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A Tour of config.yaml

Tim Sehn
REFERENCE
23 min read

Hot on the heels of my overview of Dolt configuration, I'm going to do a deep dive on config.yaml, the configuration file for a Dolt SQL Server. As I was writing the configuration overview, I realized our documentation on our main configuration file was somewhat lacking. This blog article attempts to rectify that situation.

Overview

Here is a complete config.yaml file populated with all the default values for every key. We'll dive into each key before the "Advanced configuration" comment individually. I'll have a follow up article or articles on all the configuration in the Advanced Configuration section.

log_level: info

behavior:
  read_only: false
  autocommit: true
  disable_client_multi_statements: false
  dolt_transaction_commit: false
  event_scheduler: "ON"

user:
  name: ""
  password: ""

listener:
  host: localhost
  port: 3306
  max_connections: 100
  read_timeout_millis: 28800000
  write_timeout_millis: 28800000
  tls_key: null
  tls_cert: null
  require_secure_transport: null
  allow_cleartext_passwords: null

max_logged_query_len: 0

data_dir: .
cfg_dir: .doltcfg
privilege_file: .doltcfg/privileges.db
branch_control_file: .doltcfg/branch_control.db

# Advanced Configuration
metrics:
  labels: {}
  host: null
  port: -1

remotesapi:
  port: null
  read_only: null

system_variables: {}

user_session_vars: []

jwks: []

# Cluster configuration has required defaults.
# cluster: {}

For the examples in this article, I use a database named config_blog with a single table defined by:

create table t (
  id int primary key,
  words varchar(100)
)

log_level

This configuration value is used to increase or decease the log level of your Dolt SQL server. Logs by default are printed to STDERR and STDOUT.

From the dolt sql-server help documentation:

Level of logging provided. Options are: trace, debug, info, warning, error, and fatal.

Default: info

Values:

Possible values from most logging to least. Each log level logs everything below it plus the values at the listed level.

  1. trace: Logs server messages including MySQL wire protocol messages. Useful for debugging client/server communication issues.
  2. debug: Logs all queries, results, and latencies. Useful when trying to debug bad query behavior like what query is causing an error. Note, SQL queries often contain sensitive data so this log level is not recommended for production use.
  3. info: Logs informational messages but not queries. This log level is recommended for production deployments.
  4. warning: Logs warnings.
  5. error: Logs all errors.
  6. fatal: Logs fatal errors.

Example:

In this example, I set the log level to info and run a bad query. Then, I restart the server with debug log level an re-run the same bad query.

$ grep log_level config.yaml        
log_level: info
$ dolt sql-server --config=config.yaml
Starting server with Config HP="localhost:3310"|T="28800000"|R="false"|L="info"|S="/tmp/mysql.sock"
WARN[0000] unix socket set up failed: file already in use: /tmp/mysql.sock 
INFO[0000] Server ready. Accepting connections.         
WARN[0000] secure_file_priv is set to "", which is insecure. 
WARN[0000] Any user with GRANT FILE privileges will be able to read any file which the sql-server process can read. 
WARN[0000] Please consider restarting the server with secure_file_priv set to a safe (or non-existent) directory. 
INFO[0009] NewConnection                                 DisableClientMultiStatements=false connectionID=1
WARN[0009] error running query                           connectTime="2024-12-04 13:22:52.439832 -0800 PST m=+9.896056876" connectionDb=config_blog connectionID=1 error="column \"bad_col\" could not be found in any table in scope"

As you can see, I get the error but not the query that caused the error. Now, I stop the server using Ctrl-C and edit my config.yaml using emacs, raising the log level to debug. I restart the server and re-run the bad query in a connected client.

$ emacs config.yaml
$ grep log_level config.yaml        
log_level: debug
$ dolt sql-server --config=config.yaml
Starting server with Config HP="localhost:3310"|T="28800000"|R="false"|L="debug"|S="/tmp/mysql.sock"
DEBU[0000] Loading events                               
WARN[0000] unix socket set up failed: file already in use: /tmp/mysql.sock 
INFO[0000] Server ready. Accepting connections.         
WARN[0000] secure_file_priv is set to "", which is insecure. 
WARN[0000] Any user with GRANT FILE privileges will be able to read any file which the sql-server process can read. 
WARN[0000] Please consider restarting the server with secure_file_priv set to a safe (or non-existent) directory. 
INFO[0006] NewConnection                                 DisableClientMultiStatements=false connectionID=1
DEBU[0006] Starting query                                connectTime="2024-12-04 13:25:18.756126 -0800 PST m=+6.422378084" connectionID=1 query="select @@version_comment limit 1"
DEBU[0006] Query finished in 0 ms                        connectTime="2024-12-04 13:25:18.756126 -0800 PST m=+6.422378084" connectionID=1 query="select @@version_comment limit 1"
DEBU[0011] Starting query                                connectTime="2024-12-04 13:25:18.756126 -0800 PST m=+6.422378084" connectionID=1 query="SELECT DATABASE()"
DEBU[0011] Query finished in 0 ms                        connectTime="2024-12-04 13:25:18.756126 -0800 PST m=+6.422378084" connectionID=1 query="SELECT DATABASE()"
DEBU[0011] Starting query                                connectTime="2024-12-04 13:25:18.756126 -0800 PST m=+6.422378084" connectionDb=config_blog connectionID=1 query="show databases"
DEBU[0011] Query finished in 0 ms                        connectTime="2024-12-04 13:25:18.756126 -0800 PST m=+6.422378084" connectionDb=config_blog connectionID=1 query="show databases"
DEBU[0011] Starting query                                connectTime="2024-12-04 13:25:18.756126 -0800 PST m=+6.422378084" connectionDb=config_blog connectionID=1 query="show tables"
DEBU[0011] Query finished in 0 ms                        connectTime="2024-12-04 13:25:18.756126 -0800 PST m=+6.422378084" connectionDb=config_blog connectionID=1 query="show tables"
DEBU[0011] Starting query                                connectTime="2024-12-04 13:25:18.756126 -0800 PST m=+6.422378084" connectionDb=config_blog connectionID=1 query="SELECT * FROM `t` LIMIT 0;"
DEBU[0011] Query finished in 0 ms                        connectTime="2024-12-04 13:25:18.756126 -0800 PST m=+6.422378084" connectionDb=config_blog connectionID=1 query="SELECT * FROM `t` LIMIT 0;"
DEBU[0019] Starting query                                connectTime="2024-12-04 13:25:18.756126 -0800 PST m=+6.422378084" connectionDb=config_blog connectionID=1 query="select * from t where bad_col=3"
WARN[0019] error running query                           connectTime="2024-12-04 13:25:18.756126 -0800 PST m=+6.422378084" connectionDb=config_blog connectionID=1 error="column \"bad_col\" could not be found in any table in scope" query="select * from t where bad_col=3"

I now see the bad query being run is select * from t where bad_col=3.

behavior

The behavior section of config.yaml defines configuration that determines the way the SQL engine works.

read_only

This configuration value is used to turn your SQL server into read only mode, preventing any write queries from succeeding and logging an error.

From the dolt sql-server help documentation:

If true database modification is disabled. Defaults to false.

Default: false

Values: true, false

Example:

I start the Dolt SQL server with read_only set to false. The second read_only configuration value is remotesapi.read_only which is set to null.

$ grep read_only config.yaml 
  read_only: false
  read_only: null
$ emacs config.yaml         
$ dolt sql-server --config=config.yaml
Starting server with Config HP="localhost:3310"|T="28800000"|R="false"|L="info"|S="/tmp/mysql.sock"
WARN[0000] unix socket set up failed: file already in use: /tmp/mysql.sock 
INFO[0000] Server ready. Accepting connections.         
WARN[0000] secure_file_priv is set to "", which is insecure. 
WARN[0000] Any user with GRANT FILE privileges will be able to read any file which the sql-server process can read. 
WARN[0000] Please consider restarting the server with secure_file_priv set to a safe (or non-existent) directory.

I make an insert in a connected client and it succeeds.

MySQL [config_blog]> insert into t values (0, 'first');
Query OK, 1 row affected (0.006 sec)

Now, I stop the above server using Ctrl-C and modify the config.yaml by setting read_only to true. Then, I restart the server using the new config.yaml.

$ emacs config.yaml                   
$ grep read_only config.yaml          
  read_only: true
  read_only: null
$ dolt sql-server --config=config.yaml
Starting server with Config HP="localhost:3310"|T="28800000"|R="true"|L="info"|S="/tmp/mysql.sock"
WARN[0000] unix socket set up failed: file already in use: /tmp/mysql.sock 
INFO[0000] Server ready. Accepting connections.         
WARN[0000] secure_file_priv is set to "", which is insecure. 
WARN[0000] Any user with GRANT FILE privileges will be able to read any file which the sql-server process can read. 
WARN[0000] Please consider restarting the server with secure_file_priv set to a safe (or non-existent) directory. 
INFO[0016] NewConnection                                 DisableClientMultiStatements=false connectionID=1
WARN[0016] error running query                           connectTime="2024-12-04 14:38:05.684674 -0800 PST m=+16.751230334" connectionDb=config_blog connectionID=1 error="database server is set to read only mode"

As expected, you can see the query failed with a "database server is set to read only mode". In the client, I also received the same error.

MySQL [config_blog]> insert into t values (1, 'second');
ERROR 1105 (HY000): database server is set to read only mode

autocommit

autocommit is a standard SQL database setting where every SQL statement triggers a transaction COMMIT. Without autocommit, the user is responsible for managing their own concurrency by issuing BEGIN statements at the start of transactions and COMMIT or ROLLBACK statements at the end of transactions. Most databases (ie. MySQL, Postgres) and clients (ie. ODBC, JDBC) have autocommit on by default with the notable exception of the Python client.

From the dolt sql-server help documentation:

If true every statement is committed automatically. Defaults to true. @@autocommit can also be specified in each session.

Default: true

Values: true, false

Example:

autocommit is visible under concurrency so for this example I need two connected clients. I start by starting the Dolt SQL server with autocommit on.

$ grep autocommit config.yaml 
  autocommit: true
$ dolt sql-server --config=config.yaml
Starting server with Config HP="localhost:3310"|T="28800000"|R="false"|L="info"|S="/tmp/mysql.sock"

Now I connect both clients, viewing the state of the table. In client one I see:

MySQL [config_blog]> select * from t;
+----+-------+
| id | words |
+----+-------+
|  0 | first |
+----+-------+
1 row in set (0.001 sec)

In client two I see the same thing:

MySQL [config_blog]> select * from t;
+----+-------+
| id | words |
+----+-------+
|  0 | first |
+----+-------+
1 row in set (0.001 sec)

Back in client one, I insert a value:

MySQL [config_blog]> insert into t values (1, 'second');
Query OK, 1 row affected (0.007 sec)

And I am able to see that value in client two without issuing an explicit transaction commit.

MySQL [config_blog]> select * from t;
+----+--------+
| id | words  |
+----+--------+
|  0 | first  |
|  1 | second |
+----+--------+
2 rows in set (0.004 sec)

Now, I kill the server with Ctrl-C and set autocommit to false in config.yaml.

$ emacs config.yaml 
$ grep autocommit config.yaml
  autocommit: false
$ dolt sql-server --config=config.yaml
Starting server with Config HP="localhost:3310"|T="28800000"|R="false"|L="info"|S="/tmp/mysql.sock"

Now I reconnect both clients. I should see this table in both clients:

MySQL [config_blog]> select * from t;
+----+--------+
| id | words  |
+----+--------+
|  0 | first  |
|  1 | second |
+----+--------+
2 rows in set (0.004 sec)

In client one I make an insert:

MySQL [config_blog]> insert into t values (2, 'third');
Query OK, 1 row affected (0.005 sec)

But that insert is not visible in client two:

MySQL [config_blog]> select * from t;
+----+--------+
| id | words  |
+----+--------+
|  0 | first  |
|  1 | second |
+----+--------+
2 rows in set (0.001 sec)

I must issue a commit in client one:

MySQL [config_blog]> commit;
Query OK, 0 rows affected (0.007 sec)

and a begin in client two. Now I see the insert in client two.

MySQL [config_blog]> begin;
Query OK, 0 rows affected (0.000 sec)

MySQL [config_blog]> select * from t;
+----+--------+
| id | words  |
+----+--------+
|  0 | first  |
|  1 | second |
|  2 | third  |
+----+--------+
3 rows in set (0.001 sec)

disable_client_multi_statements

By default, the Dolt SQL server can accept and process multiple SQL queries in a single statement. The default delimiter is a semicolon (ie. ;). So, you can send multiple SQL queries in the same statement as long as they are separated by a semicolon and by default Dolt will process each individually and return the results. However, some clients are not able to handle multiple result sets from a single statement. So, Dolt offers a configuration value to fail statements that contain multiple SQL queries.

Default: false

Values: true, false

Example:

In order to get the standard MySQL client to send multi-statement queries to a server, I must change the delimiter to something other than ;. The client parses queries at the defined delimiter and sends them individually. So, I start by changing the delimiter on my client to ?.

MySQL [config_blog]> delimiter '?';

Now, I issue a multi-statement query and it succeeds.

MySQL [config_blog]> insert into t values (3, 'fourth'); update t set words='first  modified' where id=0?
Query OK, 1 row affected (0.012 sec)

Query OK, 1 row affected (0.012 sec)
Rows matched: 1  Changed: 1  Warnings: 0

I stop the server using Ctrl-C. Now, I set the disable_client_multi_statement to true and restart the server:

$ emacs config.yaml
$ grep multi_statement config.yaml
  disable_client_multi_statements: true                   
$ dolt sql-server --config=config.yaml
Starting server with Config HP="localhost:3310"|T="28800000"|R="false"|L="debug"|S="/tmp/mysql.sock"

I pass in the inverse query and it will fail:

MySQL [config_blog]> delete from t where id=3; update t set words='first' where id=0?
ERROR 1105 (HY000): syntax error at position 33 near 'update'

dolt_transaction_commit

Dolt offers a setting where every transaction commit also becomes a Dolt commit. That setting can be controlled using dolt_transaction_commit in config.yaml. By default, Dolt commits are user controlled and triggered via the dolt_commit() procedure. In some cases, like when you have an existing application that is built against standard MySQL, you may want Dolt commits generated automatically. This setting enables that behavior.

From the dolt sql-server help documentation:

If true all SQL transaction commits will automatically create a Dolt commit, with a generated commit message. This is useful when a system working with Dolt wants to create versioned data, but doesn't want to directly use Dolt features such as dolt_commit()

Default: false

Values: true, false

Example:

Without dolt_transaction_commit enabled, I must issue a call to the dolt_commit() procedure to get a new entry in the log.

MySQL [config_blog]> call dolt_commit('-Am', 'Manual commit');
+----------------------------------+
| hash                             |
+----------------------------------+
| rgifn94i58hqov4mdv0efsjju0qpg964 |
+----------------------------------+
1 row in set (0.006 sec)

MySQL [config_blog]> select * from dolt_log;
+----------------------------------+-----------+-----------------+---------------------+---------------------------------+
| commit_hash                      | committer | email           | date                | message                         |
+----------------------------------+-----------+-----------------+---------------------+---------------------------------+
| rgifn94i58hqov4mdv0efsjju0qpg964 | root      | root@%          | 2024-12-05 00:48:50 | Manual commit                   |
| do1tvb8g442jvggv4e3nfqp3fmqt0u5a | timsehn   | tim@dolthub.com | 2024-12-03 19:16:49 | Inіtialіze datа rеposіtory      |
+----------------------------------+-----------+-----------------+---------------------+---------------------------------+
2 rows in set (0.001 sec)

After I enable dolt_transaction_commit and restart the server:

$ emacs config.yaml 
$ grep dolt_transaction_commit config.yaml 
  dolt_transaction_commit: true
$ dolt sql-server --config=config.yaml    
Starting server with Config HP="localhost:3310"|T="28800000"|R="false"|L="debug"|S="/tmp/mysql.sock"

Every write statement becomes a Dolt commit:

MySQL [config_blog]> insert into t values (4, 'dolt commit');
Query OK, 1 row affected (0.009 sec)

MySQL [config_blog]> select * from dolt_log;
+----------------------------------+------------+-----------------+---------------------+---------------------------------+
| commit_hash                      | committer  | email           | date                | message                         |
+----------------------------------+------------+-----------------+---------------------+---------------------------------+
| vmikac4f7s4395v0v43dtfcbhrmtmo41 | configblog | tim@dolthub.com | 2024-12-05 00:51:32 | Transaction commit              |
| rgifn94i58hqov4mdv0efsjju0qpg964 | root       | root@%          | 2024-12-05 00:48:50 | Manual commit                   |
| do1tvb8g442jvggv4e3nfqp3fmqt0u5a | timsehn    | tim@dolthub.com | 2024-12-03 19:16:49 | Inіtialіze datа rеposіtory      |
+----------------------------------+------------+-----------------+---------------------+---------------------------------+

Note, I lose control of the commit message in this mode. The commit is made by the server user, in this case configblog, in contrast to manual commits which are made by the client user root.

event_scheduler

Dolt supports MySQL events. Events are scheduled jobs created using the CREATE EVENT SQL statement. Event scheduling is on by default but can be disabled using this configuration setting. Note, only events on the main branch will be executed by the event scheduler. Events can be used to schedule Dolt commits at intervals if you don't have access to the application code for your application, but also don't want a commit at every SQL transaction.

Default: "ON"

Values: "ON", "OFF"

Example:

I start the Dolt SQL server in debug mode so we can see event execution in the logs. I create an event to create a Dolt commit every minute. Notice the --allow-empty flag. This allows Dolt to commit without error even when nothing has changed in the database.

[config_blog]> CREATE EVENT make_dolt_commits ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 MINUTE DO CALL dolt_commit('-A', '--allow-empty', '-m', 'Commit created using an event');
Query OK, 0 rows affected (0.011 sec)

Now, we wait a minute and in the logs we see that the event has fired, as expected.

DEBU[0090] Executing event config_blog.make_dolt_commits, seconds until execution: -28.759227 
DEBU[0090] executing event config_blog.make_dolt_commits  query="CALL dolt_commit('-A', '--allow-empty', '-m', 'Commit created using an event')"

We can inspect the Dolt log and see indeed the commit succeeded.

MySQL [config_blog]> select * from dolt_log;
+----------------------------------+------------+-----------------+---------------------+---------------------------------+
| commit_hash                      | committer  | email           | date                | message                         |
+----------------------------------+------------+-----------------+---------------------+---------------------------------+
| im7qq2ja3nfqnc75khtuli8krla3s3fm | root       | root@%          | 2024-12-05 20:19:04 | Commit created using an event   |
| vmikac4f7s4395v0v43dtfcbhrmtmo41 | configblog | tim@dolthub.com | 2024-12-05 00:51:32 | Transaction commit              |
| rgifn94i58hqov4mdv0efsjju0qpg964 | root       | root@%          | 2024-12-05 00:48:50 | Manual commit                   |
| do1tvb8g442jvggv4e3nfqp3fmqt0u5a | timsehn    | tim@dolthub.com | 2024-12-03 19:16:49 | Inіtialіze datа rеposіtory      |
+----------------------------------+------------+-----------------+---------------------+---------------------------------+

Now stop the server and stop event execution using config.yaml.

$ emacs config.yaml
$ grep event_scheduler config.yaml 
  event_scheduler: "OFF"                   
$ dolt sql-server --config=config.yaml
Starting server with Config HP="localhost:3310"|T="28800000"|R="false"|L="debug"|S="/tmp/mysql.sock"

We do not see any more commits in the debug log or in the Dolt log.

user

The user section configures the default user for the server. If this section is undefined, the default user for the server is root with no password.

name

The name of the default user for the server to accept connections from. Additional users can be added using standard CREATE USER syntax.

From the dolt sql-server help documentation:

The username that connections should use for authentication

Default: ""

Values: Any string less than or equal to 32 characters

Example:

I add a user name to the config.yaml and start the server.

$ emacs config.yaml                   
$ grep name config.yaml
  name: "user"
$ dolt sql-server --config=config.yaml
Starting server with Config HP="localhost:3310"|T="28800000"|R="false"|L="debug"|S="/tmp/mysql.sock"

Then in another shell I connect with that user.

$ mysql -h 127.0.0.1 -P 3310 -u user 
WARNING: option --ssl-verify-server-cert is disabled, because of an insecure passwordless login.
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 8.0.33 Dolt

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

Note, I can no longer log in using the user named root.

$ mysql -h 127.0.0.1 -P 3310 -u root
WARNING: option --ssl-verify-server-cert is disabled, because of an insecure passwordless login.
ERROR 2027 (HY000): Received malformed packet

password

The password of the default user for the server to accept connections from.

From the dolt sql-server help documentation:

The password that connections should use for authentication.

Default: ""

Values: Any string less than or equal to 32 characters

Example:

Continuing the above example from user, I will now add a password for the default user.

$ emacs config.yaml                   
$ grep password config.yaml     
  password: "password"
  allow_cleartext_passwords: null
$ dolt sql-server --config=config.yaml
Starting server with Config HP="localhost:3310"|T="28800000"|R="false"|L="debug"|S="/tmp/mysql.sock"

Now, I cannot connect with no password.

$ mysql -h 127.0.0.1 -P 3310 -u user                        
WARNING: option --ssl-verify-server-cert is disabled, because of an insecure passwordless login.
ERROR 1045 (28000): Access denied for user 'user'

In order to connect to a server with a plain text password, I must pass the --skip-ssl option to the MySQL client. I can connect using 127.0.0.1 or localhost.

$ mysql -h 127.0.0.1 -P 3310 -u root --skip-ssl
WARNING: option --ssl-verify-server-cert is disabled, because of an insecure passwordless login.
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 8.0.33 Dolt

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MySQL [(none)]>

listener

The listener section of config.yaml is configuration for the SQL server transport layer.

host

The host defines the address of the server that Dolt is running on.

From the dolt sql-server help documentation:

The host address that the server will run on. This may be localhost or an IPv4 or IPv6 address

Default: localhost

Values: localhost or an IPv4 or IPv6 address

Example:

This is a bit of a hard one to show off as valid values for this field on my laptop are localhost or 127.0.0.1. I change the value to 127.0.0.1.

$ emacs config.yaml                   
$ grep host: config.yaml 
  host: 127.0.0.1
  host: null
$ dolt sql-server --config=config.yaml
Starting server with Config HP="127.0.0.1:3310"|T="28800000"|R="false"|L="debug"

You notice the starting server message now says 127.0.0.1 instead of localhost.

port

The port on the server used to accept connections. The default is 3306. Be careful because that is also the MySQL and MariaDB default port so you either need to stop your MySQL server to run Dolt, or change the Dolt port to something else.

From the dolt sql-server help documentation:

The port that the server should listen on

Default: 3306

Values: Any integer between 1024 to 49151.

Example:

Astute readers may have noticed I've been running this example on port 3310 the whole time. I'm using port 3306 for my long-running Wikipedia import. I have this port configured in muy config.yaml. The second and third port settings are for a Remote API and a metrics endpoint which are not covered in this article.

$ grep port config.yaml  
  port: 3310
  require_secure_transport: null
  port: -1
  port: null
$ dolt sql-server --config=config.yaml
Starting server with Config HP="localhost:3310"|T="28800000"|R="false"|L="debug"|S="/tmp/mysql.sock"

max_connections

The maximum number of simultaneous connections the server will accept. Connections over the limit queue until an existing connection is terminated.

From the dolt sql-server help documentation:

The number of simultaneous connections that the server will accept

Default: 100

Values: Any integer between 1 and 100,000.

Example:

I configure a server with a single maximum connection.

$ grep max_connections config.yaml    
  max_connections: 1
$ dolt sql-server --config=config.yaml
Starting server with Config HP="127.0.0.1:3310"|T="28800000"|R="false"|L="debug"

I connect with a client one with no issue.

$ mysql -h 127.0.0.1 -P 3310 -u root
WARNING: option --ssl-verify-server-cert is disabled, because of an insecure passwordless login.
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 8.0.33 Dolt

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MySQL [(none)]>

If I connect with another client, it just hangs:

$ mysql -h 127.0.0.1 -P 3310 -u root
WARNING: option --ssl-verify-server-cert is disabled, because of an insecure passwordless login.

If I exit client one:

MySQL [(none)]> exit
Bye

Client two connects.

$ mysql -h 127.0.0.1 -P 3310 -u root
WARNING: option --ssl-verify-server-cert is disabled, because of an insecure passwordless login.
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 8.0.33 Dolt

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MySQL [(none)]>

read_timeout_millis

This setting controls when the server will time out a connection where no packets are sent. The value is defined in milliseconds. If the server does not read a packet from the connected client for the listed number of milliseconds a timeout error is returned and the connection is killed. The option is equivalent to net_read_timeout in MySQL. Most MySQL clients send keep alive packets to avoid this timeout. Use this to control bad client connections.

From the dolt sql-server help documentation:

The number of milliseconds that the server will wait for a read operation

Default: 28800000

Values: Any integer between 1 and the max 64-bit integer (9,223,372,036,854,775,807).

Example:

I set the read timeout to 1 millisecond and start the server.

$ emacs config.yaml 
$ grep read_timeout config.yaml 
  read_timeout_millis: 1
$ dolt sql-server --config=config.yaml
Starting server with Config HP="127.0.0.1:3310"|T="1"|R="false"|L="debug"

Now, I'll issue a select sleep(5) in a client which occupies the client so it does not send packets.

$ mysql -h 127.0.0.1 -P 3310 -u root
WARNING: option --ssl-verify-server-cert is disabled, because of an insecure passwordless login.
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MySQL connection id is 5
Server version: 8.0.33

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MySQL [(none)]> select sleep(5);
ERROR 2006 (HY000): Server has gone away
No connection. Trying to reconnect...
Connection id:    1
Current database: *** NONE ***

ERROR 1105 (HY000): row read wait bigger than connection timeout

The query fails and the connection is killed.

write_timeout_millis

This setting controls when the server will time out a connection where it cannot send packets. The value is defined in milliseconds. If the server does not write a packet to the connected client for the listed number of milliseconds a timeout error is returned and the connection is killed. The option is equivalent to net_write_timeout in MySQL. Use this to control bad client connections.

From the dolt sql-server help documentation:

The number of milliseconds that the server will wait for a write operation

Default: 28800000

Values: Any integer between 1 and the max 64-bit integer (9,223,372,036,854,775,807).

Example:

We were a bit confused how to trigger this timeout and could only do it within Dolt code. Practically, we think this type of timeout is triggered very rarely in the wild.

tls_key

tls_key, tls_cert, and require_secure_transport as used together and are covered in this article. tls_key is the path to the key file to use for secure transport.

From the dolt sql-server help documentation:

The path to the TLS key used for secure transport

Default: null

Values: A path on your filesystem to a .pem file.

tls_cert

tls_key, tls_cert, and require_secure_transport as used together and are covered in this article. tls_cert is the path to the ket file to use for secure transport.

From the dolt sql-server help documentation:

The path to the TLS certificate used for secure transport

Default: null

Values: A path on your filesystem to a .pem file.

require_secure_transport

tls_key, tls_cert, and require_secure_transport as used together and are covered in this article. Setting require_secure_transport enables TLS using the listed tls_key and tls_cert files.

From the dolt sql-server help documentation:

Boolean flag to turn on TLS/SSL transport

Default: null

Values: null or true

Example:

Dolt source code comes with a signed key and cert .pem file. Set the following variables in your config.yaml. I have my Dolt source code stored at ~/dolthub/git/dolt/.

  tls_key: "/Users/timsehn/dolthub/git/dolt/go/libraries/doltcore/servercfg/tes\
tdata/chain_key.pem"
  tls_cert: "/Users/timsehn/dolthub/git/dolt/go/libraries/doltcore/servercfg/te\
stdata/chain_cert.pem"
  require_secure_transport: true

Now I connect and run status and I can see I am on a SSL connection.

$ mysql -h 127.0.0.1 -P 3310 -u root
WARNING: option --ssl-verify-server-cert is disabled, because of an insecure passwordless login.
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 8.0.33 Dolt

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MySQL [(none)]> source
ERROR: Usage: \. <filename> | source <filename>
MySQL [(none)]> status
--------------
mysql from 11.6.2-MariaDB, client 15.2 for osx10.20 (arm64) using  EditLine wrapper

Connection id:		1
Current database:	
Current user:		root@%
SSL:			Cipher in use is TLS_AES_128_GCM_SHA256, cert is UNKNOWN
Current pager:		stdout
Using outfile:		''
Using delimiter:	;
Server:			MySQL
Server version:		8.0.33 Dolt
Protocol version:	10
Connection:		127.0.0.1 via TCP/IP
Server characterset:	utf8mb4
Db     characterset:	utf8mb4
Client characterset:	utf8mb4
Conn.  characterset:	utf8mb4
TCP port:		3310
--------------

allow_cleartext_passwords

This is a bit of an advanced option. allow_cleartext_passwords only affects the mysql_clear_password auth plugin, which is only used for JSON Web Token (JWT) authentication. Other auth plugins protect the password (e.g. mysql_native_password does a hash scramble, caching_sha2_password requires an encrypted connection), but mysql_clear_password sends the plaintext password over the wire. If you are using JWT authentication you must enable allow_cleartext_passwords or require_secure_transport.

Default: false

Values: true, false, or null

max_logged_query_len

max_logged_query_len sets the maximum amount of characters Dolt will log in the server logs. We had an issue where very long queries, like seen in dumps would overflow buffers in some log monitoring utilities. This setting allows the user to truncate log lines at a maximum length to avoid such failure modes. This only effects queries so you must also set the log level to debug or above to see an effect.

From the dolt sql-server help documentation:

If greater than zero, truncates query strings in logging to the number of characters given.

Default: 0

Values: non-negative integer

Example:

I set the log_level to debug and the max_logged_query_len to 10 and start theDolt SQL server.

$ grep log_level config.yaml 
log_level: debug
$ grep max_log config.yaml  
max_logged_query_len: 10
$ dolt sql-server --config=config.yaml
Starting server with Config HP="127.0.0.1:3310"|T="28800000"|R="false"|L="debug"

Now, all queries are truncated to 10 characters in the logs:

DEBU[0020] Starting query                                connectTime="2024-12-06 14:21:58.139943 -0800 PST m=+3.826578251" connectionDb=config_blog connectionID=1 query="select * f..."

data_dir

The data_dir, config_dir, privilege_file and branch_control_file work in conjunction to tell Dolt where to create and load various artifacts needed for the running of the database. data dir defaults to the current working directory. data_dir configures the root directory and is used by config_dir, privilege_file and branch_control_file.

From the dolt sql-server help documentation:

A directory where the server will load dolt databases to serve, and create new ones. Defaults to the current directory.

Default: .

Values: Any filesystem path

config_dir

config_dir is a directory where Dolt will load and store configuration used by the database. Configuration includes the privilege_file and branch_control_file used to store users/grants and branch permissions configuration respectively. This defaults to the $data_dir/doltcfg directory.

From the dolt sql-server help documentation:

A directory where the server will load and store non-database configuration data, such as permission information. Defaults $data_dir/.doltcfg

Default: .doltcfg

Values: Any filesystem path

privilege_file

The privilege_file is a file used to store and load users/grants configuration.

From the dolt sql-server help documentation:

Path to a file to load and store users and grants. Defaults to $doltcfg-dir/privileges.db. Will be created as needed.

Default: .doltcfg/privileges.db

Values: Any filesystem path

branch_control_file

The branch_control_file is a file used to store and load users/grants configuration.

From the dolt sql-server help documentation:

Path to a file to load and store branch control permissions. Defaults to $doltcfg-dir/branch_control.db. Will be created as needed.

Default: .doltcfg/branch_control.db

Values: Any filesystem path

Example:

data_dir, config_dir, privilege_file and branch_control_file can all be set to independent filesystem locations but we recommend only using data_dir to change the location of your database storage. It is common to have data stored on a different mounted drive than where the server binary or logs are stored.

I set the data_dir to /tmp.

$ grep data_dir config.yaml 
data_dir: /tmp
$ dolt sql-server --config=config.yaml
Starting server with Config HP="127.0.0.1:3310"|T="28800000"|R="false"|L="debug"

This is a new directory so there are no databases in it.

$ mysql -h 127.0.0.1 -P 3310 -u root
WARNING: option --ssl-verify-server-cert is disabled, because of an insecure passwordless login.
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 8.0.33 Dolt

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MySQL [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
+--------------------+
2 rows in set (0.000 sec)

After we create a database named tmp:

MySQL [(none)]> create database tmp;
Query OK, 1 row affected (0.135 sec)

We can see the .dolt directory in /tmp/tmp:

$ ls -al /tmp/tmp 
total 0
drwxr-xr-x  3 timsehn  wheel   96 Dec  6 14:26 .
drwxrwxrwt  7 root     wheel  224 Dec  6 14:26 ..
drwxr-xr-x  7 timsehn  wheel  224 Dec  6 14:26 .dolt

Conclusion

That covers all the standard configuration values for config.yaml. We'll have follow up articles for the advanced configuration. More configuration questions? Come by our Discord and just ask. We're happy to help.

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