compression.maxTotalZstdWindowBytes

Limits aggregate advertised zstd decoder-window bytes across active sessions for one imtcp listener.

This parameter applies to imtcp: TCP Syslog Input Module.

Name:

compression.maxTotalZstdWindowBytes

Scope:

input/module

Type:

integer

Default:

0

Required?:

no

Introduced:

8.2608.0

Description

compression.maxTotalZstdWindowBytes limits the sum of advertised zstd decoder-window sizes retained by active compressed sessions on one imtcp listener. It applies only when compression.mode="stream:always" and compression.driver="zstd" are active. A frame whose reservation would exceed the limit is rejected and its session is closed without affecting already admitted sessions.

The default 0 leaves aggregate decoder-window memory unlimited for compatibility. This setting is independent of compression.maxDecompressedBytesPerReceive, which limits decompressed output from one TCP receive operation.

The secure-default policy controls omitted values:

  • compatibility.defaults.secure="backward-compatible" accepts the unlimited default silently.

  • compatibility.defaults.secure="warn" accepts it and emits a startup warning. Explicitly setting 0 acknowledges unlimited operation and suppresses that warning.

  • compatibility.defaults.secure="strict" requires an explicitly configured positive value and rejects omitted or explicit-zero values.

The accounting uses the window size declared by each zstd frame. It bounds the dominant retained decoder-window allocation, but does not attempt to account for every byte of decoder bookkeeping or unrelated per-connection memory.

RainerScript usage

input(
    type="imtcp"
    address="127.0.0.1"
    port="514"
    compression.mode="stream:always"
    compression.driver="zstd"
    compression.maxTotalZstdWindowBytes="536870912"
)

YAML usage

inputs:
  - type: imtcp
    address: "127.0.0.1"
    port: "514"
    compression.mode: "stream:always"
    compression.driver: "zstd"
    compression.maxTotalZstdWindowBytes: "536870912"

The same parameter may be placed on module(load="imtcp" ...) or its YAML module entry to provide an explicitly configured default inherited by inputs.

See also

See also compression.mode, compression.driver, compression.maxDecompressedBytesPerReceive, and imtcp: TCP Syslog Input Module.

Support: rsyslog Assistant | GitHub Discussions | GitHub Issues: rsyslog source project

Contributing: Source & docs: rsyslog source project

© 2008–2026 Rainer Gerhards and others. Licensed under the Apache License 2.0.