pgstore

Package pgstore is a PostgreSQL-based storage engine for the SCS session package.

Usage

Installation

Either:

$ go get github.com/alexedwards/scs/engine/pgstore

Or (recommended) use use gvt to vendor the engine/pgstore and session sub-packages:

$ gvt fetch github.com/alexedwards/scs/engine/pgstore
$ gvt fetch github.com/alexedwards/scs/session

Setup

You should have a working PostgreSQL database containing a sessions table with the definition:

CREATE TABLE sessions (
  token TEXT PRIMARY KEY,
  data BYTEA NOT NULL,
  expiry TIMESTAMPTZ NOT NULL
);
CREATE INDEX sessions_expiry_idx ON sessions (expiry);

Example

package main

import (
    "database/sql"
    "io"
    "log"
    "net/http"
    "time"

    "github.com/alexedwards/scs/engine/pgstore"
    "github.com/alexedwards/scs/session"
)

func main() {
    // Establish a database/sql pool
    db, err := sql.Open("postgres", "postgres://user:pass@localhost/db")
    if err != nil {
        log.Fatal(err)
    }
    defer db.Close()

    // Create a new PGStore instance using the existing database/sql pool, 
    // with a cleanup interval of 5 minutes.
    engine := pgstore.New(db, 5*time.Minute)

    sessionManager := session.Manage(engine)
    http.HandleFunc("/put", putHandler)
    http.HandleFunc("/get", getHandler)
    http.ListenAndServe(":4000", sessionManager(http.DefaultServeMux))
}

func putHandler(w http.ResponseWriter, r *http.Request) {
    err := session.PutString(r, "message", "Hello world!")
    if err != nil {
        http.Error(w, err.Error(), 500)
    }
}

func getHandler(w http.ResponseWriter, r *http.Request) {
    msg, err := session.GetString(r, "message")
    if err != nil {
        http.Error(w, err.Error(), 500)
    }
    io.WriteString(w, msg)
}

Cleaning up expired session data

The pgstore package provides a background 'cleanup' goroutine to delete expired session data. This stops the database table from holding on to invalid sessions indefinitely and growing unnecessarily large.

You can specify how frequently to run the cleanup when creating a new PGstore instance:

// Run a cleanup every 30 minutes.
pgstore.New(db, 30*time.Minute)

// Setting the cleanup interval to zero prevents the cleanup from being run.
pgstore.New(db, 0)

Terminating the cleanup goroutine

It's rare that the cleanup goroutine for a PGStore instance needs to be terminated. It is generally intended to be long-lived and run for the lifetime of your application.

However, there may be occasions when your use of a PGStore instance is transient. A common example would be using it in a short-lived test function. In this scenario, the cleanup goroutine (which will run forever) will prevent the PGStore object from being garbage collected even after the test function has finished. You can prevent this by manually calling StopCleanup().

For example:

func TestExample(t *testing.T) {
    db, err := sql.Open("postgres", "postgres://user:pass@localhost/db")
    if err != nil {
        t.Fatal(err)
    }
    defer db.Close()

    engine := New(db, time.Second)
    defer engine.StopCleanup()

    // Run test...
}

Notes

The pgstore package is underpinned by the excellent pq driver.

Full godoc documentation: https://godoc.org/github.com/alexedwards/scs/engine/pgstore.