pantsbuild · chris-smith-zocdoc · Feb 16, 2025
diff --git a/src/python/pants/engine/process.py b/src/python/pants/engine/process.py
@@ -50,6 +50,18 @@ class ProcessCacheScope(Enum):
     PER_SESSION = "per_session"
 
 
+@dataclass(frozen=True)
+class ProcessConcurrencyRange:
+    min: int | None = None
+    max: int | None = None
+
+@dataclass(frozen=True)
+class ProcessConcurrencyExclusive:
+    pass
+
+ProcessConcurrency = ProcessConcurrencyRange | ProcessConcurrencyExclusive
+
+
 @dataclass(frozen=True)
 class Process:
     argv: tuple[str, ...]
@@ -66,7 +78,7 @@ class Process:
     timeout_seconds: int | float
     jdk_home: str | None
     execution_slot_variable: str | None
-    concurrency_available: int
+    concurrency: ProcessConcurrency | None
     cache_scope: ProcessCacheScope
     remote_cache_speculation_delay_millis: int
     attempt: int
@@ -89,6 +101,7 @@ def __init__(
         jdk_home: str | None = None,
         execution_slot_variable: str | None = None,
         concurrency_available: int = 0,
+        concurrency: ProcessConcurrency | None = None,
         cache_scope: ProcessCacheScope = ProcessCacheScope.SUCCESSFUL,
         remote_cache_speculation_delay_millis: int = 0,
         attempt: int = 0,
@@ -146,6 +159,7 @@ def __init__(
         object.__setattr__(self, "jdk_home", jdk_home)
         object.__setattr__(self, "execution_slot_variable", execution_slot_variable)
         object.__setattr__(self, "concurrency_available", concurrency_available)
+        object.__setattr__(self, "concurrency", concurrency)
         object.__setattr__(self, "cache_scope", cache_scope)
         object.__setattr__(
             self, "remote_cache_speculation_delay_millis", remote_cache_speculation_delay_millis

diff --git a/src/rust/engine/process_execution/remote/src/remote_tests.rs b/src/rust/engine/process_execution/remote/src/remote_tests.rs
@@ -100,6 +100,7 @@ async fn make_execute_request() {
         jdk_home: None,
         execution_slot_variable: None,
         concurrency_available: 0,
+        concurrency: None,
         cache_scope: ProcessCacheScope::Always,
         execution_environment: make_environment(Platform::Linux_x86_64),
         remote_cache_speculation_delay: std::time::Duration::from_millis(0),
@@ -193,6 +194,7 @@ async fn make_execute_request_with_instance_name() {
         jdk_home: None,
         execution_slot_variable: None,
         concurrency_available: 0,
+        concurrency: None,
         cache_scope: ProcessCacheScope::Always,
         execution_environment: ProcessExecutionEnvironment {
             name: None,
@@ -306,6 +308,7 @@ async fn make_execute_request_with_cache_key_gen_version() {
         jdk_home: None,
         execution_slot_variable: None,
         concurrency_available: 0,
+        concurrency: None,
         cache_scope: ProcessCacheScope::Always,
         execution_environment: make_environment(Platform::Linux_x86_64),
         remote_cache_speculation_delay: std::time::Duration::from_millis(0),
@@ -580,6 +583,7 @@ async fn make_execute_request_with_timeout() {
         jdk_home: None,
         execution_slot_variable: None,
         concurrency_available: 0,
+        concurrency: None,
         cache_scope: ProcessCacheScope::Always,
         execution_environment: make_environment(Platform::Linux_x86_64),
         remote_cache_speculation_delay: std::time::Duration::from_millis(0),
@@ -680,6 +684,7 @@ async fn make_execute_request_with_append_only_caches() {
         jdk_home: None,
         execution_slot_variable: None,
         concurrency_available: 0,
+        concurrency: None,
         cache_scope: ProcessCacheScope::Always,
         execution_environment: make_environment(Platform::Linux_x86_64),
         remote_cache_speculation_delay: std::time::Duration::from_millis(0),
@@ -840,6 +845,7 @@ async fn make_execute_request_using_immutable_inputs() {
         jdk_home: None,
         execution_slot_variable: None,
         concurrency_available: 0,
+        concurrency: None,
         cache_scope: ProcessCacheScope::Always,
         execution_environment: make_environment(Platform::Linux_x86_64),
         remote_cache_speculation_delay: std::time::Duration::from_millis(0),

diff --git a/src/rust/engine/process_execution/src/bounded.rs b/src/rust/engine/process_execution/src/bounded.rs
@@ -18,7 +18,7 @@ use tokio::sync::{Notify, Semaphore, SemaphorePermit};
 use tokio::time::sleep;
 use workunit_store::{in_workunit, RunningWorkunit};
 
-use crate::{Context, FallibleProcessResultWithPlatform, Process, ProcessError};
+use crate::{Context, FallibleProcessResultWithPlatform, Process, ProcessError, ProcessConcurrency};
 
 lazy_static! {
   // TODO: Runtime formatting is unstable in Rust, so we imitate it.
@@ -32,6 +32,11 @@ lazy_static! {
 /// If a Process sets a non-zero `concurrency_available` value, it may be preempted (i.e. canceled
 /// and restarted) with a new concurrency value for a short period after starting.
 ///
+/// If a Process provides a `concurrency` value with different min and max values, 
+/// it will occupy a minimum of `min` cores and a maximum of `max` cores on the semaphore and 
+/// may be preempted (i.e. canceled and restarted) with a new concurrency value for a short 
+/// period after starting.
+///
 #[derive(Clone)]
 pub struct CommandRunner {
     inner: Arc<dyn crate::CommandRunner>,
@@ -72,7 +77,26 @@ impl crate::CommandRunner for CommandRunner {
         workunit: &mut RunningWorkunit,
         process: Process,
     ) -> Result<FallibleProcessResultWithPlatform, ProcessError> {
-        let semaphore_acquisition = self.sema.acquire(process.concurrency_available);
+
+        let total_concurrency = self.sema.state.lock().total_concurrency;
+        let min_concurrency = match process.concurrency {
+            Some(ProcessConcurrency::Range { min, .. }) => min.unwrap_or(1),
+            Some(ProcessConcurrency::Exclusive) => total_concurrency,
+            None => process.concurrency_available,
+        };
+
+        let max_concurrency = match process.concurrency {
+            Some(ProcessConcurrency::Range { max, .. }) => max.unwrap_or(min_concurrency),
+            Some(ProcessConcurrency::Exclusive) => total_concurrency,
+            None => process.concurrency_available,
+        };
+
+        let min_concurrency = min(max(min_concurrency, 1), total_concurrency);
+        let max_concurrency = min(max_concurrency, total_concurrency);
+
+        log::debug!("Acquiring semaphore for process {} with min_concurrency: {}, max_concurrency: {}", process.description, min_concurrency, max_concurrency);
+
+        let semaphore_acquisition = self.sema.acquire(min_concurrency, max_concurrency);
         let permit = in_workunit!(
             "acquire_command_runner_slot",
             // TODO: The UI uses the presence of a blocked workunit below a parent as an indication that
@@ -243,7 +267,7 @@ impl AsyncSemaphore {
         F: FnOnce(usize) -> B,
         B: Future<Output = O>,
     {
-        let permit = self.acquire(1).await;
+        let permit = self.acquire(1, 1).await;
         let res = f(permit.task.id).await;
         drop(permit);
         res
@@ -254,8 +278,8 @@ impl AsyncSemaphore {
     /// the given amount of concurrency. The amount actually acquired will be reported on the
     /// returned Permit.
     ///
-    pub async fn acquire(&self, concurrency_desired: usize) -> Permit<'_> {
-        let permit = self.sema.acquire().await.expect("semaphore closed");
+    pub async fn acquire(&self, min_concurrency: usize, max_concurrency: usize,) -> Permit<'_> {
+        let permit = self.sema.acquire_many(min_concurrency as u32).await.expect("semaphore closed");
         let task = {
             let mut state = self.state.lock();
             let id = state
@@ -270,7 +294,7 @@ impl AsyncSemaphore {
             //
             // This is because we cannot anticipate the number of inbound processes, and we never want to
             // delay a process from starting.
-            let concurrency_desired = max(concurrency_desired, 1);
+            let concurrency_desired = max(max_concurrency, min_concurrency);
             let concurrency_actual = min(
                 concurrency_desired,
                 state.total_concurrency / (state.tasks.len() + 1),

diff --git a/src/rust/engine/process_execution/src/lib.rs b/src/rust/engine/process_execution/src/lib.rs
@@ -8,6 +8,7 @@ use std::collections::{BTreeMap, BTreeSet, HashSet};
 use std::convert::TryFrom;
 use std::fmt::{self, Debug, Display};
 use std::path::PathBuf;
+use std::str::FromStr;
 use std::sync::Arc;
 
 use async_trait::async_trait;
@@ -485,6 +486,29 @@ pub struct ProcessExecutionEnvironment {
     pub strategy: ProcessExecutionStrategy,
 }
 
+#[derive(DeepSizeOf, Debug, Clone, Hash, PartialEq, Eq, Serialize)]
+pub enum ProcessConcurrency {
+    /// A range of acceptable cpu cores with optional bounds
+    Range {
+        // Minimum number of cores to use, defaults to 1
+        min: Option<usize>,
+        // Maximum number of cores to use, defaults to min
+        max: Option<usize>,
+    },
+    /// Exclusive access to all cores
+    Exclusive,
+}
+
+// TODO Unclear why I need this or when its invoked, compile error for CommandSpec
+impl FromStr for ProcessConcurrency {
+    type Err = core::convert::Infallible;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        log::warn!("Parsing process concurrency from string: {s}");
+        Ok(ProcessConcurrency::Range { min: Some(1), max: Some(1) })
+    }
+}
+
 ///
 /// A process to be executed.
 ///
@@ -543,6 +567,9 @@ pub struct Process {
     /// started or finished).
     pub concurrency_available: usize,
 
+    /// The number of cores required for this process to run.
+    pub concurrency: Option<ProcessConcurrency>,
+
     #[derivative(PartialEq = "ignore", Hash = "ignore")]
     pub description: String,
 
@@ -616,6 +643,7 @@ impl Process {
             jdk_home: None,
             execution_slot_variable: None,
             concurrency_available: 0,
+            concurrency: None,
             cache_scope: ProcessCacheScope::Successful,
             execution_environment: ProcessExecutionEnvironment {
                 name: None,

diff --git a/src/rust/engine/process_executor/src/main.rs b/src/rust/engine/process_executor/src/main.rs
@@ -15,7 +15,7 @@ use fs::{DirectoryDigest, Permissions, RelativePath};
 use hashing::{Digest, Fingerprint};
 use process_execution::{
     local::KeepSandboxes, CacheContentBehavior, Context, InputDigests, NamedCaches, Platform,
-    ProcessCacheScope, ProcessExecutionEnvironment, ProcessExecutionStrategy,
+    ProcessCacheScope, ProcessConcurrency, ProcessExecutionEnvironment, ProcessExecutionStrategy,
 };
 use prost::Message;
 use protos::gen::build::bazel::remote::execution::v2::{Action, Command};
@@ -75,6 +75,9 @@ struct CommandSpec {
     #[structopt(long)]
     concurrency_available: Option<usize>,
 
+    #[structopt(long)]
+    concurrency: Option<ProcessConcurrency>,
+
     #[structopt(long)]
     cache_key_gen_version: Option<String>,
 }
@@ -547,6 +550,7 @@ async fn make_request_from_flat_args(
         jdk_home: args.command.jdk.clone(),
         execution_slot_variable: None,
         concurrency_available: args.command.concurrency_available.unwrap_or(0),
+        concurrency: args.command.concurrency.clone(),
         cache_scope: ProcessCacheScope::Always,
         execution_environment,
         remote_cache_speculation_delay: Duration::from_millis(0),
@@ -633,6 +637,7 @@ async fn extract_request_from_action_digest(
         }),
         execution_slot_variable: None,
         concurrency_available: 0,
+        concurrency: None,
         description: "".to_string(),
         level: Level::Error,
         append_only_caches: BTreeMap::new(),

diff --git a/src/rust/engine/src/nodes/execute_process.rs b/src/rust/engine/src/nodes/execute_process.rs
@@ -9,11 +9,11 @@ use deepsize::DeepSizeOf;
 use fs::RelativePath;
 use graph::CompoundNode;
 use process_execution::{
-    self, CacheName, InputDigests, Process, ProcessCacheScope, ProcessExecutionStrategy,
-    ProcessResultSource,
+    self, CacheName, InputDigests, Process, ProcessCacheScope, ProcessConcurrency, ProcessExecutionStrategy, ProcessResultSource
 };
 use pyo3::prelude::{PyAny, Python};
 use pyo3::pybacked::PyBackedStr;
+use pyo3::types::{PyAnyMethods, PyStringMethods, PyTypeMethods};
 use pyo3::Bound;
 use store::{self, Store, StoreError};
 use workunit_store::{
@@ -124,6 +124,27 @@ impl ExecuteProcess {
                 .map_err(|e| format!("Failed to get `execution_slot_variable` for field: {e}"))?;
 
         let concurrency_available: usize = externs::getattr(value, "concurrency_available")?;
+
+        let concurrency_value: Option<Bound<'_, PyAny>> = externs::getattr(value, "concurrency")?;
+        let concurrency: Option<ProcessConcurrency> = match concurrency_value {
+            None => Ok(None),
+            Some(conc) => {
+                let py_type = conc.get_type();
+                let py_name = py_type.name().unwrap();
+                let type_name = py_name.to_str().unwrap();
+                match type_name {
+                    "ProcessConcurrencyRange" => {
+                        let min: Option<usize> = externs::getattr(&conc, "min")?;
+                        let max: Option<usize> = externs::getattr(&conc, "max")?;
+                        Ok(Some(ProcessConcurrency::Range { min, max }))
+                    }
+                    "ProcessConcurrencyExclusive" => Ok(Some(ProcessConcurrency::Exclusive)),
+                    _ => Err(format!("Unknown ProcessConcurrency type: {}", type_name)),
+                }
+            }
+        }?;
+
+        log::debug!("Parsed concurrency: {:?}", concurrency);
 
         let cache_scope: ProcessCacheScope = {
             let cache_scope_enum: Bound<'_, PyAny> = externs::getattr(value, "cache_scope")?;
@@ -151,6 +172,7 @@ impl ExecuteProcess {
             jdk_home,
             execution_slot_variable,
             concurrency_available,
+            concurrency,
             cache_scope,
             execution_environment: process_config.environment,
             remote_cache_speculation_delay,