Ansible Deployment

Use TiDB-Ansible to deploy a TiKV cluster on multiple nodes.

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This guide describes how to install and deploy TiKV using Ansible. Ansible is an IT automation tool that can configure systems, deploy software, and orchestrate more advanced IT tasks such as continuous deployments or zero downtime rolling updates.

TiDB-Ansible is a TiDB cluster deployment tool developed by PingCAP, based on Ansible playbook. TiDB-Ansible enables you to quickly deploy a new TiKV cluster which includes PD, TiKV, and the cluster monitoring modules.

Prepare

Before you start, make sure you have:

  1. Several target machines that meet the following requirements:

    • 4 or more machines
      • A standard TiKV cluster contains 6 machines. You can use 4 machines for testing.
    • CentOS 7.3 (64 bit) or later with Python 2.7 installed, x86_64 architecture (AMD64)
    • Network between machines

    Note: When you deploy TiKV using Ansible, use SSD disks for the data directory of TiKV and PD nodes. Otherwise, the system will not perform well. For more details, see Software and Hardware Requirements.

  2. A Control Machine that meets the following requirements:

    Note: The Control Machine can be one of the target machines.

    • CentOS 7.3 (64 bit) or later with Python 2.7 installed
    • Access to the Internet
    • Git installed

Step 1: Install system dependencies on the Control Machine

Log in to the Control Machine using the root user account, and run the corresponding command according to your operating system.

If you use a Control Machine installed with CentOS 7, run the following command:

$ yum -y install epel-release git curl sshpass
$ yum -y install python-pip

If you use a Control Machine installed with Ubuntu, run the following command:

$ apt-get -y install git curl sshpass python-pip

Step 2: Create the tidb user on the Control Machine and generate the SSH key

Make sure you have logged in to the Control Machine using the root user account, and then run the following command.

Create the tidb user.

$ useradd -m -d /home/tidb tidb

Set a password for the tidb user account:

$ passwd tidb

Configure sudo without password for the tidb user account by adding tidb ALL=(ALL) NOPASSWD: ALL to the end of the sudo file:

$ visudo
tidb ALL=(ALL) NOPASSWD: ALL

Generate the SSH key:

Execute the su command to switch the user from root to tidb. Create the SSH key for the tidb user account and hit the Enter key when Enter passphrase is prompted. After successful execution, the SSH private key file is /home/tidb/.ssh/id_rsa, and the SSH public key file is /home/tidb/.ssh/id_rsa.pub.

$ su - tidb
$ ssh-keygen -t rsa

Step 3: Download TiDB-Ansible to the Control Machine

  1. Log in to the Control Machine using the tidb user account and enter the /home/tidb directory.

  2. Download the corresponding TiDB-Ansible version from the TiDB-Ansible project. The default folder name is tidb-ansible.

    • Download the 3.0 GA version:

      $ git clone -b release-3.0 https://github.com/pingcap/tidb-ansible.git
    • Download the master version:

      $ git clone https://github.com/pingcap/tidb-ansible.git

    Note: It is required to download tidb-ansible to the /home/tidb directory using the tidb user account. If you download it to the /root directory, a privilege issue occurs.

    If you have questions regarding which version to use, email to info@pingcap.com for more information or file an issue.

Step 4: Install Ansible and its dependencies on the Control Machine

Make sure you have logged in to the Control Machine using the tidb user account.

It is required to use pip to install Ansible and its dependencies, otherwise a compatibility issue occurs. Currently, the tidb-ansible release-3.0 branch is compatible with Ansible 2.4 and Ansible 2.5.

Install Ansible and the dependencies on the Control Machine:

$ cd /home/tidb/tidb-ansible
$ sudo pip install -r ./requirements.txt

Ansible and the related dependencies are in the tidb-ansible/requirements.txt file.

View the version of Ansible:

$ ansible --version
ansible 2.5.0

Step 5: Configure the SSH mutual trust and sudo rules on the Control Machine

Make sure you have logged in to the Control Machine using the tidb user account.

Add the IPs of your target machines to the [servers] section of the hosts.ini file.

$ cd /home/tidb/tidb-ansible
$ vi hosts.ini
[servers]
172.16.10.1
172.16.10.2
172.16.10.3
172.16.10.4
172.16.10.5
172.16.10.6

[all:vars]
username = tidb
ntp_server = pool.ntp.org

Run the following command and input the root user account password of your target machines.

$ ansible-playbook -i hosts.ini create_users.yml -u root -k

This step creates the tidb user account on the target machines, and configures the sudo rules and the SSH mutual trust between the Control Machine and the target machines.

Note: To configure the SSH mutual trust and sudo without password manually, see How to manually configure the SSH mutual trust and sudo without password.

Step 6: Install the NTP service on the target machines

Note: If the time and time zone of all your target machines are same, the NTP service is on and is normally synchronizing time, you can ignore this step. See How to check whether the NTP service is normal.

Make sure you have logged in to the Control Machine using the tidb user account, run the following command:

$ cd /home/tidb/tidb-ansible
$ ansible-playbook -i hosts.ini deploy_ntp.yml -u tidb -b

The NTP service is installed and started using the software repository that comes with the system on the target machines. The default NTP server list in the installation package is used. The related server parameter is in the /etc/ntp.conf configuration file.

To make the NTP service start synchronizing as soon as possible, the system executes the ntpdate command to set the local date and time by polling ntp_server in the hosts.ini file. The default server is pool.ntp.org, and you can also replace it with your NTP server.

Step 7: Configure the CPUfreq governor mode on the target machine

For details about CPUfreq, see the CPUfreq Governor documentation.

Set the CPUfreq governor mode to performance to make full use of CPU performance.

Check the governor modes supported by the system

You can run the cpupower frequency-info --governors command to check the governor modes which the system supports:

$ cpupower frequency-info --governors
analyzing CPU 0:
  available cpufreq governors: performance powersave

Taking the above code for example, the system supports the performance and powersave modes.

Note: As the following shows, if it returns “Not Available”, it means that the current system does not support CPUfreq configuration and you can skip this step.

$ cpupower frequency-info --governors
analyzing CPU 0:
   available cpufreq governors: Not Available

Check the current governor mode

You can run the cpupower frequency-info --policy command to check the current CPUfreq governor mode:

$ cpupower frequency-info --policy
analyzing CPU 0:
  current policy: frequency should be within 1.20 GHz and 3.20 GHz.
                  The governor "powersave" may decide which speed to use
                  within this range.

As the above code shows, the current mode is powersave in this example.

Change the governor mode

  • You can run the following command to change the current mode to performance:

    $ cpupower frequency-set --governor performance
  • You can also run the following command to set the mode on the target machine in batches:

    $ ansible -i hosts.ini all -m shell -a "cpupower frequency-set --governor performance" -u tidb -b

Step 8: Mount the data disk ext4 filesystem with options on the target machines

Log in to the Control Machine using the root user account.

Format your data disks to the ext4 filesystem and mount the filesystem with the nodelalloc and noatime options. It is required to mount the nodelalloc option, or else the Ansible deployment cannot pass the test. The noatime option is optional.

Note: If your data disks have been formatted to ext4 and have mounted the options, you can uninstall it by running the $ umount /dev/nvme0n1 command, follow the steps starting from editing the /etc/fstab file, and remount the filesystem with options.

Take the /dev/nvme0n1 data disk as an example:

View the data disk.

$ fdisk -l
Disk /dev/nvme0n1: 1000 GB

Create the partition table.

$ parted -s -a optimal /dev/nvme0n1 mklabel gpt -- mkpart primary ext4 1 -1

Format the data disk to the ext4 filesystem.

$ mkfs.ext4 /dev/nvme0n1

View the partition UUID of the data disk. (In this example, the UUID of nvme0n1 is c51eb23b-195c-4061-92a9-3fad812cc12f.)

 $ lsblk -f
 NAME    FSTYPE LABEL UUID                                 MOUNTPOINT
 sda
 ├─sda1  ext4         237b634b-a565-477b-8371-6dff0c41f5ab /boot
 ├─sda2  swap         f414c5c0-f823-4bb1-8fdf-e531173a72ed
 └─sda3  ext4         547909c1-398d-4696-94c6-03e43e317b60 /
 sr0
 nvme0n1 ext4         c51eb23b-195c-4061-92a9-3fad812cc12f

Edit the /etc/fstab file and add the mount options.

$ vi /etc/fstab
UUID=c51eb23b-195c-4061-92a9-3fad812cc12f /data1 ext4 defaults,nodelalloc,noatime 0 2

Mount the data disk.

$ mkdir /data1
$ mount -a

Check using the following command.

$ mount -t ext4
/dev/nvme0n1 on /data1 type ext4 (rw,noatime,nodelalloc,data=ordered)

If the filesystem is ext4 and nodelalloc is included in the mount options, you have successfully mount the data disk ext4 filesystem with options on the target machines.

Step 9: Edit the inventory.ini file to orchestrate the TiKV cluster

Edit the tidb-ansible/inventory.ini file to orchestrate the TiKV cluster. The standard TiKV cluster contains 6 machines: 3 PD nodes and 3 TiKV nodes.

  • Deploy at least 3 instances for TiKV.
  • Do not deploy TiKV together with PD on the same machine.
  • Use the first PD machine as the monitoring machine.

Note:

  • Leave [tidb_servers] in the inventory.ini file empty, because this deployment is for the TiKV cluster, not the TiDB cluster.
  • It is required to use the internal IP address to deploy. If the SSH port of the target machines is not the default 22 port, you need to add the ansible_port variable. For example, TiDB1 ansible_host=172.16.10.1 ansible_port=5555.

You can choose one of the following two types of cluster topology according to your scenario:

Option 1: Use the cluster topology of a single TiKV instance on each TiKV node

NameHost IPServices
node1172.16.10.1PD1
node2172.16.10.2PD2
node3172.16.10.3PD3
node4172.16.10.4TiKV1
node5172.16.10.5TiKV2
node6172.16.10.6TiKV3

Edit the inventory.ini file as follows:

[tidb_servers]

[pd_servers]
172.16.10.1
172.16.10.2
172.16.10.3

[tikv_servers]
172.16.10.4
172.16.10.5
172.16.10.6

[monitoring_servers]
172.16.10.1

[grafana_servers]
172.16.10.1

[monitored_servers]
172.16.10.1
172.16.10.2
172.16.10.3
172.16.10.4
172.16.10.5
172.16.10.6

Option 2: Use the cluster topology of multiple TiKV instances on each TiKV node

Take two TiKV instances on each TiKV node as an example:

NameHost IPServices
node1172.16.10.1PD1
node2172.16.10.2PD2
node3172.16.10.3PD3
node4172.16.10.4TiKV1-1, TiKV1-2
node5172.16.10.5TiKV2-1, TiKV2-2
node6172.16.10.6TiKV3-1, TiKV3-2
[tidb_servers]

[pd_servers]
172.16.10.1
172.16.10.2
172.16.10.3

[tikv_servers]
TiKV1-1 ansible_host=172.16.10.4 deploy_dir=/data1/deploy tikv_port=20171 labels="host=tikv1"
TiKV1-2 ansible_host=172.16.10.4 deploy_dir=/data2/deploy tikv_port=20172 labels="host=tikv1"
TiKV2-1 ansible_host=172.16.10.5 deploy_dir=/data1/deploy tikv_port=20171 labels="host=tikv2"
TiKV2-2 ansible_host=172.16.10.5 deploy_dir=/data2/deploy tikv_port=20172 labels="host=tikv2"
TiKV3-1 ansible_host=172.16.10.6 deploy_dir=/data1/deploy tikv_port=20171 labels="host=tikv3"
TiKV3-2 ansible_host=172.16.10.6 deploy_dir=/data2/deploy tikv_port=20172 labels="host=tikv3"

[monitoring_servers]
172.16.10.1

[grafana_servers]
172.16.10.1

[monitored_servers]
172.16.10.1
172.16.10.2
172.16.10.3
172.16.10.4
172.16.10.5
172.16.10.6

...

[pd_servers:vars]
location_labels = ["host"]

Edit the parameters in the service configuration file:

  1. For the cluster topology of multiple TiKV instances on each TiKV node, you need to edit the block-cache-size parameter in tidb-ansible/conf/tikv.yml:

    • rocksdb defaultcf block-cache-size(GB): MEM * 80% / number of TiKV instances * 30%
    • rocksdb writecf block-cache-size(GB): MEM * 80% / number of TiKV instances * 45%
    • rocksdb lockcf block-cache-size(GB): MEM * 80% / number of TiKV instances * 2.5% (128 MB at a minimum)
    • raftdb defaultcf block-cache-size(GB): MEM * 80% / number of TiKV instances * 2.5% (128 MB at a minimum)
  2. For the cluster topology of multiple TiKV instances on each TiKV node, you need to edit the high-concurrency, normal-concurrency and low-concurrency parameters in the tidb-ansible/conf/tikv.yml file:

    readpool:
    coprocessor:
        # Notice: if CPU_NUM > 8, default thread pool size for coprocessors
        # will be set to CPU_NUM * 0.8.
        # high-concurrency: 8
        # normal-concurrency: 8
        # low-concurrency: 8
    

    Recommended configuration: number of TiKV instances * parameter value = CPU_Vcores * 0.8.

  3. If multiple TiKV instances are deployed on a same physical disk, edit the capacity parameter in conf/tikv.yml:

    • capacity: total disk capacity / number of TiKV instances (the unit is GB)

Step 10: Edit variables in the inventory.ini file

Edit the deploy_dir variable to configure the deployment directory.

The global variable is set to /home/tidb/deploy by default, and it applies to all services. If the data disk is mounted on the /data1 directory, you can set it to /data1/deploy. For example:

## Global variables
[all:vars]
deploy_dir = /data1/deploy

Note: To separately set the deployment directory for a service, you can configure the host variable while configuring the service host list in the inventory.ini file. It is required to add the first column alias, to avoid confusion in scenarios of mixed services deployment.

TiKV1-1 ansible_host=172.16.10.4 deploy_dir=/data1/deploy

Set the deploy_without_tidb variable to True.

deploy_without_tidb = True

Step 11: Deploy the TiKV cluster

When ansible-playbook executes the Playbook, the default concurrency number is 5. If many target machines are deployed, you can add the -f parameter to specify the concurrency, such as ansible-playbook deploy.yml -f 10.

The following example uses tidb as the user who runs the service.

Check the tidb-ansible/inventory.ini file to make sure ansible_user = tidb.

## Connection
# ssh via normal user
ansible_user = tidb

Make sure the SSH mutual trust and sudo without password are successfully configured.

  • Run the following command and if all servers return tidb, then the SSH mutual trust is successfully configured:

    ansible -i inventory.ini all -m shell -a 'whoami'
  • Run the following command and if all servers return root, then sudo without password of the tidb user is successfully configured:

    ansible -i inventory.ini all -m shell -a 'whoami' -b

Download the TiKV binary to the Control Machine.

ansible-playbook local_prepare.yml

Initialize the system environment and modify the kernel parameters.

ansible-playbook bootstrap.yml

Deploy the TiKV cluster.

ansible-playbook deploy.yml

Start the TiKV cluster.

ansible-playbook start.yml

You can check whether the TiKV cluster has been successfully deployed using the following command:

curl 172.16.10.1:2379/pd/api/v1/stores

If you want to try the Go client, see Try Two Types of APIs.

Stop the TiKV cluster

If you want to stop the TiKV cluster, run the following command:

ansible-playbook stop.yml

Destroy the TiKV cluster

Warning: Before you clean the cluster data or destroy the TiKV cluster, make sure you do not need it any more.
  • If you do not need the data any more, you can clean up the data for test using the following command:

    ansible-playbook unsafe_cleanup_data.yml
  • If you do not need the TiKV cluster any more, you can destroy it using the following command:

    ansible-playbook unsafe_cleanup.yml

Note: If the deployment directory is a mount point, an error might be reported, but the implementation result remains unaffected. You can just ignore the error.