# Atlas analytics nodes and read preference tags > Source-anchored research for Atlas analytics nodes and read preference tags. Run status: COMPLETED. Parent: [Long-running secondary reads in sharded clusters](https://llms-explorer.com/tree/long-running-secondary-reads-in-sharded-clusters/) · 6 facets · 17 facts · page: https://llms-explorer.com/tree/atlas-analytics-nodes-and-read-preference-tags/ ## Definitions - With secondaryPreferred, no eligible tagged secondary means fallback to the primary without applying tags. An analytics tag therefore does not prevent primary reads under this mode. (high confidence) — [source](https://github.com/mongodb/specifications/blob/master/source/server-selection/server-selection.md) ## How it works - Inference from the Datadog and JDBC reports: verify destination-node metrics through the actual connector, because a syntactically plausible analytics-tag configuration does not prove that integration preserves or accepts it. (medium confidence) — [source](https://github.com/DataDog/integrations-core/issues/17942) ## How-to and procedures - Use readPreference=secondary&readPreferenceTags=nodeType:ANALYTICS to select analytics nodes for reads. Atlas and Fivetran document this exact combination. (medium confidence) — [source](https://www.mongodb.com/docs/atlas/reference/replica-set-tags.md) ## Problems, failure modes and limitations - Atlas warns that strict analytics targeting can fail during compaction initial sync, disk scale-down, and NVMe tier changes; its availability example adds an empty-tag fallback. (low confidence) (verified as of 2026-10-14) — [source](https://www.mongodb.com/docs/atlas/reference/replica-set-tags.md) - A 2026 Terraform Google provider feature request describes missing MongoDB additional_options support for Datastream analytics-tag routing. It is evidence of a reported provisioning gap at that time, not a verified current provider limitation. (low confidence) — [source](https://github.com/hashicorp/terraform-provider-google/issues/27750) - Datadog issue 17942 records a June 2024 Mongo integration configuration rejecting readPreferenceTags values with a not-a-valid-value error. A November 2024 contributor recommended per-host monitoring instances. This historical report does not establish a current driver-wide defect. (low confidence) — [source](https://github.com/DataDog/integrations-core/issues/17942) ## Comparisons and alternatives - With secondary and only the analytics tag set, lack of eligible matching secondaries causes read selection to fail rather than use the primary. (high confidence) — [source](https://github.com/mongodb/specifications/blob/master/source/server-selection/server-selection.md) - Atlas predefined replica-set tags differ from user-managed resource tags; users cannot change the predefined replica-set tags. (low confidence) — [source](https://www.mongodb.com/docs/atlas/reference/replica-set-tags.md) ## Facts and statements - Atlas provides fixed replica-set tags distinct from user-managed resource tags. nodeType:ANALYTICS identifies analytics nodes; workloadType:OPERATIONAL identifies electable and read-only nodes. (low confidence) (verified as of 2026-10-14) — [source](https://www.mongodb.com/docs/atlas/reference/replica-set-tags.md) - Tag sets are tried in order; the first set matching eligible candidates wins. A trailing empty readPreferenceTags= under secondary permits fallback to other secondaries, broadening eligibility beyond analytics nodes. (high confidence) — [source](https://github.com/mongodb/specifications/blob/master/source/server-selection/server-selection.md) - In a sharded topology, the driver selects a mongos without applying read-preference tags to that choice. It forwards the read preference to mongos for downstream selection. (low confidence) — [source](https://github.com/mongodb/specifications/blob/master/source/server-selection/server-selection.md) - A September 2022 incident report describes analytics-node unavailability sending secondaryPreferred reads to the primary, degrading service and contributing to failover. The author changed the analytics connection to secondary. (low confidence) — [source](https://pmclain.com/mongodb/2022/09/28/fun-with-mongodb-atlas-analytics-nodes.html) - DRIVERS-2563 records historical mongos replica-set-monitor bugs that did not honor tag-list preference order. It identifies SERVER-51835 and explains how queries could spread beyond the preferred hosts. This is historical evidence, not a claim that every current release is affected. (low confidence) — [source](https://jira.mongodb.org/browse/DRIVERS-2563) - Datadog issue 17942 reports Mongo integration 6.2.0 rejecting configured analytics tags with "not a valid value for readpreferencetags". A Datadog contributor advised one monitoring integration instance per database host. (low confidence) — [source](https://github.com/DataDog/integrations-core/issues/17942) - A July 2025 Atlas SQL JDBC issue reports analytics tags being ignored while secondary mode worked; the reporter observed correct analytics targeting through the native Java driver. Treat this as a connector-specific report, not proof that native Atlas routing ignores tags. (low confidence) — [source](https://github.com/mongodb/mongo-jdbc-driver/issues/362) - Atlas supplies nodeType:ANALYTICS for analytics secondaries. Its documented targeting string is readPreference=secondary&readPreferenceTags=nodeType:ANALYTICS&readConcernLevel=local. (high confidence) — [source](https://www.mongodb.com/docs/atlas/reference/replica-set-tags.md) - Within one tag set, every specified key/value pair must match. Mode and maxStalenessSeconds filter candidates before ordered tag matching. (low confidence) — [source](https://github.com/mongodb/specifications/blob/master/source/server-selection/server-selection.md)