Vary lading.yaml configs under Antithesis #1922
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| [package] | ||
| name = "harness" | ||
| version = "0.1.0" | ||
| edition = "2024" | ||
| license = "MIT" | ||
| publish = false | ||
| description = "Shared Antithesis harness for lading scenarios: per-timeline config sampling." | ||
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| [lib] | ||
| doctest = false | ||
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| [[bin]] | ||
| name = "first_sample_config" | ||
| path = "src/bin/first_sample_config.rs" | ||
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| [lints] | ||
| workspace = true | ||
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| [dependencies] | ||
| lading = { path = "../../../lading" } | ||
| lading-payload = { path = "../../../lading_payload" } | ||
| lading-antithesis = { workspace = true, features = ["antithesis"] } | ||
| antithesis_sdk = { workspace = true, features = ["full", "rand_v0_10"] } | ||
| byte-unit = { workspace = true, features = ["std"] } | ||
| rand = { workspace = true, features = ["thread_rng", "std_rng"] } | ||
| serde_yaml = { workspace = true } | ||
| anyhow = { workspace = true } |
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| //! Antithesis `first_` command: sample this timeline's lading config and release | ||
| //! the blocked system-under-test. | ||
| //! | ||
| //! Runs once per timeline after `setup_complete`, so the `AntithesisRng` draws | ||
| //! are post-snapshot decisions Antithesis branches: each timeline boots lading | ||
| //! under its own sampled config. Writes the config to the shared volume, tags | ||
| //! the sample for triage, then writes the `ready` sentinel last so the config is | ||
| //! always present before the SUT unblocks. | ||
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| use std::path::PathBuf; | ||
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| use anyhow::Context; | ||
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| fn main() -> anyhow::Result<()> { | ||
| lading_antithesis::init(); | ||
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| let dir: PathBuf = | ||
| std::env::var_os("CONFIG_DIR").map_or_else(|| PathBuf::from("/shared"), PathBuf::from); | ||
| std::fs::create_dir_all(&dir) | ||
| .with_context(|| format!("create config dir {}", dir.display()))?; | ||
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| // Draw structured choices from AntithesisRng so Antithesis branches each pick | ||
| // and explores the config menu across timelines. UnwrapErr adapts the SDK's | ||
| // fallible RNG to rand's infallible RngCore. | ||
| let mut rng = rand::rand_core::UnwrapErr(antithesis_sdk::random::AntithesisRng); | ||
| let cfg = harness::config::sample(&mut rng); | ||
| let variant = harness::config::variant_label(&cfg.variant); | ||
| let yaml = harness::config::to_yaml(&cfg).context("serialize sampled config")?; | ||
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| let config_path = dir.join("lading.yaml"); | ||
| std::fs::write(&config_path, yaml.as_bytes()) | ||
| .with_context(|| format!("write {}", config_path.display()))?; | ||
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| // Per-timeline anchor: counting these in triage shows how many distinct | ||
| // variants the run explored. | ||
| lading_antithesis::reachable!("first_sample_config sampled a config", { "variant": variant }); | ||
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| let ready = dir.join("ready"); | ||
| std::fs::write(&ready, b"ready\n") | ||
| .with_context(|| format!("write sentinel {}", ready.display()))?; | ||
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| Ok(()) | ||
| } | ||
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| //! Per-timeline lading config sampling. | ||
| //! | ||
| //! The sampler builds lading's real [`tcp::Config`] so the value menu is exactly | ||
| //! the config schema, then serializes it under the `generator: [{ tcp: … }]` | ||
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This ellipsis, the second ellipsis in the AGENTS.md reference: AGENTS.md:L151-L158 Useful? React with 👍 / 👎. |
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| //! shape lading parses. The transport is fixed to TCP against the sink oracle, | ||
| //! which counts bytes and so catches any payload variant; only the free axes | ||
| //! (payload variant, rate, connections, block sizes, seed) vary. Transport | ||
| //! variation waits on a multi-protocol sink. | ||
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| use lading::generator::tcp; | ||
| use rand::seq::IndexedRandom; | ||
| use rand::{Rng, RngExt}; | ||
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| /// Fixed address of the sink oracle every sampled config targets. | ||
| const SINK_ADDR: &str = "sink:9000"; | ||
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| /// Payload variants the TCP sink catches with no decoding. All are fieldless, so | ||
| /// they need no extra configuration to sample. | ||
| fn variant_menu() -> [lading_payload::Config; 6] { | ||
| [ | ||
| lading_payload::Config::Ascii, | ||
| lading_payload::Config::Syslog5424, | ||
| lading_payload::Config::Json, | ||
| lading_payload::Config::Fluent, | ||
| lading_payload::Config::ApacheCommon, | ||
| lading_payload::Config::DatadogLog, | ||
| ] | ||
| } | ||
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| /// Sample a lading TCP generator config for one timeline. | ||
| /// | ||
| /// Draws the payload variant, throughput, parallel connections, and seed from | ||
| /// `rng`; the transport and target stay fixed to the sink. | ||
| #[must_use] | ||
| pub fn sample<R: Rng>(rng: &mut R) -> tcp::Config { | ||
| // Structured choices come from the caller's rng -- AntithesisRng in | ||
| // production -- so Antithesis branches each pick and sweeps the menu. | ||
| let variant = variant_menu() | ||
| .choose(rng) | ||
| .cloned() | ||
| .unwrap_or(lading_payload::Config::Ascii); | ||
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| let bps_mib = [1_u64, 5, 10, 50, 100].choose(rng).copied().unwrap_or(10); | ||
| let bytes_per_second_bytes = bps_mib * 1024 * 1024; | ||
| let bytes_per_second = Some(byte_unit::Byte::from_u64(bytes_per_second_bytes)); | ||
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| let parallel_connections = rng.random_range(1..=8_u16); | ||
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| // Cap the block size at the smallest per-connection throttle capacity. lading | ||
| // divides `bytes_per_second` evenly across `parallel_connections`; a block | ||
| // larger than a worker's divided capacity is rejected by the throttle, and | ||
| // the TCP worker then busy-spins discarding it with no backoff. Keeping | ||
| // `maximum_block_size <= bytes_per_second / parallel_connections` guarantees | ||
| // every block fits, so no timeline degrades into a discard spin. | ||
| let per_connection_capacity = bytes_per_second_bytes / u64::from(parallel_connections); | ||
| let maximum_block_size = | ||
| byte_unit::Byte::from_u64(per_connection_capacity.clamp(1, 1024 * 1024)); | ||
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| // lading seeds its own payload PRNG from `seed`. The Antithesis docs warn | ||
| // against seeding your own RNG from SDK randomness, so draw the seed from | ||
| // system entropy rather than the (Antithesis) `rng`. This makes payload byte | ||
| // content opaque to Antithesis and effectively fixed across timelines, which | ||
| // is fine: the sink asserts on bytes received, not on content. | ||
| let mut seed = [0u8; 32]; | ||
| rand::rng().fill_bytes(&mut seed); | ||
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When AGENTS.md reference: AGENTS.md:L86-L92 Useful? React with 👍 / 👎. |
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| tcp::Config { | ||
| seed, | ||
| addr: SINK_ADDR.to_string(), | ||
| variant, | ||
| bytes_per_second, | ||
| maximum_block_size, | ||
| maximum_prebuild_cache_size_bytes: byte_unit::Byte::from_u64(8 * 1024 * 1024), | ||
| parallel_connections, | ||
| throttle: None, | ||
| } | ||
| } | ||
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| /// Serialize a sampled `tcp::Config` into the top-level `generator: [{ tcp: … }]` | ||
| /// YAML that lading consumes. | ||
| /// | ||
| /// # Errors | ||
| /// | ||
| /// Returns an error if serialization fails. | ||
| pub fn to_yaml(cfg: &tcp::Config) -> Result<String, serde_yaml::Error> { | ||
| let mut tcp_item = serde_yaml::Mapping::new(); | ||
| tcp_item.insert(serde_yaml::Value::from("tcp"), serde_yaml::to_value(cfg)?); | ||
| let generators = serde_yaml::Value::Sequence(vec![serde_yaml::Value::Mapping(tcp_item)]); | ||
| let mut top = serde_yaml::Mapping::new(); | ||
| top.insert(serde_yaml::Value::from("generator"), generators); | ||
| serde_yaml::to_string(&serde_yaml::Value::Mapping(top)) | ||
| } | ||
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| /// Short, stable label for a payload variant, for tagging the Antithesis sample. | ||
| #[must_use] | ||
| pub fn variant_label(variant: &lading_payload::Config) -> &'static str { | ||
| match variant { | ||
| lading_payload::Config::Ascii => "ascii", | ||
| lading_payload::Config::Syslog5424 => "syslog5424", | ||
| lading_payload::Config::Json => "json", | ||
| lading_payload::Config::Fluent => "fluent", | ||
| lading_payload::Config::ApacheCommon => "apache_common", | ||
| lading_payload::Config::DatadogLog => "datadog_log", | ||
| _ => "other", | ||
| } | ||
| } | ||
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| #[cfg(test)] | ||
| mod tests { | ||
| use super::{sample, to_yaml}; | ||
| use rand::SeedableRng; | ||
| use rand::rngs::StdRng; | ||
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| #[test] | ||
| fn sampled_config_deserializes_as_valid_lading_config() { | ||
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These three randomized-invariant checks are ordinary unit tests over a hard-coded set of 256 seeds, so they neither use the repository's required property-test strategy nor provide shrinking when serialization or block-capacity invariants fail. Express the sampled-config invariants as AGENTS.md reference: AGENTS.md:L121-L132 Useful? React with 👍 / 👎. |
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| // The load-bearing invariant: whatever we sample must be a config lading | ||
| // actually accepts. Sweep many seeds so the whole menu is exercised. | ||
| for s in 0..256_u64 { | ||
| let mut rng = StdRng::seed_from_u64(s); | ||
| let cfg = sample(&mut rng); | ||
| let yaml = to_yaml(&cfg).expect("serialize sampled config"); | ||
| let parsed: Result<lading::config::Config, _> = serde_yaml::from_str(&yaml); | ||
| assert!( | ||
| parsed.is_ok(), | ||
| "seed {s} produced a config lading rejects: {err:?}\n{yaml}", | ||
| err = parsed.err() | ||
| ); | ||
| } | ||
| } | ||
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| #[test] | ||
| fn sampled_config_holds_invariants() { | ||
| for s in 0..256_u64 { | ||
| let mut rng = StdRng::seed_from_u64(s); | ||
| let cfg = sample(&mut rng); | ||
| assert_eq!(cfg.addr, "sink:9000"); | ||
| assert!((1..=8).contains(&cfg.parallel_connections)); | ||
| assert!(cfg.bytes_per_second.is_some()); | ||
| } | ||
| } | ||
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| #[test] | ||
| fn block_size_never_exceeds_per_connection_capacity() { | ||
| // Regression: lading divides bytes_per_second across parallel_connections, | ||
| // and a block larger than a worker's divided capacity busy-spins on | ||
| // discard. maximum_block_size must fit the smallest per-connection share. | ||
| for s in 0..256_u64 { | ||
| let mut rng = StdRng::seed_from_u64(s); | ||
| let cfg = sample(&mut rng); | ||
| let bps = cfg.bytes_per_second.expect("bytes_per_second set").as_u64(); | ||
| let per_connection = bps / u64::from(cfg.parallel_connections); | ||
| assert!( | ||
| cfg.maximum_block_size.as_u64() <= per_connection, | ||
| "seed {s}: block {block} exceeds per-connection capacity {per_connection}", | ||
| block = cfg.maximum_block_size.as_u64() | ||
| ); | ||
| } | ||
| } | ||
| } | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,9 @@ | ||
| //! Shared Antithesis harness for lading scenarios. | ||
| //! | ||
| //! Holds the per-timeline config-variation mechanism every scenario reuses: | ||
| //! [`config::sample`] draws a lading generator config from a value menu, and the | ||
| //! `first_sample_config` command serializes it to the shared volume the | ||
| //! system-under-test boots from. The menu is built from lading's own | ||
| //! `tcp::Config`, so it cannot drift from the real config schema. | ||
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| pub mod config; |
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This context string and the two later write-error contexts use anonymous
{}placeholders, contrary to the repository's named-format-argument convention. Give each displayed path a named argument so these newly added diagnostics follow the required formatting style.AGENTS.md reference: AGENTS.md:L111-L116
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