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Displaying posts with tag: troubleshooting (reset)
The Difference Between Lock Wait Timeout And Deadlock

If you use ACID transactional databases, you’ve probably heard of lock wait timeouts and deadlocks. What are these? And how are they different?

It’s inevitable that many of us will come across these phenomena at some point. Most databases use locking strategies to make sure that data stays consistent when multiple users (or connections, or processes) are reading and modifying the data concurrently.  The locks ensure that only one operation can alter a specific portion of the data at a time as well as serializing changes to further mitigate these race conditions. Without this locking, confusing and incorrect behaviors can happen.

Lock wait timeouts and deadlocks both arise from certain locking mechanisms. A lock wait timeout results when one user gets a lock on some data and holds it while another user …

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Database Objects migration to RDS/ Aurora (AWS)

The world of application and its related services are migrating more towards cloud, because of availability, Elasticity, Manageability etc. While moving the entire stack we need to be very cautious while migrating the database part.

Migration of DB servers is not a simple lift and shift operation, Rather it would require a proper planning and more cautious in maintaining data consistency with existing DB server and cloud server by means of native replication or by using any third party tools.

The best way to migrate the existing MySQL database to RDS, in my opinion, is by using “logical backup“. Some of the logical backup tools as below,

Mysqldump — single threaded (widely used)

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How NOT to Monitor Your Database

Do you have experience putting out backend database fires? What were some things you wished you had done differently? Proactive database monitoring is more cost efficient, manageable, and sanity-saving than reactive monitoring. We reviewed some of the most common mistakes - too many log messages, metric “melting pots,” retroactive changes, incomplete visibility, undefined KPIs - and put together an action plan on how to prevent them. From our experience, we've listed out the top 5 biggest (and preventable!) database monitoring pitfalls.

Log Levels

There never seem to be enough logging levels to capture the desired granularity and relevance of a log message accurately. Is it INFO, TRACE, or DEBUG? What if it’s DEBUG but it’s for a condition we should WARN about? Is there really a linear hierarchy here? If you’re like most people, you’ve seen …

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How NOT to Monitor Your Database

Do you have experience putting out backend database fires? What were some things you wished you had done differently? Proactive database monitoring is more cost efficient, manageable, and sanity-saving than reactive monitoring. We reviewed some of the most common mistakes - too many log messages, metric “melting pots,” retroactive changes, incomplete visibility, undefined KPIs - and put together an action plan on how to prevent them. From our experience, we've listed out the top 5 biggest (and preventable!) database monitoring pitfalls.

Log Levels

There never seem to be enough logging levels to capture the desired granularity and relevance of a log message accurately. Is it INFO, TRACE, or DEBUG? What if it’s DEBUG but it’s for a condition we should WARN about? Is there really a linear hierarchy here? If you’re like most people, you’ve seen …

[Read more]
Troubleshooting MySQL Concurrency Issues with Load Testing Tools Webinar: Q & A

In this blog, I will provide answers to the Q & A for the Troubleshooting MySQL Concurrency Issues with Load Testing Tools webinar.

First, I want to thank everybody for attending my May 23, 2018, webinar on troubleshooting tools for MySQL. The recording and slides for the webinar are available here. Below is the list of your questions that I was unable to answer fully during the webinar.

Q: What do you recommend for benchmarking NDB cluster? Which should be used and how?

A: The issue with benchmarking NDB cluster is not the tool choice, …

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ProxySQL Series: Handling resource expensive(bad) Queries in MySQL

This is our fourth blog in the ProxySQL Series

  1. MySQL Replication Read-write Split up
  2. Seamless Replication Switchover Using MHA
  3. Mirroring MySQL Queries

This blog focuses on how to quickly find and address badly written queries using ProxySQL without any downtime and change in application code.

When we get an incident about the high usage on a production master, then mostly it is because of unexpected spike in Traffic (QPS) or slow queries.

Below was the status when we were doing the …

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Presentation : MySQL Timeout Variables Explained

MySQL has multiple timeout variables these slides helps to give an overview of the different  timeout variables and their purposes briefly.

Handling long duration SST(timeout) in PXC with systemd

In this blog post, We will be explaining about the timeouts in SST on systemd implementation which we faced recently in Percona XtraDB Cluster  during our Consulting with a client. State Snapshot Transfers (SST) refers to complete data sync from one of the nodes from the cluster to the joining node.

SST will happen for one or more reasons listed below.

  1. Initial sync to join a node to cluster.
  2. Node is out of cluster and lost its ability to join back due to data corruption or inconsistencies and also when the node went far behind the node, …
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Basic Internal Troubleshooting Tools for MySQL Server Webinar: Q & A

In this blog, I will provide answers to the Q & A for the Basic Internal Troubleshooting Tools for MySQL Server webinar.

First, I want to thank everybody for attending my February 15, 2018, webinar on troubleshooting tools for MySQL. The recording and slides for the webinar are available here. Below is the list of your questions that I was unable to answer fully during the webinar.

Q: How do we prevent the schema prefix from appearing in the show create view. This is causing issue with restore on another server with a different DB. See the issue …

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Investigating a MySQL dead lock

I was involved in one of the development support for MySQL. Here is an interesting case

The application needs a Sequence generator as it was not present inbuilt with MySQL ( MariaDB will have it in 10.3 ) they have made sequence generator function with ‘select for update‘ statement. But it tends to cause more locking at high concurrency with their XtraDB Cluster deployment.

To get rid of this , the sequence generation were made as direct Update queries and sequence is fetched using Select @next.

UPDATE EO_PK_TABLE SET PK = (@next := PK …
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