Migrate Data from Amazon Aurora to TiDB

This document describes how to migrate data from Amazon Aurora to TiDB. The migration process uses DB snapshot, which saves a lot of space and time.

The whole migration has two processes:

• Import full data to TiDB using TiDB Lightning
• Replicate incremental data to TiDB using DM (optional)

Prerequisites

• Install Dumpling and TiDB Lightning
• Get the target database privileges required for TiDB Lightning.

Import full data to TiDB

Step 1. Export an Aurora snapshot to Amazon S3

1. In Aurora, query the current binlog position by running the following command:

   mysql> SHOW MASTER STATUS;
   

   The output is similar to the following. Record the binlog name and position for later use.

   +------------------+----------+--------------+------------------+-------------------+
   | File             | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
   +------------------+----------+--------------+------------------+-------------------+
   | mysql-bin.000002 |    52806 |              |                  |                   |
   +------------------+----------+--------------+------------------+-------------------+
   1 row in set (0.012 sec)
   

2. Export the Aurora snapshot. For detailed steps, refer to Exporting DB snapshot data to Amazon S3.

After you obtain the binlog position, export the snapshot within 5 minutes. Otherwise, the recorded binlog position might be outdated and thus cause data conflict during the incremental replication.

After the two steps above, make sure you have the following information ready:

• The Aurora binlog name and position at the time of the snapshot creation.
• The S3 path where the snapshot is stored, and the SecretKey and AccessKey with access to the S3 path.

Step 2. Export schema

Because the snapshot file from Aurora does not contain the DDL statements, you need to export the schema using Dumpling and create the schema in the target database using TiDB Lightning. If you want to manually create the schema, you can skip this step.

Export the schema using Dumpling by running the following command. The command includes the --filter parameter to only export the desired table schema:

tiup dumpling --host ${host} --port 3306 --user root --password ${password} --filter 'my_db1.table[12]' --no-data --output 's3://my-bucket/schema-backup' --filter "mydb.*"

The parameters used in the command above are as follows. For more parameters, refer to Dumpling overview.

Step 3. Create the TiDB Lightning configuration file

Create the tidb-lightning.toml configuration file as follows:

vim tidb-lightning.toml

[tidb]

# The target TiDB cluster information.
host = ${host}                # e.g.: 172.16.32.1
port = ${port}                # e.g.: 4000
user = "${user_name}          # e.g.: "root"
password = "${password}"      # e.g.: "rootroot"
status-port = ${status-port}  # Obtains the table schema information from TiDB status port, e.g.: 10080
pd-addr = "${ip}:${port}"     # The cluster PD address, e.g.: 172.16.31.3:2379. TiDB Lightning obtains some information from PD. When backend = "local", you must specify status-port and pd-addr correctly. Otherwise, the import will be abnormal.

[tikv-importer]
# "local": Default backend. The local backend is recommended to import large volumes of data (1 TiB or more). During the import, the target TiDB cluster cannot provide any service.
# "tidb": The "tidb" backend is recommended to import data less than 1 TiB. During the import, the target TiDB cluster can provide service normally.
backend = "local"

# Set the temporary storage directory for the sorted Key-Value files. The directory must be empty, and the storage space must be greater than the size of the dataset to be imported. For better import performance, it is recommended to use a directory different from `data-source-dir` and use flash storage, which can use I/O exclusively.
sorted-kv-dir = "/mnt/ssd/sorted-kv-dir"

[mydumper]
# The path that stores the snapshot file.
data-source-dir = "${s3_path}"  # e.g.: s3://my-bucket/sql-backup

[[mydumper.files]]
# The expression that parses the parquet file.
pattern = '(?i)^(?:[^/]*/)*([a-z0-9_]+)\.([a-z0-9_]+)/(?:[^/]*/)*(?:[a-z0-9\-_.]+\.(parquet))$'
schema = '$1'
table = '$2'
type = '$3'

If you need to enable TLS in the TiDB cluster, refer to TiDB Lightning Configuration.

Step 4. Import full data to TiDB

1. Create the tables in the target database using TiDB Lightning:

   tiup tidb-lightning -config tidb-lightning.toml -d 's3://my-bucket/schema-backup'
   

2. Start the import by running tidb-lightning. If you launch the program directly in the command line, the process might exit unexpectedly after receiving a SIGHUP signal. In this case, it is recommended to run the program using a nohup or screen tool. For example:

   Pass the SecretKey and AccessKey that have access to the S3 storage path as environment variables to the Dumpling node. You can also read the credentials from ~/.aws/credentials.

   export AWS_ACCESS_KEY_ID=${access_key}
   export AWS_SECRET_ACCESS_KEY=${secret_key}
   nohup tiup tidb-lightning -config tidb-lightning.toml > nohup.out 2>&1 &
   

3. After the import starts, you can check the progress of the import by either of the following methods:

   • grep the keyword progress in the log. The progress is updated every 5 minutes by default.
   • Check progress in the monitoring dashboard.
   • Check progress in the TiDB Lightning web interface.

4. After TiDB Lightning completes the import, it exits automatically. Check whether tidb-lightning.log contains the whole procedure completed in the last lines. If yes, the import is successful. If no, the import encounters an error. Address the error as instructed in the error message.

If you encounter any problem during the import, refer to TiDB Lightning FAQ for troubleshooting.

Replicate incremental data to TiDB (optional)

Prerequisites

• Install DM.
• Get the source database and target database privileges required for DM.

Step 1: Create the data source

1. Create the source1.yaml file as follows:

   # Must be unique.
   source-id: "mysql-01"
   # Configures whether DM-worker uses the global transaction identifier (GTID) to pull binlogs. To enable this mode, the upstream MySQL must also enable GTID. If the upstream MySQL service is configured to switch master between different nodes automatically, GTID mode is required.
   enable-gtid: false
   
   from:
     host: "${host}"         # e.g.: 172.16.10.81
     user: "root"
     password: "${password}" # Supported but not recommended to use plaintext password. It is recommended to use `dmctl encrypt` to encrypt the plaintext password before using it.
     port: 3306
   

2. Load the data source configuration to the DM cluster using tiup dmctl by running the following command:

   tiup dmctl --master-addr ${advertise-addr} operate-source create source1.yaml
   

   The parameters used in the command above are described as follows:

   Parameter	Description
   --master-addr	The {advertise-addr} of any DM-master in the cluster where dmctl is to be connected, e.g.: 172.16.10.71:8261
   operate-source create	Loads the data source to the DM cluster.

Step 2: Create the migration task

Create the task1.yaml file as follows:

# Task name. Multiple tasks that are running at the same time must each have a unique name.
name: "test"
# Task mode. Options are:
# - full: only performs full data migration.
# - incremental: only performs binlog real-time replication.
# - all: full data migration + binlog real-time replication.
task-mode: "incremental"
# The configuration of the target TiDB database.
target-database:
  host: "${host}"                   # e.g.: 172.16.10.83
  port: 4000
  user: "root"
  password: "${password}"           # Supported but not recommended to use a plaintext password. It is recommended to use `dmctl encrypt` to encrypt the plaintext password before using it.

# Global configuration for block and allow lists. Each instance can reference the configuration by name.
block-allow-list:                     # If the DM version is earlier than v2.0.0-beta.2, use black-white-list.
  listA:                              # Name.
    do-tables:                        # Allow list for the upstream tables to be migrated.
    - db-name: "test_db"              # Name of databases to be migrated.
      tbl-name: "test_table"          # Name of tables to be migrated.

# Configures the data source.
mysql-instances:
  - source-id: "mysql-01"               # Data source ID, i.e., source-id in source1.yaml
    block-allow-list: "listA"           # References the block-allow-list configuration above.
#       syncer-config-name: "global"    # References the syncers incremental data configuration.
    meta:                               # When task-mode is "incremental" and the downstream database does not have a checkpoint, DM uses the binlog position as the starting point. If the downstream database has a checkpoint, DM uses the checkpoint as the starting point.
      binlog-name: "mysql-bin.000004"   # The binlog position recorded in "Step 1. Export an Aurora snapshot to Amazon S3". When the upstream database has source-replica switching, GTID mode is required.
      binlog-pos: 109227
      # binlog-gtid: "09bec856-ba95-11ea-850a-58f2b4af5188:1-9"

   # (Optional) If you need to incrementally replicate data that has already been migrated in the full data migration, you need to enable the safe mode to avoid the incremental data replication error.
   # This scenario is common in the following case: the full migration data does not belong to the data source's consistency snapshot, and after that, DM starts to replicate incremental data from a position earlier than the full migration.
   # syncers:            # The running configurations of the sync processing unit.
   #   global:            # Configuration name.
   #     safe-mode: true  # If this field is set to true, DM changes INSERT of the data source to REPLACE for the target database, and changes UPDATE of the data source to DELETE and REPLACE for the target database. This is to ensure that when the table schema contains a primary key or unique index, DML statements can be imported repeatedly. In the first minute of starting or resuming an incremental replication task, DM automatically enables the safe mode.

The YAML file above is the minimum configuration required for the migration task. For more configuration items, refer to DM Advanced Task Configuration File.

Step 3. Run the migration task

Before you start the migration task, to reduce the probability of errors, it is recommended to confirm that the configuration meets the requirements of DM by running the check-task command:

tiup dmctl --master-addr ${advertise-addr} check-task task.yaml

After that, start the migration task by running tiup dmctl:

tiup dmctl --master-addr ${advertise-addr} start-task task.yaml

The parameters used in the command above are described as follows:

If the task fails to start, check the prompt message and fix the configuration. After that, you can re-run the command above to start the task.

If you encounter any problem, refer to DM error handling and DM FAQ.

Step 4. Check the migration task status

To learn whether the DM cluster has an ongoing migration task and the task status, run the query-status command using tiup dmctl:

tiup dmctl --master-addr ${advertise-addr} query-status ${task-name}

For a detailed interpretation of the results, refer to Query Status.

Step 5. Monitor the task and view logs

To view the history status of the migration task and other internal metrics, take the following steps.

If you have deployed Prometheus, Alertmanager, and Grafana when you deployed DM using TiUP, you can access Grafana using the IP address and port specified during the deployment. You can then select DM dashboard to view DM-related monitoring metrics.

When DM is running, DM-worker, DM-master, and dmctl print the related information in logs. The log directories of these components are as follows:

• DM-master: specified by the DM-master process parameter --log-file. If you deploy DM using TiUP, the log directory is /dm-deploy/dm-master-8261/log/ by default.
• DM-worker: specified by the DM-worker process parameter --log-file. If you deploy DM using TiUP, the log directory is /dm-deploy/dm-worker-8262/log/ by default.

What's next

• Pause the migration task.
• Resume the migration task.
• Stop the migration task.
• Export and import the cluster data source and task configuration.
• Handle failed DDL statements.