redis commands streams xadd

XADD

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Append an entry to a stream

Usage: XADD key ID field value.
The ID must always be greater than the previous ID.
You can set an ID, but '*' (asterisk) is usual so Redis always generates a larger ID.

Note after failover

If master A fails and replica B is promoted, XADD is rejected when B's timestamp is behind A's. Keep server clocks in sync.

When you specify an ID

• If the source data already has a value you can use as an ID, specifying it is a good option. For example, if a sensor emits millisecond IDs and Redis receives them once per second, they will not collide.
• You can also generate the first part of the ID with a key.
  INCR sensor-1234-timestamp
• XADD sensor-0001 0-1 temperature 101
  0 or 0-0 cannot be used as an ID.
• XADD sensor-0001 1000 temperature 102
  You may omit sequenceNumber.

Options

• NOMKSTREAM
  Does not create a new key. Appends only to an existing stream. No Make Stream.
  This prevents creating a key by mistake.
  Added in version 6.2.
• MAXLEN
  To cap stream length while appending, use MAXLEN as below.
  XADD sensor-1234 MAXLEN 10 * temperature 100
  Delete and append run as one operation, so this is slower than append-only.   There is a special option for that case:
  XADD sensor-1234 MAXLEN ~ 10 * temperature 100
  ~ deletes only when it can do so cheaply.
• MINID
  threshold is an ID. Entries with an ID less than that ID are deleted.
  Added in version 6.2.
• LIMIT
  Limits how many entries are deleted. Added in version 6.2.

Syntax

XADD key [NOMKSTREAM] [MAXLEN|MINID [=|~] threshold [LIMIT count]] *|ID field value [field value ...]

• Available since version 5.0.0.
• NOMKSTREAM, MINID, and LIMIT were added in version 6.2.
• Time complexity is O(log(N)), where N is the number of entries already in the stream.
• Returns the ID.