Incompatible changes in ArangoDB 3.10

It is recommended to check the following list of incompatible changes before upgrading to ArangoDB 3.10, and adjust any client programs if necessary.

The following incompatible changes have been made in ArangoDB 3.10:

Empty Document Updates

ArangoDB 3.10 adds back the optimization for empty document update operations (i.e. updates in which no attributes were specified to be updated). Such updates were handled in a special way in ArangoDB until including 3.7.12, so that no actual writes were performed and replicated. This also included the _rev value of documents not being changed on an empty update.

ArangoDB 3.7.13 and 3.8.0 changed this behavior so that empty document updates actually performed a write operation, leading to the replication of changes and modification of the _rev value of affected.

ArangoDB 3.10 adds back the optimal behavior for empty document updates, which no longer perform a write operation, do not need to be replicated and do not change the documents’ _rev values.

Foxx / Server Console

Previously a call to db._version(true) inside a Foxx app or the server console would return a different structure than the same call from arangosh. Foxx/server console would return { <details> } while arangosh would return { server: ..., license: ..., version: ..., details: { <details> }}.

This is now unified so that the result structure is always consistent with the one in arangosh. Any Foxx app or script that ran in the server console which used db._version(true) must now be changed to use db._version(true).details instead.

Indexes

The fulltext index type is now deprecated in favor of ArangoSearch. Fulltext indexes are still usable in this version of ArangoDB, although their usage is now discouraged.

Geo Indexes

After an upgrade to 3.10 or higher, consider to drop and recreate geo indexes. GeoJSON polygons are interpreted slightly differently (and more correctly) in the newer versions.

Legacy geo indexes will continue to work and continue to produce the same results as in earlier versions, since they will have the option legacyPolygons implicitly set to true.

Newly created indexes will have legacyPolygons set to false by default and thus enable the new polygon parsing.

Note that linear rings are not normalized automatically from version 3.10 onward, following the GeoJSON standard. The “interior” of a polygon strictly conforms to the GeoJSON standard: it lies to the left of the boundary line (in the direction of travel along the boundary line on the surface of the Earth). This can be the “larger” connected component of the surface, or the smaller one. Note that this differs from the interpretation of GeoJSON polygons in version 3.9 and older:

This can mean that old polygon GeoJSON data in the database is suddenly interpreted in a different way. See Legacy Polygons for details. Also see the definition of Polygons.

Maximum Array / Object Nesting

When reading any data from JSON or VelocyPack input or when serializing any data to JSON or VelocyPack, there is a maximum recursion depth for nested arrays and objects, which is slightly below 200. Arrays or objects with higher nesting than this will cause Too deep nesting in Array/Object exceptions. The limit is also enforced when converting any server data to JavaScript in Foxx, or when sending JavaScript input data from Foxx to a server API. This maximum recursion depth is hard-coded in arangod and all client tools.

Startup Options

Handling of Invalid Startup Options

Starting with ArangoDB 3.10, the arangod executable and all other client tools use more specific process exit codes in the following situations:

• An unknown startup option name is used: Previously, the exit code was 1. Now, the exit code when using an invalid option is 3 (symbolic exit code name EXIT_INVALID_OPTION_NAME).
• An invalid value is used for a startup option (e.g. a number that is outside the allowed range for the option’s underlying value type, or a string value is used for a numeric option): Previously, the exit code was 1. Now, the exit code for these case is 4 (symbolic exit code name EXIT_INVALID_OPTION_VALUE).
• A config file is specified that does not exist: Previously, the exit code was either 1 or 6 (symbolic exit code name EXIT_CONFIG_NOT_FOUND). Now, the exit code in this case is always 6 (EXIT_CONFIG_NOT_FOUND).
• A structurally invalid config file is used, e.g. the config file contains a line that cannot be parsed: Previously, the exit code in this situation was 1. Now, it is always 6 (symbolic exit code name EXIT_CONFIG_NOT_FOUND).

Note that this change can affect any custom scripts that check for startup failures using the specific exit code 1. These scripts should be adjusted so that they check for a non-zero exit code. They can opt into more specific error handling using the additional exit codes mentioned above, in order to distinguish between different kinds of startup errors.

Web Interface Options

The --frontend.* startup options were renamed to --web-interface.*:

• --frontend.proxy-request.check is now --web-interface.proxy-request.check
• --frontend.trusted-proxy is now --web-interface.trusted-proxy
• --frontend.version-check is now --web-interface.version-check

The former startup options are still supported for backward compatibility.

RocksDB Options

The default value of the --rocksdb.cache-index-and-filter-blocks startup option was changed from false to true. This makes RocksDB track all loaded index and filter blocks in the block cache, so they are accounted against the RocksDB’s block cache memory limit. The default value for the --rocksdb.enforce-block-cache-size-limit startup option was also changed from false to true to make the RocksDB block cache not temporarily exceed the configured memory limit.

These default value changes will make RocksDB adhere much better to the configured memory limit (configurable via --rocksdb.block-cache-size). The changes may have a small negative impact on performance because, if the block cache is not large enough to hold the data plus the index and filter blocks, additional disk I/O may need to be performed compared to the previous versions. This is a trade-off between memory usage predictability and performance, and ArangoDB 3.10 will default to more stable and predictable memory usage. If there is still unused RAM capacity available, it may be sensible to increase the total size of the RocksDB block cache, by increasing --rocksdb.block-cache-size. Due to the changed configuration, the block cache size limit will not be exceeded anymore.

It is possible to opt out of these changes and get back the memory and performance characteristics of the previous versions by setting the --rocksdb.cache-index-and-filter-blocks and --rocksdb.enforce-block-cache-size-limit startup options to false on startup.

RocksDB File Format

ArangoDB 3.10 internally switches to RocksDB’s format_version 5, which can still be read by older versions of ArangoDB. However, ArangoDB 3.10 uses the LZ4 compression scheme to reduce the size of RocksDB .sst files from LSM tree level 2 onwards. This compression scheme is not supported in ArangoDB versions before 3.10, so any database files created with ArangoDB 3.10 or higher cannot be opened with versions before 3.10. The internal checksum type of RocksDB .sst files has been changed to xxHash64 in ArangoDB 3.10 for a slight performance improvement.

Pregel Options

Pregel jobs now have configurable minimum, maximum and default parallelism values. You can set them by the following startup options:

• --pregel.min-parallelism: minimum parallelism usable in Pregel jobs. Defaults to 1.
• --pregel.max-parallelism: maximum parallelism usable in Pregel jobs. Defaults to the number of available cores.
• --pregel.parallelism: default parallelism to use in Pregel jobs. Defaults to the number of available cores divided by 4. The result will be clamped to a value between 1 and 16.

Pregel now also stores its temporary data in memory-mapped files on disk by default, whereas in previous versions the default behavior was to buffer it to RAM. Storing temporary data in memory-mapped files rather than in RAM has the advantage of lowering the RAM usage, which reduces the likelihood of out-of-memory situations. However, storing the files on disk requires disk capacity, so that instead of running out of RAM it is now possible to run out of disk space.

For more information on the new options, please refer to ArangoDB Server Pregel Options.

HTTP RESTful API

Validation of collections in named graphs

The /_api/gharial endpoints for named graphs have changed:

• If you reference a vertex collection in the _from or _to attribute of an edge that doesn’t belong to the graph, an error with the number 1947 is returned. The HTTP status code of such an ERROR_GRAPH_REFERENCED_VERTEX_COLLECTION_NOT_USED error has been changed from 400 to 404. This change aligns the behavior to the similar ERROR_GRAPH_EDGE_COLLECTION_NOT_USED error (number 1930).

• Write operations now check if the specified vertex or edge collection is part of the graph definition. If you try to create a vertex via POST /_api/gharial/{graph}/vertex/{collection} but the collection doesn’t belong to the graph, then the ERROR_GRAPH_REFERENCED_VERTEX_COLLECTION_NOT_USED error is returned. If you try to create an edge via POST /_api/gharial/{graph}/edge/{collection} but the collection doesn’t belong to the graph, then the error is ERROR_GRAPH_EDGE_COLLECTION_NOT_USED.

Encoding of revision IDs

Introduced in: v3.8.8, v3.9.4, v3.10.1

• GET /_api/collection/<collection-name>/revision: The revision ID was previously returned as numeric value, and now it is returned as a string value with either numeric encoding or HLC-encoding inside.
• GET /_api/collection/<collection-name>/checksum: The revision ID in the revision attribute was previously encoded as a numeric value in single server, and as a string in cluster. This is now unified so that the revision attribute always contains a string value with either numeric encoding or HLC-encoding inside.

Client Tools

arangobench

Renamed the --concurrency startup option to --threads.

The following deprecated arangobench testcases have been removed from arangobench:

• aqltrx
• aqlv8
• counttrx
• deadlocktrx
• multi-collection
• multitrx
• random-shapes
• shapes
• shapes-append
• skiplist
• stream-cursor

These test cases had been deprecated since ArangoDB 3.9.

The testcase hash was renamed to persistent-index to better reflect its scope.

arangoexport

To improve naming consistency across different client tools, the existing arangoexport startup options --query and --query-max-runtime were renamed to --custom-query and --custom-query-max-runtime.

Using the old option names (--query and --query-max-runtime) is still supported and will implicitly use the --custom-query and --custom-query-max-runtime options under the hood. Client scripts should eventually be updated to use the new option name, however.

ArangoDB Starter

The ArangoDB Starter comes with the following usability improvements:

• Headers are now added to generated command files, indicating the purpose of the file.
• The process output is now shown when errors occur during process startup.
• When passing through other database options, explicit hints are now displayed to indicate how to pass those options.
• The Starter now returns exit code 1 if it encounters any errors while starting. Previously, the exit code was 0. Note that this change can affect any custom scripts that check for startup errors or invalid command line options. These scripts can be adjusted so that they check for a non-zero exit code.