Managing an RDS Proxy - Amazon Relational Database Service

Managing an RDS Proxy

Following, you can find an explanation of how to manage RDS Proxy operation and configuration. These procedures help your application make the most efficient use of database connections and achieve maximum connection reuse. The more that you can take advantage of connection reuse, the more CPU and memory overhead that you can save. This in turn reduces latency for your application and enables the database to devote more of its resources to processing application requests.

Modifying an RDS Proxy

You can change certain settings associated with a proxy after you create the proxy. You do so by modifying the proxy itself, its associated target group, or both. Each proxy has an associated target group.

To modify the settings for a proxy

  1. Sign in to the AWS Management Console and open the Amazon RDS console at https://console.aws.amazon.com/rds/.

  2. In the navigation pane, choose Proxies.

  3. In the list of proxies, choose the proxy whose settings you want to modify or go to its details page.

  4. For Actions, choose Modify.

  5. Enter or choose the properties to modify. You can modify the following:

    • Proxy identifier – Rename the proxy by entering a new identifier.

    • Require Transport Layer Security – Turn the requirement for Transport layer Security (TLS) on or off.

    • Idle client connection timeout – Enter a time period for the idle client connection timeout.

    • Secrets Manager secrets – Add or remove Secrets Manager secrets. These secrets correspond to database user names and passwords.

    • IAM role – Change the IAM role used to retrieve the secrets from Secrets Manager.

    • IAM Authentication – Require or disallow IAM authentication for connections to the proxy.

    • VPC security group – Add or remove VPC security groups for the proxy to use.

    • Enable enhanced logging – Enable or disable enhanced logging.

  6. Choose Modify.

If you didn't find the settings listed that you want to change, use the following procedure to update the target group for the proxy. The target group associated with a proxy controls the settings related to the physical database connections. Each proxy has one associated target group named default, which is created automatically along with the proxy.

You can only modify the target group from the proxy details page, not from the list on the Proxies page.

To modify the settings for a proxy target group

  1. On the Proxies page, go to the details page for a proxy.

  2. For Target groups, choose the default link. Currently, all proxies have a single target group named default.

  3. On the details page for the default target group, choose Modify.

  4. Choose new settings for the properties that you can modify:

    • Database – Choose a different RDS DB instance or Aurora cluster.

    • Connection pool maximum connections – Adjust what percentage of the maximum available connections the proxy can use.

    • Session pinning filters – (Optional) Choose a session pinning filter. Doing this can help reduce performance issues due to insufficient transaction-level reuse for connections. Using this setting requires understanding of application behavior and the circumstances under which RDS Proxy pins a session to a database connection. Currently, the setting isn't supported for PostgreSQL and the only choice is EXCLUDE_VARIABLE_SETS.

    • Connection borrow timeout – Adjust the connection borrow timeout interval. This setting applies when the maximum number of connections is already being used for the proxy. The setting determines how long the proxy waits for a connection to become available before returning a timeout error.

    • Initialization query – (Optional) Add an initialization query, or modify the current one. You can specify one or more SQL statements for the proxy to run when opening each new database connection. The setting is typically used with SET statements to make sure that each connection has identical settings such as time zone and character set. For multiple statements, use semicolons as the separator. You can also include multiple variables in a single SET statement, such as SET x=1, y=2. Initialization query is not currently supported for PostgreSQL.

    You can't change certain properties, such as the target group identifier and the database engine.

  5. Choose Modify target group.

To modify a proxy using the AWS CLI, use the commands modify-db-proxy, modify-db-proxy-target-group, deregister-db-proxy-targets, and register-db-proxy-targets.

With the modify-db-proxy command, you can change properties such as the following:

  • The set of Secrets Manager secrets used by the proxy.

  • Whether TLS is required.

  • The idle client timeout.

  • Whether to log additional information from SQL statements for debugging.

  • The IAM role used to retrieve Secrets Manager secrets.

  • The security groups used by the proxy.

The following example shows how to rename an existing proxy.

aws rds modify-db-proxy --db-proxy-name the-proxy --new-db-proxy-name the_new_name

To modify connection-related settings or rename the target group, use the modify-db-proxy-target-group command. Currently, all proxies have a single target group named default. When working with this target group, you specify the name of the proxy and default for the name of the target group.

The following example shows how to first check the MaxIdleConnectionsPercent setting for a proxy and then change it, using the target group.

aws rds describe-db-proxy-target-groups --db-proxy-name the-proxy { "TargetGroups": [ { "Status": "available", "UpdatedDate": "2019-11-30T16:49:30.342Z", "ConnectionPoolConfig": { "MaxIdleConnectionsPercent": 50, "ConnectionBorrowTimeout": 120, "MaxConnectionsPercent": 100, "SessionPinningFilters": [] }, "TargetGroupName": "default", "CreatedDate": "2019-11-30T16:49:27.940Z", "DBProxyName": "the-proxy", "IsDefault": true } ] } aws rds modify-db-proxy-target-group --db-proxy-name the-proxy --target-group-name default --connection-pool-config ' { "MaxIdleConnectionsPercent": 75 }' { "DBProxyTargetGroup": { "Status": "available", "UpdatedDate": "2019-12-02T04:09:50.420Z", "ConnectionPoolConfig": { "MaxIdleConnectionsPercent": 75, "ConnectionBorrowTimeout": 120, "MaxConnectionsPercent": 100, "SessionPinningFilters": [] }, "TargetGroupName": "default", "CreatedDate": "2019-11-30T16:49:27.940Z", "DBProxyName": "the-proxy", "IsDefault": true } }

With the deregister-db-proxy-targets and register-db-proxy-targets commands, you change which RDS DB instance or Aurora DB cluster the proxy is associated with through its target group. Currently, each proxy can connect to one RDS DB instance or Aurora DB cluster. The target group tracks the connection details for all the RDS DB instances in a Multi-AZ configuration. Or the target group tracks the connection details for all the DB instances in an Aurora cluster.

The following example starts with a proxy that is associated with an Aurora MySQL cluster named cluster-56-2020-02-25-1399. The example shows how to change the proxy so that it can connect to a different cluster named provisioned-cluster.

When you work with an RDS DB instance, you specify the --db-instance-identifier option. When you work with an Aurora DB cluster, you specify the --db-cluster-identifier option instead.

The following example modifies an Aurora MySQL proxy. An Aurora PostgreSQL proxy has port 5432.

aws rds describe-db-proxy-targets --db-proxy-name the-proxy { "Targets": [ { "Endpoint": "instance-9814.demo.us-east-1.rds.amazonaws.com", "Type": "RDS_INSTANCE", "Port": 3306, "RdsResourceId": "instance-9814" }, { "Endpoint": "instance-8898.demo.us-east-1.rds.amazonaws.com", "Type": "RDS_INSTANCE", "Port": 3306, "RdsResourceId": "instance-8898" }, { "Endpoint": "instance-1018.demo.us-east-1.rds.amazonaws.com", "Type": "RDS_INSTANCE", "Port": 3306, "RdsResourceId": "instance-1018" }, { "Type": "TRACKED_CLUSTER", "Port": 0, "RdsResourceId": "cluster-56-2020-02-25-1399" }, { "Endpoint": "instance-4330.demo.us-east-1.rds.amazonaws.com", "Type": "RDS_INSTANCE", "Port": 3306, "RdsResourceId": "instance-4330" } ] } aws rds deregister-db-proxy-targets --db-proxy-name the-proxy --db-cluster-identifier cluster-56-2020-02-25-1399 aws rds describe-db-proxy-targets --db-proxy-name the-proxy { "Targets": [] } aws rds register-db-proxy-targets --db-proxy-name the-proxy --db-cluster-identifier provisioned-cluster { "DBProxyTargets": [ { "Type": "TRACKED_CLUSTER", "Port": 0, "RdsResourceId": "provisioned-cluster" }, { "Endpoint": "gkldje.demo.us-east-1.rds.amazonaws.com", "Type": "RDS_INSTANCE", "Port": 3306, "RdsResourceId": "gkldje" }, { "Endpoint": "provisioned-1.demo.us-east-1.rds.amazonaws.com", "Type": "RDS_INSTANCE", "Port": 3306, "RdsResourceId": "provisioned-1" } ] }

To modify a proxy using the RDS API, you use the operations ModifyDBProxy, ModifyDBProxyTargetGroup, DeregisterDBProxyTargets, and RegisterDBProxyTargets operations.

With ModifyDBProxy, you can change properties such as the following:

  • The set of Secrets Manager secrets used by the proxy.

  • Whether TLS is required.

  • The idle client timeout.

  • Whether to log additional information from SQL statements for debugging.

  • The IAM role used to retrieve Secrets Manager secrets.

  • The security groups used by the proxy.

With ModifyDBProxyTargetGroup, you can modify connection-related settings or rename the target group. Currently, all proxies have a single target group named default. When working with this target group, you specify the name of the proxy and default for the name of the target group.

With DeregisterDBProxyTargets and RegisterDBProxyTargets, you change which RDS DB instance or Aurora DB cluster the proxy is associated with through its target group. Currently, each proxy can connect to one RDS DB instance or Aurora DB cluster. The target group tracks the connection details for all the RDS DB instances in a Multi-AZ configuration, or all the DB instances in an Aurora cluster.

Adding a new database user

In some cases, you might add a new database user to an RDS DB instance or Aurora cluster that's associated with a proxy. If so, add or repurpose a Secrets Manager secret to store the credentials for that user. To do this, choose one of the following options:

  • Create a new Secrets Manager secret, using the procedure described in Setting up database credentials in AWS Secrets Manager.

  • Update the IAM role to give RDS Proxy access to the new Secrets Manager secret. To do so, update the resources section of the IAM role policy.

  • If the new user takes the place of an existing one, update the credentials stored in the proxy's Secrets Manager secret for the existing user.

Changing the password for a database user

In some cases, you might change the password for a database user in an RDS DB instance or Aurora cluster that's associated with a proxy. If so, update the corresponding Secrets Manager secret with the new password.

Configuring connection settings

To adjust RDS Proxy's connection pooling, you can modify the following settings:

IdleClientTimeout

You can specify how long a client connection can be idle before the proxy can close it. The default is 1,800 seconds (30 minutes).

A client connection is considered idle when the application doesn't submit a new request within the specified time after the previous request completed. The underlying database connection stays open and is returned to the connection pool. Thus, it's available to be reused for new client connections. If you want the proxy to proactively remove stale connections, consider lowering the idle client connection timeout. If your workload establishes frequent connections with the proxy, consider raising the idle client connection timeout to save the cost of establishing connections.

This setting is represented by the Idle client connection timeout field in the RDS console and the IdleClientTimeout setting in the AWS CLI and the API. To learn how to change the value of the Idle client connection timeout field in the RDS console, see AWS Management Console. To learn how to change the value of the IdleClientTimeout setting, see the CLI command modify-db-proxy or the API operation ModifyDBProxy.

MaxConnectionsPercent

You can limit the number of connections that an RDS Proxy can establish with the database. You specify the limit as a percentage of the maximum connections available for your database. The proxy doesn't create all of these connections in advance. This setting reserves the right for the proxy to establish these connections as the workload needs them.

For example, suppose that you configured RDS Proxy to use 75 percent of the maximum connections for your database. In this case, your database supports a maximum of 1,000 concurrent connections. Here, RDS Proxy can open up to 750 database connections.

This setting is represented by the Connection pool maximum connections field in the RDS console and the MaxConnectionsPercent setting in the AWS CLI and the API. To learn how to change the value of the Connection pool maximum connections field in the RDS console, see AWS Management Console. To learn how to change the value of the MaxConnectionsPercent setting, see the CLI command modify-db-proxy-target-group or the API operation ModifyDBProxyTargetGroup.

For information on database connection limits, see Maximum number of database connections.

MaxIdleConnectionsPercent

You can control the number of idle database connections that RDS Proxy can keep in the connection pool. RDS Proxy considers a database connection in it's pool to be idle when there's been no activity on the connection for five minutes.

You specify the limit as a percentage of the maximum connections available for your database. The default value is 50 percent of MaxConnectionsPercent, and the upper limit is the value of MaxConnectionsPercent. With a high value, the proxy leaves a high percentage of idle database connections open. With a low value, the proxy closes a high percentage of idle database connections. If your workloads are unpredictable, consider setting a high value for MaxIdleConnectionsPercent. Doing so means that RDS Proxy can accommodate surges in activity without opening a lot of new database connections.

This setting is represented by the MaxIdleConnectionsPercent setting of DBProxyTargetGroup in the AWS CLI and the API. To learn how to change the value of the MaxIdleConnectionsPercent setting, see the CLI command modify-db-proxy-target-group or the API operation ModifyDBProxyTargetGroup.

Note

RDS Proxy closes database connections some time after 24 hours when they are no longer in use. The proxy performs this action regardless of the value of the maximum idle connections setting.

For information on database connection limits, see Maximum number of database connections.

ConnectionBorrowTimeout

You can choose how long RDS Proxy waits for a database connection in the connection pool to become available for use before returning a timeout error. The default is 120 seconds. This setting applies when the number of connections is at the maximum, and so no connections are available in the connection pool. It also applies if no appropriate database instance is available to handle the request because, for example, a failover operation is in process. Using this setting, you can set the best wait period for your application without having to change the query timeout in your application code.

This setting is represented by the Connection borrow timeout field in the RDS console or the ConnectionBorrowTimeout setting of DBProxyTargetGroup in the AWS CLI or API. To learn how to change the value of the Connection borrow timeout field in the RDS console, see AWS Management Console. To learn how to change the value of the ConnectionBorrowTimeout setting, see the CLI command modify-db-proxy-target-group or the API operation ModifyDBProxyTargetGroup.

Avoiding pinning

Multiplexing is more efficient when database requests don't rely on state information from previous requests. In that case, RDS Proxy can reuse a connection at the conclusion of each transaction. Examples of such state information include most variables and configuration parameters that you can change through SET or SELECT statements. SQL transactions on a client connection can multiplex between underlying database connections by default.

Your connections to the proxy can enter a state known as pinning. When a connection is pinned, each later transaction uses the same underlying database connection until the session ends. Other client connections also can't reuse that database connection until the session ends. The session ends when the client connection is dropped.

RDS Proxy automatically pins a client connection to a specific DB connection when it detects a session state change that isn't appropriate for other sessions. Pinning reduces the effectiveness of connection reuse. If all or almost all of your connections experience pinning, consider modifying your application code or workload to reduce the conditions that cause the pinning.

For example, suppose that your application changes a session variable or configuration parameter. In this case, later statements can rely on the new variable or parameter to be in effect. Thus, when RDS Proxy processes requests to change session variables or configuration settings, it pins that session to the DB connection. That way, the session state remains in effect for all later transactions in the same session.

For some database engines, this rule doesn't apply to all parameters that you can set. RDS Proxy tracks certain statements and variables. Thus RDS Proxy doesn't pin the session when you modify them. In this case, RDS Proxy only reuses the connection for other sessions that have the same values for those settings. For details about what RDS Proxy tracks for a database engine, see the following:

What RDS Proxy tracks for RDS for SQL Server databases

Following are the SQL Server statements that RDS Proxy tracks:

  • USE

  • SET ANSI_NULLS

  • SET ANSI_PADDING

  • SET ANSI_WARNINGS

  • SET ARITHABORT

  • SET CONCAT_NULL_YIELDS_NULL

  • SET CURSOR_CLOSE_ON_COMMIT

  • SET DATEFIRST

  • SET DATEFORMAT

  • SET LANGUAGE

  • SET LOCK_TIMEOUT

  • SET NUMERIC_ROUNDABORT

  • SET QUOTED_IDENTIFIER

  • SET TEXTSIZE

  • SET TRANSACTION ISOLATION LEVEL

What RDS Proxy tracks for RDS for MariaDB and RDS for MySQL databases

Following are the MySQL and MariaDB statements that RDS Proxy tracks:

  • DROP DATABASE

  • DROP SCHEMA

  • USE

Following are the MySQL and MariaDB variables that RDS Proxy tracks:

  • AUTOCOMMIT

  • AUTO_INCREMENT_INCREMENT

  • CHARACTER SET (or CHAR SET)

  • CHARACTER_SET_CLIENT

  • CHARACTER_SET_DATABASE

  • CHARACTER_SET_FILESYSTEM

  • CHARACTER_SET_CONNECTION

  • CHARACTER_SET_RESULTS

  • CHARACTER_SET_SERVER

  • COLLATION_CONNECTION

  • COLLATION_DATABASE

  • COLLATION_SERVER

  • INTERACTIVE_TIMEOUT

  • NAMES

  • NET_WRITE_TIMEOUT

  • QUERY_CACHE_TYPE

  • SESSION_TRACK_SCHEMA

  • SQL_MODE

  • TIME_ZONE

  • TRANSACTION_ISOLATION (or TX_ISOLATION)

  • TRANSACTION_READ_ONLY (or TX_READ_ONLY)

  • WAIT_TIMEOUT

Minimizing pinning

Performance tuning for RDS Proxy involves trying to maximize transaction-level connection reuse (multiplexing) by minimizing pinning.

In some cases, RDS Proxy can't be sure that it's safe to reuse a database connection outside of the current session. In these cases, it keeps the session on the same connection until the session ends. This fallback behavior is called pinning.

You can minimize pinning by doing the following:

  • Avoid unnecessary database requests that might cause pinning.

  • Set variables and configuration settings consistently across all connections. That way, later sessions are more likely to reuse connections that have those particular settings.

    However, for PostgreSQL setting a variable leads to session pinning.

  • For a MySQL engine family database, apply a session pinning filter to the proxy. You can exempt certain kinds of operations from pinning the session if you know that doing so doesn't affect the correct operation of your application.

  • See how frequently pinning occurs by monitoring the Amazon CloudWatch metric DatabaseConnectionsCurrentlySessionPinned. For information about this and other CloudWatch metrics, see Monitoring RDS Proxy metrics with Amazon CloudWatch.

  • If you use SET statements to perform identical initialization for each client connection, you can do so while preserving transaction-level multiplexing. In this case, you move the statements that set up the initial session state into the initialization query used by a proxy. This property is a string containing one or more SQL statements, separated by semicolons.

    For example, you can define an initialization query for a proxy that sets certain configuration parameters. Then, RDS Proxy applies those settings whenever it sets up a new connection for that proxy. You can remove the corresponding SET statements from your application code, so that they don't interfere with transaction-level multiplexing.

    For metrics about how often pinning occurs for a proxy, see Monitoring RDS Proxy metrics with Amazon CloudWatch.

Conditions that cause pinning for all engine families

The proxy pins the session to the current connection in the following situations where multiplexing might cause unexpected behavior:

  • Any statement with a text size greater than 16 KB causes the proxy to pin the session.

  • Prepared statements cause the proxy to pin the session. This rule applies whether the prepared statement uses SQL text or the binary protocol.

Conditions that cause pinning for RDS for Microsoft SQL Server

For RDS for SQL Server, the following interactions also cause pinning:

  • Using multiple active result sets (MARS). For information about MARS, see the SQL Server documentation.

  • Using distributed transaction coordinator (DTC) communication.

  • Creating temporary tables, transactions, cursors, or prepared statements.

  • Using the following SET statements:

    • SET ANSI_DEFAULTS

    • SET ANSI_NULL_DFLT

    • SET ARITHIGNORE

    • SET DEADLOCK_PRIORITY

    • SET FIPS_FLAGGER

    • SET FMTONLY

    • SET FORCEPLAN

    • SET IDENTITY_INSERT

    • SET NOCOUNT

    • SET NOEXEC

    • SET OFFSETS

    • SET PARSEONLY

    • SET QUERY_GOVERNOR_COST_LIMIT

    • SET REMOTE_PROC_TRANSACTIONS

    • SET ROWCOUNT

    • SET SHOWPLAN_ALL, SHOWPLAN_TEXT, and SHOWPLAN_XML

    • SET STATISTICS

    • SET XACT_ABORT

Conditions that cause pinning for RDS for MariaDB and RDS for MySQL

For MySQL and MariaDB, the following interactions also cause pinning:

  • Explicit table lock statements LOCK TABLE, LOCK TABLES, or FLUSH TABLES WITH READ LOCK cause the proxy to pin the session.

  • Creating named locks by using GET_LOCK causes the proxy to pin the session.

  • Setting a user variable or a system variable (with some exceptions) causes the proxy to pin the session. If this situation reduces your connection reuse too much, you can choose for SET operations not to cause pinning. For information about how to do so by setting the session pinning filters property, see Creating an RDS Proxy and Modifying an RDS Proxy.

  • Creating a temporary table causes the proxy to pin the session. That way, the contents of the temporary table are preserved throughout the session regardless of transaction boundaries.

  • Calling the functions ROW_COUNT, FOUND_ROWS, and LAST_INSERT_ID sometimes causes pinning.

Calling stored procedures and stored functions doesn't cause pinning. RDS Proxy doesn't detect any session state changes resulting from such calls. Therefore, make sure that your application doesn't change session state inside stored routines and rely on that session state to persist across transactions. For example, if a stored procedure creates a temporary table that is intended to persist across transactions, that application currently isn't compatible with RDS Proxy.

If you have expert knowledge about your application behavior, you can skip the pinning behavior for certain application statements. To do so, choose the Session pinning filters option when creating the proxy. Currently, you can opt out of session pinning for setting session variables and configuration settings.

Conditions that cause pinning for RDS for PostgreSQL

For PostgreSQL, the following interactions also cause pinning:

  • Using SET commands

  • Using the PostgreSQL extended query protocol such as by using JDBC default settings

  • Creating temporary sequences, tables, or views

  • Declaring cursors

  • Discarding the session state

  • Listening on a notification channel

  • Loading a library module such as auto_explain

  • Manipulating sequences using functions such as nextval and setval

  • Interacting with locks using functions such as pg_advisory_lock and pg_try_advisory_lock

  • Using prepared statements, setting parameters, or resetting a parameter to its default

Deleting an RDS Proxy

You can delete a proxy if you no longer need it. You might delete a proxy because the application that was using it is no longer relevant. Or you might delete a proxy if you take the DB instance or cluster associated with it out of service.

To delete a proxy

  1. Sign in to the AWS Management Console and open the Amazon RDS console at https://console.aws.amazon.com/rds/.

  2. In the navigation pane, choose Proxies.

  3. Choose the proxy to delete from the list.

  4. Choose Delete Proxy.

To delete a DB proxy, use the AWS CLI command delete-db-proxy. To remove related associations, also use the deregister-db-proxy-targets command.

aws rds delete-db-proxy --name proxy_name
aws rds deregister-db-proxy-targets --db-proxy-name proxy_name [--target-group-name target_group_name] [--target-ids comma_separated_list] # or [--db-instance-identifiers instance_id] # or [--db-cluster-identifiers cluster_id]

To delete a DB proxy, call the Amazon RDS API function DeleteDBProxy. To delete related items and associations, you also call the functions DeleteDBProxyTargetGroup and DeregisterDBProxyTargets.