Incompatible changes in ArangoDB 2.7

It is recommended to check the following list of incompatible changes before upgrading to ArangoDB 2.7, and adjust any client programs if necessary.

AQL changes

DISTINCT is now a keyword in AQL.

AQL queries that use DISTINCT (in lower, upper or mixed case) as an identifier (i.e. as a variable, a collection name or a function name) will stop working. To make such queries working again, each occurrence of DISTINCT in an AQL query should be enclosed in backticks. This will turn DISTINCT from a keyword into an identifier again.

The AQL function SKIPLIST() has been removed in ArangoDB 2.7. This function was deprecated in ArangoDB 2.6. It was a left-over from times when the query optimizer wasn’t able to use skiplist indexes together with filters, skip and limit values. Since this issue been fixed since version 2.3, there is no AQL replacement function for SKIPLIST. Queries that use the SKIPLIST function can be fixed by using the usual combination of FOR, FILTER and LIMIT, e.g.

    FOR doc IN @@collection 
      FILTER doc.value >= @value 
      SORT doc.value DESC 
      LIMIT 1 
      RETURN doc

Foxx changes

Bundling and compilation

The assets property is no longer supported in Foxx manifests and is scheduled to be removed in a future version of ArangoDB. The files property can still be used to serve static assets but it is recommended to use separate tooling to compile and bundle your assets.

Manifest scripts

The properties setup and teardown have been moved into the scripts property map:

Before:

{
  ...
  "setup": "scripts/setup.js",
  "teardown": "scripts/teardown.js"
}

After:

{
  ...
  "scripts": {
    "setup": "scripts/setup.js",
    "teardown": "scripts/teardown.js"
  }
}

Foxx Queues

Function-based Foxx Queue job types are no longer supported. To learn about how you can use the new script-based job types see the Foxx queues module.

Foxx Sessions

The jwt and type options have been removed from the activateSessions API.

If you want to replicate the behavior of the jwt option you can use the JWT functions in the crypto module. A JWT-based session storage that doesn’t write sessions to the database is available as the sessions-jwt app in the Foxx app store.

The session type is now inferred from the presence of the cookie or header options (allowing you to enable support for both). If you want to use the default settings for cookie or header you can pass the value true instead.

The sessionStorageApp option has been removed in favor of the sessionStorage option.

Before:

var Foxx = require('org/arangodb/foxx');
var ctrl = new Foxx.Controller(applicationContext);

ctrl.activateSessions({
  sessionStorageApp: 'some-sessions-app',
  type: 'cookie'
});

After:

ctrl.activateSessions({
  sessionStorage: applicationContext.dependencies.sessions.sessionStorage,
  cookie: true
});

Request module

The module org/arangodb/request uses an internal library function for sending HTTP requests. This library functionally unconditionally set an HTTP header Accept-Encoding: gzip in all outgoing HTTP requests, without client code having to set this header explicitly.

This has been fixed in 2.7, so Accept-Encoding: gzip is not set automatically anymore. Additionally the header User-Agent: ArangoDB is not set automatically either. If client applications rely on these headers being sent, they are free to add it when constructing requests using the request module.

The internal.download() function is also affected by this change. Again, the header can be added here if required by passing it via a headers sub-attribute in the third parameter (options) to this function.

arangodump / backups

The filenames in dumps created by arangodump now contain not only the name of the dumped collection, but also an additional 32-digit hash value. This is done to prevent overwriting dump files in case-insensitive file systems when there exist multiple collections with the same name (but with different cases).

This change leads to changed filenames in dumps created by arangodump. If any client scripts depend on the filenames in the dump output directory being equal to the collection name plus one of the suffixes .structure.json and .data.json, they need to be adjusted.

Starting with ArangoDB 2.7, the file names will contain an underscore plus the 32-digit MD5 value (represented in hexadecimal notation) of the collection name.

For example, when arangodump dumps data of two collections test and Test, the filenames in previous versions of ArangoDB were:

• test.structure.json (definitions for collection test)
• test.data.json (data for collection test)
• Test.structure.json (definitions for collection Test)
• Test.data.json (data for collection Test)

In 2.7, the filenames will be:

• test_098f6bcd4621d373cade4e832627b4f6.structure.json (definitions for collection test)
• test_098f6bcd4621d373cade4e832627b4f6.data.json (data for collection test)
• Test_0cbc6611f5540bd0809a388dc95a615b.structure.json (definitions for collection Test)
• Test_0cbc6611f5540bd0809a388dc95a615b.data.json (data for collection Test)

Starting / stopping

When starting arangod, the server will now drop the process privileges to the specified values in options --server.uid and --server.gid instantly after parsing the startup options.

That means when either --server.uid or --server.gid are set, the privilege change will happen earlier. This may prevent binding the server to an endpoint with a port number lower than 1024 if the arangodb user has no privileges for that. Previous versions of ArangoDB changed the privileges later, so some startup actions were still carried out under the invoking user (i.e. likely root when started via init.d or system scripts) and especially binding to low port numbers was still possible there.

The default privileges for user arangodb will not be sufficient for binding to port numbers lower than 1024. To have an ArangoDB 2.7 bind to a port number lower than 1024, it needs to be started with either a different privileged user, or the privileges of the arangodb user have to raised manually beforehand.

Additionally, Linux startup scripts and systemd configuration for arangod now will adjust the NOFILE (number of open files) limits for the process. The limit value is set to 131072 (128k) when ArangoDB is started via start/stop commands. The goal of this change is to prevent arangod from running out of available file descriptors for socket connections and datafiles.

Connection handling

arangod will now actually close lingering client connections when idle for at least the duration specified in the --server.keep-alive-timeout startup option.

In previous versions of ArangoDB, idle connections were not closed by the server when the timeout was reached and the client was still connected. Now the connection is properly closed by the server in case of timeout. Client applications relying on the old behavior may now need to reconnect to the server when their idle connections time out and get closed (note: connections being idle for a long time may be closed by the OS or firewalls anyway - client applications should be aware of that and try to reconnect).

Option changes

Configure options removed

The following options for configure have been removed because they were unused or exotic:

• --enable-timings
• --enable-figures

Startup options added

The following configuration options have been added in 2.7:

• --database.query-cache-max-results: sets the maximum number of results in AQL query result cache per database
• --database.query-cache-mode: sets the mode for the AQL query results cache. Possible values are on, off and demand. The default value is off

Miscellaneous changes

Simple queries

Many simple queries provide a skip() function that can be used to skip over a certain number of documents in the result. This function allowed specifying negative offsets in previous versions of ArangoDB. Specifying a negative offset led to the query result being iterated in reverse order, so skipping was performed from the back of the result. As most simple queries do not provide a guaranteed result order, skipping from the back of a result with unspecific order seems a rather exotic use case and was removed to increase consistency with AQL, which also does not provide negative skip values.

Negative skip values were deprecated in ArangoDB 2.6.

Tasks API

The undocumented function addJob() has been removed from the org/arangodb/tasks module in ArangoDB 2.7.

Runtime endpoints manipulation API

The following HTTP REST API methods for runtime manipulation of server endpoints have been removed in ArangoDB 2.7:

• POST /_api/endpoint: to dynamically add an endpoint while the server was running
• DELETE /_api/endpoint: to dynamically remove an endpoint while the server was running

This change also affects the equivalent JavaScript endpoint manipulation methods available in Foxx. The following functions have been removed in ArangoDB 2.7:

• db._configureEndpoint()
• db._removeEndpoint()