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fix(android): size proxy runtime workers by device capacity #1373

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923e940
fix(android): bound JNI string local references
maybeknott May 23, 2026
29dae21
fix(android): size proxy runtime workers by device capacity
maybeknott May 23, 2026
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48 changes: 33 additions & 15 deletions src/android_jni.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,7 @@ use std::path::PathBuf;
use std::sync::atomic::{AtomicU64, Ordering};
use std::sync::{Arc, Mutex, OnceLock};

use jni::objects::{JClass, JString};
use jni::objects::{JClass, JObject, JString};
use jni::sys::{jboolean, jlong, jstring, JNI_FALSE, JNI_TRUE};
use jni::JNIEnv;
use tokio::runtime::Runtime;
Expand Down Expand Up @@ -70,6 +70,8 @@ extern "C" {

const ANDROID_LOG_INFO: i32 = 4;
const LOG_RING_CAP: usize = 500;
const ANDROID_RUNTIME_MIN_WORKERS: usize = 2;
const ANDROID_RUNTIME_MAX_WORKERS: usize = 4;

fn log_ring() -> &'static Mutex<VecDeque<String>> {
static RING: OnceLock<Mutex<VecDeque<String>>> = OnceLock::new();
Expand Down Expand Up @@ -145,10 +147,26 @@ fn jstring_to_string(env: &mut JNIEnv, s: &JString) -> String {
.unwrap_or_else(|_| String::new())
}

/// Helper: String -> jstring, returning null on allocation failure.
fn string_to_jstring(env: &mut JNIEnv, value: &str) -> jstring {
let obj: jni::errors::Result<JObject> = env.with_local_frame_returning_local(4, |env| {
env.new_string(value).map(JObject::from)
});
obj.map(|s| s.into_raw() as jstring)
.unwrap_or(std::ptr::null_mut())
}

fn safe<F: FnOnce() -> R + std::panic::UnwindSafe, R>(default: R, f: F) -> R {
std::panic::catch_unwind(f).unwrap_or(default)
}

fn android_runtime_worker_threads() -> usize {
std::thread::available_parallelism()
.map(|n| n.get())
.unwrap_or(ANDROID_RUNTIME_MIN_WORKERS)
.clamp(ANDROID_RUNTIME_MIN_WORKERS, ANDROID_RUNTIME_MAX_WORKERS)
}

/// Build a throwaway tokio runtime for one-shot blocking calls from JNI.
/// Small, single-worker — sufficient for probes and cert ops.
fn one_shot_runtime() -> Option<Runtime> {
Expand Down Expand Up @@ -201,8 +219,9 @@ pub extern "system" fn Java_com_therealaleph_mhrv_Native_startProxy(

// Try to build the runtime first — if allocation fails we want to
// know before spinning up anything stateful.
let worker_threads = android_runtime_worker_threads();
let rt = match tokio::runtime::Builder::new_multi_thread()
.worker_threads(4)
.worker_threads(worker_threads)
.enable_all()
.thread_name("mhrv-worker")
.build()
Expand All @@ -213,6 +232,7 @@ pub extern "system" fn Java_com_therealaleph_mhrv_Native_startProxy(
return 0i64;
}
};
tracing::info!("android: tokio runtime worker_threads={}", worker_threads);

let base = crate::data_dir::data_dir();
let mitm = match MitmCertManager::new_in(&base) {
Expand Down Expand Up @@ -327,11 +347,11 @@ pub extern "system" fn Java_com_therealaleph_mhrv_Native_exportCa(
/// `Native.version()` -> String. Trivial smoke test for the JNI linkage.
#[no_mangle]
pub extern "system" fn Java_com_therealaleph_mhrv_Native_version<'a>(
env: JNIEnv<'a>,
mut env: JNIEnv<'a>,
_class: JClass,
) -> jstring {
let v = env!("CARGO_PKG_VERSION");
env.new_string(v).map(|s| s.into_raw()).unwrap_or(std::ptr::null_mut())
string_to_jstring(&mut env, v)
}

/// `Native.drainLogs()` -> String. Returns the full ring buffer as a single
Expand All @@ -340,7 +360,7 @@ pub extern "system" fn Java_com_therealaleph_mhrv_Native_version<'a>(
/// for display. Empty string when there's nothing to read.
#[no_mangle]
pub extern "system" fn Java_com_therealaleph_mhrv_Native_drainLogs<'a>(
env: JNIEnv<'a>,
mut env: JNIEnv<'a>,
_class: JClass,
) -> jstring {
let out = safe(String::new(), AssertUnwindSafe(|| {
Expand All @@ -351,7 +371,7 @@ pub extern "system" fn Java_com_therealaleph_mhrv_Native_drainLogs<'a>(
let lines: Vec<String> = g.drain(..).collect();
lines.join("\n")
}));
env.new_string(out).map(|s| s.into_raw()).unwrap_or(std::ptr::null_mut())
string_to_jstring(&mut env, &out)
}

/// `Native.checkUpdate()` -> String. Runs the same `update_check::check`
Expand All @@ -367,7 +387,7 @@ pub extern "system" fn Java_com_therealaleph_mhrv_Native_drainLogs<'a>(
/// Blocking — hit from a background dispatcher.
#[no_mangle]
pub extern "system" fn Java_com_therealaleph_mhrv_Native_checkUpdate<'a>(
env: JNIEnv<'a>,
mut env: JNIEnv<'a>,
_class: JClass,
) -> jstring {
let result_json = safe(
Expand All @@ -383,9 +403,7 @@ pub extern "system" fn Java_com_therealaleph_mhrv_Native_checkUpdate<'a>(
update_check_to_json(&outcome)
}),
);
env.new_string(result_json)
.map(|s| s.into_raw())
.unwrap_or(std::ptr::null_mut())
string_to_jstring(&mut env, &result_json)
}

fn update_check_to_json(u: &crate::update_check::UpdateCheck) -> String {
Expand Down Expand Up @@ -455,7 +473,7 @@ pub extern "system" fn Java_com_therealaleph_mhrv_Native_testSni<'a>(
_ => r#"{"ok":false,"error":"unknown"}"#.to_string(),
}
}));
env.new_string(result_json).map(|s| s.into_raw()).unwrap_or(std::ptr::null_mut())
string_to_jstring(&mut env, &result_json)
}

/// `Native.statsJson(long handle)` -> String. Returns a JSON blob with the
Expand All @@ -466,7 +484,7 @@ pub extern "system" fn Java_com_therealaleph_mhrv_Native_testSni<'a>(
/// timer to render the "Usage today (estimated)" card.
#[no_mangle]
pub extern "system" fn Java_com_therealaleph_mhrv_Native_statsJson<'a>(
env: JNIEnv<'a>,
mut env: JNIEnv<'a>,
_class: JClass,
handle: jlong,
) -> jstring {
Expand All @@ -483,21 +501,21 @@ pub extern "system" fn Java_com_therealaleph_mhrv_Native_statsJson<'a>(
};
f.snapshot_stats().to_json()
}));
env.new_string(out).map(|s| s.into_raw()).unwrap_or(std::ptr::null_mut())
string_to_jstring(&mut env, &out)
}

/// `Native.pipelineDebugJson()` -> String. Snapshot of pipeline debug state:
/// elevated session count, batch semaphore usage, recent ramp/drop events.
/// Temporary — for the debug overlay.
#[no_mangle]
pub extern "system" fn Java_com_therealaleph_mhrv_Native_pipelineDebugJson<'a>(
env: JNIEnv<'a>,
mut env: JNIEnv<'a>,
_class: JClass,
) -> jstring {
let out = safe(String::new(), AssertUnwindSafe(|| {
crate::tunnel_client::pipeline_debug::to_json()
}));
env.new_string(out).map(|s| s.into_raw()).unwrap_or(std::ptr::null_mut())
string_to_jstring(&mut env, &out)
}

// ---------------------------------------------------------------------------
Expand Down
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