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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](https://www.musl-libc.org/) 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 Nehalem 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 Nehalem architecture and upwards):
* SSE2
* SSE3
* SSE4.1
* SSE4.2
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.
```
$ arangod --version
...
optimization-flags: -march=nehalem -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
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:
using default storage engine 'rocksdb', as no storage engine was explicitly selected via the `--server.storage-engine` option.
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 (`geo1`and `geo2`) are **deprecated**.
APIs for creating indexes (`ArangoCollection.ensureIndex`) will continue to support
`geo1`and `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](../Downgrading/README.md) 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:
```json
{
"code": 200,
"error": false,
"result": [
{
"name": "UnitTests::mytest1",
"code": "function () { return 1; }",
"isDeterministic": false
}
]
}
```
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):
```json
{
"code": "201",
"error": false,
"isNewlyCreated": true
}
```
- `DELETE /_api/aqlfunction` now returns the number of deleted functions:
```json
{
"code": 200,
"error": false,
"deletedCount": 10
}
```
- `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
versions before ArangoDB 3.4
- `enterprise-compat`: default sharding used by ArangoDB enterprise
versions before ArangoDB 3.4
- `enterprise-smart-edge-compat`: default sharding used by smart edge
collections in ArangoDB enterprise versions before ArangoDB 3.4
- `hash`: default sharding used by ArangoDB 3.4 for new collections
(excluding smart edge collections)
- `enterprise-hash-smart-edge`: default sharding used by ArangoDB 3.4
for new smart edge collections
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
---
- 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:
FOR doc IN NEAR(myCollection, 2.5, 3) RETURN doc
FOR doc IN NEAR(@@collection, 2.5, 3) RETURN doc
FOR doc IN FULLTEXT("myCollection", "body", "foxx") RETURN doc
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:
FOR name IN ["col1", "col2"] FOR doc IN NEAR(name, 2.5, 3) RETURN doc
FOR doc IN collection
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.
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.
expression 3.3 result 3.4 result TO_NUMBER()
0 + "1a" 0 + 1 = 1 0 + 0 = 0 TO_NUMBER("1a") = 0
0 + "1 " 0 + 1 = 1 0 + 1 = 1 TO_NUMBER("1 ") = 1
0 + " 1" 0 + 1 = 1 0 + 1 = 1 TO_NUMBER(" 1") = 1
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
- database server nodes in a cluster
- cluster plan application on database 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 database 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`:
This API has several limitations (including low result set sizes) and has
effectively been unmaintained since the introduction of AQL's general
*TRAVERSAL* clause.
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 (`geo1`and `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](https://docs.arangodb.com/3.3/Manual/Foxx/LegacyMode.html).
To upgrade an existing Foxx application that still uses the legacy mode, please
follow the steps described in [the manual](https://docs.arangodb.com/3.3/Manual/Foxx/Migrating2x/).
* 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:
FOR doc in geoSort
SORT DISTANCE(doc.latitude, doc.longitude, 0, 0)
LIMIT 5
RETURN doc
`WITHIN` can be substituted with the following AQL since ArangoDB 3.2:
FOR doc in geoFilter
FILTER DISTANCE(doc.latitude, doc.longitude, 0, 0) < 2000
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: https://docs.arangodb.com/3.4/Manual/Foxx/Deployment/FoxxCLI/
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