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Package dbcontrol limits the number of active connections for database/sql. Implementations of Go's database/sql package prior to Go 1.2, don't let the user put a limit on the number of active connections to the underlying DB. If enough concurrent requests are made, so that the package runs out of available connections, then more are requested from the driver no matter how many you have at the pool already. Hence, unless you take precautions in your design/code, or there's specific support from the actual DB driver you're using, you are likely to hit some other limit (DB engine itself, OS) or simply run out of resources. None of those situations are desirable, of course. If you hit DB or OS limits on the number of connections, then many of your statements will start failing cause no connection is available for them to use. You can get around it if you're lucky enough to have driver support, but then you are tied to a particular DB. This package is a wrapper on Go's standard database/sql, providing a general mechanism so that you're free to use statements as usual, yet have the number of active connections limited. A wrapper DB type is declared, that supports all standard operations from database/sql. To use it, you should set the maximum number of connections you want to allow, just like: All databases opened by the package afterwards will use a maximum of 10 connections. You can change this setting as often as you wish, but keep in mind that the number is bound to databases as they are opened, i.e., changing this concurrency setting has no effect on already-opened databases. Note also that you can get the default non-limited behavior by setting concurrency to zero. To open a DB you proceed just like with the database/sql package, like so: Note that sql.Row, sql.Rows and sql.Stmt types are overridden by this package, but that's probably transparent unless you declare the types explicitly. If you declare variables using the := operator you'll be fine. Usage now follows the expected pattern from database/sql: The full set of features at database/sql is supported, including transactions, even though not all functions need to be overridden. This package was designed to provide the feature with minimum overhead, and thus uses knowledge of database/sql internals to know when locking is required/appropriate. As an extension, you can set a channel to receive the locking duration each time a connection has to be waited for. This can work as an aid to help you tune the pool size or otherwise work around concurrency problems. You can also set a channel where notifications will be sent every time a connection is held for longer than a certain timeout. The notification includes the full stack trace of the caller at the time the connection was requested. This can prove useful to identify long-running queries that are locking connections, and possibly impeding others from running. The feature can be turned on and off at will. A small performance penalty will be paid if on (that of retrieving the caller's stack), but none if the feature is off (the default). Note that only functions specific to this package or with altered semantics are documented. Please refer to the database/sql package documentation for more information.
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purl: pkg:golang/github.com/%21vivid%21cortex/dbcontrol
License: MIT
Latest release: about 4 years ago
First release: about 4 years ago
Namespace: github.com/VividCortex
Stars: 29 on GitHub
Forks: 4 on GitHub
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Last synced: about 6 hours ago