Struct JournalConfig 

pub struct JournalConfig {

    pub max_object_size_bytes: u64,
    pub max_decompressed_bytes: usize,
    pub max_field_name_len: usize,
    pub max_fields_per_entry: usize,
    pub max_journal_files: usize,
    pub max_open_files: usize,
    pub mmap_policy: MmapPolicy,
    pub max_object_chain_steps: usize,
    pub max_query_terms: usize,
    pub allow_mmap_online: bool,
    pub include_journal_tilde: bool,
    pub poll_interval: Duration,
    pub live_channel_capacity: usize,
    pub max_live_batch_entries: usize,
    pub max_live_replay_entries: Option<usize>,
    pub live_queue_full_policy: LiveQueueFullPolicy,
}

Runtime configuration for crate::Journal.

These limits are primarily defensive: they bound memory use and traversal work when reading malformed, truncated, or unexpectedly large journal files.

Defaults are conservative for general-purpose readers. Increase limits only for known-good deployments with unusually large entries or many journal files. Lower JournalConfig::poll_interval when live tail latency matters and a platform watcher is not available.

Fields

max_object_size_bytes: u64

Maximum object size accepted from the journal file.

This bounds allocation when reading ENTRY, DATA, and related objects.

max_decompressed_bytes: usize

Maximum bytes allowed after decompressing a DATA payload.

This protects callers from compressed payloads that expand unexpectedly.

max_field_name_len: usize

Maximum length of a field name.

systemd field names are normally short uppercase identifiers such as MESSAGE or _SYSTEMD_UNIT.

max_fields_per_entry: usize

Maximum number of fields accepted per entry.

Entries exceeding this limit are treated as malformed or unsupported for this reader.

max_journal_files: usize

Maximum number of journal files included from a single scan.

Discovery fails with crate::SdJournalError::LimitExceeded if this limit is exceeded.

max_open_files: usize

Maximum journal files kept open by one reader.

Queries switch to a low-memory streaming merge when discovery finds more files than this limit. Set this to 1 for the lowest file-descriptor and mmap footprint.

mmap_policy: MmapPolicy

Runtime mmap policy.

MmapPolicy::Never forces bounded file I/O even when the mmap feature is enabled.

max_object_chain_steps: usize

Maximum number of steps when traversing any next_* chain.

This bounds work when following linked object chains in corrupt or adversarial files.

max_query_terms: usize

Maximum number of query terms (matches) accepted per query.

Unit helpers and OR groups can expand into several internal terms.

allow_mmap_online: bool

Whether to allow mmap for STATE_ONLINE journal files that may still be written.

The default is false because concurrently modified files are safer to read through explicit file I/O. Offline and archived files may still use mmap when the mmap feature is enabled, unless JournalConfig::mmap_policy is MmapPolicy::Never.

include_journal_tilde: bool

Whether to include *.journal~ temporary or incomplete files during discovery.

Keep this disabled unless the application explicitly wants best-effort access to temporary journal files.

poll_interval: Duration

Polling interval used as fallback when inotify is unavailable or unreliable.

This affects crate::LiveJournal latency only on fallback polling paths.

live_channel_capacity: usize

Maximum queued live entries per subscription.

Live subscriptions use bounded queues. This prevents slow consumers from growing memory without limit.

max_live_batch_entries: usize

Maximum entries decoded or dispatched by one live-engine cycle.

Replay, topology refresh, and modified-file reads are split across multiple crate::LiveJournal::poll_once cycles when more entries remain.

max_live_replay_entries: Option<usize>

Optional maximum matching historical entries replayed for a single subscription.

None means the replay has no total entry cap, but work is still batched by JournalConfig::max_live_batch_entries and delivered through bounded subscription queues.

Set this to Some(n) to fail with crate::SdJournalError::LimitExceeded after n matching replay entries for a subscription.

live_queue_full_policy: LiveQueueFullPolicy

Behavior when a subscription queue is full.

Trait Implementations

impl Clone for JournalConfig

fn clone(&self) -> JournalConfig

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for JournalConfig

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for JournalConfig

fn default() -> Self

Returns the “default value” for a type.