Paging in gopkg.in/ldap.v2

Over the last couple of months I’ve been working more and more with the awesome LDAP package for Go available on gopkg.in/ldap.v2 but only today I needed to do paging. The documentation didn’t contain any example or other hints outside of the existence of the ControlPaging so it took me a while to get it to work.

The basic idea with that is that when you create a new search request, you can pass a slice of so-called “controls” that act as extension points for the core LDAP protocol-suite. LDAP core doesn’t specify any sort of paging for dealing with large result sets, but luckily RFC2696 specifies such a control which is implemented in the ControlPaging struct:

paging := ldap.NewControlPaging(100)
for {
    req := ldap.NewSearchRequest(baseDN, ldap.ScopeWholeSubtree,
        ldap.DerefAlways, 0, 0, false, filter,
        []string{"name", "member"}, []ldap.Control{paging})
    result, err := conn.Search(req)

    ...

    resultCtrl := ldap.FindControl(result.Controls, paging.GetControlType())
    if resultCtrl == nil {
        break
    }
    if pagingCtrl, ok := resultCtrl.(*ldap.ControlPaging); ok {
        if len(pagingCtrl.Cookie) == 0 {
            break
        }
        paging.SetCookie(pagingCtrl.Cookie)
    }
}

What I do here, is to first create a new ControlPaging object with a page size of 100. Next, I include this control in the controls parameter when creating a new search request. Once I’m through with processing the entries that have been returned for the “current page”, I update the paging control with the cookie returned from the server and continue to do requests until either I don’t get a new paging control back from the server or its cookie is empty.

I will probably refine that example and create a PR for the project if time permits.

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