We introduced how to create a PaddlePaddle Job with a single node on Kuberentes in the
previous document.
In this article, we will introduce how to craete a PaddlePaddle job with multiple nodes
In this article, we will introduce how to create a PaddlePaddle job with multiple nodes
on Kubernetes cluster.
## Overall Architecture
Before creating a training job, the users need to deploy the Python scripts and
training data which have already been sliced on the precast path in the distributed file
system(We can use the different type of Kuberentes Volumes to mount different distributed
file system). Before start training, The program would copy the training data into the
Before creating a training job, the users need to slice the training data and deploy
the Python scripts along with it into the distributed file system
(We can use the different type of Kuberentes Volumes to mount different distributed
file systems). Before training starts, The program will copy the training data into the
Container and also save the models at the same path during training. The global architecture
is as follows:
The above figure describes a distributed training architecture which contains 3 nodes, each
Pod would mount a folder of the distributed file system to save training data and models
by Kubernetes Volume. Kubernetes created 3 Pod for this training phase and scheduled these on
3 nodes, each Pod has a PaddlePaddle container. After the containers have been created,
PaddlePaddle would start up the communication between PServer and Trainer and read training
Pod mounts a folder of the distributed file system to save training data and models
by Kubernetes Volume. Kubernetes created 3 Pods for this training phase and scheduled these on
3 nodes, each Pod has a PaddlePaddle container. After the containers car created,
PaddlePaddle starts up the communication between PServer and Trainer and read training
data for this training job.
As the description above, we can start up a PaddlePaddle distributed training job on a ready
Kubernetes cluster as the following steps:
As the description above, we can start up a PaddlePaddle distributed training job on a
Kubernetes ready cluster with the following steps:
1.[Build PaddlePaddle Docker Image](#Build a Docker Image)
1.[Split training data and upload to the distributed file system](#Upload Training Data)
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@@ -35,16 +35,13 @@ We will introduce these steps as follows:
### Build a Docker Image
PaddlePaddle Docker Image needs to support the runtime environment of `Paddle PServer` and
`Paddle Trainer` process and this Docker Image has the two import features:
Training docker image needs to package the paddle pserver and paddle trainer runtimes, as well as two more processes before we can kick off the training:
- Copy the training data into the container.
- Generate the start arguments of `Paddle PServer` and `Paddle Training` process.
- Copying the training data into container.
- Generating the initialization arguments for `Paddle PServer` and `Paddle Training` processes.
Because of the official Docker Image `paddlepaddle/paddle:latest` has already included the
PaddlePaddle executable file, but above features so that we can use the official Docker Image as
a base Image and add some additional scripts to finish the work of building a new image.
You can reference [Dockerfile](https://github.com/PaddlePaddle/Paddle/blob/develop/doc/howto/usage/cluster/src/k8s_train/Dockerfile).
Since the paddlepaddle official docker image already has the runtimes we need, we'll take it as the base image and pack some additional scripts for the processes mentioned above to build our training image. for more detail, please find from the following link:
@@ -58,17 +55,17 @@ And then upload the new Docker Image to a Docker hub:
docker push [YOUR_REPO]/paddle:mypaddle
```
**[NOTE]**, in the above command arguments, `[YOUR_REPO]` representative your Docker repository,
you need to use your repository instead of it. We will use `[YOUR_REPO]/paddle:mypaddle` to
**[NOTE]**, in the above command arguments, `[YOUR_REPO]` represents your Docker repository,
you need to use your repository instead of it. We will replace it with your respository name to
represent the Docker Image which built in this step.
### Prepare Training Data
We can download and split the training job by creating a Kubernetes Job, or custom your image
by editing [k8s_train](./src/k8s_train/README.md).
by editing [k8s_train](./src/k8s_train/).
Before creating a Job, we need to bind a [persistenVolumeClaim](https://kubernetes.io/docs/user-guide/persistent-volumes) by the different type of
the different distributed file system, the generated dataset would be saved on this volume.
the different file system, the generated dataset would be saved on this volume.
```yaml
apiVersion:batch/v1
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@@ -100,7 +97,13 @@ spec:
restartPolicy:Never
```
If success, you can see some information like this:
Create the Job with the following command:
```bash
> kubectl create -f xxx.yaml
```
If created successfully, you can see some information like this:
```base
[root@paddle-kubernetes-node0 nfsdir]$ tree -d
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@@ -117,13 +120,13 @@ If success, you can see some information like this:
```
The `paddle-cluster-job` above is the job name for this training job; we need 3
PaddlePaddle training node and save the split training data on `paddle-cluster-job` path,
the folder `0`, `1` and `2` representative the `training_id` on each node, `quick_start` folder is used to store training data, `output` folder is used to store the models and logs.
PaddlePaddle training nodes and save the split training data in `paddle-cluster-job` path,
the folder `0`, `1` and `2` represents the `training_id` on each node, `quick_start` folder is used to store training data, `output` folder is used to store the models and logs.
### Create a Job
Kubernetes allow users to create an object with YAML files, and we can use a command-line tool
Kubernetes allow users to create objects with YAML files, and we can use a command-line tool
to create it.
The Job YAML file describes that which Docker Image would be used in this training job, how much nodes would be created, what's the startup arguments of `Paddle PServer/Trainer` process and what's the type of Volumes. You can find the details of the YAML filed in
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@@ -177,8 +180,8 @@ spec:
In the above YAML file:
-`metadata.name`, The job name.
-`parallelism`, The Kubernetes Job would create `parallelism` Pods at the same time.
-`completions`, The Job would become the success status only the number of successful Pod(the exit code is 0)
-`parallelism`, Whether the Kubernetes Job would create `parallelism` Pods at the same time.
-`completions`, The Job would become the success status only when the number of successful Pod(the exit code is 0)
is equal to `completions`.
-`volumeMounts`, the name field `jobpath` is a key, the `mountPath` field represents
the path in the container, and we can define the `jobpath` in `volumes` filed, use `hostPath`
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@@ -209,13 +212,15 @@ kubectl create -f job.yaml
```
Upon successful creation, Kubernetes would create 3 Pods as PaddlePaddle training node,
, pull the Docker image and begin to train.
pull the Docker image and begin to train.
### Checkout the Output
At the process of training, we can check the logs and the output models, such as we store
the output on `output` folder. **NOTE**, `node_0`, `node_1` and `node_2` represent the
At the process of training, we can check the logs and the output models which is stored in
the `output` folder.
**NOTE**, `node_0`, `node_1` and `node_2` represent the
`trainer_id` of the PaddlePaddle training job rather than the node id of Kubernetes.
@@ -314,11 +319,12 @@ And then query the status of all the other Pods of this Job by the function `get
idMap=getIdMap(podlist)
```
**NOTE**: `getPodList()` would fetch all the pod in the current namespace, if some Pods are running, may cause some error. We will use [statfulesets](https://kubernetes.io/docs/concepts/abstractions/controllers/statefulsets) instead of
**NOTE**: `getPodList()` would prefetch all the Pods in the current namespace, if some
Pods are alreay running, it may cause some error. We will use [statfulesets](https://kubernetes.io/docs/concepts/abstractions/controllers/statefulsets) instead of
Kubernetes Pod or Replicaset in the future.
For the implement of `getIdMap(podlist)`, this function would fetch each IP address of
`podlist` and then sort them to generate `trainer_id`.
The function `getIdMap(podlist)` fetches IPs addresses of `podlist` and then sort them
to generate `trainer_id`.
```python
defgetIdMap(podlist):
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@@ -340,9 +346,10 @@ so that we can start up them by `startPaddle(idMap, train_args_dict)`.
### Create Job
The main goal of `startPaddle` is generating the arguments of `Paddle PServer` and `Paddle Trainer` processes. Such as `Paddle Trainer`, we parse the environment variable and then get
`PADDLE_NIC`, `PADDLE_PORT`, `PADDLE_PORTS_NUM` and etc..., finally find `trainerId` from
`idMap` according to its IP address.
The main goal of `startPaddle` is generating the arguments of `Paddle PServer` and
`Paddle Trainer` processes. Take `Paddle Trainer` as an example, we parse the
environment variable and then get `PADDLE_NIC`, `PADDLE_PORT`, `PADDLE_PORTS_NUM` and etc...,
finally find `trainerId` from `idMap` according to its IP address.
