API Changes in ArangoDB 3.8

This document summarizes the HTTP API changes and other API changes in ArangoDB 3.8. The target audience for this document are developers who maintain drivers and integrations for ArangoDB 3.8.


Collection API

The following changes affect the behavior of the RESTful collection APIs at endpoints starting with path /_api/collection/:

The collection properties indexBuckets, journalSize, doCompact and isVolatile only had a meaning for the MMFiles storage engine, which is not available anymore since ArangoDB 3.7.

ArangoDB 3.8 now removes any special handling for these obsolete collection properties, meaning these attributes will not be processed by the server and not be returned by any server APIs. Using these attributes in any API call will be ignored, and will not trigger any errors.

Client applications and tests that rely on the behavior that setting any of these obsolete properties produces an error on the server side may need to be adjusted now.

Www-Authenticate response header

ArangoDB 3.8 adds back the Www-Authenticate response header for HTTP server responses with a status code of 401. Returning the Www-Authenticate header for 401 responses is required by the HTTP/1.1 specification and was also advertised functionality in the ArangoDB documentation, but wasn’t happening in practice.

Now the functionality of returning Www-Authenticate response headers for HTTP 401 responses is restored, along with the already advertised functionality of suppressing this header in case the client sends an X-Omit-Www-Authenticate header with the request.

This change should not have any impact for client applications that use ArangoDB as a database only. It may have an effect for Foxx applications that use HTTP 401 status code responses and that will now see this extra header getting returned.

Endpoint return value changes

  • The endpoint /_api/replication/clusterInventory returns, among other things, an array of the existing collections. Each collection has a planVersion attribute, which in ArangoDB 3.8 is now hard-coded to the value of 1.

    Before 3.7, the most recent Plan version from the agency was returned inside planVersion for each collection. In 3.7, the attribute contained the Plan version that was in use when the in-memory LogicalCollection object was last constructed. The object was always reconstructed in case the underlying Plan data for the collection changed, or when a collection contained links to ArangoSearch Views. This made the attribute relatively useless for any real-world use cases, and so we are now hard-coding it to simplify the internal code. Using the attribute in client applications is also deprecated.

  • The endpoint /_api/transaction previously would allow users to list, query, commit, and abort transactions operating in any database as long as the user had sufficient permissions. Now the endpoint will restrict operations to transactions within the current database.

  • The HTTP API for starting a Pregel run /_api/control-pregel now returns the Pregel execution number as a stringified execution number, e.g. “12345” instead of 12345. This is not downwards-compatible, so all client applications that depend on the return value being a numeric value need to be adjusted to handle a string return value and convert that string into a number.

Endpoints added

  • The cursor API endpoint PUT /_api/cursor/<cursor-id> to retrieve more data from an existing AQL query cursor is now also available under POST /_api/cursor/<cursor-id>.

    The new POST API is a drop-in replacement for the existing PUT API and functionally equivalent to it. The benefit of using the POST API is that HTTP POST requests will not be considered as idempotent, so proxies may not retry them if they fail. This was the case with the existing PUT API, as HTTP PUT requests can be considered idempotent according to the HTTP specification.

    The POST API is not yet used by ArangoDB 3.8, including the web UI and the client tools. This is to ensure the compatibility of 3.8 with earlier versions, which may be in use during upgrade to 3.8, or with one of the 3.8 client tools. The PUT API will remain fully functional in this version of ArangoDB and the next. The following version of ArangoDB will switch to using the POST variant instead of the PUT for its own requests, including web UI and client tools. Driver maintainers should eventually move to the POST variant of the cursor API as well. This is safe for drivers targeting 3.8 or higher.

  • The new REST endpoint at GET /_admin/log/entries can be used to retrieve server log messages in a more intuitive format than the already existing API at GET /_admin/log.

    The new API returns all matching log messages in an array, with one array entry per log message. Each log message is returned as an object containing the properties of the log message:

      "total" : 13,
      "messages": [
          "id" : 12,
          "topic" : "general",
          "level" : "INFO",
          "date" : "2021-02-07T01:00:21Z",
          "message" : "[cf3f4] {general} ArangoDB (version 3.8.0-devel enterprise [linux]) is ready for business. Have fun!"
          "id" : 11,
          "topic" : "general",
          "level" : "INFO",
          "date" : "2021-02-07T01:00:21Z",
          "message" : "[99d80] {general} You are using a milestone/alpha/beta/preview version ('3.8.0-devel') of ArangoDB"

    The previous API returned an object with 5 attributes at the top-level instead, which contained arrays with the attribute values of all log messages:

      "totalAmount" : 13,
      "lid" : [
      "topic" : [
      "level" : [
      "timestamp" : [
      "text" : [
        "[cf3f4] {general} ArangoDB (version 3.8.0-devel enterprise [linux]) is ready for business. Have fun!", 
        "[99d80] {general} You are using a milestone/alpha/beta/preview version ('3.8.0-devel') of ArangoDB"

    The old API endpoint GET /_admin/log for retrieving log messages is now deprecated, although it will stay available for some time.

  • Added endpoint for new version “v2” of the metrics API:

    GET /_admin/metrics/v2 will return Prometheus-format of the server metrics.

    The old endpoint GET /_admin/metrics is still supported but is considered to be obsolete from 3.8 on and will be removed in a future version. Also see Features and Improvements in 3.8.

    In the new API V2, there are quite a lot more metrics than in previous versions and a lot have been renamed to follow Prometheus conventions. Below is a list of renamed metrics:

    /_admin/metrics /_admin/metrics/v2
    arangodb_agency_cache_callback_count arangodb_agency_cache_callback_number
    arangodb_agency_callback_count arangodb_agency_callback_number
    arangodb_agency_callback_registered arangodb_agency_callback_registered_total
    arangodb_agency_read_no_leader arangodb_agency_read_no_leader_total
    arangodb_agency_read_ok arangodb_agency_read_ok_total
    arangodb_agency_supervision_accum_runtime_msec arangodb_agency_supervision_accum_runtime_msec_total
    arangodb_agency_supervision_accum_runtime_wait_for_replication_msec arangodb_agency_supervision_accum_runtime_wait_for_replication_msec_total
    arangodb_agency_supervision_failed_server_count arangodb_agency_supervision_failed_server_total
    arangodb_agency_write_no_leader arangodb_agency_write_no_leader_total
    arangodb_agency_write_ok arangodb_agency_write_ok_total
    arangodb_aql_all_query arangodb_aql_all_query_total
    arangodb_aql_slow_query arangodb_aql_slow_query_total
    arangodb_aql_total_query_time_msec arangodb_aql_total_query_time_msec_total
    arangodb_collection_lock_acquisition_micros arangodb_collection_lock_acquisition_micros_total
    arangodb_collection_lock_sequential_mode arangodb_collection_lock_sequential_mode_total
    arangodb_collection_lock_timeouts_exclusive arangodb_collection_lock_timeouts_exclusive_total
    arangodb_collection_lock_timeouts_write arangodb_collection_lock_timeouts_write_total
    arangodb_collection_truncates arangodb_collection_truncates_total
    arangodb_collection_truncates_replication arangodb_collection_truncates_replication_total
    arangodb_connection_connections_current arangodb_connection_pool_connections_current
    arangodb_connection_leases_successful arangodb_connection_pool_leases_successful_total
    arangodb_connection_pool_connections_created arangodb_connection_pool_connections_created_total
    arangodb_connection_pool_leases_failed arangodb_connection_pool_leases_failed_total
    arangodb_document_writes arangodb_document_writes_total
    arangodb_document_writes_replication arangodb_document_writes_replication_total
    arangodb_dropped_followers_count arangodb_dropped_followers_total
    arangodb_heartbeat_failures arangodb_heartbeat_failures_total
    arangodb_http_request_statistics_async_requests arangodb_http_request_statistics_async_requests_total
    arangodb_http_request_statistics_http_delete_requests arangodb_http_request_statistics_http_delete_requests_total
    arangodb_http_request_statistics_http_get_requests arangodb_http_request_statistics_http_get_requests_total
    arangodb_http_request_statistics_http_head_requests arangodb_http_request_statistics_http_head_requests_total
    arangodb_http_request_statistics_http_options_requests arangodb_http_request_statistics_http_options_requests_total
    arangodb_http_request_statistics_http_patch_requests arangodb_http_request_statistics_http_patch_requests_total
    arangodb_http_request_statistics_http_post_requests arangodb_http_request_statistics_http_post_requests_total
    arangodb_http_request_statistics_http_put_requests arangodb_http_request_statistics_http_put_requests_total
    arangodb_http_request_statistics_other_http_requests arangodb_http_request_statistics_other_http_requests_total
    arangodb_http_request_statistics_superuser_requests arangodb_http_request_statistics_superuser_requests_total
    arangodb_http_request_statistics_total_requests arangodb_http_request_statistics_total_requests_total
    arangodb_http_request_statistics_user_requests arangodb_http_request_statistics_user_requests_total
    arangodb_intermediate_commits arangodb_intermediate_commits_total
    arangodb_load_current_accum_runtime_msec arangodb_load_current_accum_runtime_msec_total
    arangodb_load_plan_accum_runtime_msec arangodb_load_plan_accum_runtime_msec_total
    arangodb_maintenance_action_accum_queue_time_msec arangodb_maintenance_action_accum_queue_time_msec_total
    arangodb_maintenance_action_accum_runtime_msec arangodb_maintenance_action_accum_runtime_msec_total
    arangodb_maintenance_action_done_counter arangodb_maintenance_action_done_total
    arangodb_maintenance_action_duplicate_counter arangodb_maintenance_action_duplicate_total
    arangodb_maintenance_action_failure_counter arangodb_maintenance_action_failure_total
    arangodb_maintenance_action_registered_counter arangodb_maintenance_action_registered_total
    arangodb_maintenance_agency_sync_accum_runtime_msec arangodb_maintenance_agency_sync_accum_runtime_msec_total
    arangodb_maintenance_phase1_accum_runtime_msec arangodb_maintenance_phase1_accum_runtime_msec_total
    arangodb_maintenance_phase2_accum_runtime_msec arangodb_maintenance_phase2_accum_runtime_msec_total
    arangodb_network_forwarded_requests arangodb_network_forwarded_requests_total
    arangodb_network_request_timeouts arangodb_network_request_timeouts_total
    arangodb_process_statistics_major_page_faults arangodb_process_statistics_major_page_faults_total
    arangodb_process_statistics_minor_page_faults arangodb_process_statistics_minor_page_faults_total
    arangodb_refused_followers_count arangodb_refused_followers_total
    arangodb_replication_cluster_inventory_requests arangodb_replication_cluster_inventory_requests_total
    arangodb_replication_dump_apply_time arangodb_replication_dump_apply_time_total
    arangodb_replication_dump_bytes_received arangodb_replication_dump_bytes_received_total
    arangodb_replication_dump_documents arangodb_replication_dump_documents_total
    arangodb_replication_dump_requests arangodb_replication_dump_requests_total
    arangodb_replication_dump_request_time arangodb_replication_dump_request_time_total
    arangodb_replication_failed_connects arangodb_replication_failed_connects_total
    arangodb_replication_initial_chunks_requests_time arangodb_replication_initial_chunks_requests_time_total
    arangodb_replication_initial_docs_requests_time arangodb_replication_initial_docs_requests_time_total
    arangodb_replication_initial_insert_apply_time arangodb_replication_initial_insert_apply_time_total
    arangodb_replication_initial_keys_requests_time arangodb_replication_initial_keys_requests_time_total
    arangodb_replication_initial_lookup_time arangodb_replication_initial_lookup_time_total
    arangodb_replication_initial_remove_apply_time arangodb_replication_initial_remove_apply_time_total
    arangodb_replication_initial_sync_bytes_received arangodb_replication_initial_sync_bytes_received_total
    arangodb_replication_initial_sync_docs_inserted arangodb_replication_initial_sync_docs_inserted_total
    arangodb_replication_initial_sync_docs_removed arangodb_replication_initial_sync_docs_removed_total
    arangodb_replication_initial_sync_docs_requested arangodb_replication_initial_sync_docs_requested_total
    arangodb_replication_initial_sync_docs_requests arangodb_replication_initial_sync_docs_requests_total
    arangodb_replication_initial_sync_keys_requests arangodb_replication_initial_sync_keys_requests_total
    arangodb_replication_synchronous_requests_total_number arangodb_replication_synchronous_requests_total_number_total
    arangodb_replication_synchronous_requests_total_time arangodb_replication_synchronous_requests_total_time_total
    arangodb_replication_tailing_apply_time arangodb_replication_tailing_apply_time_total
    arangodb_replication_tailing_bytes_received arangodb_replication_tailing_bytes_received_total
    arangodb_replication_tailing_documents arangodb_replication_tailing_documents_total
    arangodb_replication_tailing_follow_tick_failures arangodb_replication_tailing_follow_tick_failures_total
    arangodb_replication_tailing_markers arangodb_replication_tailing_markers_total
    arangodb_replication_tailing_removals arangodb_replication_tailing_removals_total
    arangodb_replication_tailing_requests arangodb_replication_tailing_requests_total
    arangodb_replication_tailing_request_time arangodb_replication_tailing_request_time_total
    arangodb_scheduler_queue_full_failures arangodb_scheduler_queue_full_failures_total
    arangodb_scheduler_threads_started arangodb_scheduler_threads_started_total
    arangodb_scheduler_threads_stopped arangodb_scheduler_threads_stopped_total
    arangodb_server_statistics_server_uptime arangodb_server_statistics_server_uptime_total
    arangodb_shards_leader_count arangodb_shards_leader_number
    arangodb_shards_total_count arangodb_shards_number
    arangodb_sync_wrong_checksum arangodb_sync_wrong_checksum_total
    arangodb_transactions_aborted arangodb_transactions_aborted_total
    arangodb_transactions_committed arangodb_transactions_committed_total
    arangodb_transactions_expired arangodb_transactions_expired_total
    arangodb_transactions_started arangodb_transactions_started_total
    arangodb_v8_context_created arangodb_v8_context_created_total
    arangodb_v8_context_creation_time_msec arangodb_v8_context_creation_time_msec_total
    arangodb_v8_context_destroyed arangodb_v8_context_destroyed_total
    arangodb_v8_context_entered arangodb_v8_context_entered_total
    arangodb_v8_context_enter_failures arangodb_v8_context_enter_failures_total
    arangodb_v8_context_exited arangodb_v8_context_exited_total
    rocksdbengine_throttle_bps rocksdb_engine_throttle_bps
    rocksdb_write_stalls arangodb_rocksdb_write_stalls_total
    rocksdb_write_stops arangodb_rocksdb_write_stops_total

Endpoints augmented

  • The REST endpoint at GET /_api/engine/stats now returns useful information in cluster setups too. Previously calling this API on a Coordinator always produced an empty JSON object result, whereas now it will produce a JSON object with one key per DB-Server. The mapped value per DB-Server are the engine statistics for this particular server.

    The return value structure is different to the return value structure in single server, where the return value is a simple JSON object with the statistics at the top level.

  • The REST endpoint for creating indexes, POST /_api/index, can now handle the attribute estimates, which determines if the to-be-created index should maintain selectivity estimates or not. If not specified, the default value for this attribute is true for indexes of type “persistent”, so that selectivity estimates are maintained. They can be optionally turned off by setting the attribute to false. Turning off selectivity estimates can have a slightly positive effect on write performance. The attribute will only be picked up for indexes of type “persistent”, “hash” and “skiplist” (where the latter two are aliases for “persistent” nowadays).

  • The REST endpoint at GET /_api/collection/<collection>/checksum now also works in cluster setups. In previous versions, this endpoint was not supported in cluster setups and returned HTTP 501 (Not implemented).

  • The HTTP REST API endpoint POST /_api/cursor can now handle an additional sub-attribute fillBlockCache for its options attribute. fillBlockCache controls whether the to-be-executed query should populate the RocksDB block cache with the data read by the query. This is an optional attribute, and its default value is true, meaning that the block cache will be populated (introduced in v3.8.1).

Endpoints deprecated

The API endpoints /_admin/statistics and /_admin/statistics-description are now deprecated in favor of the new metrics API endpoint /_admin/metrics/v2. The metrics endpoint provides a lot more information than the statistics endpoints, and will also be augmented with more metrics in the future. The statistics endpoints will still be functional in 3.8, but will eventually be removed in a future version of ArangoDB.

The REST API endpoint /_api/export is also deprecated in ArangoDB 3.8. This endpoint was previously only present in single server, but never supported in cluster deployments. The purpose of the endpoint was to provide the full data of a collection without holding collection locks for a long time, which was useful for the MMFile storage engine with its collection-level locks. If the functionality provided by this endpoint is still required by client applications, running a streaming AQL query to export the collection data can be used as a substitution.

Endpoints removed

The API endpoint /_admin/repair/distributeShardsLike for repairing the distributeShardsLike settings of cluster collections introduced before version 3.2.12 or 3.3.4 respectively, is now deprecated and removed from documentation.

There should not be any reasons to use this API with 3.8 or higher, and there was never any driver or official script support for it. The endpoint will be removed in ArangoDB 3.9.

JavaScript API

  • The JavaScript API for starting a Pregel run /_api/control-pregel now returns the Pregel execution number as a stringified execution number, e.g. “12345” instead of 12345. This is not downwards-compatible. Foxx services, arangosh scripts etc. that depend on the return value being a numeric value may need to be adjusted to handle a string return value and convert that string into a number.

ArangoDB Server Environment Variables

The new environment variable TZ_DATA can be used to specify the path to the directory containing the timezone information database for ArangoDB. That directory is normally named tzdata and is shipped with ArangoDB releases. It is normally not required to set this environment variable, but it may be necessary in unusual setups with non-conventional directory layouts and paths.