Json2Ldap adds directory server fail-over and load-balancing

24 January 2013

The new year began with the third major release of Json2Ldap, the cool JSON web API for accessing directory servers such as MS Active Directory, OpenLDAP and OpenDJ.

This post is a summary of what’s in the new 3.0 version.

Directory server fail-over and load-balancing

Resilience and scalability is a common requirement in enterprise and SaaS applications. You can now configure Json2Ldap to fail-over between two or more directory servers, or alternatively, to perform round-robin directory server selection.

Fail-over is a common strategy to provide backup in case your primary LDAP server fails. To handle such situations you can specify a secondary, tertiary, and so on servers for Json2Ldap to connect to if the primary becomes unavailable.

To configure fail-over:

json2ldap.defaultLDAPServer.selectionAlgorithm = FAILOVER
json2ldap.defaultLDAPServer.url = ldap://192.168.1.10 ldap://192.168.1.20
json2ldap.defaultLDAPServer.connectTimeout = 500

The above configuration will set a secondary LDAP server on IP 192.168.1.20. Json2Ldap will direct new ldap.connect requests to it if it’s not able to connect to the primary server within 500 milliseconds.

Round-robin is the alternative server selection method. It provides for load-balancing between multiple servers and is also a form of fail-over in case one or more of the servers in the set become unavailable.

To configure round-robin selection with two servers, using again a connect time-out of 500ms:

json2ldap.defaultLDAPServer.selectionAlgorithm = ROUND-ROBIN
json2ldap.defaultLDAPServer.url = ldap://192.168.1.10 ldap://192.168.1.20
json2ldap.defaultLDAPServer.connectTimeout = 500

Configuration of fail-over and round-robin is explained in detail in the Json2Ldap docs.

Support for Virtual-List-View searches

The Virtual-List-View (VLV) control (draft-ietf-ldapext-ldapv3-vlv-09) allows web clients to retrieve an arbitrary subset of an LDAP search result. You can think of it as a sophisticated makeover of the Simple Paged Results (RFC 2696) control. The VLV control allows you to specify an offset into the result set and a number of entries to get before and after the offset position. This can for instance be of great help in devising efficient browsing web UIs when the result sets are expected to be huge.

To apply VLV to an ldap.search request add a parameter like this:

"vlv" : { "offset":50, "after":24 }

This will ask to return 25 entries at offset fifty. Note that the VLV control also requires the presence of a sort control in order to determine the entry order, e.g.:

"sort" : { "key":"givenName" }

I have put together a list of the directory servers that support Virtual-List-View. A brief look at the list will show you that it’s widely supported. You may however have to create specific indexes in your directory to enable it. Check you server documentation for that.

Use of the VLV control in Json2Ldap is detailed in the ldap.search API docs.

Normalising attribute names

The attribute names that Json2Ldap returns with ldap.getEntry, ldap.search and ldap.getRootDSE appear as defined in the directory schema. However, if you don’t have prior knowledge of their letter-case retrieving them from the result JSON object can be a bit of a problem.

var givenName = result["givenName"];

The solution to this has been to normalise all names, e.g. converting them to lower-case, before processing the result.

Json2Ldap 3.0 added a new optional normalize parameter to solve this problem. With it all attribute names in the result will be normalised, or converted to lower-case. So you don’t have to worry about the extra conversion. It will be done for you, quite efficiently, inside Json2Ldap.

Retrieving subordinate subtree entries

The ldap.search SUBORDINATE_SUBTREE scope parameter has been renamed to SUBORDINATES. This is the only breaking change in the Json2Ldap web API and was done to make the parameter compatible with the LDAP URL schema.

API keys

You can now also specify API keys to ensure only selected web clients can access the web API of Json2Ldap. These are passed as an optional apiKey parameter to each web call. You can define API keys for global access as well as keys that are only for certain API calls. Check out the API key configuration to find out more.

The classic X.509 client certificate access controls are still supported.

Simplified configuration files

Json2Ldap 3.0 moved the configuration parameters from the web.xml file to a set of simpler text properties files that continue to follow the established semantics. Many of the configuration properties were also given better and more intuitive names. As a result the whole task of configuring Json2Ldap should have become easier and less error-prone (by switching from XML to simple key / value properties). Adding a web UI configuration editor is on the roadmap for 2013 / 2014.

Ready to try out Json2Ldap 3.0?

You can get a copy of Json2Ldap 3.0 for evaluation from the product downloads section. Existing subscribers should have already been notified and received their download links for the full version.

[You’re welcome to get in touch with us if you have questions about the new version or feedback to share.

The full 3.0 change log is on the Json2Ldap datasheet.