NameNodeProxy
Another HDFS Federation solution from bytedance.
Features
- NameNode RPC proxy instead of ViewFS, no client-side changes.
- Multiple language client (i.e. snakebite) support.
- Stateless. Easy to scale to multiple instances.
- High throughput with little latency introduced.
- Request throttle. Single NameNode malfunction will not affect globally.
Compared with ViewFS and WebHDFS:
NNProxy | ViewFS | WebHDFS | |
---|---|---|---|
Multiple language support | Yes | No | Yes |
Unified APIs provided | Yes | Yes | No |
Mount table stored in | Zookeeper | Configuration | Configuration |
* Client-side configurations are not usually easy to change | |||
Client-side library | No | Heavy | Light |
Call latency introduced | Medium | No latency | High |
Centralized cache support | Yes | Yes | No |
Benchmark
Benchmark result with NameNode Benchmark 0.4:
Direct TPS | NNProxy TPS (3 proxy instances) | |
---|---|---|
create_write @ 16maps | 263,294 | 247,799 |
create_write @ 128maps | 3,008,604 | 2,563,465 |
rename @ 128maps | 474,671 | 471,240 |
Build
IMPORTANT: NNProxy works only with patched NameNode. See /hadoop-patches
in git repository. These patches add proxy support to hadoop-common
library. Each of them must be applied before compiling.
Build with maven:
$ cd nnproxy/hadoop-nnproxy
$ mvn package -DskipTests
Built jar are shaded with necessary libraries, which can run with hadoop jar
.
Deploy
Organize working directory as follows:
bin/
bin/nnproxy
lib/
lib/hadoop-nnproxy-0.1.0.jar
Then run bin/nnproxy
with configuration arguments to start proxy server.
Note that before starting proxy server, a mount table must be deployed first.
For example:
# Setup zk environment, for simplicity, not necessary
export NNPROXY_ZK_QUORUM="127.0.0.1:2181"
export NNPROXY_MOUNT_TABLE_ZKPATH="/hadoop/hdfs/mounts"
export NNPROXY_OPTS="-Ddfs.nnproxy.mount-table.zk.quorum=$NNPROXY_ZK_QUORUM -Ddfs.nnproxy.mount-table.zk.path=$NNPROXY_MOUNT_TABLE_ZKPATH"
# Deploy mount table, example above mounts / to hdfs://toutiaonn0 and /data
# to hdfs://toutiaonn1. In which case, accessing /data/recommend would be
# transparently redirected to hdfs://toutiaonn1/data/recommend.
# In this example, toutiaonn0 and toutiaonn1 are fs names configured with
# auto failover HA. Using ip:port directly (non-HA setup) are also fesible.
echo 'hdfs://toutiaonn0 /' > mounts
echo 'hdfs://toutiaonn1 /data' >> mounts
cat mounts | bin/nnproxy load $NNPROXY_OPTS
# Run proxy (remember these args)
bin/nnproxy proxy $NNPROXY_OPTS
Look into class com.bytedance.hadoop.hdfs.ProxyConfig
for more configurations available.
Proxy server metrics are also available with hadoop-metrics2.
Mount table management
Once proxy server is started, it watches mount table node on ZooKeeper for further changes.
Run bin/nnproxy dump $NNPROXY_OPTS
to dump current mount table to stdout.
Run bin/nnproxy load $NNPROXY_OPTS
to load mount table from stdin.
One can also alter data stored in mount table ZK node directly (or possibly build APIs or UIs). All these changes take effect immediately.
Mount table are delimited text with 3 columns: targetFS
, path
and attributes
, in that order.
For example:
hdfs://toutiaonn0 / none
hdfs://toutiaonn1 /data none
Each row advises proxy to redirect path
and its children to specified targetFS
. attributes
are currently reserved and is of no use.
Future work
- Support
readonly
attribute in mounts - More kind of operations through proxy
License
Copyright 2016 Bytedance Inc.
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.