Mikel  Okuneva

Mikel Okuneva

1600020000

PostgreSQL synchronous_commit Options and Synchronous Standby Replication

I find myself discussing and explaining sychronous_commit with many PostgreSQL users, especially with novice users. So, I thought of noting down all the key points as a blog post which will be useful for more users. Recently I got an opportunity to talk about some related topics in our PostgreSQL Percona Tech Days.

What Is sychronous_commit All About?

This is the parameter by which we can decide when a transaction-commit can be acknowledged back to the client as successful.

So this parameter is not just about synchronous standbys, but it has a wider meaning and implication which is useful for standalone PostgreSQL instances as well. To better understand, we should look at the overall WAL record propagation and various stages from which a commit confirmation is acceptable. This allows us to opt for varying levels of durability for each transaction. The lesser the durability selection, the faster the acknowledgment, which improves the overall throughput and performance of the system.

WAL Propagation

PostgreSQL WAL (Write Ahead Log) is the record of changes/activities on the Primary side and can be considered as a journal/ledger of the changes happening in the database. The following diagram shows the flow of WAL propagation in a local primary PostgreSQL instance and a remote hot standby instance.

#database #tutorial #postgresql #synchronous commit #synchronous standby replication #wal propagation

What is GEEK

Buddha Community

PostgreSQL synchronous_commit Options and Synchronous Standby Replication
Mikel  Okuneva

Mikel Okuneva

1600020000

PostgreSQL synchronous_commit Options and Synchronous Standby Replication

I find myself discussing and explaining sychronous_commit with many PostgreSQL users, especially with novice users. So, I thought of noting down all the key points as a blog post which will be useful for more users. Recently I got an opportunity to talk about some related topics in our PostgreSQL Percona Tech Days.

What Is sychronous_commit All About?

This is the parameter by which we can decide when a transaction-commit can be acknowledged back to the client as successful.

So this parameter is not just about synchronous standbys, but it has a wider meaning and implication which is useful for standalone PostgreSQL instances as well. To better understand, we should look at the overall WAL record propagation and various stages from which a commit confirmation is acceptable. This allows us to opt for varying levels of durability for each transaction. The lesser the durability selection, the faster the acknowledgment, which improves the overall throughput and performance of the system.

WAL Propagation

PostgreSQL WAL (Write Ahead Log) is the record of changes/activities on the Primary side and can be considered as a journal/ledger of the changes happening in the database. The following diagram shows the flow of WAL propagation in a local primary PostgreSQL instance and a remote hot standby instance.

#database #tutorial #postgresql #synchronous commit #synchronous standby replication #wal propagation

PostgreSQL Connection Pooling: Part 4 – PgBouncer vs. Pgpool-II

In our previous posts in this series, we spoke at length about using PgBouncer  and Pgpool-II , the connection pool architecture and pros and cons of leveraging one for your PostgreSQL deployment. In our final post, we will put them head-to-head in a detailed feature comparison and compare the results of PgBouncer vs. Pgpool-II performance for your PostgreSQL hosting !

The bottom line – Pgpool-II is a great tool if you need load-balancing and high availability. Connection pooling is almost a bonus you get alongside. PgBouncer does only one thing, but does it really well. If the objective is to limit the number of connections and reduce resource consumption, PgBouncer wins hands down.

It is also perfectly fine to use both PgBouncer and Pgpool-II in a chain – you can have a PgBouncer to provide connection pooling, which talks to a Pgpool-II instance that provides high availability and load balancing. This gives you the best of both worlds!

Using PgBouncer with Pgpool-II - Connection Pooling Diagram

PostgreSQL Connection Pooling: Part 4 – PgBouncer vs. Pgpool-II

CLICK TO TWEET

Performance Testing

While PgBouncer may seem to be the better option in theory, theory can often be misleading. So, we pitted the two connection poolers head-to-head, using the standard pgbench tool, to see which one provides better transactions per second throughput through a benchmark test. For good measure, we ran the same tests without a connection pooler too.

Testing Conditions

All of the PostgreSQL benchmark tests were run under the following conditions:

  1. Initialized pgbench using a scale factor of 100.
  2. Disabled auto-vacuuming on the PostgreSQL instance to prevent interference.
  3. No other workload was working at the time.
  4. Used the default pgbench script to run the tests.
  5. Used default settings for both PgBouncer and Pgpool-II, except max_children*. All PostgreSQL limits were also set to their defaults.
  6. All tests ran as a single thread, on a single-CPU, 2-core machine, for a duration of 5 minutes.
  7. Forced pgbench to create a new connection for each transaction using the -C option. This emulates modern web application workloads and is the whole reason to use a pooler!

We ran each iteration for 5 minutes to ensure any noise averaged out. Here is how the middleware was installed:

  • For PgBouncer, we installed it on the same box as the PostgreSQL server(s). This is the configuration we use in our managed PostgreSQL clusters. Since PgBouncer is a very light-weight process, installing it on the box has no impact on overall performance.
  • For Pgpool-II, we tested both when the Pgpool-II instance was installed on the same machine as PostgreSQL (on box column), and when it was installed on a different machine (off box column). As expected, the performance is much better when Pgpool-II is off the box as it doesn’t have to compete with the PostgreSQL server for resources.

Throughput Benchmark

Here are the transactions per second (TPS) results for each scenario across a range of number of clients:

#database #developer #performance #postgresql #connection control #connection pooler #connection pooler performance #connection queue #high availability #load balancing #number of connections #performance testing #pgbench #pgbouncer #pgbouncer and pgpool-ii #pgbouncer vs pgpool #pgpool-ii #pooling modes #postgresql connection pooling #postgresql limits #resource consumption #throughput benchmark #transactions per second #without pooling

Trace  Hoeger

Trace Hoeger

1633730400

How to Do Synchronous Replication in PostgreSQL and YugabyteDB

I have seen a people comparing YugabyteDB and PostgreSQL, and surprised by the different throughput when running a simple test on a from a single session. The purpose of a distributed database is to scale out. When running on a single node without the need for High-Availability-without-data-loss (this is a tautology), a monolith database will always perform with lower latency. Because a distributed DB is designed to ensure the persistence (the D in ACID) though RPC (remote procedure calls) rather than local writes.

#yugabytedb  #postgresql 


 

Stephania  Von

Stephania Von

1595946660

What is the difference between synchronous and asynchronous replication in postgresql

In this session we are going to about key differences between synchronous and asynchronous replication in PostgreSQL.

i) The concept of replication is changed Happening in one database are replicated into other databases

ii) It can be made in two ways
1) synchronous replication
2) Asynchronous replication

Asynchronous replication:

  • It’s a standard way To replicate data in PostgreSQL

  • Advantages of this replication are low overhead, simplicity & robustness.

  • As a result of async replication is the ideal solution of automatic failover
    And enterprise-grade pregnancies

synchronous replication:

If you are not ready to take the risk of losing a cothe mmit sync replication is best solution

  • It ensures the highest possible security of our transactions

#postgresql

Database conversion and synchronization software. DBConvert Studio

A new version 2.0 of DBConvert Studio is available. It is intended for DBAs who need complex migrations between databases and synchronization between the most popular DBMS.

DBConvert Studio supports the most popular on-premises databases and Database Cloud platforms. It becomes a brilliant all-in-one solution, combining robust database migration engines with an updated, user-friendly interface.

Since version 2.0, it has fully 64-bit database migration engines that handle large database tables. Older 32-bit kernels limited RAM allocation for tables to 2 GB.

Synchronization engines for MySQL, Microsoft SQL Server, SQLite, Firebird, and Oracle improved. Synchronization speed increased up to 30%.

Check out DBConvert Studio web page for more information.

#database #migration #synchronization #mysql #sql-server #postgresql