refactor(pageserver): rely on serde derive for toml deserialization (#7656)

This PR simplifies the pageserver configuration parsing as follows:

* introduce the `pageserver_api::config::ConfigToml` type
* implement `Default` for `ConfigToml`
* use serde derive to do the brain-dead leg-work of processing the toml
document
  * use `serde(default)` to fill in default values
* in `pageserver` crate:
* use `toml_edit` to deserialize the pageserver.toml string into a
`ConfigToml`
  * `PageServerConfig::parse_and_validate` then
    * consumes the `ConfigToml`
    * destructures it exhaustively into its constituent fields
    * constructs the `PageServerConfig`

The rules are:

* in `ConfigToml`, use `deny_unknown_fields` everywhere
* static default values go in `pageserver_api`
* if there cannot be a static default value (e.g. which default IO
engine to use, because it depends on the runtime), make the field in
`ConfigToml` an `Option`
* if runtime-augmentation of a value is needed, do that in
`parse_and_validate`
* a good example is `virtual_file_io_engine` or `l0_flush`, both of
which need to execute code to determine the effective value in
`PageServerConf`

The benefits:

* massive amount of brain-dead repetitive code can be deleted
* "unused variable" compile-time errors when removing a config value,
due to the exhaustive destructuring in `parse_and_validate`
* compile-time errors guide you when adding a new config field

Drawbacks:

* serde derive is sometimes a bit too magical
* `deny_unknown_fields` is easy to miss

Future Work / Benefits:
* make `neon_local` use `pageserver_api` to construct `ConfigToml` and
write it to `pageserver.toml`
* This provides more type safety / coompile-time errors than the current
approach.

### Refs

Fixes #3682 

### Future Work

* `remote_storage` deser doesn't reject unknown fields
https://github.com/neondatabase/neon/issues/8915
* clean up `libs/pageserver_api/src/config.rs` further
  * break up into multiple files, at least for tenant config
* move `models` as appropriate / refine distinction between config and
API models / be explicit about when it's the same
  * use `pub(crate)` visibility on `mod defaults` to detect stale values

libs/pageserver_api/Cargo.toml

@@ -4,6 +4,10 @@ version = "0.1.0"
 edition.workspace = true
 license.workspace = true
 
+[features]
+# See pageserver/Cargo.toml
+testing = ["dep:nix"]
+
 [dependencies]
 serde.workspace = true
 serde_with.workspace = true
@@ -23,6 +27,12 @@ thiserror.workspace = true
 humantime-serde.workspace = true
 chrono = { workspace = true, features = ["serde"] }
 itertools.workspace = true
+storage_broker.workspace = true
+camino = {workspace = true, features = ["serde1"]}
+remote_storage.workspace = true
+postgres_backend.workspace = true
+nix = {workspace = true, optional = true}
+reqwest.workspace = true
 
 [dev-dependencies]
 bincode.workspace = true

libs/pageserver_api/src/config.rs

@@ -1,15 +1,28 @@
-use std::collections::HashMap;
-
-use const_format::formatcp;
+use camino::Utf8PathBuf;
 
 #[cfg(test)]
 mod tests;
 
+use const_format::formatcp;
 pub const DEFAULT_PG_LISTEN_PORT: u16 = 64000;
 pub const DEFAULT_PG_LISTEN_ADDR: &str = formatcp!("127.0.0.1:{DEFAULT_PG_LISTEN_PORT}");
 pub const DEFAULT_HTTP_LISTEN_PORT: u16 = 9898;
 pub const DEFAULT_HTTP_LISTEN_ADDR: &str = formatcp!("127.0.0.1:{DEFAULT_HTTP_LISTEN_PORT}");
 
+use postgres_backend::AuthType;
+use remote_storage::RemoteStorageConfig;
+use serde_with::serde_as;
+use std::{
+    collections::HashMap,
+    num::{NonZeroU64, NonZeroUsize},
+    str::FromStr,
+    time::Duration,
+};
+use utils::logging::LogFormat;
+
+use crate::models::ImageCompressionAlgorithm;
+use crate::models::LsnLease;
+
 // Certain metadata (e.g. externally-addressable name, AZ) is delivered
 // as a separate structure.  This information is not neeed by the pageserver
 // itself, it is only used for registering the pageserver with the control
@@ -29,3 +42,511 @@ pub struct NodeMetadata {
     #[serde(flatten)]
     pub other: HashMap<String, serde_json::Value>,
 }
+
+/// `pageserver.toml`
+///
+/// We use serde derive with `#[serde(default)]` to generate a deserializer
+/// that fills in the default values for each config field.
+///
+/// If there cannot be a static default value because we need to make runtime
+/// checks to determine the default, make it an `Option` (which defaults to None).
+/// The runtime check should be done in the consuming crate, i.e., `pageserver`.
+#[serde_as]
+#[derive(Clone, Debug, serde::Deserialize, serde::Serialize)]
+#[serde(default, deny_unknown_fields)]
+pub struct ConfigToml {
+    // types mapped 1:1 into the runtime PageServerConfig type
+    pub listen_pg_addr: String,
+    pub listen_http_addr: String,
+    pub availability_zone: Option<String>,
+    #[serde(with = "humantime_serde")]
+    pub wait_lsn_timeout: Duration,
+    #[serde(with = "humantime_serde")]
+    pub wal_redo_timeout: Duration,
+    pub superuser: String,
+    pub page_cache_size: usize,
+    pub max_file_descriptors: usize,
+    pub pg_distrib_dir: Option<Utf8PathBuf>,
+    #[serde_as(as = "serde_with::DisplayFromStr")]
+    pub http_auth_type: AuthType,
+    #[serde_as(as = "serde_with::DisplayFromStr")]
+    pub pg_auth_type: AuthType,
+    pub auth_validation_public_key_path: Option<Utf8PathBuf>,
+    pub remote_storage: Option<RemoteStorageConfig>,
+    pub tenant_config: TenantConfigToml,
+    #[serde_as(as = "serde_with::DisplayFromStr")]
+    pub broker_endpoint: storage_broker::Uri,
+    #[serde(with = "humantime_serde")]
+    pub broker_keepalive_interval: Duration,
+    #[serde_as(as = "serde_with::DisplayFromStr")]
+    pub log_format: LogFormat,
+    pub concurrent_tenant_warmup: NonZeroUsize,
+    pub concurrent_tenant_size_logical_size_queries: NonZeroUsize,
+    #[serde(with = "humantime_serde")]
+    pub metric_collection_interval: Duration,
+    pub metric_collection_endpoint: Option<reqwest::Url>,
+    pub metric_collection_bucket: Option<RemoteStorageConfig>,
+    #[serde(with = "humantime_serde")]
+    pub synthetic_size_calculation_interval: Duration,
+    pub disk_usage_based_eviction: Option<DiskUsageEvictionTaskConfig>,
+    pub test_remote_failures: u64,
+    pub ondemand_download_behavior_treat_error_as_warn: bool,
+    #[serde(with = "humantime_serde")]
+    pub background_task_maximum_delay: Duration,
+    pub control_plane_api: Option<reqwest::Url>,
+    pub control_plane_api_token: Option<String>,
+    pub control_plane_emergency_mode: bool,
+    pub heatmap_upload_concurrency: usize,
+    pub secondary_download_concurrency: usize,
+    pub virtual_file_io_engine: Option<crate::models::virtual_file::IoEngineKind>,
+    pub ingest_batch_size: u64,
+    pub max_vectored_read_bytes: MaxVectoredReadBytes,
+    pub image_compression: ImageCompressionAlgorithm,
+    pub ephemeral_bytes_per_memory_kb: usize,
+    pub l0_flush: Option<crate::models::L0FlushConfig>,
+    pub compact_level0_phase1_value_access: CompactL0Phase1ValueAccess,
+    pub virtual_file_direct_io: crate::models::virtual_file::DirectIoMode,
+    pub io_buffer_alignment: usize,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
+#[serde(deny_unknown_fields)]
+pub struct DiskUsageEvictionTaskConfig {
+    pub max_usage_pct: utils::serde_percent::Percent,
+    pub min_avail_bytes: u64,
+    #[serde(with = "humantime_serde")]
+    pub period: Duration,
+    #[cfg(feature = "testing")]
+    pub mock_statvfs: Option<statvfs::mock::Behavior>,
+    /// Select sorting for evicted layers
+    #[serde(default)]
+    pub eviction_order: EvictionOrder,
+}
+
+pub mod statvfs {
+    pub mod mock {
+        #[derive(Debug, Clone, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
+        #[serde(tag = "type")]
+        pub enum Behavior {
+            Success {
+                blocksize: u64,
+                total_blocks: u64,
+                name_filter: Option<utils::serde_regex::Regex>,
+            },
+            #[cfg(feature = "testing")]
+            Failure { mocked_error: MockedError },
+        }
+
+        #[cfg(feature = "testing")]
+        #[derive(Debug, Clone, Copy, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
+        #[allow(clippy::upper_case_acronyms)]
+        pub enum MockedError {
+            EIO,
+        }
+
+        #[cfg(feature = "testing")]
+        impl From<MockedError> for nix::Error {
+            fn from(e: MockedError) -> Self {
+                match e {
+                    MockedError::EIO => nix::Error::EIO,
+                }
+            }
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
+#[serde(tag = "type", content = "args")]
+pub enum EvictionOrder {
+    RelativeAccessed {
+        highest_layer_count_loses_first: bool,
+    },
+}
+
+impl Default for EvictionOrder {
+    fn default() -> Self {
+        Self::RelativeAccessed {
+            highest_layer_count_loses_first: true,
+        }
+    }
+}
+
+#[derive(
+    Eq,
+    PartialEq,
+    Debug,
+    Copy,
+    Clone,
+    strum_macros::EnumString,
+    strum_macros::Display,
+    serde_with::DeserializeFromStr,
+    serde_with::SerializeDisplay,
+)]
+#[strum(serialize_all = "kebab-case")]
+pub enum GetVectoredImpl {
+    Sequential,
+    Vectored,
+}
+
+#[derive(
+    Eq,
+    PartialEq,
+    Debug,
+    Copy,
+    Clone,
+    strum_macros::EnumString,
+    strum_macros::Display,
+    serde_with::DeserializeFromStr,
+    serde_with::SerializeDisplay,
+)]
+#[strum(serialize_all = "kebab-case")]
+pub enum GetImpl {
+    Legacy,
+    Vectored,
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
+#[serde(transparent)]
+pub struct MaxVectoredReadBytes(pub NonZeroUsize);
+
+#[derive(Debug, PartialEq, Eq, Clone, serde::Deserialize, serde::Serialize)]
+#[serde(tag = "mode", rename_all = "kebab-case", deny_unknown_fields)]
+pub enum CompactL0Phase1ValueAccess {
+    /// The old way.
+    PageCachedBlobIo,
+    /// The new way.
+    StreamingKmerge {
+        /// If set, we run both the old way and the new way, validate that
+        /// they are identical (=> [`CompactL0BypassPageCacheValidation`]),
+        /// and if the validation fails,
+        /// - in tests: fail them with a panic or
+        /// - in prod, log a rate-limited warning and use the old way's results.
+        ///
+        /// If not set, we only run the new way and trust its results.
+        validate: Option<CompactL0BypassPageCacheValidation>,
+    },
+}
+
+/// See [`CompactL0Phase1ValueAccess::StreamingKmerge`].
+#[derive(Debug, PartialEq, Eq, Clone, serde::Deserialize, serde::Serialize)]
+#[serde(rename_all = "kebab-case")]
+pub enum CompactL0BypassPageCacheValidation {
+    /// Validate that the series of (key, lsn) pairs are the same.
+    KeyLsn,
+    /// Validate that the entire output of old and new way is identical.
+    KeyLsnValue,
+}
+
+impl Default for CompactL0Phase1ValueAccess {
+    fn default() -> Self {
+        CompactL0Phase1ValueAccess::StreamingKmerge {
+            // TODO(https://github.com/neondatabase/neon/issues/8184): change to None once confident
+            validate: Some(CompactL0BypassPageCacheValidation::KeyLsnValue),
+        }
+    }
+}
+
+/// A tenant's calcuated configuration, which is the result of merging a
+/// tenant's TenantConfOpt with the global TenantConf from PageServerConf.
+///
+/// For storing and transmitting individual tenant's configuration, see
+/// TenantConfOpt.
+#[derive(Debug, Clone, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
+#[serde(deny_unknown_fields, default)]
+pub struct TenantConfigToml {
+    // Flush out an inmemory layer, if it's holding WAL older than this
+    // This puts a backstop on how much WAL needs to be re-digested if the
+    // page server crashes.
+    // This parameter actually determines L0 layer file size.
+    pub checkpoint_distance: u64,
+    // Inmemory layer is also flushed at least once in checkpoint_timeout to
+    // eventually upload WAL after activity is stopped.
+    #[serde(with = "humantime_serde")]
+    pub checkpoint_timeout: Duration,
+    // Target file size, when creating image and delta layers.
+    // This parameter determines L1 layer file size.
+    pub compaction_target_size: u64,
+    // How often to check if there's compaction work to be done.
+    // Duration::ZERO means automatic compaction is disabled.
+    #[serde(with = "humantime_serde")]
+    pub compaction_period: Duration,
+    // Level0 delta layer threshold for compaction.
+    pub compaction_threshold: usize,
+    pub compaction_algorithm: crate::models::CompactionAlgorithmSettings,
+    // Determines how much history is retained, to allow
+    // branching and read replicas at an older point in time.
+    // The unit is #of bytes of WAL.
+    // Page versions older than this are garbage collected away.
+    pub gc_horizon: u64,
+    // Interval at which garbage collection is triggered.
+    // Duration::ZERO means automatic GC is disabled
+    #[serde(with = "humantime_serde")]
+    pub gc_period: Duration,
+    // Delta layer churn threshold to create L1 image layers.
+    pub image_creation_threshold: usize,
+    // Determines how much history is retained, to allow
+    // branching and read replicas at an older point in time.
+    // The unit is time.
+    // Page versions older than this are garbage collected away.
+    #[serde(with = "humantime_serde")]
+    pub pitr_interval: Duration,
+    /// Maximum amount of time to wait while opening a connection to receive wal, before erroring.
+    #[serde(with = "humantime_serde")]
+    pub walreceiver_connect_timeout: Duration,
+    /// Considers safekeepers stalled after no WAL updates were received longer than this threshold.
+    /// A stalled safekeeper will be changed to a newer one when it appears.
+    #[serde(with = "humantime_serde")]
+    pub lagging_wal_timeout: Duration,
+    /// Considers safekeepers lagging when their WAL is behind another safekeeper for more than this threshold.
+    /// A lagging safekeeper will be changed after `lagging_wal_timeout` time elapses since the last WAL update,
+    /// to avoid eager reconnects.
+    pub max_lsn_wal_lag: NonZeroU64,
+    pub eviction_policy: crate::models::EvictionPolicy,
+    pub min_resident_size_override: Option<u64>,
+    // See the corresponding metric's help string.
+    #[serde(with = "humantime_serde")]
+    pub evictions_low_residence_duration_metric_threshold: Duration,
+
+    /// If non-zero, the period between uploads of a heatmap from attached tenants.  This
+    /// may be disabled if a Tenant will not have secondary locations: only secondary
+    /// locations will use the heatmap uploaded by attached locations.
+    #[serde(with = "humantime_serde")]
+    pub heatmap_period: Duration,
+
+    /// If true then SLRU segments are dowloaded on demand, if false SLRU segments are included in basebackup
+    pub lazy_slru_download: bool,
+
+    pub timeline_get_throttle: crate::models::ThrottleConfig,
+
+    // How much WAL must be ingested before checking again whether a new image layer is required.
+    // Expresed in multiples of checkpoint distance.
+    pub image_layer_creation_check_threshold: u8,
+
+    /// Switch to a new aux file policy. Switching this flag requires the user has not written any aux file into
+    /// the storage before, and this flag cannot be switched back. Otherwise there will be data corruptions.
+    /// There is a `last_aux_file_policy` flag which gets persisted in `index_part.json` once the first aux
+    /// file is written.
+    pub switch_aux_file_policy: crate::models::AuxFilePolicy,
+
+    /// The length for an explicit LSN lease request.
+    /// Layers needed to reconstruct pages at LSN will not be GC-ed during this interval.
+    #[serde(with = "humantime_serde")]
+    pub lsn_lease_length: Duration,
+
+    /// The length for an implicit LSN lease granted as part of `get_lsn_by_timestamp` request.
+    /// Layers needed to reconstruct pages at LSN will not be GC-ed during this interval.
+    #[serde(with = "humantime_serde")]
+    pub lsn_lease_length_for_ts: Duration,
+}
+
+pub mod defaults {
+    use crate::models::ImageCompressionAlgorithm;
+
+    pub use storage_broker::DEFAULT_ENDPOINT as BROKER_DEFAULT_ENDPOINT;
+
+    pub const DEFAULT_WAIT_LSN_TIMEOUT: &str = "300 s";
+    pub const DEFAULT_WAL_REDO_TIMEOUT: &str = "60 s";
+
+    pub const DEFAULT_SUPERUSER: &str = "cloud_admin";
+
+    pub const DEFAULT_PAGE_CACHE_SIZE: usize = 8192;
+    pub const DEFAULT_MAX_FILE_DESCRIPTORS: usize = 100;
+
+    pub const DEFAULT_LOG_FORMAT: &str = "plain";
+
+    pub const DEFAULT_CONCURRENT_TENANT_WARMUP: usize = 8;
+
+    pub const DEFAULT_CONCURRENT_TENANT_SIZE_LOGICAL_SIZE_QUERIES: usize = 1;
+
+    pub const DEFAULT_METRIC_COLLECTION_INTERVAL: &str = "10 min";
+    pub const DEFAULT_METRIC_COLLECTION_ENDPOINT: Option<reqwest::Url> = None;
+    pub const DEFAULT_SYNTHETIC_SIZE_CALCULATION_INTERVAL: &str = "10 min";
+    pub const DEFAULT_BACKGROUND_TASK_MAXIMUM_DELAY: &str = "10s";
+
+    pub const DEFAULT_HEATMAP_UPLOAD_CONCURRENCY: usize = 8;
+    pub const DEFAULT_SECONDARY_DOWNLOAD_CONCURRENCY: usize = 1;
+
+    pub const DEFAULT_INGEST_BATCH_SIZE: u64 = 100;
+
+    pub const DEFAULT_MAX_VECTORED_READ_BYTES: usize = 128 * 1024; // 128 KiB
+
+    pub const DEFAULT_IMAGE_COMPRESSION: ImageCompressionAlgorithm =
+        ImageCompressionAlgorithm::Zstd { level: Some(1) };
+
+    pub const DEFAULT_VALIDATE_VECTORED_GET: bool = false;
+
+    pub const DEFAULT_EPHEMERAL_BYTES_PER_MEMORY_KB: usize = 0;
+
+    pub const DEFAULT_IO_BUFFER_ALIGNMENT: usize = 512;
+}
+
+impl Default for ConfigToml {
+    fn default() -> Self {
+        use defaults::*;
+
+        Self {
+            listen_pg_addr: (DEFAULT_PG_LISTEN_ADDR.to_string()),
+            listen_http_addr: (DEFAULT_HTTP_LISTEN_ADDR.to_string()),
+            availability_zone: (None),
+            wait_lsn_timeout: (humantime::parse_duration(DEFAULT_WAIT_LSN_TIMEOUT)
+                .expect("cannot parse default wait lsn timeout")),
+            wal_redo_timeout: (humantime::parse_duration(DEFAULT_WAL_REDO_TIMEOUT)
+                .expect("cannot parse default wal redo timeout")),
+            superuser: (DEFAULT_SUPERUSER.to_string()),
+            page_cache_size: (DEFAULT_PAGE_CACHE_SIZE),
+            max_file_descriptors: (DEFAULT_MAX_FILE_DESCRIPTORS),
+            pg_distrib_dir: None, // Utf8PathBuf::from("./pg_install"), // TODO: formely, this was std::env::current_dir()
+            http_auth_type: (AuthType::Trust),
+            pg_auth_type: (AuthType::Trust),
+            auth_validation_public_key_path: (None),
+            remote_storage: None,
+            broker_endpoint: (storage_broker::DEFAULT_ENDPOINT
+                .parse()
+                .expect("failed to parse default broker endpoint")),
+            broker_keepalive_interval: (humantime::parse_duration(
+                storage_broker::DEFAULT_KEEPALIVE_INTERVAL,
+            )
+            .expect("cannot parse default keepalive interval")),
+            log_format: (LogFormat::from_str(DEFAULT_LOG_FORMAT).unwrap()),
+
+            concurrent_tenant_warmup: (NonZeroUsize::new(DEFAULT_CONCURRENT_TENANT_WARMUP)
+                .expect("Invalid default constant")),
+            concurrent_tenant_size_logical_size_queries: NonZeroUsize::new(1).unwrap(),
+            metric_collection_interval: (humantime::parse_duration(
+                DEFAULT_METRIC_COLLECTION_INTERVAL,
+            )
+            .expect("cannot parse default metric collection interval")),
+            synthetic_size_calculation_interval: (humantime::parse_duration(
+                DEFAULT_SYNTHETIC_SIZE_CALCULATION_INTERVAL,
+            )
+            .expect("cannot parse default synthetic size calculation interval")),
+            metric_collection_endpoint: (DEFAULT_METRIC_COLLECTION_ENDPOINT),
+
+            metric_collection_bucket: (None),
+
+            disk_usage_based_eviction: (None),
+
+            test_remote_failures: (0),
+
+            ondemand_download_behavior_treat_error_as_warn: (false),
+
+            background_task_maximum_delay: (humantime::parse_duration(
+                DEFAULT_BACKGROUND_TASK_MAXIMUM_DELAY,
+            )
+            .unwrap()),
+
+            control_plane_api: (None),
+            control_plane_api_token: (None),
+            control_plane_emergency_mode: (false),
+
+            heatmap_upload_concurrency: (DEFAULT_HEATMAP_UPLOAD_CONCURRENCY),
+            secondary_download_concurrency: (DEFAULT_SECONDARY_DOWNLOAD_CONCURRENCY),
+
+            ingest_batch_size: (DEFAULT_INGEST_BATCH_SIZE),
+
+            virtual_file_io_engine: None,
+
+            max_vectored_read_bytes: (MaxVectoredReadBytes(
+                NonZeroUsize::new(DEFAULT_MAX_VECTORED_READ_BYTES).unwrap(),
+            )),
+            image_compression: (DEFAULT_IMAGE_COMPRESSION),
+            ephemeral_bytes_per_memory_kb: (DEFAULT_EPHEMERAL_BYTES_PER_MEMORY_KB),
+            l0_flush: None,
+            compact_level0_phase1_value_access: CompactL0Phase1ValueAccess::default(),
+            virtual_file_direct_io: crate::models::virtual_file::DirectIoMode::default(),
+
+            io_buffer_alignment: DEFAULT_IO_BUFFER_ALIGNMENT,
+
+            tenant_config: TenantConfigToml::default(),
+        }
+    }
+}
+
+pub mod tenant_conf_defaults {
+
+    // FIXME: This current value is very low. I would imagine something like 1 GB or 10 GB
+    // would be more appropriate. But a low value forces the code to be exercised more,
+    // which is good for now to trigger bugs.
+    // This parameter actually determines L0 layer file size.
+    pub const DEFAULT_CHECKPOINT_DISTANCE: u64 = 256 * 1024 * 1024;
+    pub const DEFAULT_CHECKPOINT_TIMEOUT: &str = "10 m";
+
+    // FIXME the below configs are only used by legacy algorithm. The new algorithm
+    // has different parameters.
+
+    // Target file size, when creating image and delta layers.
+    // This parameter determines L1 layer file size.
+    pub const DEFAULT_COMPACTION_TARGET_SIZE: u64 = 128 * 1024 * 1024;
+
+    pub const DEFAULT_COMPACTION_PERIOD: &str = "20 s";
+    pub const DEFAULT_COMPACTION_THRESHOLD: usize = 10;
+    pub const DEFAULT_COMPACTION_ALGORITHM: crate::models::CompactionAlgorithm =
+        crate::models::CompactionAlgorithm::Legacy;
+
+    pub const DEFAULT_GC_HORIZON: u64 = 64 * 1024 * 1024;
+
+    // Large DEFAULT_GC_PERIOD is fine as long as PITR_INTERVAL is larger.
+    // If there's a need to decrease this value, first make sure that GC
+    // doesn't hold a layer map write lock for non-trivial operations.
+    // Relevant: https://github.com/neondatabase/neon/issues/3394
+    pub const DEFAULT_GC_PERIOD: &str = "1 hr";
+    pub const DEFAULT_IMAGE_CREATION_THRESHOLD: usize = 3;
+    pub const DEFAULT_PITR_INTERVAL: &str = "7 days";
+    pub const DEFAULT_WALRECEIVER_CONNECT_TIMEOUT: &str = "10 seconds";
+    pub const DEFAULT_WALRECEIVER_LAGGING_WAL_TIMEOUT: &str = "10 seconds";
+    // The default limit on WAL lag should be set to avoid causing disconnects under high throughput
+    // scenarios: since the broker stats are updated ~1/s, a value of 1GiB should be sufficient for
+    // throughputs up to 1GiB/s per timeline.
+    pub const DEFAULT_MAX_WALRECEIVER_LSN_WAL_LAG: u64 = 1024 * 1024 * 1024;
+    pub const DEFAULT_EVICTIONS_LOW_RESIDENCE_DURATION_METRIC_THRESHOLD: &str = "24 hour";
+    // By default ingest enough WAL for two new L0 layers before checking if new image
+    // image layers should be created.
+    pub const DEFAULT_IMAGE_LAYER_CREATION_CHECK_THRESHOLD: u8 = 2;
+
+    pub const DEFAULT_INGEST_BATCH_SIZE: u64 = 100;
+}
+
+impl Default for TenantConfigToml {
+    fn default() -> Self {
+        use tenant_conf_defaults::*;
+        Self {
+            checkpoint_distance: DEFAULT_CHECKPOINT_DISTANCE,
+            checkpoint_timeout: humantime::parse_duration(DEFAULT_CHECKPOINT_TIMEOUT)
+                .expect("cannot parse default checkpoint timeout"),
+            compaction_target_size: DEFAULT_COMPACTION_TARGET_SIZE,
+            compaction_period: humantime::parse_duration(DEFAULT_COMPACTION_PERIOD)
+                .expect("cannot parse default compaction period"),
+            compaction_threshold: DEFAULT_COMPACTION_THRESHOLD,
+            compaction_algorithm: crate::models::CompactionAlgorithmSettings {
+                kind: DEFAULT_COMPACTION_ALGORITHM,
+            },
+            gc_horizon: DEFAULT_GC_HORIZON,
+            gc_period: humantime::parse_duration(DEFAULT_GC_PERIOD)
+                .expect("cannot parse default gc period"),
+            image_creation_threshold: DEFAULT_IMAGE_CREATION_THRESHOLD,
+            pitr_interval: humantime::parse_duration(DEFAULT_PITR_INTERVAL)
+                .expect("cannot parse default PITR interval"),
+            walreceiver_connect_timeout: humantime::parse_duration(
+                DEFAULT_WALRECEIVER_CONNECT_TIMEOUT,
+            )
+            .expect("cannot parse default walreceiver connect timeout"),
+            lagging_wal_timeout: humantime::parse_duration(DEFAULT_WALRECEIVER_LAGGING_WAL_TIMEOUT)
+                .expect("cannot parse default walreceiver lagging wal timeout"),
+            max_lsn_wal_lag: NonZeroU64::new(DEFAULT_MAX_WALRECEIVER_LSN_WAL_LAG)
+                .expect("cannot parse default max walreceiver Lsn wal lag"),
+            eviction_policy: crate::models::EvictionPolicy::NoEviction,
+            min_resident_size_override: None,
+            evictions_low_residence_duration_metric_threshold: humantime::parse_duration(
+                DEFAULT_EVICTIONS_LOW_RESIDENCE_DURATION_METRIC_THRESHOLD,
+            )
+            .expect("cannot parse default evictions_low_residence_duration_metric_threshold"),
+            heatmap_period: Duration::ZERO,
+            lazy_slru_download: false,
+            timeline_get_throttle: crate::models::ThrottleConfig::disabled(),
+            image_layer_creation_check_threshold: DEFAULT_IMAGE_LAYER_CREATION_CHECK_THRESHOLD,
+            switch_aux_file_policy: crate::models::AuxFilePolicy::default_tenant_config(),
+            lsn_lease_length: LsnLease::DEFAULT_LENGTH,
+            lsn_lease_length_for_ts: LsnLease::DEFAULT_LENGTH_FOR_TS,
+        }
+    }
+}

libs/pageserver_api/src/models.rs

@@ -6,6 +6,7 @@ pub use utilization::PageserverUtilization;
 
 use std::{
     collections::HashMap,
+    fmt::Display,
     io::{BufRead, Read},
     num::{NonZeroU32, NonZeroU64, NonZeroUsize},
     str::FromStr,
@@ -435,7 +436,9 @@ pub enum CompactionAlgorithm {
     Tiered,
 }
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+#[derive(
+    Debug, Clone, Copy, PartialEq, Eq, serde_with::DeserializeFromStr, serde_with::SerializeDisplay,
+)]
 pub enum ImageCompressionAlgorithm {
     // Disabled for writes, support decompressing during read path
     Disabled,
@@ -470,11 +473,33 @@ impl FromStr for ImageCompressionAlgorithm {
     }
 }
 
+impl Display for ImageCompressionAlgorithm {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            ImageCompressionAlgorithm::Disabled => write!(f, "disabled"),
+            ImageCompressionAlgorithm::Zstd { level } => {
+                if let Some(level) = level {
+                    write!(f, "zstd({})", level)
+                } else {
+                    write!(f, "zstd")
+                }
+            }
+        }
+    }
+}
+
 #[derive(Eq, PartialEq, Debug, Clone, Serialize, Deserialize)]
 pub struct CompactionAlgorithmSettings {
     pub kind: CompactionAlgorithm,
 }
 
+#[derive(Debug, PartialEq, Eq, Clone, serde::Deserialize, serde::Serialize)]
+#[serde(tag = "mode", rename_all = "kebab-case", deny_unknown_fields)]
+pub enum L0FlushConfig {
+    #[serde(rename_all = "snake_case")]
+    Direct { max_concurrency: NonZeroUsize },
+}
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
 pub struct EvictionPolicyLayerAccessThreshold {
     #[serde(with = "humantime_serde")]
@@ -1656,21 +1681,33 @@ mod tests {
     #[test]
     fn test_image_compression_algorithm_parsing() {
         use ImageCompressionAlgorithm::*;
-        assert_eq!(
-            ImageCompressionAlgorithm::from_str("disabled").unwrap(),
-            Disabled
-        );
-        assert_eq!(
-            ImageCompressionAlgorithm::from_str("zstd").unwrap(),
-            Zstd { level: None }
-        );
-        assert_eq!(
-            ImageCompressionAlgorithm::from_str("zstd(18)").unwrap(),
-            Zstd { level: Some(18) }
-        );
-        assert_eq!(
-            ImageCompressionAlgorithm::from_str("zstd(-3)").unwrap(),
-            Zstd { level: Some(-3) }
-        );
+        let cases = [
+            ("disabled", Disabled),
+            ("zstd", Zstd { level: None }),
+            ("zstd(18)", Zstd { level: Some(18) }),
+            ("zstd(-3)", Zstd { level: Some(-3) }),
+        ];
+
+        for (display, expected) in cases {
+            assert_eq!(
+                ImageCompressionAlgorithm::from_str(display).unwrap(),
+                expected,
+                "parsing works"
+            );
+            assert_eq!(format!("{expected}"), display, "Display FromStr roundtrip");
+
+            let ser = serde_json::to_string(&expected).expect("serialization");
+            assert_eq!(
+                serde_json::from_str::<ImageCompressionAlgorithm>(&ser).unwrap(),
+                expected,
+                "serde roundtrip"
+            );
+
+            assert_eq!(
+                serde_json::Value::String(display.to_string()),
+                serde_json::to_value(expected).unwrap(),
+                "Display is the serde serialization"
+            );
+        }
     }
 }