Struct mz_persist_client::PersistConfig

pub struct PersistConfig {

    pub now: NowFn,
    pub blob_target_size: usize,
    pub batch_builder_max_outstanding_parts: usize,
    pub compaction_enabled: bool,
    pub compaction_memory_bound_bytes: usize,
    pub compaction_heuristic_min_inputs: usize,
    pub compaction_heuristic_min_parts: usize,
    pub compaction_heuristic_min_updates: usize,
    pub compaction_concurrency_limit: usize,
    pub compaction_queue_size: usize,
    pub gc_batch_part_delete_concurrency_limit: usize,
    pub compaction_minimum_timeout: Duration,
    pub consensus_connection_pool_max_size: usize,
    pub consensus_connection_pool_ttl: Duration,
    pub consensus_connection_pool_ttl_stagger: Duration,
    pub state_versions_recent_live_diffs_limit: usize,
    pub writer_lease_duration: Duration,
    pub reader_lease_duration: Duration,
    pub critical_downgrade_interval: Duration,
    pub hostname: String,
    /* private fields */
}

The tunable knobs for persist.

Fields

now: NowFn

A clock to use for all leasing and other non-debugging use.

blob_target_size: usize

A target maximum size of blob payloads in bytes. If a logical “batch” is bigger than this, it will be broken up into smaller, independent pieces. This is best-effort, not a guarantee (though as of 2022-06-09, we happen to always respect it). This target size doesn’t apply for an individual update that exceeds it in size, but that scenario is almost certainly a mis-use of the system.

batch_builder_max_outstanding_parts: usize

The maximum number of parts (s3 blobs) that crate::batch::BatchBuilder will pipeline before back-pressuring crate::batch::BatchBuilder::add calls on previous ones finishing.

compaction_enabled: bool

Whether to physically and logically compact batches in blob storage.

compaction_memory_bound_bytes: usize

The upper bound on compaction’s memory consumption. The value must be at least 4*blob_target_size. Increasing this value beyond the minimum allows compaction to merge together more runs at once, providing greater consolidation of updates, at the cost of greater memory usage.

compaction_heuristic_min_inputs: usize

In Compactor::compact_and_apply, we do the compaction (don’t skip it) if the number of inputs is at least this many. Compaction is performed if any of the heuristic criteria are met (they are OR’d).

compaction_heuristic_min_parts: usize

In Compactor::compact_and_apply, we do the compaction (don’t skip it) if the number of batch parts is at least this many. Compaction is performed if any of the heuristic criteria are met (they are OR’d).

compaction_heuristic_min_updates: usize

In Compactor::compact_and_apply, we do the compaction (don’t skip it) if the number of updates is at least this many. Compaction is performed if any of the heuristic criteria are met (they are OR’d).

compaction_concurrency_limit: usize

In Compactor::compact_and_apply_background, the maximum number of concurrent compaction requests that can execute for a given shard.

compaction_queue_size: usize

In Compactor::compact_and_apply_background, the maximum number of pending compaction requests to queue.

gc_batch_part_delete_concurrency_limit: usize

The maximum number of concurrent blob deletes during garbage collection.

compaction_minimum_timeout: Duration

In Compactor::compact_and_apply_background, the minimum amount of time to allow a compaction request to run before timing it out. A request may be given a timeout greater than this value depending on the inputs’ size

consensus_connection_pool_max_size: usize

The maximum size of the connection pool to Postgres/CRDB when performing consensus reads and writes.

consensus_connection_pool_ttl: Duration

The minimum TTL of a connection to Postgres/CRDB before it is proactively terminated. Connections are routinely culled to balance load against the downstream database.

consensus_connection_pool_ttl_stagger: Duration

The minimum time between TTLing connections to Postgres/CRDB. This delay is used to stagger reconnections to avoid stampedes and high tail latencies. This value should be much less than consensus_connection_pool_ttl so that reconnections are biased towards terminating the oldest connections first. A value of consensus_connection_pool_ttl / consensus_connection_pool_max_size is likely a good place to start so that all connections are rotated when the pool is fully used.

state_versions_recent_live_diffs_limit: usize

The # of diffs to initially scan when fetching the latest consensus state, to determine which requests go down the fast vs slow path. Should be large enough to fetch all live diffs in the steady-state, and small enough to query Consensus at high volume. Steady-state usage should accommodate readers that require seqno-holds for reasonable amounts of time, which to start we say is 10s of minutes.

This value ought to be defined in terms of NEED_ROLLUP_THRESHOLD to approximate when we expect rollups to be written and therefore when old states will be truncated by GC.

writer_lease_duration: Duration

Length of time after a writer’s last operation after which the writer may be expired.

reader_lease_duration: Duration

Length of time after a reader’s last operation after which the reader may be expired.

critical_downgrade_interval: Duration

Length of time between critical handles’ calls to downgrade since

hostname: String

Hostname of this persist user. Stored in state and used for debugging.

Implementations

impl PersistConfig

pub fn new(build_info: &BuildInfo, now: NowFn) -> Self

Returns a new instance of PersistConfig with default tuning.

impl PersistConfig

pub const DEFAULT_BLOB_TARGET_SIZE: usize = 134_217_728usize

Default value for PersistConfig::blob_target_size.

pub const DEFAULT_COMPACTION_MINIMUM_TIMEOUT: Duration = _

Default value for PersistConfig::compaction_minimum_timeout.

Trait Implementations

impl Clone for PersistConfig

fn clone(&self) -> PersistConfig

Returns a copy of the value.

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

Performs copy-assignment from source.

impl ConsensusKnobs for PersistConfig

fn connection_pool_max_size(&self) -> usize

Maximum number of connections allowed in a pool.

fn connection_pool_ttl(&self) -> Duration

Minimum TTL of a connection. It is expected that connections are routinely culled to balance load to the backing store of Consensus.

fn connection_pool_ttl_stagger(&self) -> Duration

Minimum time between TTLing connections. Helps stagger reconnections to avoid stampeding the backing store of Consensus.

impl Debug for PersistConfig

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

Formats the value using the given formatter.