PgConf.Russia 2017

Streaming replication has been introduced in 2010 and quickly became one of the most popular features of PostgreSQL. Today, it is hard to imagine PostgreSQL installation without streaming replication. With its stability, high efficiency and ease of configuration one would have thought it is an optimal feature. However, while using it you might sometimes enter murky waters. This often can be resolved by using a combination of built-in and third party troubleshooting tools. In my talk I will provide an overview of these tools and explain how with their help one can diagnose, understand and eliminate problems related to streaming replication. I will also go through the most frequent issues occurring when streaming replication is used and will propose possible solutions. This talk is primarily aimed at DBAs and system administrators who use PostgreSQL in their day-to-day.

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< Query failed: ERROR: deadlock detected
< DETAIL: Process 17371 waits for ShareLock on transaction 102733872; Blocked by process.
< Process 10414 waits for ShareLock on transaction 102733874; Blocked by process 17371.

Such "unpleasant" messages from the server can seriously puzzle the developer. When working with locks, in particular, with transactions in general, it is necessary to take into account the features of the implementation of client libraries, which can cause the above exception.

In the short talk, the mechanics of the interaction of locks will be explained, main attention being paid to causes of deadlocks. References to the relevant documentation pages will be given. A technique of "bypassing" this problem of concurrent data access will be described and illustrated with some generalized examples from practice are shown. The talk will be interesting to database developers and administrators as well as the client-side application developers.

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We will discuss some tricks and patterns while developing web-application architecture based on ORM technology with Postgresql functions implementation with Python Django as an example. Also we will consider some ways of building the business logic inside a database with keeping Django framework opportunities and implementation of it's built-in admin panel.

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