Incompatible changes in ArangoDB 3.4

It is recommended to check the following list of incompatible changes before upgrading to ArangoDB 3.4, and adjust any client programs if necessary.

The following incompatible changes have been made in ArangoDB 3.4:

Release packages

The official ArangoDB release packages for Linux are now built as static executables linked with the musl libc standard library. For Linux, there are release packages for the Debian-based family of Linux distributions (.deb), and packages for RedHat-based distributions (.rpm). There are no specialized binaries for the individual Linux distributions nor for their individual subversions.

The release packages are intended to be reasonably portable (see minimum supported architectures below) and should run on a variety of different Linux distributions and versions.

Release packages are provided for Windows and macOS as well.

Supported architectures

The minimum supported architecture for the official release packages of ArangoDB is now the Westmere architecture.

All release packages are built with compiler optimizations that require at least this architecture. The following CPU features are required for running an official release package (note: these are all included in the Westmere architecture and upwards):

  • SSE2
  • SSE3
  • SSE4.1
  • SSE4.2
  • PCLMUL

In case the target platform does not conform to these requirements, ArangoDB may not work correctly.

The compiled-in architecture optimizations can be retrieved on most platforms by invoking the arangod binary with the --version option. The optimization switches will then show up in the output in the line starting with optimization-flags, e.g.

  1. $ arangod --version
  2. ...
  3. optimization-flags: -march=westmere -msse2 -msse3 -mssse3 -msse4.1 -msse4.2 -mno-sse4a -mno-avx -mno-fma -mno-bmi2 -mno-avx2 -mno-xop -mno-fma4 -mno-avx512f -mno-avx512vl -mno-avx512pf -mno-avx512er -mno-avx512cd -mno-avx512dq -mno-avx512bw -mno-avx512ifma -mno-avx512vbmi
  4. platform: linux

Note that to get even more target-specific optimizations, it is possible for end users to compile ArangoDB on their own with compiler optimizations tailored to the target environment.

Target host requirements

When the ArangoDB service is started on a Linux host, it will switch to user arangodb and group arangodb at some point during the startup process. This user and group are created during ArangoDB package installation as usual.

However, if either the group arangodb or the user arangodb cannot be found in the target hosts local /etc/group or /etc/passwd storage (for example, because system users and groups are stored centrally using NIS, LDAP etc.), then the underlying group-lookup implementation used by ArangoDB will always consult the local nscd (name-service cache daemon) for this. Effectively this requires a running nscd instance on hosts that ArangoDB is installed on and that do store the operating system users in a place other than the host-local /etc/group and /etc/passwd.

Storage engine

In ArangoDB 3.4, the default storage engine for new installations is the RocksDB engine. This differs to previous versions (3.2 and 3.3), in which the default storage engine was the MMFiles engine.

The MMFiles engine can still be explicitly selected as the storage engine for all new installations. It’s only that the “auto” setting for selecting the storage engine will now use the RocksDB engine instead of MMFiles engine.

In the following scenarios, the effectively selected storage engine for new installations will be RocksDB:

  • --server.storage-engine rocksdb
  • --server.storage-engine auto
  • --server.storage-engine option not specified

The MMFiles storage engine will be selected for new installations only when explicitly selected:

  • --server.storage-engine mmfiles

To make users aware of that the RocksDB storage engine was chosen automatically due to an explicit other storage engine selection, 3.4 will come up with the following startup warning:

  1. using default storage engine 'rocksdb', as no storage engine was explicitly selected via the `--server.storage-engine` option.
  2. please note that default storage engine has changed from 'mmfiles' to 'rocksdb' in ArangoDB 3.4

On upgrade, any existing ArangoDB installation will keep its previously selected storage engine. The change of the default storage engine in 3.4 is thus only relevant for new ArangoDB installations and/or existing cluster setups for which new server nodes get added later. All server nodes in a cluster setup should use the same storage engine to work reliably. Using different storage engines in a cluster is unsupported.

To validate that the different nodes in a cluster deployment use the same storage engine throughout the entire cluster, there is now a startup check performed by each Coordinator. Each Coordinator will contact all DB-Servers and check if the same engine on the DB-Server is the same as its local storage engine. In case there is any discrepancy, the Coordinator will abort its startup.

Geo indexes

  • The on-disk storage format for indexes of type geo has changed for the RocksDB storage engine. This also affects geo1 and geo2 indexes.

    This requires users to start the arangod process with the --database.auto-upgrade true option to allow ArangoDB recreating these indexes using the new on-disk format.

    The on-disk format for geo indexes is incompatible with the on-disk format used in 3.3 and 3.2, so an in-place downgrade from 3.4 to 3.3 is not supported.

  • Geo indexes will now be reported no longer as geo1 or geo2 but as type geo. The two previously known geo index types (geo1and geo2) are deprecated. APIs for creating indexes (ArangoCollection.ensureIndex) will continue to support geo1and geo2.

RocksDB engine data storage format

Installations that start using ArangoDB 3.4 will use an optimized on-disk format for storing documents using the RocksDB storage engine. The RocksDB engine will also a new table format version that was added in a recent version of the RocksDB library and that is not available in ArangoDB versions before 3.4.

This format cannot be used with ArangoDB 3.3 or before, meaning it is not possible to perform an in-place downgrade from a fresh 3.4 install to 3.3 or earlier when using the RocksDB engine. For more information on how to downgrade, please refer to the Downgrading chapter.

Installations that were originally set up with older versions of ArangoDB (e.g. 3.2 or 3.3) will continue to use the existing on-disk format for the RocksDB engine even with ArangoDB 3.4 (unless you install a fresh 3.4 package and restore a backup of your data on this fresh installation).

In order to use the new binary format with existing data, it is required to create a logical dump of the database data, shut down the server, erase the database directory and restore the data from the logical dump. To minimize downtime you can alternatively run a second arangod instance in your system, that replicates the original data; once the replication has reached completion, you can switch the instances.

RocksDB intermediate commits

Intermediate commits in the rocksdb engine are now only enabled in standalone AQL queries (not within a JS transaction), standalone truncate as well as for the “import” API.

The options intermediateCommitCount and intermediateCommitSize will have no affect anymore on transactions started via /_api/transaction, or db._executeTransaction().

RocksDB background sync thread

The RocksDB storage engine in 3.4 has a background WAL syncing thread that by default syncs RocksDB’s WAL to disk every 100 milliseconds. This may cause additional background I/Os compared to ArangoDB 3.3, but will distribute the sync calls more evenly over time than the all-or-nothing file syncs that were performed by previous versions of ArangoDB.

The syncing interval can be configured by adjusting the configuration option --rocksdb.sync-interval.

Note: this option is not supported on Windows platforms. Setting the sync interval to to a value greater than 0 will produce a startup warning on Windows.

RocksDB write buffer size

The total amount of data to build up in all in-memory write buffers (backed by log files) is now by default restricted to a certain fraction of the available physical RAM. This helps restricting memory usage for the arangod process, but may have an effect on the RocksDB storage engine’s write performance.

In ArangoDB 3.3 the governing configuration option --rocksdb.total-write-buffer-size had a default value of 0, which meant that the memory usage was not limited. ArangoDB 3.4 now changes the default value to about 40% of available physical RAM, and 512MiB for setups with less than 4GiB of RAM.

Threading and request handling

The processing of incoming requests and the execution of requests by server threads has changed in 3.4.

Previous ArangoDB versions had a hard-coded implicit lower bound of 64 running threads, and up to which they would increase the number of running server threads. That value could be increased further by adjusting the option --server.maximal-threads. The configuration option --server.threads existed, but did not effectively set or limit the number of running threads.

In ArangoDB 3.4, the number of threads ArangoDB uses for request handling can now be strictly bounded by configuration options.

The number of server threads is now configured by the following startup options:

  • --server.minimal-threads: determines the minimum number of request processing threads the server will start and always keep around
  • --server.maximal-threads: determines the maximum number of request processing threads the server will start for request handling. If that number of threads is already running, arangod will not start further threads for request handling

The actual number of request processing threads is adjusted dynamically at runtime and will float between --server.minimal-threads and --server.maximal-threads.

HTTP REST API

The following incompatible changes were made in context of ArangoDB’s HTTP REST APIs:

  • The following, partly undocumented internal REST APIs have been removed in ArangoDB 3.4:

    • GET /_admin/test
    • GET /_admin/clusterCheckPort
    • GET /_admin/cluster-test
    • GET /_admin/routing/routes
    • GET /_admin/statistics/short
    • GET /_admin/statistics/long
    • GET /_admin/auth/reload

  • GET /_api/index will now return type geo for geo indexes, not type geo1 or geo2 as previous versions did.

    For geo indexes, the index API will not return the attributes constraint and ignoreNull anymore. These attributes were initially deprecated in ArangoDB 2.5

  • GET /_api/aqlfunction was migrated to match the general structure of ArangoDB replies. It now returns an object with a “result” attribute that contains the list of available AQL user functions:

    1. {
    2.   "code": 200,
    3.   "error": false,
    4.   "result": [
    5.     {
    6.       "name": "UnitTests::mytest1",
    7.       "code": "function () { return 1; }",
    8.       "isDeterministic": false
    9.     }
    10.   ]
    11. }

    In previous versions, this REST API returned only the list of available AQL user functions on the top level of the response. Each AQL user function description now also contains the ‘isDeterministic’ attribute.

  • if authentication is turned on, requests to databases by users with insufficient access rights will be answered with HTTP 401 (Forbidden) instead of HTTP 404 (Not found).

  • the REST handler for user permissions at /_api/user will now return HTTP 404 (Not found) when trying to grant or revoke user permissions for a non-existing collection.

    This affects the HTTP PUT calls to the endpoint /_api/user/<user>/<database>/<collection> for collections that do not exist.

The following APIs have been added or augmented:

  • additional stream attribute in queries HTTP API

    The REST APIs for retrieving the list of currently running and slow queries at GET /_api/query/current and GET /_api/query/slow are now returning an additional attribute stream for each query.

    This attribute indicates whether the query was started using a streaming cursor.

  • POST /_api/document/{collection} now supports repsert (replace-insert).

    This can be achieved by using the URL parameter overwrite=true. When set to true, insertion will not fail in case of a primary key conflict, but turn into a replace operation.

    When an insert turns into a replace, the previous version of the document can be retrieved by passing the URL parameter returnOld=true

  • POST /_api/aqlfunction now includes an “isNewlyCreated” attribute that indicates if a new function was created or if an existing one was replaced (in addition to the “code” attribute, which remains 200 for replacement and 201 for creation):

    1. {
    2.   "code": "201",
    3.   "error": false,
    4.   "isNewlyCreated": true
    5. }

  • DELETE /_api/aqlfunction now returns the number of deleted functions:

    1. {
    2.   "code": 200,
    3.   "error": false,
    4.   "deletedCount": 10
    5. }

  • GET /_admin/status now returns the attribute operationMode in addition to mode. The attribute writeOpsEnabled is now also represented by the new attribute readOnly, which is has an inverted value compared to the original attribute. The old attributes are deprecated in favor of the new ones.

  • POST /_api/collection now will process the optional shardingStrategy attribute in the response body in cluster mode.

    This attribute specifies the name of the sharding strategy to use for the collection. Since ArangoDB 3.4 there are different sharding strategies to select from when creating a new collection. The selected shardingStrategy value will remain fixed for the collection and cannot be changed afterwards. This is important to make the collection keep its sharding settings and always find documents already distributed to shards using the same initial sharding algorithm.

    The available sharding strategies are:

    • community-compat: default sharding used by ArangoDB Community Edition before version 3.4
    • enterprise-compat: default sharding used by ArangoDB Enterprise Edition before version 3.4
    • enterprise-smart-edge-compat: default sharding used by smart edge collections in ArangoDB Enterprise Edition before version 3.4
    • hash: default sharding used for new collections starting from version 3.4 (excluding smart edge collections)
    • enterprise-hash-smart-edge: default sharding used for new smart edge collections starting from version 3.4

    If no sharding strategy is specified, the default will be hash for all collections, and enterprise-hash-smart-edge for all smart edge collections (requires the Enterprise Edition of ArangoDB). Manually overriding the sharding strategy does not yet provide a benefit, but it may later in case other sharding strategies are added.

    In single-server mode, the shardingStrategy attribute is meaningless and will be ignored.

  • a new API for inspecting the contents of the AQL query results cache has been added to endpoint GET /_api/query/cache/entries

    This API returns the current contents of the AQL query results cache of the currently selected database.

  • APIs for view management have been added at endpoint /_api/view.

  • The REST APIs for modifying graphs at endpoint /_api/gharial now support returning the old revision of vertices / edges after modifying them. The APIs also supports returning the just-inserted vertex / edge. This is in line with the already existing single-document functionality provided at endpoint /_api/document.

    The old/new revisions can be accessed by passing the URL parameters returnOld and returnNew to the following endpoints:

    • /_api/gharial/<graph>/vertex/<collection>
    • /_api/gharial/<graph>/edge/<collection>

    The exception from this is that the HTTP DELETE verb for these APIs does not support returnOld because that would make the existing API incompatible.

AQL

  • all AQL date functions in 3.4 may raise an “invalid date value” warning when given a syntactically invalid date string as an input. The rules for valid date strings have been made more strict in ArangoDB 3.4.

    In previous versions, passing in a date value with a one-digit hour, minute or second component worked just fine, and the date was considered valid.

    From ArangoDB 3.4 onwards, using date values with a one-digit hour, minute or second component will render the date value invalid, and make the underlying date functions return a value of null and issue an “invalid date value” warning.

    The following overview details which values are considered valid and invalid in the respective ArangoDB versions:

    Date string3.33.4
    “2019-07-01 05:02:34”validvalid
    “2019-7-1 05:02:34”validvalid
    “2019-7-1 5:02:34”validinvalid
    “2019-7-1 05:2:34”validinvalid
    “2019-7-1 05:02:4”validinvalid
    “2019-07-01T05:02:34”validvalid
    “2019-7-1T05:02:34”validvalid
    “2019-7-1T5:02:34”validinvalid
    “2019-7-1T05:2:34”validinvalid
    “2019-7-1T05:02:4”validinvalid

  • the AQL functions CALL and APPLY may now throw the errors 1540 (ERROR_QUERY_FUNCTION_NAME_UNKNOWN) and 1541 (ERROR_QUERY_FUNCTION_ARGUMENT_TYPE_MISMATCH) instead of error 1582 (ERROR_QUERY_FUNCTION_NOT_FOUND) in some situations.

  • the existing “fulltext-index-optimizer” optimizer rule has been removed because its duty is now handled by the new “replace-function-with-index” rule.

  • the behavior of the fullCount option for AQL queries has changed so that it will only take into account LIMIT statements on the top level of the query.

    LIMIT statements in subqueries will not have any effect on the fullCount results any more.

  • the AQL functions NEAR, WITHIN, WITHIN_RECTANGLE and FULLTEXT do not support accessing collections dynamically anymore.

    The name of the underlying collection and the name of the index attribute to be used have to specified using either collection name identifiers, string literals or bind parameters, but must not be specified using query variables.

    For example, the following AQL queries are ok:

    1. FOR doc IN NEAR(myCollection, 2.5, 3) RETURN doc
    2. FOR doc IN NEAR(@@collection, 2.5, 3) RETURN doc
    3. FOR doc IN FULLTEXT("myCollection", "body", "foxx") RETURN doc
    4. FOR doc IN FULLTEXT(@@collection, @attribute, "foxx") RETURN doc

    Contrary, the following queries will fail to execute with 3.4 because of dynamic collection/attribute names used in them:

    1. FOR name IN ["col1", "col2"] FOR doc IN NEAR(name, 2.5, 3) RETURN doc
    3. FOR doc IN collection 
    4.   FOR match IN FULLTEXT(PARSE_IDENTIFIER(doc).collection, PARSE_IDENTIFIER(doc).key, "foxx") RETURN doc

  • the AQL warning 1577 (“collection used in expression”) will not occur anymore

    It was used in previous versions of ArangoDB when the name of a collection was used in an expression in an AQL query, e.g.

    1. RETURN c1 + c2

    Due to internal changes in AQL this is not detected anymore in 3.4, so this particular warning will not be raised.

    Additionally, using collections in arbitrary AQL expressions as above is unsupported in a mixed cluster that is running a 3.3 Coordinator and 3.4 DB-Server(s). The DB-Server(s) running 3.4 will in this case not be able to use a collection in an arbitrary expression, and instead throw an error.

  • the undocumented built-in visitor functions for AQL traversals have been removed, as they were based on JavaScript implementations:

    • HASATTRIBUTESVISITOR
    • PROJECTINGVISITOR
    • IDVISITOR
    • KEYVISITOR
    • COUNTINGVISITOR

    Using any of these functions from inside AQL will now produce an error.

  • in previous versions, the AQL optimizer used two different ways of converting strings into numbers. The two different ways have been unified into a single way that behaves like the TO_NUMBER AQL function, which is also the documented behavior.

    The change affects arithmetic operations with strings that contain numbers and other trailing characters, e.g.

    1. expression         3.3 result          3.4 result       TO_NUMBER()
    2. 0 + "1a"           0 + 1 = 1           0 + 0 = 0        TO_NUMBER("1a") = 0
    3. 0 + "1 "           0 + 1 = 1           0 + 1 = 1        TO_NUMBER("1 ") = 1
    4. 0 + " 1"           0 + 1 = 1           0 + 1 = 1        TO_NUMBER(" 1") = 1
    5. 0 + "a1"           0 + 0 = 0           0 + 0 = 0        TO_NUMBER("a1") = 0

  • the AQL function DATE_NOW is now marked as deterministic internally, meaning that the optimizer may evaluate the function at query compile time and not at query runtime. This will mean that calling the function repeatedly inside the same query will now always produce the same result, whereas in previous versions of ArangoDB the function may have generated different results.

    Each AQL query that is run will still evaluate the result value of the DATE_NOW function independently, but only once at the beginning of the query. This is most often what is desired anyway, but the change makes DATE_NOW useless to measure time differences inside a single query.

  • the internal AQL function PASSTHRU (which simply returns its call argument) has been changed from being non-deterministic to being deterministic, provided its call argument is also deterministic. This change should not affect end users, as PASSTHRU is intended to be used for internal testing only. Should end users use this AQL function in any query and need a wrapper to make query parts non-deterministic, the NOOPT AQL function can stand in as a non-deterministic variant of PASSTHRU

  • the AQL query optimizer will by default now create at most 128 different execution plans per AQL query. In previous versions the maximum number of plans was 192.

    Normally the AQL query optimizer will generate a single execution plan per AQL query, but there are some cases in which it creates multiple competing plans. More plans can lead to better optimized queries, however, plan creation has its costs. The more plans are created and shipped through the optimization pipeline, the more time will be spent in the optimizer. To make the optimizer better cope with some edge cases, the maximum number of plans to create is now strictly enforced and was lowered compared to previous versions of ArangoDB.

    Note that this default maximum value can be adjusted globally by setting the startup option --query.optimizer-max-plans or on a per-query basis by setting a query’s maxNumberOfPlans option.

  • When creating query execution plans for a query, the query optimizer was fetching the number of documents of the underlying collections in case multiple query execution plans were generated. The optimizer used these counts as part of its internal decisions and execution plan costs calculations.

    Fetching the number of documents of a collection can have measurable overhead in a cluster, so ArangoDB 3.4 now caches the “number of documents” that are referred to when creating query execution plans. This may save a few roundtrips in case the same collections are frequently accessed using AQL queries.

    The “number of documents” value was not and is not supposed to be 100% accurate in this stage, as it is used for rough cost estimates only. It is possible however that when explaining an execution plan, the “number of documents” estimated for a collection is using a cached stale value, and that the estimates change slightly over time even if the underlying collection is not modified.

  • AQL query results that are served from the AQL query results cache can now return the fullCount attribute as part of the query statistics. Alongside the fullCount attribute, other query statistics will be returned. However, these statistics will reflect figures generated during the initial query execution, so especially a query’s executionTime figure may be misleading for a cached query result.

Usage of V8

The internal usage of the V8 JavaScript engine for non-user actions has been reduced in ArangoDB 3.4. Several APIs have been rewritten to not depend on V8 and thus do not require using the V8 engine nor a V8 context for execution anymore.

Compared to ArangoDB 3.3, the following parts of ArangoDB can now be used without the V8 engine:

  • Agency nodes in a cluster
  • DB-Server nodes in a cluster
  • cluster plan application on DB-Server nodes
  • all of AQL (with the exception of user-defined functions)
  • the graph modification APIs at endpoint /_api/gharial
  • background statistics gathering

Reduced usage of V8 in ArangoDB may allow end users to lower the configured numbers of V8 contexts to start. In terms of configuration options, these are:

  • --javascript.v8-contexts: the maximum number of V8 contexts to create (high-water mark)
  • --javascript.v8-contexts-minimum: the minimum number of V8 contexts to create at server start and to keep around permanently (low-water mark)

The default values for these startup options have not been changed in ArangoDB 3.4, but depending on the actual workload, 3.4 ArangoDB instances may need less V8 contexts than 3.3.

As mentioned above, Agency and DB-Server nodes in a cluster does not require V8 for any operation in 3.4, so the V8 engine is turned off entirely on such nodes, regardless of the number of configured V8 contexts there.

The V8 engine is still enabled on Coordinator servers in a cluster and on single server instances. Here the numbe of started V8 contexts may actually be reduced in case a lot of the above features are used.

Startup option changes

For arangod, the following startup options have changed:

  • the number of server threads is now configured by the following startup options:

    • --server.minimal-threads: determines the minimum number of request processing threads the server will start
    • --server.maximal-threads: determines the maximum number of request processing threads the server will start

    The actual number of request processing threads is adjusted dynamically at runtime and will float between --server.minimal-threads and --server.maximal-threads.

  • the default value for the existing startup option --javascript.gc-interval has been increased from every 1000 to every 2000 requests, and the default value for the option --javascript.gc-frequency has been increased from 30 to 60 seconds.

    This will make the V8 garbage collection run less often by default than in previous versions, reducing CPU load a bit and leaving more V8 contexts available on average.

  • the startup option --cluster.my-local-info has been removed in favor of persisted server UUIDs.

    The option --cluster.my-local-info was deprecated since ArangoDB 3.3.

  • the startup option --database.check-30-revisions was removed. It was used for checking the revision ids of documents for having been created with ArangoDB 3.0, which required a dump & restore migration of the data to 3.1.

    As direct upgrades from ArangoDB 3.0 to 3.4 or from 3.1 to 3.4 are not supported, this option has been removed in 3.4.

  • the startup option --server.session-timeout has been obsoleted. Setting this option will not have any effect.

  • the option --replication.automatic-failover was renamed to --replication.active-failover

    Using the old option name will still work in ArangoDB 3.4, but support for the old option name will be removed in future versions of ArangoDB.

  • the option --rocksdb.block-align-data-blocks has been added

    If set to true, data blocks stored by the RocksDB engine are aligned on lesser of page size and block size, which may waste some memory but may reduce the number of cross-page I/Os operations.

    The default value for this option is false.

    As mentioned above, ArangoDB 3.4 changes the default value of the configuration option --rocksdb.total-write-buffer-size to about 40% of available physical RAM, and 512MiB for setups with less than 4GiB of RAM. In ArangoDB 3.3 this option had a default value of 0, which meant that the memory usage for write buffers was not limited.

Permissions

The behavior of permissions for databases and collections changed:

The new fallback rule for databases for which no access level is explicitly specified is now:

  • Choose the higher access level of:
    • A wildcard database grant
    • A database grant on the _system database

The new fallback rule for collections for which no access level is explicitly specified is now:

  • Choose the higher access level of:
    • Any wildcard access grant in the same database, or on "*"
    • The access level for the current database
    • The access level for the _system database

SSLv2

Support for SSLv2 has been removed from arangod and all client tools.

Startup will now be aborted when using SSLv2 for a server endpoint, or when connecting with one of the client tools via an SSLv2 connection.

SSLv2 has been disabled in the OpenSSL library by default in recent versions because of security vulnerabilities inherent in this protocol.

As it is not safe at all to use this protocol, the support for it has also been stopped in ArangoDB. End users that use SSLv2 for connecting to ArangoDB should change the protocol from SSLv2 to TLSv12 if possible, by adjusting the value of the --ssl.protocol startup option.

Replication

By default, database-specific and global replication appliers use a slightly different configuration in 3.4 than in 3.3. In 3.4 the default value for the configuration option requireFromPresent is now true, meaning the follower will abort the replication when it detects gaps in the leader’s stream of events. Such gaps can happen if the leader has pruned WAL log files with events that have not been fetched by a follower yet, which may happen for example if the network connectivity between follower and leader is bad.

Previous versions of ArangoDB 3.3 used a default value of false for requireFromPresent, meaning that any such gaps in the replication data exchange will not cause the replication to stop. 3.4 now stops replication by default and writes according errors to the log. Replication can automatically be restarted in this case by setting the autoResync replication configuration option to true.

Mixed-engine clusters

Starting a cluster with Coordinators and DB-Servers using different storage engines is not supported. Doing it anyway will now log an error and abort a Coordinator’s startup.

Previous versions of ArangoDB did not detect the usage of different storage engines in a cluster, but the runtime behavior of the cluster was undefined.

Client tools

The client tool arangoimp has been renamed to arangoimport for consistency.

Release packages will still install arangoimp as a symlink to arangoimport, so user scripts invoking arangoimp do not need to be changed to work with ArangoDB 3.4. However, user scripts invoking arangoimp should eventually be changed to use arangoimport instead, as that will be the long-term supported way of running imports.

The tools arangodump and arangorestore will now by default work with two threads when extracting data from a server or loading data back into a server resp. The number of threads to use can be adjusted for both tools by adjusting the --threads parameter when invoking them. This change is noteworthy because in previous versions of ArangoDB both tools were single-threaded and only processed one collection at a time, while starting with ArangoDB 3.4 by default they will process two collections at a time, with the intended benefit of completing their work faster. However, this may create higher load on servers than in previous versions of ArangoDB. If the load produced by arangodump or arangorestore is higher than desired, please consider setting their --threads parameter to a value of 1 when invoking them.

In the ArangoShell, the undocumented JavaScript module @arangodb/actions has been removed. This module contained the methods printRouting and printFlatRouting, which were used for debugging purposes only.

In the ArangoShell, the undocumented JavaScript functions reloadAuth and routingCache have been removed from the internal module.

Foxx applications

The undocumented JavaScript module @arangodb/database-version has been removed, so it cannot be use from Foxx applications anymore The module only provided the current version of the database, so any client-side invocations can easily be replaced by using the db._version() instead.

The ShapedJson JavaScript object prototype, a remainder from ArangoDB 2.8 for encapsulating database documents, has been removed in ArangoDB 3.4.

Miscellaneous changes

For the MMFiles engine, the compactor thread(s) were renamed from “Compactor” to “MMFilesCompactor”.

This change will be visible only on systems which allow assigning names to threads.

Deprecated features

The following features and APIs are deprecated in ArangoDB 3.4, and will be removed in future versions of ArangoDB:

  • the JavaScript-based traversal REST API at /_api/traversal and the underlaying traversal module @arangodb/graph/traversal:

    This API has several limitations (including low result set sizes) and has effectively been unmaintained since the introduction of native AQL traversal.

    It is recommended to migrate client applications that use the REST API at /_api/traversal to use AQL-based traversal queries instead.

  • the REST API for simple queries at /_api/simple:

    The simple queries provided by the /_api/simple endpoint are limited in functionality and will internally resort to AQL queries anyway. It is advised that client applications also use the equivalent AQL queries instead of using the simple query API, because that is more flexible and allows greater control of how the queries are executed.

  • the REST API for querying endpoints at /_api/endpoint:

    The API /_api/endpoint is deprecated since ArangoDB version 3.1. For cluster mode there is /_api/cluster/endpoints to find all current Coordinator endpoints.

  • accessing collections via their numeric IDs instead of their names. This mostly affects the REST APIs at

    • /_api/collection/<collection-id>
    • /_api/document/<collection-id>
    • /_api/simple

    Note that in ArangoDB 3.4 it is still possible to access collections via their numeric ID, but the preferred way to access a collections is by its user-defined name.

  • the REST API for WAL tailing at /_api/replication/logger-follow:

    The logger-follow WAL tailing API has several limitations. A better API was introduced at endpoint /_api/wal/tail in ArangoDB 3.3.

    Client applications using the old tailing API at /_api/replication/logger-follow should switch to the new API eventually.

  • the result attributes mode and writeOpsEnabled in the REST API for querying a server’s status at /_admin/status:

    GET /_admin/status returns the additional attributes operationMode and readOnly now, which should be used in favor of the old attributes.

  • creating geo indexes via any APIs with one of the types geo1 or geo2:

    The two previously known geo index types (geo1and geo2) are deprecated now. Instead, when creating geo indexes, the type geo should be used.

    The types geo1 and geo2 will still work in ArangoDB 3.4, but may be removed in future versions.

  • the persistent index type is marked for removal in 4.0.0 and is thus deprecated.

    This index type was added when there was only the MMFiles storage engine as kind of a stop gap. We recommend to switch to RocksDB engine, which persists all index types with no difference between skiplist and persistent indexes.

  • the legacy mode for Foxx applications from ArangoDB 2.8 or earlier:

    The legacy mode is described in more detail in the Foxx manual. To upgrade an existing Foxx application that still uses the legacy mode, please follow the steps described in the manual.

  • the AQL geo functions NEAR, WITHIN, WITHIN_RECTANGLE and IS_IN_POLYGON:

    The special purpose NEAR AQL function can be substituted with the following AQL (provided there is a geo index present on the doc.latitude and doc.longitude attributes) since ArangoDB 3.2:

    1. FOR doc in geoSort
    2.   SORT DISTANCE(doc.latitude, doc.longitude, 0, 0)
    3.   LIMIT 5
    4.   RETURN doc

    WITHIN can be substituted with the following AQL since ArangoDB 3.2:

    1. FOR doc in geoFilter
    2.   FILTER DISTANCE(doc.latitude, doc.longitude, 0, 0) < 2000
    3.   RETURN doc

    Compared to using the special purpose AQL functions this approach has the advantage that it is more composable, and will also honor any LIMIT values used in the AQL query.

    In ArangoDB 3.4, NEAR, WITHIN, WITHIN_RECTANGLE and IS_IN_POLYGON will still work and automatically be rewritten by the AQL query optimizer to the above forms. However, AQL queries using the deprecated AQL functions should eventually be adjusted.

  • using the arangoimp binary instead of arangoimport

    arangoimp has been renamed to arangoimport for consistency in ArangoDB 3.4, and arangoimp is just a symbolic link to arangoimport now. arangoimp is there for compatibility only, but client scripts should eventually be migrated to use arangoimport instead.

  • the foxx-manager executable is deprecated and will be removed in ArangoDB 4.

    Please use Foxx CLI instead.