Applications should be written taking into account that errors
will eventually happen and, in particular, database application
developers usually consider this while writing their
applications.
Although the concepts required to write such applications are
commonly taught in database courses and to some extent are widely
spread, building a reliable and fault-tolerant database
application is still not an easy task and hides some pitfalls
that we intend to highlight in this post with a set of
suggestions or tips.
In what follows, we consider that the execution flow in a
database application is characterized by two distinct phases:
connection and business logic. In the connection phase, the
application connects to a database, sets up the environment and
passes the control to the business logic phases. In this phase,
it gets inputs from a source, which may be an operator, another
application or a component within the same …
In this post, we are going to show how to develop fault-tolerant
applications using MySQL Fabric, or simply Fabric, which
is an approach to building high availability sharding
solutions for MySQL and that has recently become available
for download as a labs release (http://labs.mysql.com/). We are going to focus
on Fabric's high availability aspects but to find out more on
sharding readers may check out the following blog post:
Servers managed by Fabric are registered in a MySQL Server instance, called backing store, and are …
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In MySQL we have the typical behaviour that we open and close connections very often and rapidly. So we have very short-living connections to the server. This can lead in extreme cases to the situation that the maximum number of TCP ports are exhausted.
The maximum number of TCP ports we can find with:
# cat /proc/sys/net/ipv4/ip_local_port_range 32768 61000
In this example we can have in maximum (61000 - 32768 = 28232) connections concurrently open.
When a TCP connections closes the port cannot be reused
immediately afterwards because the Operating System has to wait
for the duration of the TIME_WAIT interval (maximum
segment lifetime, MSL). This we can see with the command:
# netstat -nat Active Internet connections (servers and established) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 0.0.0.0:10050 …[Read more]
The occurrence of failures and crashes can compromise the high
availability of your database system affecting your revenue and
reputation. Therefore, it is fundamental to minimize downtime and
have an efficient strategy for crash recovery.
Replication and failover are commonly applied to deal with those
situations. However, other types of failures can also affect the
recovery process. In fact, the occurrence of unanticipated faults
can really be an headache! Thus, it is better to be prepared and
implement a good fault-tolerant failover strategy.
Performing failover is not trivial. It requires the execution of
several steps in order to ensure data consistency (i.e., no data
loss) -- especially if the "best" candidate to become the new
master is not the most up-to-date.
Note that, one might desire that the slave with the best hardware
should become the new master. In this case, the candidate must be …
Percona Server version 5.6.13-60.6
Percona is glad to announce the fourth Release Candidate of Percona Server 5.6.13-60.6 (downloads are available here and from the Percona Software Repositories).
Based on MySQL 5.6.13, including all the bug fixes in it, Percona Server 5.6.13-60.6 is the fourth RC release in the Percona Server 5.6 series. All of Percona‘s software is open-source and …
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MySQL 5.7.2 features enhanced Multi-threaded slave which
can be used to apply transactions in parallel even within a
single database. Internal details of its working can be found in
an earlier post. In this post we will
see how we can configure our replication slave to use this
enhancement.
MySQL 5.7.2 has a new system variable
--slave-parallel-type which is dynamic. It can
be set to the following values:
1. DATABASE : (Default) Use the db partitioned MTS
(1 worker per database)
2. LOGICAL_CLOCK: Use logical clock based
parallelization mode.
Apart from this the original option of
--slave-parallel-workers=N is still valid and it sets that
number of workers that we need to spawn. Also since the slave
leverages the group of transactions that have …
IntroductionRe-applying binary logs generated from highly
concurrent master on the slave has always been an area of focus.
It is important for various reasons. First, in real-time systems,
it becomes extremely important for the slave to keep up with the
master. This can only be guaranteed if the slaves’ performance in
reapplying the transactions from the binary log is similar (or
at-least comparable) to that of master, which is accepting
queries directly from multiple clients. Second, in synchronous
replication scenarios, having a fast slaves, aids in reducing the
response times as seen by the clients to the master. This can be
made possible by applying transactions from the binary log in
parallel. However if left uncontrolled, a simple round-robin
multi-threaded applying will lead to inconsistency and the slave
will no longer be the exact replica of the leader.
The infamous out of order commit problemThe Out of order
execution of transaction …
Learn how Modernizing Medicine, an electronic medical records company, serves thousands of customers and leverages Continuent Tungsten to manage databases on Amazon AWS. Modernizing Medicine is as fast growing SaaS company, offering electronic medical records management solution for thousands of small and medium-sizes dermatology, ophthalmology, optometry, plastic surgery, cosmetic and
The MariaDB project is pleased to announce the immediate availability of MariaDB 5.5.33a. This is a Stable (GA) release. See the Release Notes and Changelog for detailed information on this release and the What is MariaDB 5.5? page in the AskMonty Knowledgebase for general information about the MariaDB 5.5 series.
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“Will you expand the next webcast to 90 minutes? This one was
too interesting to last only one hour” was one of the
questions we got during the “Tuning MySQL for Great Product Performance: The
Fundamentals, Updated for MySQL 5.6” webinar on August
27th. The engineers on Q&A got a lot of good (and more
technical) questions during the webcast. For those of you
who were unable to join us live, I’ve posted the questions and
answers below, and you can listen to a recording of the webinar
and get a .pdf of slides at this link.
The webinar was created specifically for the software and …