Actually plugins (#421)

* more plugins

* clean up

* fix tests

* fix flakey test

src/plugins/query_logger.rs

@@ -0,0 +1,49 @@
+//! Log all queries to stdout (or somewhere else, why not).
+
+use crate::{
+    errors::Error,
+    plugins::{Plugin, PluginOutput},
+    query_router::QueryRouter,
+};
+use arc_swap::ArcSwap;
+use async_trait::async_trait;
+use log::info;
+use once_cell::sync::Lazy;
+use sqlparser::ast::Statement;
+use std::sync::Arc;
+
+static ENABLED: Lazy<ArcSwap<bool>> = Lazy::new(|| ArcSwap::from_pointee(false));
+
+pub struct QueryLogger;
+
+pub fn setup() {
+    ENABLED.store(Arc::new(true));
+
+    info!("Logging queries to stdout");
+}
+
+pub fn disable() {
+    ENABLED.store(Arc::new(false));
+}
+
+pub fn enabled() -> bool {
+    **ENABLED.load()
+}
+
+#[async_trait]
+impl Plugin for QueryLogger {
+    async fn run(
+        &mut self,
+        _query_router: &QueryRouter,
+        ast: &Vec<Statement>,
+    ) -> Result<PluginOutput, Error> {
+        let query = ast
+            .iter()
+            .map(|q| q.to_string())
+            .collect::<Vec<String>>()
+            .join("; ");
+        info!("{}", query);
+
+        Ok(PluginOutput::Allow)
+    }
+}