Observe cgroup information on Linux (#918)

* Observe cgroup information on Linux

This commit reads the cgroup memory controller and pulls limit et al information
for each observed pid. I've copied telemetry names directly from Linux without
consideration; I am open to a prefix for this new data or a different scheme. I
intend to follow on with pulls from the CPU controller as well.

Signed-off-by: Brian L. Troutwine <brian.troutwine@datadoghq.com>

* parse CPU controller data as well

Signed-off-by: Brian L. Troutwine <brian.troutwine@datadoghq.com>

* update changelog

Signed-off-by: Brian L. Troutwine <brian.troutwine@datadoghq.com>

* prefix cgroup metrics

Signed-off-by: Brian L. Troutwine <brian.troutwine@datadoghq.com>

* prefix cgroup metrics, tidy up

Signed-off-by: Brian L. Troutwine <brian.troutwine@datadoghq.com>

---------

Signed-off-by: Brian L. Troutwine <brian.troutwine@datadoghq.com>

CHANGELOG.md

@@ -5,6 +5,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## Unreleased
+### Added
+- Retrieve memory, CPU information from cgroup controller for every pid observed on Linux.
 
 ## [0.22.0-rc1]
 ### Fixed

lading/Cargo.toml

@@ -54,7 +54,7 @@ uuid = { workspace = true }
 zstd = "0.13.1"
 
 [target.'cfg(target_os = "linux")'.dependencies]
-cgroups-rs = "0.3"
+cgroups-rs = { version = "0.3", default-features = false, features = [] }
 procfs = { version = "0.15", default-features = false, features = [] }
 async-pidfd = "0.1"
 

lading/src/observer/linux.rs

@@ -357,6 +357,9 @@ impl Sampler {
             if let Some(memory_controller) =
                 cgroup.controller_of::<cgroups_rs::memory::MemController>()
             {
+                let mut labels = Vec::from(&labels);
+                labels.push(("cgroup", String::from(cgroup.path())));
+
                 let mem_stat = memory_controller.memory_stat();
 
                 let inactive_file = if cgroup.v2() {
@@ -372,6 +375,40 @@ impl Sampler {
                 };
 
                 gauge!("working_set_bytes", &labels).set(working_set as f64);
+                gauge!("memory.working_set_bytes", &labels).set(working_set as f64);
+
+                gauge!("memory.fail_cnt", &labels).set(mem_stat.fail_cnt as f64);
+                gauge!("memory.limit_bytes", &labels).set(mem_stat.limit_in_bytes as f64);
+                gauge!("memory.usage_in_bytes", &labels).set(mem_stat.usage_in_bytes as f64);
+                gauge!("memory.max_usage_in_bytes", &labels)
+                    .set(mem_stat.max_usage_in_bytes as f64);
+                gauge!("memory.soft_limit_in_bytes", &labels)
+                    .set(mem_stat.soft_limit_in_bytes as f64);
+            }
+            // Load the CPU controller and get the cpu.stat String out of the
+            // cgroup, parse whatever fields are present and report them back
+            // out as metrics.
+            if let Some(cpu_controller) = cgroup.controller_of::<cgroups_rs::cpu::CpuController>() {
+                let mut labels = Vec::from(&labels);
+                labels.push(("cgroup", String::from(cgroup.path())));
+
+                let cpu = cpu_controller.cpu();
+                for line in cpu.stat.lines() {
+                    let mut fields = line.split_whitespace();
+                    let metric_name = fields.next().unwrap_or_default();
+                    let value = fields.next().unwrap_or_default();
+                    gauge!(format!("cpu.{metric_name}"), &labels)
+                        .set(value.parse::<f64>().unwrap_or_default());
+                }
+                if let Ok(shares) = cpu_controller.shares() {
+                    gauge!("cpu.shares", &labels).set(shares as f64);
+                }
+                if let Ok(cfs_period) = cpu_controller.cfs_period() {
+                    gauge!("cpu.cfs_period", &labels).set(cfs_period as f64);
+                }
+                if let Ok(cfs_quota) = cpu_controller.cfs_quota() {
+                    gauge!("cpu.cfs_quota", &labels).set(cfs_quota as f64);
+                }
             }
         }