feat(flow): frontend client for handle sql (#5761)

* feat: frontend client for handle sql

* refactor: per review

* chore: revert unnecessary change

src/client/src/lib.rs

@@ -16,7 +16,6 @@
 
 mod client;
 pub mod client_manager;
-#[cfg(feature = "testing")]
 mod database;
 pub mod error;
 pub mod flow;
@@ -34,7 +33,6 @@ pub use common_recordbatch::{RecordBatches, SendableRecordBatchStream};
 use snafu::OptionExt;
 
 pub use self::client::Client;
-#[cfg(feature = "testing")]
 pub use self::database::Database;
 pub use self::error::{Error, Result};
 use crate::error::{IllegalDatabaseResponseSnafu, ServerSnafu};

src/flow/src/lib.rs

@@ -33,6 +33,7 @@ mod expr;
 pub mod heartbeat;
 mod metrics;
 mod plan;
+mod recording_rules;
 mod repr;
 mod server;
 mod transform;

src/flow/src/recording_rules.rs

@@ -0,0 +1,23 @@
+// Copyright 2023 Greptime Team
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Run flow as recording rule which is time-window-aware normal query triggered when new data arrives
+
+use std::time::Duration;
+
+mod frontend_client;
+
+/// TODO(discord9): make those constants configurable
+/// The default rule engine query timeout is 10 minutes
+pub const DEFAULT_RULE_ENGINE_QUERY_TIMEOUT: Duration = Duration::from_secs(10 * 60);

src/flow/src/recording_rules/frontend_client.rs

@@ -0,0 +1,148 @@
+// Copyright 2023 Greptime Team
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Frontend client to run flow as recording rule which is time-window-aware normal query triggered every tick set by user
+
+use std::sync::Arc;
+
+use client::{Client, Database, DEFAULT_CATALOG_NAME, DEFAULT_SCHEMA_NAME};
+use common_error::ext::BoxedError;
+use common_grpc::channel_manager::{ChannelConfig, ChannelManager};
+use common_meta::cluster::{NodeInfo, NodeInfoKey, Role};
+use common_meta::peer::Peer;
+use common_meta::rpc::store::RangeRequest;
+use meta_client::client::MetaClient;
+use snafu::ResultExt;
+
+use crate::error::{ExternalSnafu, UnexpectedSnafu};
+use crate::recording_rules::DEFAULT_RULE_ENGINE_QUERY_TIMEOUT;
+use crate::Error;
+
+fn default_channel_mgr() -> ChannelManager {
+    let cfg = ChannelConfig::new().timeout(DEFAULT_RULE_ENGINE_QUERY_TIMEOUT);
+    ChannelManager::with_config(cfg)
+}
+
+fn client_from_urls(addrs: Vec<String>) -> Client {
+    Client::with_manager_and_urls(default_channel_mgr(), addrs)
+}
+
+/// A simple frontend client able to execute sql using grpc protocol
+#[derive(Debug)]
+pub enum FrontendClient {
+    Distributed {
+        meta_client: Arc<MetaClient>,
+    },
+    Standalone {
+        /// for the sake of simplicity still use grpc even in standalone mode
+        /// notice the client here should all be lazy, so that can wait after frontend is booted then make conn
+        /// TODO(discord9): not use grpc under standalone mode
+        database_client: DatabaseWithPeer,
+    },
+}
+
+#[derive(Debug, Clone)]
+pub struct DatabaseWithPeer {
+    pub database: Database,
+    pub peer: Peer,
+}
+
+impl DatabaseWithPeer {
+    fn new(database: Database, peer: Peer) -> Self {
+        Self { database, peer }
+    }
+}
+
+impl FrontendClient {
+    pub fn from_meta_client(meta_client: Arc<MetaClient>) -> Self {
+        Self::Distributed { meta_client }
+    }
+
+    pub fn from_static_grpc_addr(addr: String) -> Self {
+        let peer = Peer {
+            id: 0,
+            addr: addr.clone(),
+        };
+
+        let client = client_from_urls(vec![addr]);
+        let database = Database::new(DEFAULT_CATALOG_NAME, DEFAULT_SCHEMA_NAME, client);
+        Self::Standalone {
+            database_client: DatabaseWithPeer::new(database, peer),
+        }
+    }
+}
+
+impl FrontendClient {
+    async fn scan_for_frontend(&self) -> Result<Vec<(NodeInfoKey, NodeInfo)>, Error> {
+        let Self::Distributed { meta_client, .. } = self else {
+            return Ok(vec![]);
+        };
+        let cluster_client = meta_client
+            .cluster_client()
+            .map_err(BoxedError::new)
+            .context(ExternalSnafu)?;
+
+        let prefix = NodeInfoKey::key_prefix_with_role(Role::Frontend);
+        let req = RangeRequest::new().with_prefix(prefix);
+        let resp = cluster_client
+            .range(req)
+            .await
+            .map_err(BoxedError::new)
+            .context(ExternalSnafu)?;
+        let mut res = Vec::with_capacity(resp.kvs.len());
+        for kv in resp.kvs {
+            let key = NodeInfoKey::try_from(kv.key)
+                .map_err(BoxedError::new)
+                .context(ExternalSnafu)?;
+
+            let val = NodeInfo::try_from(kv.value)
+                .map_err(BoxedError::new)
+                .context(ExternalSnafu)?;
+            res.push((key, val));
+        }
+        Ok(res)
+    }
+
+    /// Get the database with max `last_activity_ts`
+    async fn get_last_active_frontend(&self) -> Result<DatabaseWithPeer, Error> {
+        if let Self::Standalone { database_client } = self {
+            return Ok(database_client.clone());
+        }
+
+        let frontends = self.scan_for_frontend().await?;
+        let mut peer = None;
+
+        if let Some((_, val)) = frontends.iter().max_by_key(|(_, val)| val.last_activity_ts) {
+            peer = Some(val.peer.clone());
+        }
+
+        let Some(peer) = peer else {
+            UnexpectedSnafu {
+                reason: format!("No frontend available: {:?}", frontends),
+            }
+            .fail()?
+        };
+        let client = client_from_urls(vec![peer.addr.clone()]);
+        let database = Database::new(DEFAULT_CATALOG_NAME, DEFAULT_SCHEMA_NAME, client);
+        Ok(DatabaseWithPeer::new(database, peer))
+    }
+
+    /// Get a database client, and possibly update it before returning.
+    pub async fn get_database_client(&self) -> Result<DatabaseWithPeer, Error> {
+        match self {
+            Self::Standalone { database_client } => Ok(database_client.clone()),
+            Self::Distributed { meta_client: _ } => self.get_last_active_frontend().await,
+        }
+    }
+}