postgresstore

README

postgresstore

A PostgreSQL based session store for SCS using the pq driver.

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);

The database user for your application must have SELECT, INSERT, UPDATE and DELETE permissions on this table.

Example

package main

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

	"github.com/alexedwards/scs/v2"
	"github.com/alexedwards/scs/postgresstore"

	_ "github.com/lib/pq"
)

var sessionManager *scs.SessionManager

func main() {
	// Establish connection to PostgreSQL.
	db, err := sql.Open("postgres", "postgres://username:password@host/dbname")
	if err != nil {
		log.Fatal(err)
	}
	defer db.Close()

	// Initialize a new session manager and configure it to use postgresstore as the session store.
	sessionManager = scs.New()
	sessionManager.Store = postgresstore.New(db)

	mux := http.NewServeMux()
	mux.HandleFunc("/put", putHandler)
	mux.HandleFunc("/get", getHandler)

	http.ListenAndServe(":4000", sessionManager.LoadAndSave(mux))
}

func putHandler(w http.ResponseWriter, r *http.Request) {
	sessionManager.Put(r.Context(), "message", "Hello from a session!")
}

func getHandler(w http.ResponseWriter, r *http.Request) {
	msg := sessionManager.GetString(r.Context(), "message")
	io.WriteString(w, msg)
}

Expired Session Cleanup

This 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. By default the cleanup runs every 5 minutes. You can change this by using the NewWithCleanupInterval() function to initialize your session store. For example:

// Run a cleanup every 30 minutes.
postgresstore.NewWithCleanupInterval(db, 30*time.Minute)

// Disable the cleanup goroutine by setting the cleanup interval to zero.
postgresstore.NewWithCleanupInterval(db, 0)

Terminating the Cleanup Goroutine

It's rare that the cleanup goroutine 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 session store 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 session store instance from being garbage collected even after the test function has finished. You can prevent this by either disabling the cleanup goroutine altogether (as described above) or by stopping it using the StopCleanup() method. For example:

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

	store := postgresstore.New(db)
	defer store.StopCleanup()

	sessionManager = scs.New()
	sessionManager.Store = store

	// Run test...
}

Documentation

Index

• type PostgresStore
  • func New(db *sql.DB) *PostgresStore
  • func NewWithCleanupInterval(db *sql.DB, cleanupInterval time.Duration) *PostgresStore
  • func (p *PostgresStore) All() (map[string][]byte, error)
  • func (p *PostgresStore) Commit(token string, b []byte, expiry time.Time) error
  • func (p *PostgresStore) Delete(token string) error
  • func (p *PostgresStore) Find(token string) (b []byte, exists bool, err error)
  • func (p *PostgresStore) StopCleanup()

Types

type PostgresStore

type PostgresStore struct {
	// contains filtered or unexported fields
}

PostgresStore represents the session store.

func New

func New(db *sql.DB) *PostgresStore

New returns a new PostgresStore instance, with a background cleanup goroutine that runs every 5 minutes to remove expired session data.

func NewWithCleanupInterval

func NewWithCleanupInterval(db *sql.DB, cleanupInterval time.Duration) *PostgresStore

NewWithCleanupInterval returns a new PostgresStore instance. The cleanupInterval parameter controls how frequently expired session data is removed by the background cleanup goroutine. Setting it to 0 prevents the cleanup goroutine from running (i.e. expired sessions will not be removed).

func (*PostgresStore) All

func (p *PostgresStore) All() (map[string][]byte, error)

All returns a map containing the token and data for all active (i.e. not expired) sessions in the PostgresStore instance.

func (*PostgresStore) Commit

func (p *PostgresStore) Commit(token string, b []byte, expiry time.Time) error

Commit adds a session token and data to the PostgresStore instance with the given expiry time. If the session token already exists, then the data and expiry time are updated.

func (*PostgresStore) Delete

func (p *PostgresStore) Delete(token string) error

Delete removes a session token and corresponding data from the PostgresStore instance.

func (*PostgresStore) Find

func (p *PostgresStore) Find(token string) (b []byte, exists bool, err error)

Find returns the data for a given session token from the PostgresStore instance. If the session token is not found or is expired, the returned exists flag will be set to false.

func (*PostgresStore) StopCleanup

func (p *PostgresStore) StopCleanup()

StopCleanup terminates the background cleanup goroutine for the PostgresStore instance. It's rare to terminate this; generally PostgresStore instances and their cleanup goroutines are intended to be long-lived and run for the lifetime of your application.

There may be occasions though when your use of the PostgresStore is transient. An example is creating a new PostgresStore instance in a test function. In this scenario, the cleanup goroutine (which will run forever) will prevent the PostgresStore object from being garbage collected even after the test function has finished. You can prevent this by manually calling StopCleanup.