Replication and Binary Log Server System Variables
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Updates made to the source DB instance are asynchronously copied to the Read Replica. You can reduce the load on your source DB instance by routing read queries from your applications to the Read Replica. Using Read Replicas, you can elastically scale out beyond the capacity constraints of a single DB instance for read-heavy database workloads. The information following doesn't apply to setting up replication with an instance that is running on an Amazon EC2 instance or that is on-premises.
When you create a Read Replica, you first specify an existing DB instance as the source. Then Amazon RDS takes a snapshot of the source instance and creates a sync_binlog performance instance from the snapshot. The Read Replica operates as a DB instance that allows only read-only connections. Applications connect to a Read Replica the same way they do to any DB instance.
Amazon RDS establishes any AWS security configurations needed to enable the secure channel, such as adding security group entries. PostgreSQL DB instances use a secure connection that you can encrypt by setting the ssl parameter to 1 for both the source and the replica instances. Deploying one or more Read Replicas for a given sync_binlog performance DB instance might make sense in a variety of scenarios, including sync_binlog performance following:.
You can direct this excess read traffic to one or more Read Replicas. Serving read traffic while the source DB instance is unavailable. For this use case, keep in mind that the data on the Read Replica might be "stale" because the source DB instance is unavailable. Business reporting or data warehousing scenarios where you might want business reporting sync_binlog performance to run against a Read Replica, rather than your primary, production DB instance. By default, a Read Replica is created with the same storage type as the source DB instance.
However, you can create a Read Replica that has a different storage type from the source DB instance based on the options listed sync_binlog performance the following table.
Amazon RDS doesn't support circular replication. You can't configure a DB instance to serve as a replication source for an existing DB instance; you can only create a new Read Replica from an existing DB instance.
Writing to tables with indexes on a Read Replica. When the ReplicaLag metric reaches 0, the replica has caught up to the source DB instance. If the ReplicaLag metric returns -1, then replication is currently not sync_binlog performance. The parameter value specifies the number of logs to keep. It's created by sync_binlog performance special connection that transmits write sync_binlog performance log WAL data between the source DB instance and sync_binlog performance Read Replica where PostgreSQL asynchronously streams database changes as they are made.
PostgreSQL uses a "replication" role to perform streaming replication. The role is privileged, but can't be used to modify any data. PostgreSQL uses a single process for sync_binlog performance replication.
Amazon RDS sets the necessary parameters and sync_binlog performance for the source DB instance and the Read Replica without any service interruption. A snapshot is taken of the source DB instance, and this snapshot becomes the Read Replica. No outage occurs when you delete a Read Replica. You can create up to five Read Replicas from one source DB instance. For replication to sync_binlog performance effectively, each Read Replica should have the same amount of compute and storage resources as the source DB instance.
If you scale the source DB instance, you should also scale the Read Replicas. However, the Read Replica doesn't become the new source Sync_binlog performance instance automatically. The Read Replica, when promoted, stops receiving WAL communications and is no longer a read-only instance. You must set up any replication you intend to have going forward because the promoted Read Replica is now a new source DB instance.
Before a Sync_binlog performance instance can serve as a source DB instance, you must enable automatic backups on the source DB instance by setting the backup retention period to a value other than 0.
These situations include the following:. This situation causes replication to stop. If you set the parameter sync_binlog performance too low, you can cause a Read Replica to fall so far sync_binlog performance that streaming replication stops.
This recovery process continues until the Read Replica has caught up enough to continue streaming replication. When this process is complete, PostgreSQL attempts to re-establish streaming replication. You can create up to five Read Replicas from one DB instance. For replication to operate effectively, each Read Replica should have as the same amount of compute and storage resources as the source DB instance. You can't have more than four instances involved in a replication chain.
Sync_binlog performance Replicas are designed to support read queries, but you might need occasional updates. For example, you might need to add an index to speed the specific types of queries accessing the replica.
You can run multiple concurrent Read Replica create or delete actions that reference the same source Sync_binlog performance instance, as long as you stay within the limit of five Read Replicas for the source instance.
You use Multi-AZ deployments to improve the durability and availability of critical data, but you can't use the Multi-AZ secondary to serve read-only queries. If the source instance of a Multi-AZ deployment fails over to the secondary, any associated Read Sync_binlog performance automatically switch to use the secondary now primary as their replication source.
Sync_binlog performance RDS creates a standby of your replica in another Availability Zone for sync_binlog performance support for the replica. In these cases, you must manually delete and recreate the Read Replicas.
You can reduce the chance of this happening in MySQL 5. These settings might reduce performance, so test their impact before implementing the changes to a production environment.
These problems are less likely to occur if you use MySQL 5. For instances running MySQL 5. You can stop and restart the replication process on an Amazon RDS DB instance by calling the system stored procedures mysql. You sync_binlog performance do this when replicating between two Amazon RDS instances for long-running operations such as creating large indexes. You also need to stop and start replication when importing or exporting databases.
You sync_binlog performance explicitly delete Read Replicas, using the same mechanisms for deleting a DB instance.
If you delete the source DB instance without deleting the replicas, each replica is promoted to a standalone DB instance. If replication is stopped for more than 30 consecutive days, either manually or due to a replication error, Amazon RDS terminates replication between the master DB instance and sync_binlog performance Read Replicas.
It does so to prevent increased storage requirements on the master DB instance and long failover times. The Read Replica DB instance is still available. However, replication can't be resumed because the binary logs required by the Read Replica are deleted from the master DB instance after replication is terminated.
You can create a new Read Replica for the master DB instance to reestablish replication. An active, long-running transaction can slow the process of creating the Read Replica. We recommend that you wait for long-running transactions to complete before creating a Read Replica. If you create multiple Read Replicas in parallel from the same source DB instance, Amazon RDS takes only one snapshot at the start of the first create action. When creating a Read Replica, there are a few things to consider.
First, you must enable automatic backups on the source DB instance by setting the backup retention period to a value other than 0. These steps are sync_binlog performance to ensure that the Read Replica has a consistent copy of your data.
These steps are not required if all of your tables use a transactional sync_binlog performance such as InnoDB. Stop all data manipulation language DML and data definition language DDL operations on non-transactional tables in the source DB instance and wait for them to complete. Once the Read Replica is available, unlock the tables of the source Sync_binlog performance instance and resume normal database operations.
For Instance actionschoose Create read replica. Choose the instance specifications you want to use. For Multi-AZ deploymentchoose Yes to create a standby of sync_binlog performance replica in another Availability Zone for failover support for the replica. Choose the settings you want to use. For DB instance identifier sync_binlog performance, type a name for the Read Replica.
Adjust other settings as needed. When you promote a Read Replica, the DB instance is rebooted before it becomes available. There are several reasons you might want to promote a Read Replica to a standalone DB instance:. Then you can promote the Read Replica and direct your applications to use the promoted instance.
Sharding — Sharding embodies the "share-nothing" architecture and essentially involves breaking a large database into several smaller databases. One common way to split a sync_binlog performance is splitting sync_binlog performance that are not joined in the same query onto different hosts. Another method is duplicating a table across multiple hosts and then using a hashing algorithm to determine which host receives a given sync_binlog performance. You can create Read Replicas corresponding to each of your shards smaller databases and promote them when you decide to convert them into standalone shards.
You can then carve out the key space if you are splitting rows or distribution of tables for each of the shards depending on your requirements. Implementing failure recovery — You can sync_binlog performance Read Replica promotion as a data recovery scheme if the source DB instance fails.
However, if you require synchronous replication, automatic failure detection, and failover, we recommend that you run your DB instance as a Multi-AZ deployment instead. If you are aware of sync_binlog performance ramifications and limitations of asynchronous replication and you still want to use Read Replica promotion for data recovery, you can do so.
To do this, first create a Read Replica and then monitor the source DB instance for failures. In the event of a failure, do the following:. When you promote a Sync_binlog performance Replica, the new DB instance that is created retains the backup retention period, the backup window, and the parameter sync_binlog performance of the former Read Replica source.
The promotion process can take several minutes or longer to complete, depending on the size of the Read Replica. Because the promoted DB instance is no longer a Read Replica, you can't use it as a replication target. Backup duration is a function of the amount of changes to the database since the previous backup.
If you plan to promote a Read Replica to a standalone instance, we recommend that you enable backups and complete at least one backup prior to promotion.