConn,
     config: &Config,
@@ -23,10 +34,30 @@ pub fn find_queries_to_cache(
             AND digest_text NOT LIKE '%?=?%'
             AND s.sum_rows_sent > 0
             AND q.rule_id IS NULL
-            ORDER BY s.sum_rows_sent DESC",
-            config.source_hostgroup, config.readyset_user
+            ORDER BY s.sum_rows_sent DESC
+            LIMIT {}",
+            config.source_hostgroup,
+            config.readyset_user,
+            (config.number_of_queries * 2)
         ))
-        .expect("Failed to query proxysql_conn");
+        .expect("Failed to find queries to cache");
+    rows
+}
+
+/// This function is used to check the current list of queries routed to Readyset.
+///
+/// # Arguments
+/// * `conn` - A mutable reference to a pooled connection to ProxySQL.
+///
+/// # Returns
+/// A vector of tuples containing the digest_text, digest, and schemaname of the queries that are currently routed to ReadySet.
+pub fn find_queries_routed_to_readyset(conn: &mut PooledConn) -> Vec<String> {
+    let rows: Vec<String> = conn
+        .query(format!(
+            "SELECT digest FROM mysql_query_rules WHERE comment LIKE '{}%' OR comment LIKE '{}%'",
+            MIRROR_QUERY_TOKEN, DESTINATION_QUERY_TOKEN
+        ))
+        .expect("Failed to find queries routed to ReadySet");
     rows
 }
 
@@ -65,10 +96,10 @@ pub fn add_query_rule(
     let datetime_now: DateTime<Local> = Local::now();
     let date_formatted = datetime_now.format("%Y-%m-%d %H:%M:%S");
     if config.warmup_time.is_some() {
-        conn.query_drop(format!("INSERT INTO mysql_query_rules (username, mirror_hostgroup, active, digest, apply, comment) VALUES ('{}', {}, 1, '{}', 1, 'Mirror by readyset scheduler at: {}')", config.readyset_user, config.readyset_hostgroup, digest, date_formatted)).expect("Failed to insert into mysql_query_rules");
+        conn.query_drop(format!("INSERT INTO mysql_query_rules (username, mirror_hostgroup, active, digest, apply, comment) VALUES ('{}', {}, 1, '{}', 1, '{}: {}')", config.readyset_user, config.readyset_hostgroup, digest, MIRROR_QUERY_TOKEN, date_formatted)).expect("Failed to insert into mysql_query_rules");
         messages::print_info("Inserted warm-up rule");
     } else {
-        conn.query_drop(format!("INSERT INTO mysql_query_rules (username, destination_hostgroup, active, digest, apply, comment) VALUES ('{}', {}, 1, '{}', 1, 'Added by readyset scheduler at: {}')", config.readyset_user, config.readyset_hostgroup, digest, date_formatted)).expect("Failed to insert into mysql_query_rules");
+        conn.query_drop(format!("INSERT INTO mysql_query_rules (username, destination_hostgroup, active, digest, apply, comment) VALUES ('{}', {}, 1, '{}', 1, '{}: {}')", config.readyset_user, config.readyset_hostgroup, digest, DESTINATION_QUERY_TOKEN, date_formatted)).expect("Failed to insert into mysql_query_rules");
         messages::print_info("Inserted destination rule");
     }
     Ok(true)
@@ -90,7 +121,7 @@ pub fn adjust_mirror_rules(conn: &mut PooledConn, config: &Config) -> Result<boo
     let datetime_now: DateTime<Local> = Local::now();
     let tz = datetime_now.format("%z").to_string();
     let date_formatted = datetime_now.format("%Y-%m-%d %H:%M:%S");
-    let rows: Vec<(u16, String)> = conn.query("SELECT rule_id, comment FROM mysql_query_rules WHERE comment LIKE 'Mirror by readyset scheduler at: ____-__-__ __:__:__';").expect("Failed to select mirror rules");
+    let rows: Vec<(u16, String)> = conn.query(format!("SELECT rule_id, comment FROM mysql_query_rules WHERE comment LIKE '{}: ____-__-__ __:__:__';", MIRROR_QUERY_TOKEN)).expect("Failed to select mirror rules");
     for (rule_id, comment) in rows {
         let datetime_mirror_str = comment
             .split("Mirror by readyset scheduler at:")
@@ -128,9 +159,13 @@ pub fn query_discovery(
 ) {
     let mut queries_added_or_change = adjust_mirror_rules(proxysql_conn, config).unwrap();
 
+    let mut current_queries_digest: Vec<String> = find_queries_routed_to_readyset(proxysql_conn);
     let rows: Vec<(String, String, String)> = find_queries_to_cache(proxysql_conn, config);
 
     for (digest_text, digest, schema) in rows {
+        if current_queries_digest.len() > config.number_of_queries as usize {
+            break;
+        }
         let digest_text = replace_placeholders(&digest_text);
         messages::print_info(format!("Going to test query support for {}", digest_text).as_str());
         let supported = check_readyset_query_support(readyset_conn, &digest_text, &schema);
@@ -144,6 +179,7 @@ pub fn query_discovery(
                 queries_added_or_change = true;
                 cache_query(readyset_conn, &digest_text).expect("Failed to create readyset cache");
                 add_query_rule(proxysql_conn, &digest, config).expect("Failed to add query rule");
+                current_queries_digest.push(digest);
             }
             Ok(false) => {
                 messages::print_info("Query is not supported");