This is archived documentation for InfluxData product versions that are no longer maintained. For newer documentation, see the latest InfluxData documentation.
An InfluxQL function that returns an aggregated value across a set of points. See InfluxQL Functions for a complete list of the available and upcoming aggregations.
A collection of servers running InfluxDB nodes. All nodes in a cluster have the same users, databases, retention policies, and continuous queries. See Clustering for how to set up an InfluxDB cluster.
A node running only the consensus service.
The InfluxDB service that participates in the raft consensus group. A cluster must have at least three nodes running the consensus service (consensus or hybrid nodes), but it can have more. There should be an odd number of nodes running the consensus service in a cluster.
The number of consensus services that can fail before the cluster is degraded is ⌈n/2 + 1⌉ where
n is the number of consensus services in the cluster.
Thus, an even number of consensus services offer no additional redundancy or resiliency.
The consensus service ensures consistency across the cluster for node membership, databases, retention policies, users, continuous queries, shard metadata, and subscriptions.
continuous query (CQ)
An InfluxQL query that runs automatically and periodically within a database.
Continuous queries require a function in the
SELECT clause and must include a
GROUP BY time() clause.
See Continuous Queries.
Related entries: function
The node that receives write and query requests for the cluster.
A node running only the data service.
The InfluxDB service that persists time-series data to the node. A cluster must have at least one node (data or hybrid nodes) running the data service, but may have any number beyond one.
A logical container for users, retention policies, continuous queries, and time series data.
The attribute of the retention policy that determines how long InfluxDB stores data. Data older than the duration are automatically dropped from the database. See Database Management for how to set duration.
The key-value pair in InfluxDB’s data structure that records metadata and the actual data value. Fields are required in InfluxDB’s data structure and they are not indexed - queries on field values scan all points that match the specified time range and, as a result, are not performant relative to tags.
Query tip: Compare fields to tags; tags are indexed.
The key part of the key-value pair that makes up a field. Field keys are strings and they store metadata.
The collection of field keys and field values on a point.
The value part of the key-value pair that makes up a field. Field values are the actual data; they can be strings, floats, integers, or Booleans. A field value is always associated with a timestamp.
Field values are not indexed - queries on field values scan all points that match the specified time range and, as a result, are not performant.
Query tip: Compare field values to tag values; tag values are indexed.
InfluxQL aggregations, selectors, and transformations. See InfluxQL Functions for a complete list of InfluxQL functions.
A durable queue of data destined for a server which was unavailable at the time the data was received. Coordinating nodes temporarily store queued data when a target node for a write is down for a short period of time.
A node running both the consensus and data services.
Tokens which refer to database names, retention policy names, user names, measurement names, tag keys, and field keys. See Query Language Specification.
The text based format for writing points to InfluxDB. See Line Protocol.
The part of InfluxDB’s structure that describes the data stored in the associated fields. Measurements are strings.
Contains internal information about the status of the system. That includes user information, database and shard metadata, and which retention policies are enabled.
The part of InfluxDB’s data structure that consists of a single collection of fields in a series. Each point is uniquely identified by its series and timestamp.
You cannot store more than one point with the same timestamp in the same series. Instead, when you write a new point to the same series with the same timestamp as an existing point in that series, the field set becomes the union of the old field set and the new field set, where any ties go to the new field set. For an example, see Frequently Encountered Issues.
The attribute of the retention policy that determines how many copies of the data are stored in the cluster.
InfluxDB replicates data across
N data nodes, where
N is the replication factor.
To maintain data availability for queries, the replication factor should be less than or equal to the number of data nodes in the cluster:
- Data is fully available when the replication factor is greater than the number of unavailable data nodes.
- Data may be unavailable when the replication factor is less than the number of unavailable data nodes.
Note that there are no query performance benefits from replication. Replication is for ensuring data availability when a data node or nodes are unavailable. See Database Management for how to set the replication factor.
retention policy (RP)
The part of InfluxDB’s data structure that describes for how long InfluxDB keeps data (duration) and how many copies of this data is stored in the cluster (replication factor). RPs are unique per database and along with the measurement and tag set define a series.
When you create a database, InfluxDB automatically creates a retention policy called
default with an infinite duration and a replication factor set to the number of nodes in the cluster.
See Database Management for retention policy management.
How the data are organized in InfluxDB. The fundamentals of the InfluxDB schema are databases, retention policies, series, measurements, tag keys, tag values, and field keys. See Schema Design for more information.
An InfluxQL function that returns a single point from the range of specified points. See InfluxQL Functions for a complete list of the available and upcoming selectors.
The collection of data in InfluxDB’s data structure that share a measurement, tag set, and retention policy.
Note: The field set is not part of the series identification!
The count of all combinations of measurements and tags within a given data set.
For example, take measurement
mem_available with tags
If there are 35 different
hosts and 15 different
total_mem values then series cardinality for that measurement is
35 * 15 = 525.
To calculate series cardinality for a database add the series cardinalities for the individual measurements together.
A machine, virtual or physical, that is running InfluxDB. There should only be one InfluxDB process per server.
The key-value pair in InfluxDB’s data structure that records metadata. Tags are an optional part of InfluxDB’s data structure but they are useful for storing commonly-queried metadata; tags are indexed so queries on tags are performant. Query tip: Compare tags to fields; fields are not indexed.
The key part of the key-value pair that makes up a tag. Tag keys are strings and they store metadata. Tag keys are indexed so queries on tag keys are performant.
Query tip: Compare tag keys to field keys; field keys are not indexed.
The collection of tag keys and tag values on a point.
The value part of the key-value pair that makes up a tag. Tag values are strings and they store metadata. Tag values are indexed so queries on tag values are performant.
The date and time associated with a point. All time in InfluxDB is UTC.
Related entries: point
An InfluxQL function that returns a value or a set of values calculated from specified points, but does not return an aggregated value across those points. See InfluxQL Functions for a complete list of the available and upcoming aggregations.
There are two kinds of users in InfluxDB:
- Admin users have
WRITEaccess to all databases and full access to administrative queries and user management commands.
- Non-admin users have
WRITE) access per database.
When authentication is enabled, InfluxDB only executes HTTP requests that are sent with a valid username and password. See Authentication and Authorization.