Notes and Constraints

This section describes the constraints on using CloudTable.

Constraints on Using HBase

Currently, CloudTable does not have a security authentication mechanism. If HBase with an authentication mechanism is required, you are advised to use the HBase component in MRS.
Do not enable the MOB feature for HBase. Using this feature may lead to table data read failure and JVM crash.
For existing HBase tables, run the following command in the command line hbase shell to check whether the table description contains the keyword MOB. If it is contained, contact O&M engineers to set the table non-MOB.

desc 'Table name'

For example, if the value of IS_MOB is true in the following command output, the HBase MOB feature is enabled:
```
hbase:009:0> desc 't3'
t3
COLUMN FAMILIES DESCRIPTION
{NAME => 'd', MOB_THRESHOLD => '102400', VERSIONS => '1', KEEP_DELETED_CELLS => 'FALSE', DATA_BLOCK_ENCODING => 'NONE', TTL => 'FOREVER', MIN_VERSIONS => '0', REPLICATION_SCOPE => '0', BLOO
MFILTER => 'ROW', IN_MEMORY => 'false', IS_MOB => 'true', COMPRESSION => 'NONE', BLOCKCACHE => 'true', BLOCKSIZE => '65536'}
```

Constraints on Using Doris

When creating a table in Doris, it is advisable to avoid using a single backup to ensure data reliability. Cloud services disclaim liability for any data loss or tablet damage arising from a single backup.
Restrictions on Doris specifications: 8 vCPUs and 32 GB memory or higher are recommended for production. 4 vCPUs and 16 GB memory or 8 vCPUs and 16 GB memory can be used only for test. The cloud service does not assume any responsibility for production problems caused by small specifications.
The Doris cluster is considered as abnormal if more than half of its FE nodes are faulty or its faulty BE nodes are not less than 3.
The default query timeout duration is 300 seconds. If a query is not completed within 300 seconds, Doris will cancel the query. The timeout duration can be customized by parameter configuration. You can also implement a blocking mode similar to wait timeout.
```
mysql> SHOW VARIABLES LIKE "%query_timeout%";
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| QUERY_TIMEOUT | 300   |
+---------------+-------+
1 row in set (0.00 sec)
```
Run the following commands to change the timeout duration. (The following is an example for changing the timeout duration to 1 minute.)
```
mysql> SET query_timeout = 60;
Query OK, 0 rows affected (0.00 sec)
```
The current timeout check interval is 5 seconds. Therefore, timeout duration less than 5 seconds is not recommended.

The preceding modification example is of the session level. You can run the SET command to implement global modification.

Constraints on Using ClickHouse

When creating a table in ClickHouse, it is advised to employ the Replicated series engines to enhance data reliability. Again, cloud services disclaim liability for any data loss or damage arising from a single backup.
ClickHouse does not support the JSON and Object('json') data types.
ClickHouse's open source lab features are unstable and are not recommended for production services.

Constraints on Passwords

**Table 1** Password constraints
Item	Description
Password	The password must meet the following requirements: The password must contain 8 to 16 characters (ClickHouse) or 8 to 12 characters (Doris). The password must contain at least four types of the following characters: uppercase letters, lowercase letters, digits, and special characters ($@!%*?&) The password cannot be the same as the username or the username spelled backwards. CloudTable does not save the initial password you set for logging in to a node. Please set and keep the password. To prevent malicious attacks, you are advised to set a password with a high complexity.