mz_dyncfg_launchdarkly/
lib.rs

1// Copyright Materialize, Inc. and contributors. All rights reserved.
2//
3// Use of this software is governed by the Business Source License
4// included in the LICENSE file.
5//
6// As of the Change Date specified in that file, in accordance with
7// the Business Source License, use of this software will be governed
8// by the Apache License, Version 2.0.
9
10//! A dyncfg::ConfigSet backed by LaunchDarkly.
11
12use std::time::Duration;
13
14use launchdarkly_sdk_transport::HttpTransport;
15use launchdarkly_server_sdk as ld;
16use mz_build_info::BuildInfo;
17use mz_dyncfg::{ConfigSet, ConfigUpdates, ConfigVal};
18use mz_ore::cast::CastLossy;
19use mz_ore::task;
20use tokio::time;
21
22/// Start a background task that syncs to a ConfigSet from LaunchDarkly. `ctx_builder` can be used
23/// to add additional LD contexts. A `build` context is added automatically. Returns `Ok` after the
24/// LD client has been initialized and an initial sync completed. If the initialization takes longer
25/// than `config_sync_timeout`, an error is returned.
26///
27/// A successful initialization can take up to `config_sync_timeout`, preventing the calling service
28/// from starting for possibly up to that duration. Its value should be chosen based on the needs of
29/// the service in the case that LaunchDarkly is down.
30///
31/// If the caller chooses to continue if this function returns an error, the ConfigSet will retain
32/// its default values. Those should be chosen with this risk in mind.
33pub async fn sync_launchdarkly_to_configset<F>(
34    set: ConfigSet,
35    build_info: &'static BuildInfo,
36    ctx_builder: F,
37    // Use an option so that local dev where this is disabled still uses the same validation logic
38    // for the ConfigSet.
39    launchdarkly_sdk_key: Option<&str>,
40    config_sync_timeout: Duration,
41    config_sync_loop_interval: Option<Duration>,
42    on_update: impl Fn(&ConfigUpdates, &ConfigSet) + Send + 'static,
43) -> Result<(), anyhow::Error>
44where
45    F: FnOnce(&mut ld::MultiContextBuilder) -> Result<(), anyhow::Error>,
46{
47    // Ensure that all the ConfigVals in the set support FlagValue conversion, even if LD is
48    // disabled (preventing error skew in local vs prod settings).
49    for entry in set.entries() {
50        let _ = dyn_into_flag(entry.val())?;
51    }
52    let ld_client = if let Some(key) = launchdarkly_sdk_key {
53        // The 300s streaming read timeout must stay above LaunchDarkly's
54        // streaming heartbeat interval (roughly 3 minutes per LD's
55        // documentation), or a healthy idle stream would trip the timeout and
56        // reconnect spuriously. The same constant lives in the adapter's
57        // `SystemParameterFrontend`.
58        let transport = https_transport(Duration::from_secs(10), Duration::from_secs(300))
59            .expect("failed to create HTTPS transport");
60
61        let mut data_source = ld::StreamingDataSourceBuilder::new();
62        data_source.transport(transport.clone());
63
64        let mut event_processor = ld::EventProcessorBuilder::new();
65        event_processor.transport(transport);
66
67        let config = ld::ConfigBuilder::new(key)
68            .data_source(&data_source)
69            .event_processor(&event_processor)
70            .build()
71            .expect("valid config");
72        let client = ld::Client::build(config)?;
73        client.start_with_default_executor();
74        let init = async {
75            let max_backoff = Duration::from_secs(60);
76            let mut backoff = Duration::from_secs(5);
77
78            // TODO(materialize#38055): fix retry logic
79            loop {
80                match client.wait_for_initialization(config_sync_timeout).await {
81                    Some(true) => break,
82                    Some(false) => tracing::warn!("SyncedConfigSet failed to initialize"),
83                    None => {}
84                }
85
86                tokio::time::sleep(backoff).await;
87                backoff = (backoff * 2).min(max_backoff);
88            }
89        };
90        if tokio::time::timeout(config_sync_timeout, init)
91            .await
92            .is_err()
93        {
94            tracing::info!("SyncedConfigSet initialize on boot: initialize has timed out");
95        }
96        Some(client)
97    } else {
98        None
99    };
100
101    let synced = SyncedConfigSet {
102        set,
103        ld_client,
104        ld_ctx: ld_ctx(build_info, ctx_builder)?,
105        on_update,
106    };
107    synced.sync()?;
108    task::spawn(
109        || "SyncedConfigSet sync_loop",
110        synced.sync_loop(config_sync_loop_interval),
111    );
112    Ok(())
113}
114
115/// Builds a LaunchDarkly [`HttpTransport`] whose TLS runs on the aws-lc-rs rustls provider,
116/// trusting the platform's native root certificates.
117///
118/// Use this instead of `HyperTransport::builder().build_https()`, which hardcodes the `ring`
119/// provider. Like `build_https`, the connector also accepts plain `http` URIs, which a relay
120/// proxy or test mock may use.
121///
122/// The transport ignores `HTTP_PROXY`/`HTTPS_PROXY`/`NO_PROXY` and always connects directly.
123pub fn https_transport(
124    connect_timeout: Duration,
125    read_timeout: Duration,
126) -> Result<impl HttpTransport, std::io::Error> {
127    let connector = hyper_rustls::HttpsConnectorBuilder::new()
128        .with_provider_and_native_roots(rustls::crypto::aws_lc_rs::default_provider())?
129        .https_or_http()
130        .enable_http1()
131        .enable_http2()
132        .build();
133    // NOTE: without the transport crate's TLS features, its proxy layer sends HTTPS requests
134    // through a CONNECT tunnel in plaintext (SDK key included), because the injected connector
135    // only ever sees the proxy URI. Those features pull in `ring`, so proxies are disabled.
136    launchdarkly_sdk_transport::HyperTransport::builder()
137        .disable_proxy()
138        .connect_timeout(connect_timeout)
139        .read_timeout(read_timeout)
140        .build_with_connector(connector)
141}
142
143fn ld_ctx<F>(build_info: &'static BuildInfo, ctx_builder: F) -> Result<ld::Context, anyhow::Error>
144where
145    F: FnOnce(&mut ld::MultiContextBuilder) -> Result<(), anyhow::Error>,
146{
147    // Register multiple contexts for this client.
148    //
149    // Unfortunately, it seems that the order in which conflicting targeting
150    // rules are applied depends on the definition order of feature flag
151    // variations rather than on the order in which context are registered with
152    // the multi-context builder.
153    let mut builder = ld::MultiContextBuilder::new();
154
155    builder.add_context(
156        ld::ContextBuilder::new(build_info.sha)
157            .kind("build")
158            .set_string("semver_version", build_info.semver_version().to_string())
159            .build()
160            .map_err(|e| anyhow::anyhow!(e))?,
161    );
162
163    ctx_builder(&mut builder)?;
164
165    builder.build().map_err(|e| anyhow::anyhow!(e))
166}
167
168struct SyncedConfigSet<F>
169where
170    F: Fn(&ConfigUpdates, &ConfigSet) + Send,
171{
172    set: ConfigSet,
173    ld_client: Option<ld::Client>,
174    ld_ctx: ld::Context,
175    on_update: F,
176}
177
178impl<F: Fn(&ConfigUpdates, &ConfigSet) + Send> SyncedConfigSet<F> {
179    /// Returns a future that periodically polls LaunchDarkly and updates the ConfigSet.
180    async fn sync_loop(self, tick_interval: Option<Duration>) {
181        let Some(tick_interval) = tick_interval else {
182            tracing::info!("skipping SyncedConfigSet sync as tick_interval = None");
183            return;
184        };
185
186        let mut interval = time::interval(tick_interval);
187        interval.set_missed_tick_behavior(time::MissedTickBehavior::Skip);
188
189        tracing::info!(
190            "synchronizing SyncedConfigSet values every {} seconds",
191            tick_interval.as_secs()
192        );
193
194        loop {
195            interval.tick().await;
196
197            if let Err(err) = self.sync() {
198                tracing::info!("SyncedConfigSet: {err}");
199            }
200        }
201    }
202
203    /// Reads current values from LaunchDarkly and updates the ConfigSet.
204    fn sync(&self) -> Result<(), anyhow::Error> {
205        let mut updates = ConfigUpdates::default();
206        let Some(ld_client) = &self.ld_client else {
207            (self.on_update)(&updates, &self.set);
208            return Ok(());
209        };
210        for entry in self.set.entries() {
211            let val = dyn_into_flag(entry.val()).expect("new() verifies all configs can convert");
212            let flag_var = ld_client.variation(&self.ld_ctx, entry.name(), val);
213            let update = match (entry.val(), flag_var) {
214                (ConfigVal::Bool(_), ld::FlagValue::Bool(flag)) => ConfigVal::Bool(flag),
215                (ConfigVal::U32(_), ld::FlagValue::Number(flag)) => {
216                    ConfigVal::U32(u32::cast_lossy(flag))
217                }
218                (ConfigVal::Usize(_), ld::FlagValue::Number(flag)) => {
219                    ConfigVal::Usize(usize::cast_lossy(flag))
220                }
221                (ConfigVal::F64(_), ld::FlagValue::Number(flag)) => ConfigVal::F64(flag),
222                (ConfigVal::String(_), ld::FlagValue::Str(flag)) => ConfigVal::String(flag),
223                (ConfigVal::Duration(_), ld::FlagValue::Str(flag)) => {
224                    match humantime::parse_duration(&flag) {
225                        Ok(d) => ConfigVal::Duration(d),
226                        Err(e) => {
227                            tracing::warn!("failed to parse Duration for {}: {}", entry.name(), e);
228                            continue;
229                        }
230                    }
231                }
232                (ConfigVal::Json(_), ld::FlagValue::Json(flag)) => ConfigVal::Json(flag),
233
234                // Hardcode all others so that if ConfigVal gets new types this match block will
235                // compile error.
236                (ConfigVal::Bool(_), _)
237                | (ConfigVal::U32(_), _)
238                | (ConfigVal::Usize(_), _)
239                | (ConfigVal::F64(_), _)
240                | (ConfigVal::Duration(_), _)
241                | (ConfigVal::Json(_), _)
242                | (ConfigVal::OptUsize(_), _)
243                | (ConfigVal::String(_), _)
244                | (ConfigVal::OptString(_), _) => {
245                    tracing::warn!("LD flag type mismatch for {}", entry.name());
246                    continue;
247                }
248            };
249            tracing::debug!(
250                "updating config value {} from {:?} to {:?}",
251                &entry.name(),
252                &entry.val(),
253                update
254            );
255            updates.add_dynamic(entry.name(), update);
256        }
257        updates.apply(&self.set);
258        (self.on_update)(&updates, &self.set);
259        Ok(())
260    }
261}
262
263/// Converts a dyncfg ConfigVal into a LaunchDarkly FlagValue. Returns an error if the ConfigVal
264/// type isn't supported by the FlagValue format.
265fn dyn_into_flag(val: ConfigVal) -> Result<ld::FlagValue, anyhow::Error> {
266    // Note that errors must only (and always) occur when the ConfigVal type isn't fully supported.
267    // That is, don't error only if the current value isn't supported (like None in an Opt type):
268    // error always for an Opt value because it might be None.
269    Ok(match val {
270        ConfigVal::Bool(v) => ld::FlagValue::Bool(v),
271        ConfigVal::U32(v) => ld::FlagValue::Number(v.into()),
272        ConfigVal::Usize(v) => ld::FlagValue::Number(f64::cast_lossy(v)),
273        ConfigVal::OptUsize(_) => anyhow::bail!("OptUsize None cannot be converted to a FlagValue"),
274        ConfigVal::F64(v) => ld::FlagValue::Number(v),
275        ConfigVal::String(v) => ld::FlagValue::Str(v),
276        ConfigVal::OptString(_) => {
277            anyhow::bail!("OptString None cannot be converted to a FlagValue")
278        }
279        ConfigVal::Duration(v) => ld::FlagValue::Str(humantime::format_duration(v).to_string()),
280        ConfigVal::Json(v) => ld::FlagValue::Json(v),
281    })
282}
mz_dyncfg_launchdarkly/lib.rs

mz_dyncfg_launchdarkly/
lib.rs
