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[GitHub] [arrow-ballista] yahoNanJing opened a new pull request, #523: Provide a memory StateBackendClient

yahoNanJing opened a new pull request, #523:
URL: https://github.com/apache/arrow-ballista/pull/523

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   Closes #505.
   
    # Rationale for this change
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[GitHub] [arrow-ballista] thinkharderdev commented on a diff in pull request #523: Provide a memory StateBackendClient

Posted by GitBox <gi...@apache.org>.
thinkharderdev commented on code in PR #523:
URL: https://github.com/apache/arrow-ballista/pull/523#discussion_r1026287065


##########
ballista/scheduler/src/state/backend/memory.rs:
##########
@@ -0,0 +1,395 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you 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.
+
+use crate::state::backend::utils::sled_subscriber::{Subscriber, Subscribers};
+use crate::state::backend::{
+    Keyspace, Lock, Operation, StateBackendClient, Watch, WatchEvent,
+};
+use ballista_core::error::Result;
+use dashmap::DashMap;
+use futures::{FutureExt, Stream};
+use log::warn;
+use std::collections::{BTreeMap, HashSet};
+use std::sync::Arc;
+use tokio::sync::Mutex;
+
+type KeySpaceState = BTreeMap<String, Vec<u8>>;
+type KeyLock = Arc<Mutex<()>>;
+
+/// A [`StateBackendClient`] implementation that uses in memory map to save cluster state.
+#[derive(Clone, Default)]
+pub struct MemoryBackendClient {
+    /// The key is the KeySpace. For every KeySpace, there will be a tree map which is better for prefix filtering
+    states: DashMap<String, KeySpaceState>,
+    /// The key is the full key formatted like "/KeySpace/key". It's a flatted map
+    locks: DashMap<String, KeyLock>,
+    subscribers: Arc<Subscribers>,
+}
+
+impl MemoryBackendClient {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    fn get_space_key(keyspace: &Keyspace) -> String {
+        format!("/{:?}", keyspace)
+    }
+
+    fn get_flat_key(keyspace: &Keyspace, key: &str) -> String {
+        format!("/{:?}/{}", keyspace, key)
+    }
+}
+
+#[tonic::async_trait]
+impl StateBackendClient for MemoryBackendClient {
+    async fn get(&self, keyspace: Keyspace, key: &str) -> Result<Vec<u8>> {
+        let space_key = Self::get_space_key(&keyspace);
+        Ok(self
+            .states
+            .get(&space_key)
+            .map(|space_state| space_state.value().get(key).cloned().unwrap_or_default())
+            .unwrap_or_default())
+    }
+
+    async fn get_from_prefix(
+        &self,
+        keyspace: Keyspace,
+        prefix: &str,
+    ) -> Result<Vec<(String, Vec<u8>)>> {
+        let space_key = Self::get_space_key(&keyspace);
+        Ok(self
+            .states
+            .get(&space_key)
+            .map(|space_state| {
+                space_state
+                    .value()
+                    .range(prefix.to_owned()..)
+                    .take_while(|(k, _)| k.starts_with(prefix))
+                    .map(|e| (format!("{}/{}", space_key, e.0), e.1.clone()))
+                    .collect()
+            })
+            .unwrap_or_default())
+    }
+
+    async fn scan(
+        &self,
+        keyspace: Keyspace,
+        limit: Option<usize>,
+    ) -> Result<Vec<(String, Vec<u8>)>> {
+        let space_key = Self::get_space_key(&keyspace);
+        Ok(self
+            .states
+            .get(&space_key)
+            .map(|space_state| {
+                if let Some(limit) = limit {
+                    space_state
+                        .value()
+                        .iter()
+                        .take(limit)
+                        .map(|e| (format!("{}/{}", space_key, e.0), e.1.clone()))
+                        .collect::<Vec<(String, Vec<u8>)>>()
+                } else {
+                    space_state
+                        .value()
+                        .iter()
+                        .map(|e| (format!("{}/{}", space_key, e.0), e.1.clone()))
+                        .collect::<Vec<(String, Vec<u8>)>>()
+                }
+            })
+            .unwrap_or_default())
+    }
+
+    async fn scan_keys(&self, keyspace: Keyspace) -> Result<HashSet<String>> {
+        let space_key = Self::get_space_key(&keyspace);
+        Ok(self
+            .states
+            .get(&space_key)
+            .map(|space_state| {
+                space_state
+                    .value()
+                    .iter()
+                    .map(|e| format!("{}/{}", space_key, e.0))
+                    .collect::<HashSet<String>>()
+            })
+            .unwrap_or_default())
+    }
+
+    async fn put(&self, keyspace: Keyspace, key: String, value: Vec<u8>) -> Result<()> {
+        let space_key = Self::get_space_key(&keyspace);
+        if !self.states.contains_key(&space_key) {
+            self.states.insert(space_key.clone(), BTreeMap::default());
+        }
+        self.states
+            .get_mut(&space_key)
+            .unwrap()
+            .value_mut()
+            .insert(key.clone(), value.clone());
+
+        // Notify subscribers
+        let full_key = format!("{}/{}", space_key, key);
+        if let Some(res) = self.subscribers.reserve(&full_key) {
+            let event = WatchEvent::Put(full_key, value);
+            res.complete(&event);
+        }
+
+        Ok(())
+    }
+
+    async fn apply_txn(&self, ops: Vec<(Operation, Keyspace, String)>) -> Result<()> {
+        let mut locks = vec![];
+        for (_, keyspace, key) in ops.iter() {
+            locks.push(self.lock(keyspace.clone(), key).await?);
+        }
+
+        for (op, keyspace, key) in ops.into_iter() {
+            match op {
+                Operation::Delete => {
+                    self.delete(keyspace, &key).await?;
+                }
+                Operation::Put(value) => {
+                    self.put(keyspace, key, value).await?;
+                }
+            };
+        }
+
+        Ok(())
+    }
+
+    async fn mv(
+        &self,
+        from_keyspace: Keyspace,
+        to_keyspace: Keyspace,
+        key: &str,
+    ) -> Result<()> {
+        let from_space_key = Self::get_space_key(&from_keyspace);
+
+        if let Some(from_space_state) = self.states.get(&from_space_key) {
+            if let Some(state) = from_space_state.value().get(key) {
+                let ops = vec![
+                    (Operation::Delete, from_keyspace, key.to_owned()),
+                    (Operation::Put(state.clone()), to_keyspace, key.to_owned()),
+                ];
+                self.apply_txn(ops).await
+            } else {
+                // TODO should this return an error?

Review Comment:
   I think this should be consistent with the Sled and Etcd backends which I believe would both return an error in this scenario



##########
ballista/scheduler/src/state/backend/utils/mod.rs:
##########
@@ -0,0 +1,21 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you 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.
+
+#[allow(dead_code)]
+mod sled_oneshot;
+#[allow(dead_code)]
+pub(crate) mod sled_subscriber;

Review Comment:
   Confused about the naming here. Why is this called `sled_subscriber`? It's used by the memory backend right? 



##########
ballista/scheduler/src/state/backend/memory.rs:
##########
@@ -0,0 +1,395 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you 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.
+
+use crate::state::backend::utils::sled_subscriber::{Subscriber, Subscribers};
+use crate::state::backend::{
+    Keyspace, Lock, Operation, StateBackendClient, Watch, WatchEvent,
+};
+use ballista_core::error::Result;
+use dashmap::DashMap;
+use futures::{FutureExt, Stream};
+use log::warn;
+use std::collections::{BTreeMap, HashSet};
+use std::sync::Arc;
+use tokio::sync::Mutex;
+
+type KeySpaceState = BTreeMap<String, Vec<u8>>;
+type KeyLock = Arc<Mutex<()>>;
+
+/// A [`StateBackendClient`] implementation that uses in memory map to save cluster state.
+#[derive(Clone, Default)]
+pub struct MemoryBackendClient {
+    /// The key is the KeySpace. For every KeySpace, there will be a tree map which is better for prefix filtering
+    states: DashMap<String, KeySpaceState>,
+    /// The key is the full key formatted like "/KeySpace/key". It's a flatted map
+    locks: DashMap<String, KeyLock>,
+    subscribers: Arc<Subscribers>,
+}
+
+impl MemoryBackendClient {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    fn get_space_key(keyspace: &Keyspace) -> String {
+        format!("/{:?}", keyspace)
+    }
+
+    fn get_flat_key(keyspace: &Keyspace, key: &str) -> String {
+        format!("/{:?}/{}", keyspace, key)
+    }
+}
+
+#[tonic::async_trait]
+impl StateBackendClient for MemoryBackendClient {
+    async fn get(&self, keyspace: Keyspace, key: &str) -> Result<Vec<u8>> {
+        let space_key = Self::get_space_key(&keyspace);
+        Ok(self
+            .states
+            .get(&space_key)
+            .map(|space_state| space_state.value().get(key).cloned().unwrap_or_default())
+            .unwrap_or_default())
+    }
+
+    async fn get_from_prefix(
+        &self,
+        keyspace: Keyspace,
+        prefix: &str,
+    ) -> Result<Vec<(String, Vec<u8>)>> {
+        let space_key = Self::get_space_key(&keyspace);
+        Ok(self
+            .states
+            .get(&space_key)
+            .map(|space_state| {
+                space_state
+                    .value()
+                    .range(prefix.to_owned()..)
+                    .take_while(|(k, _)| k.starts_with(prefix))
+                    .map(|e| (format!("{}/{}", space_key, e.0), e.1.clone()))
+                    .collect()
+            })
+            .unwrap_or_default())
+    }
+
+    async fn scan(
+        &self,
+        keyspace: Keyspace,
+        limit: Option<usize>,
+    ) -> Result<Vec<(String, Vec<u8>)>> {
+        let space_key = Self::get_space_key(&keyspace);
+        Ok(self
+            .states
+            .get(&space_key)
+            .map(|space_state| {
+                if let Some(limit) = limit {
+                    space_state
+                        .value()
+                        .iter()
+                        .take(limit)
+                        .map(|e| (format!("{}/{}", space_key, e.0), e.1.clone()))
+                        .collect::<Vec<(String, Vec<u8>)>>()
+                } else {
+                    space_state
+                        .value()
+                        .iter()
+                        .map(|e| (format!("{}/{}", space_key, e.0), e.1.clone()))
+                        .collect::<Vec<(String, Vec<u8>)>>()
+                }
+            })
+            .unwrap_or_default())
+    }
+
+    async fn scan_keys(&self, keyspace: Keyspace) -> Result<HashSet<String>> {
+        let space_key = Self::get_space_key(&keyspace);
+        Ok(self
+            .states
+            .get(&space_key)
+            .map(|space_state| {
+                space_state
+                    .value()
+                    .iter()
+                    .map(|e| format!("{}/{}", space_key, e.0))
+                    .collect::<HashSet<String>>()
+            })
+            .unwrap_or_default())
+    }
+
+    async fn put(&self, keyspace: Keyspace, key: String, value: Vec<u8>) -> Result<()> {
+        let space_key = Self::get_space_key(&keyspace);
+        if !self.states.contains_key(&space_key) {
+            self.states.insert(space_key.clone(), BTreeMap::default());
+        }
+        self.states
+            .get_mut(&space_key)
+            .unwrap()
+            .value_mut()
+            .insert(key.clone(), value.clone());
+
+        // Notify subscribers
+        let full_key = format!("{}/{}", space_key, key);
+        if let Some(res) = self.subscribers.reserve(&full_key) {
+            let event = WatchEvent::Put(full_key, value);
+            res.complete(&event);
+        }
+
+        Ok(())
+    }
+
+    async fn apply_txn(&self, ops: Vec<(Operation, Keyspace, String)>) -> Result<()> {
+        let mut locks = vec![];
+        for (_, keyspace, key) in ops.iter() {
+            locks.push(self.lock(keyspace.clone(), key).await?);
+        }
+
+        for (op, keyspace, key) in ops.into_iter() {
+            match op {
+                Operation::Delete => {
+                    self.delete(keyspace, &key).await?;
+                }
+                Operation::Put(value) => {
+                    self.put(keyspace, key, value).await?;
+                }
+            };
+        }
+
+        Ok(())
+    }
+
+    async fn mv(
+        &self,
+        from_keyspace: Keyspace,
+        to_keyspace: Keyspace,
+        key: &str,
+    ) -> Result<()> {
+        let from_space_key = Self::get_space_key(&from_keyspace);
+
+        if let Some(from_space_state) = self.states.get(&from_space_key) {
+            if let Some(state) = from_space_state.value().get(key) {
+                let ops = vec![
+                    (Operation::Delete, from_keyspace, key.to_owned()),
+                    (Operation::Put(state.clone()), to_keyspace, key.to_owned()),
+                ];
+                self.apply_txn(ops).await
+            } else {
+                // TODO should this return an error?
+                warn!(
+                    "Cannot move value at {}/{}, does not exist",
+                    from_space_key, key
+                );
+                Ok(())
+            }
+        } else {
+            // TODO should this return an error?
+            warn!(
+                "Cannot move value at {}/{}, does not exist",
+                from_space_key, key
+            );
+            Ok(())
+        }
+    }
+
+    async fn lock(&self, keyspace: Keyspace, key: &str) -> Result<Box<dyn Lock>> {
+        let flat_key = Self::get_flat_key(&keyspace, key);
+        if let Some(lock) = self.locks.get_mut(&flat_key) {
+            Ok(Box::new(lock.value().clone().lock_owned().await))
+        } else {
+            let new_lock = Arc::new(Mutex::new(()));
+            self.locks.insert(flat_key, new_lock.clone());
+            Ok(Box::new(new_lock.lock_owned().await))
+        }
+    }

Review Comment:
   Hmm, I think this might allow multiple locks. 
   
   Can we use the entry API here? 
   
   ```rust
   let new_lock = Arc::new(Mutex::new(()));
   
   let lock = self.locks.entry(&flat_key).or_insert_with(|| Arc::new(Mutex::new(())));
   Ok(Box::new(lock.value().clone().lock_owned().await))
   ```



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[GitHub] [arrow-ballista] yahoNanJing commented on a diff in pull request #523: Provide a memory StateBackendClient

Posted by GitBox <gi...@apache.org>.
yahoNanJing commented on code in PR #523:
URL: https://github.com/apache/arrow-ballista/pull/523#discussion_r1027438846


##########
ballista/scheduler/src/state/backend/memory.rs:
##########
@@ -0,0 +1,395 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you 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.
+
+use crate::state::backend::utils::sled_subscriber::{Subscriber, Subscribers};
+use crate::state::backend::{
+    Keyspace, Lock, Operation, StateBackendClient, Watch, WatchEvent,
+};
+use ballista_core::error::Result;
+use dashmap::DashMap;
+use futures::{FutureExt, Stream};
+use log::warn;
+use std::collections::{BTreeMap, HashSet};
+use std::sync::Arc;
+use tokio::sync::Mutex;
+
+type KeySpaceState = BTreeMap<String, Vec<u8>>;
+type KeyLock = Arc<Mutex<()>>;
+
+/// A [`StateBackendClient`] implementation that uses in memory map to save cluster state.
+#[derive(Clone, Default)]
+pub struct MemoryBackendClient {
+    /// The key is the KeySpace. For every KeySpace, there will be a tree map which is better for prefix filtering
+    states: DashMap<String, KeySpaceState>,
+    /// The key is the full key formatted like "/KeySpace/key". It's a flatted map
+    locks: DashMap<String, KeyLock>,
+    subscribers: Arc<Subscribers>,
+}
+
+impl MemoryBackendClient {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    fn get_space_key(keyspace: &Keyspace) -> String {
+        format!("/{:?}", keyspace)
+    }
+
+    fn get_flat_key(keyspace: &Keyspace, key: &str) -> String {
+        format!("/{:?}/{}", keyspace, key)
+    }
+}
+
+#[tonic::async_trait]
+impl StateBackendClient for MemoryBackendClient {
+    async fn get(&self, keyspace: Keyspace, key: &str) -> Result<Vec<u8>> {
+        let space_key = Self::get_space_key(&keyspace);
+        Ok(self
+            .states
+            .get(&space_key)
+            .map(|space_state| space_state.value().get(key).cloned().unwrap_or_default())
+            .unwrap_or_default())
+    }
+
+    async fn get_from_prefix(
+        &self,
+        keyspace: Keyspace,
+        prefix: &str,
+    ) -> Result<Vec<(String, Vec<u8>)>> {
+        let space_key = Self::get_space_key(&keyspace);
+        Ok(self
+            .states
+            .get(&space_key)
+            .map(|space_state| {
+                space_state
+                    .value()
+                    .range(prefix.to_owned()..)
+                    .take_while(|(k, _)| k.starts_with(prefix))
+                    .map(|e| (format!("{}/{}", space_key, e.0), e.1.clone()))
+                    .collect()
+            })
+            .unwrap_or_default())
+    }
+
+    async fn scan(
+        &self,
+        keyspace: Keyspace,
+        limit: Option<usize>,
+    ) -> Result<Vec<(String, Vec<u8>)>> {
+        let space_key = Self::get_space_key(&keyspace);
+        Ok(self
+            .states
+            .get(&space_key)
+            .map(|space_state| {
+                if let Some(limit) = limit {
+                    space_state
+                        .value()
+                        .iter()
+                        .take(limit)
+                        .map(|e| (format!("{}/{}", space_key, e.0), e.1.clone()))
+                        .collect::<Vec<(String, Vec<u8>)>>()
+                } else {
+                    space_state
+                        .value()
+                        .iter()
+                        .map(|e| (format!("{}/{}", space_key, e.0), e.1.clone()))
+                        .collect::<Vec<(String, Vec<u8>)>>()
+                }
+            })
+            .unwrap_or_default())
+    }
+
+    async fn scan_keys(&self, keyspace: Keyspace) -> Result<HashSet<String>> {
+        let space_key = Self::get_space_key(&keyspace);
+        Ok(self
+            .states
+            .get(&space_key)
+            .map(|space_state| {
+                space_state
+                    .value()
+                    .iter()
+                    .map(|e| format!("{}/{}", space_key, e.0))
+                    .collect::<HashSet<String>>()
+            })
+            .unwrap_or_default())
+    }
+
+    async fn put(&self, keyspace: Keyspace, key: String, value: Vec<u8>) -> Result<()> {
+        let space_key = Self::get_space_key(&keyspace);
+        if !self.states.contains_key(&space_key) {
+            self.states.insert(space_key.clone(), BTreeMap::default());
+        }
+        self.states
+            .get_mut(&space_key)
+            .unwrap()
+            .value_mut()
+            .insert(key.clone(), value.clone());
+
+        // Notify subscribers
+        let full_key = format!("{}/{}", space_key, key);
+        if let Some(res) = self.subscribers.reserve(&full_key) {
+            let event = WatchEvent::Put(full_key, value);
+            res.complete(&event);
+        }
+
+        Ok(())
+    }
+
+    async fn apply_txn(&self, ops: Vec<(Operation, Keyspace, String)>) -> Result<()> {
+        let mut locks = vec![];
+        for (_, keyspace, key) in ops.iter() {
+            locks.push(self.lock(keyspace.clone(), key).await?);
+        }
+
+        for (op, keyspace, key) in ops.into_iter() {
+            match op {
+                Operation::Delete => {
+                    self.delete(keyspace, &key).await?;
+                }
+                Operation::Put(value) => {
+                    self.put(keyspace, key, value).await?;
+                }
+            };
+        }
+
+        Ok(())
+    }
+
+    async fn mv(
+        &self,
+        from_keyspace: Keyspace,
+        to_keyspace: Keyspace,
+        key: &str,
+    ) -> Result<()> {
+        let from_space_key = Self::get_space_key(&from_keyspace);
+
+        if let Some(from_space_state) = self.states.get(&from_space_key) {
+            if let Some(state) = from_space_state.value().get(key) {
+                let ops = vec![
+                    (Operation::Delete, from_keyspace, key.to_owned()),
+                    (Operation::Put(state.clone()), to_keyspace, key.to_owned()),
+                ];
+                self.apply_txn(ops).await
+            } else {
+                // TODO should this return an error?
+                warn!(
+                    "Cannot move value at {}/{}, does not exist",
+                    from_space_key, key
+                );
+                Ok(())
+            }
+        } else {
+            // TODO should this return an error?
+            warn!(
+                "Cannot move value at {}/{}, does not exist",
+                from_space_key, key
+            );
+            Ok(())
+        }
+    }
+
+    async fn lock(&self, keyspace: Keyspace, key: &str) -> Result<Box<dyn Lock>> {
+        let flat_key = Self::get_flat_key(&keyspace, key);
+        if let Some(lock) = self.locks.get_mut(&flat_key) {
+            Ok(Box::new(lock.value().clone().lock_owned().await))
+        } else {
+            let new_lock = Arc::new(Mutex::new(()));
+            self.locks.insert(flat_key, new_lock.clone());
+            Ok(Box::new(new_lock.lock_owned().await))
+        }
+    }

Review Comment:
   Good suggestion. I'll refine it.



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[GitHub] [arrow-ballista] yahoNanJing commented on a diff in pull request #523: Provide a memory StateBackendClient

Posted by GitBox <gi...@apache.org>.
yahoNanJing commented on code in PR #523:
URL: https://github.com/apache/arrow-ballista/pull/523#discussion_r1027425080


##########
ballista/scheduler/src/state/backend/memory.rs:
##########
@@ -0,0 +1,395 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you 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.
+
+use crate::state::backend::utils::sled_subscriber::{Subscriber, Subscribers};
+use crate::state::backend::{
+    Keyspace, Lock, Operation, StateBackendClient, Watch, WatchEvent,
+};
+use ballista_core::error::Result;
+use dashmap::DashMap;
+use futures::{FutureExt, Stream};
+use log::warn;
+use std::collections::{BTreeMap, HashSet};
+use std::sync::Arc;
+use tokio::sync::Mutex;
+
+type KeySpaceState = BTreeMap<String, Vec<u8>>;
+type KeyLock = Arc<Mutex<()>>;
+
+/// A [`StateBackendClient`] implementation that uses in memory map to save cluster state.
+#[derive(Clone, Default)]
+pub struct MemoryBackendClient {
+    /// The key is the KeySpace. For every KeySpace, there will be a tree map which is better for prefix filtering
+    states: DashMap<String, KeySpaceState>,
+    /// The key is the full key formatted like "/KeySpace/key". It's a flatted map
+    locks: DashMap<String, KeyLock>,
+    subscribers: Arc<Subscribers>,
+}
+
+impl MemoryBackendClient {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    fn get_space_key(keyspace: &Keyspace) -> String {
+        format!("/{:?}", keyspace)
+    }
+
+    fn get_flat_key(keyspace: &Keyspace, key: &str) -> String {
+        format!("/{:?}/{}", keyspace, key)
+    }
+}
+
+#[tonic::async_trait]
+impl StateBackendClient for MemoryBackendClient {
+    async fn get(&self, keyspace: Keyspace, key: &str) -> Result<Vec<u8>> {
+        let space_key = Self::get_space_key(&keyspace);
+        Ok(self
+            .states
+            .get(&space_key)
+            .map(|space_state| space_state.value().get(key).cloned().unwrap_or_default())
+            .unwrap_or_default())
+    }
+
+    async fn get_from_prefix(
+        &self,
+        keyspace: Keyspace,
+        prefix: &str,
+    ) -> Result<Vec<(String, Vec<u8>)>> {
+        let space_key = Self::get_space_key(&keyspace);
+        Ok(self
+            .states
+            .get(&space_key)
+            .map(|space_state| {
+                space_state
+                    .value()
+                    .range(prefix.to_owned()..)
+                    .take_while(|(k, _)| k.starts_with(prefix))
+                    .map(|e| (format!("{}/{}", space_key, e.0), e.1.clone()))
+                    .collect()
+            })
+            .unwrap_or_default())
+    }
+
+    async fn scan(
+        &self,
+        keyspace: Keyspace,
+        limit: Option<usize>,
+    ) -> Result<Vec<(String, Vec<u8>)>> {
+        let space_key = Self::get_space_key(&keyspace);
+        Ok(self
+            .states
+            .get(&space_key)
+            .map(|space_state| {
+                if let Some(limit) = limit {
+                    space_state
+                        .value()
+                        .iter()
+                        .take(limit)
+                        .map(|e| (format!("{}/{}", space_key, e.0), e.1.clone()))
+                        .collect::<Vec<(String, Vec<u8>)>>()
+                } else {
+                    space_state
+                        .value()
+                        .iter()
+                        .map(|e| (format!("{}/{}", space_key, e.0), e.1.clone()))
+                        .collect::<Vec<(String, Vec<u8>)>>()
+                }
+            })
+            .unwrap_or_default())
+    }
+
+    async fn scan_keys(&self, keyspace: Keyspace) -> Result<HashSet<String>> {
+        let space_key = Self::get_space_key(&keyspace);
+        Ok(self
+            .states
+            .get(&space_key)
+            .map(|space_state| {
+                space_state
+                    .value()
+                    .iter()
+                    .map(|e| format!("{}/{}", space_key, e.0))
+                    .collect::<HashSet<String>>()
+            })
+            .unwrap_or_default())
+    }
+
+    async fn put(&self, keyspace: Keyspace, key: String, value: Vec<u8>) -> Result<()> {
+        let space_key = Self::get_space_key(&keyspace);
+        if !self.states.contains_key(&space_key) {
+            self.states.insert(space_key.clone(), BTreeMap::default());
+        }
+        self.states
+            .get_mut(&space_key)
+            .unwrap()
+            .value_mut()
+            .insert(key.clone(), value.clone());
+
+        // Notify subscribers
+        let full_key = format!("{}/{}", space_key, key);
+        if let Some(res) = self.subscribers.reserve(&full_key) {
+            let event = WatchEvent::Put(full_key, value);
+            res.complete(&event);
+        }
+
+        Ok(())
+    }
+
+    async fn apply_txn(&self, ops: Vec<(Operation, Keyspace, String)>) -> Result<()> {
+        let mut locks = vec![];
+        for (_, keyspace, key) in ops.iter() {
+            locks.push(self.lock(keyspace.clone(), key).await?);
+        }
+
+        for (op, keyspace, key) in ops.into_iter() {
+            match op {
+                Operation::Delete => {
+                    self.delete(keyspace, &key).await?;
+                }
+                Operation::Put(value) => {
+                    self.put(keyspace, key, value).await?;
+                }
+            };
+        }
+
+        Ok(())
+    }
+
+    async fn mv(
+        &self,
+        from_keyspace: Keyspace,
+        to_keyspace: Keyspace,
+        key: &str,
+    ) -> Result<()> {
+        let from_space_key = Self::get_space_key(&from_keyspace);
+
+        if let Some(from_space_state) = self.states.get(&from_space_key) {
+            if let Some(state) = from_space_state.value().get(key) {
+                let ops = vec![
+                    (Operation::Delete, from_keyspace, key.to_owned()),
+                    (Operation::Put(state.clone()), to_keyspace, key.to_owned()),
+                ];
+                self.apply_txn(ops).await
+            } else {
+                // TODO should this return an error?

Review Comment:
   Actually, it's consistent with the `sled` implementation



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[GitHub] [arrow-ballista] yahoNanJing commented on pull request #523: Provide a memory StateBackendClient

Posted by GitBox <gi...@apache.org>.
yahoNanJing commented on PR #523:
URL: https://github.com/apache/arrow-ballista/pull/523#issuecomment-1322247302

   Thanks @thinkharderdev. I'll merge this PR, since it's also been verified on our internal cluster.


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[GitHub] [arrow-ballista] yahoNanJing commented on pull request #523: Provide a memory StateBackendClient

Posted by GitBox <gi...@apache.org>.
yahoNanJing commented on PR #523:
URL: https://github.com/apache/arrow-ballista/pull/523#issuecomment-1319494884

   Hi @andygrove, @thinkharderdev, @Ted-Jiang, could you help review this PR?


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[GitHub] [arrow-ballista] yahoNanJing commented on a diff in pull request #523: Provide a memory StateBackendClient

Posted by GitBox <gi...@apache.org>.
yahoNanJing commented on code in PR #523:
URL: https://github.com/apache/arrow-ballista/pull/523#discussion_r1027411347


##########
ballista/scheduler/src/state/backend/utils/mod.rs:
##########
@@ -0,0 +1,21 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you 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.
+
+#[allow(dead_code)]
+mod sled_oneshot;
+#[allow(dead_code)]
+pub(crate) mod sled_subscriber;

Review Comment:
   Hi @thinkharderdev, thanks for pointing it out. Here, I just hope to indicate these mods are the modified version from the sled crate, which may cause a bit confusing here. I'll remove the `sled_` prefix.



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[GitHub] [arrow-ballista] yahoNanJing merged pull request #523: Provide a memory StateBackendClient

Posted by GitBox <gi...@apache.org>.
yahoNanJing merged PR #523:
URL: https://github.com/apache/arrow-ballista/pull/523


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