Merge pull request #38 from appsignal/container-cpu-runtime-metrics

Fix container CPU runtime metrics

fixtures/linux/sys/fs/cgroup/cpuacct_1/cpuacct.stat

@@ -0,0 +1,2 @@
+user 14934
+system 98

fixtures/linux/sys/fs/cgroup/cpuacct_1/cpuacct.usage

@@ -0,0 +1 @@
+152657213021

fixtures/linux/sys/fs/cgroup/cpuacct_2/cpuacct.stat

@@ -0,0 +1,2 @@
+user 17783
+system 121

fixtures/linux/sys/fs/cgroup/cpuacct_2/cpuacct.usage

@@ -0,0 +1 @@
+182405617026

src/cpu/cgroup.rs

@@ -0,0 +1,351 @@
+use super::super::{Result,calculate_time_difference,time_adjusted};
+
+/// Measurement of cpu stats at a certain time
+#[derive(Debug,PartialEq)]
+pub struct CgroupCpuMeasurement {
+    pub precise_time_ns: u64,
+    pub stat: CgroupCpuStat
+}
+
+impl CgroupCpuMeasurement {
+    pub fn calculate_per_minute(&self, next_measurement: &CgroupCpuMeasurement) -> Result<CgroupCpuStat> {
+        let time_difference = calculate_time_difference(self.precise_time_ns, next_measurement.precise_time_ns)?;
+
+        Ok(CgroupCpuStat {
+            total_usage: time_adjusted("total_usage", next_measurement.stat.total_usage, self.stat.total_usage, time_difference)?,
+            user: time_adjusted("user", next_measurement.stat.user, self.stat.user, time_difference)?,
+            system: time_adjusted("system", next_measurement.stat.system, self.stat.system, time_difference)?
+        })
+    }
+}
+
+/// Container CPU stats for a minute
+#[derive(Debug,PartialEq)]
+pub struct CgroupCpuStat {
+    pub total_usage: u64,
+    pub user: u64,
+    pub system: u64
+}
+
+impl CgroupCpuStat {
+    /// Calculate the weight of the various components in percentages
+    pub fn in_percentages(&self) -> CgroupCpuStatPercentages {
+        CgroupCpuStatPercentages {
+            total_usage: self.percentage_of_total(self.total_usage),
+            user: self.percentage_of_total(self.user),
+            system: self.percentage_of_total(self.system)
+        }
+    }
+
+    fn percentage_of_total(&self, value: u64) -> f32 {
+        // 60_000_000_000 being the total value. This is 60 seconds expressed in nanoseconds.
+        (value as f32 / 60_000_000_000.0) * 100.0
+    }
+}
+
+/// Cgroup Cpu stats converted to percentages
+#[derive(Debug,PartialEq)]
+pub struct CgroupCpuStatPercentages {
+    pub total_usage: f32,
+    pub user: f32,
+    pub system: f32
+}
+
+/// Read the current CPU stats of the container.
+#[cfg(target_os = "linux")]
+pub fn read() -> Result<CgroupCpuMeasurement> {
+    os::read()
+}
+
+#[cfg(target_os = "linux")]
+mod os {
+    use std::path::Path;
+    use std::io::BufRead;
+    use time;
+    use super::super::super::{Result,file_to_buf_reader,parse_u64,path_to_string,read_file_value_as_u64,dir_exists};
+    use super::{CgroupCpuMeasurement,CgroupCpuStat};
+    use error::ProbeError;
+
+    const CPU_SYS_NUMBER_OF_FIELDS: usize = 2;
+
+    pub fn read() -> Result<CgroupCpuMeasurement> {
+        let sys_fs_dir = Path::new("/sys/fs/cgroup/cpuacct/");
+        if dir_exists(sys_fs_dir) {
+            read_and_parse_sys_stat(&sys_fs_dir)
+        } else {
+            let message = format!("Directory `{}` not found", sys_fs_dir.to_str().unwrap_or("unknown path"));
+            Err(ProbeError::UnexpectedContent(message))
+        }
+    }
+
+    pub fn read_and_parse_sys_stat(path: &Path) -> Result<CgroupCpuMeasurement> {
+        let time = time::precise_time_ns();
+        let reader = file_to_buf_reader(&path.join("cpuacct.stat"))?;
+        let total_usage = read_file_value_as_u64(&path.join("cpuacct.usage"))?;
+
+        let mut cpu = CgroupCpuStat {
+            total_usage: total_usage,
+            user: 0,
+            system: 0
+        };
+
+        let mut fields_encountered = 0;
+        for line in reader.lines() {
+            let line = line.map_err(|e| ProbeError::IO(e, path_to_string(path)))?;
+            let segments: Vec<&str> = line.split_whitespace().collect();
+            let value = parse_u64(&segments[1])?;
+            fields_encountered += match segments[0] {
+                "user" => {
+                    cpu.user = value * 10_000_000;
+                    1
+                },
+                "system" => {
+                    cpu.system = value * 10_000_000;
+                    1
+                },
+                _ => 0
+            };
+
+            if fields_encountered == CPU_SYS_NUMBER_OF_FIELDS {
+                break
+            }
+        }
+
+        if fields_encountered != CPU_SYS_NUMBER_OF_FIELDS {
+            return Err(ProbeError::UnexpectedContent("Did not encounter all expected fields".to_owned()))
+        }
+        let measurement = CgroupCpuMeasurement {
+            precise_time_ns: time,
+            stat: cpu
+        };
+        Ok(measurement)
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::{CgroupCpuMeasurement,CgroupCpuStat};
+    use super::os::read_and_parse_sys_stat;
+    use std::path::Path;
+    use error::ProbeError;
+
+    #[test]
+    fn test_read() {
+        assert!(super::read().is_ok());
+    }
+
+    #[test]
+    fn test_read_sys_measurement() {
+        let measurement = read_and_parse_sys_stat(&Path::new("fixtures/linux/sys/fs/cgroup/cpuacct_1/")).unwrap();
+        let cpu = measurement.stat;
+        assert_eq!(cpu.total_usage, 152657213021);
+        assert_eq!(cpu.user, 149340000000);
+        assert_eq!(cpu.system, 980000000);
+    }
+
+    #[test]
+    fn test_read_sys_wrong_path() {
+        match read_and_parse_sys_stat(&Path::new("bananas")) {
+            Err(ProbeError::IO(_, _)) => (),
+            r => panic!("Unexpected result: {:?}", r)
+        }
+    }
+
+    #[test]
+    fn test_read_and_parse_sys_stat_incomplete() {
+        match read_and_parse_sys_stat(&Path::new("fixtures/linux/sys/fs/cgroup/cpuacct_incomplete/")) {
+            Err(ProbeError::UnexpectedContent(_)) => (),
+            r => panic!("Unexpected result: {:?}", r)
+        }
+    }
+
+    #[test]
+    fn test_read_and_parse_sys_stat_garbage() {
+        let path = Path::new("fixtures/linux/sys/fs/cgroup/cpuacct_garbage/");
+        match read_and_parse_sys_stat(&path) {
+            Err(ProbeError::UnexpectedContent(_)) => (),
+            r => panic!("Unexpected result: {:?}", r)
+        }
+    }
+
+    #[test]
+    fn test_calculate_per_minute_wrong_times() {
+        let measurement1 = CgroupCpuMeasurement {
+            precise_time_ns: 90_000_000_000,
+            stat: CgroupCpuStat {
+                total_usage: 0,
+                user: 0,
+                system: 0
+            }
+        };
+
+        let measurement2 = CgroupCpuMeasurement {
+            precise_time_ns: 60_000_000_000,
+            stat: CgroupCpuStat {
+                total_usage: 0,
+                user: 0,
+                system: 0
+            }
+        };
+
+        match measurement1.calculate_per_minute(&measurement2) {
+            Err(ProbeError::InvalidInput(_)) => (),
+            r => panic!("Unexpected result: {:?}", r)
+        }
+    }
+
+
+    #[test]
+    fn test_cgroup_calculate_per_minute_full_minute() {
+        let measurement1 = CgroupCpuMeasurement {
+            precise_time_ns: 60_000_000_000,
+            stat: CgroupCpuStat {
+                total_usage: 6380,
+                user: 1000,
+                system: 1200
+            }
+        };
+
+        let measurement2 = CgroupCpuMeasurement {
+            precise_time_ns: 120_000_000_000,
+            stat: CgroupCpuStat {
+                total_usage: 6440,
+                user: 1006,
+                system: 1206
+            }
+        };
+
+        let expected = CgroupCpuStat {
+            total_usage: 60,
+            user: 6,
+            system: 6
+        };
+
+        let stat = measurement1.calculate_per_minute(&measurement2).unwrap();
+
+        assert_eq!(stat, expected);
+    }
+
+    #[test]
+    fn test_calculate_per_minute_partial_minute() {
+        let measurement1 = CgroupCpuMeasurement {
+            precise_time_ns: 60_000_000_000,
+            stat: CgroupCpuStat {
+                total_usage: 1_000_000_000,
+                user: 10000_000_000,
+                system: 12000_000_000
+            }
+        };
+
+        let measurement2 = CgroupCpuMeasurement {
+            precise_time_ns: 90_000_000_000,
+            stat: CgroupCpuStat {
+                total_usage: 1_500_000_000,
+                user: 10060_000_000,
+                system: 12060_000_000
+            }
+        };
+
+        let expected = CgroupCpuStat {
+            total_usage: 1_000_000_000,
+            user: 120_000_000,
+            system: 120_000_000
+        };
+
+        let stat = measurement1.calculate_per_minute(&measurement2).unwrap();
+
+        assert_eq!(stat, expected);
+    }
+
+    #[test]
+    fn test_calculate_per_minute_values_lower() {
+        let measurement1 = CgroupCpuMeasurement {
+            precise_time_ns: 60_000_000_000,
+            stat: CgroupCpuStat {
+                total_usage: 63800_000_000,
+                user: 10000_000_000,
+                system: 12000_000_000
+            }
+        };
+
+        let measurement2 = CgroupCpuMeasurement {
+            precise_time_ns: 90_000_000_000,
+            stat: CgroupCpuStat {
+                total_usage: 10400_000_000,
+                user: 1060_000_000,
+                system: 1260_000_000
+            }
+        };
+
+        match measurement1.calculate_per_minute(&measurement2) {
+            Err(ProbeError::UnexpectedContent(_)) => (),
+            r => panic!("Unexpected result: {:?}", r)
+        }
+    }
+
+    #[test]
+    fn test_in_percentages() {
+        let stat = CgroupCpuStat {
+            total_usage: 24000000000,
+            user: 16800000000,
+            system: 1200000000
+        };
+
+        let in_percentages = stat.in_percentages();
+
+        // Rounding in the floating point calculations can vary, so check if this
+        // is in the correct range.
+        assert!(in_percentages.total_usage > 39.9);
+        assert!(in_percentages.total_usage <= 40.0);
+
+        assert!(in_percentages.user > 27.9);
+        assert!(in_percentages.user <= 28.0);
+
+        assert!(in_percentages.system > 1.9);
+        assert!(in_percentages.system <= 2.0);
+    }
+
+    #[test]
+    fn test_in_percentages_fractions() {
+        let stat = CgroupCpuStat {
+            total_usage: 24000000000,
+            user: 17100000000,
+            system: 900000000
+        };
+
+        let in_percentages = stat.in_percentages();
+
+        // Rounding in the floating point calculations can vary, so check if this
+        // is in the correct range.
+        assert!(in_percentages.total_usage > 39.9);
+        assert!(in_percentages.total_usage <= 40.0);
+
+        assert!(in_percentages.user > 28.4);
+        assert!(in_percentages.user <= 28.5);
+
+        assert!(in_percentages.system > 1.4);
+        assert!(in_percentages.system <= 1.5);
+    }
+
+    #[test]
+    fn test_in_percentages_integration() {
+        let mut measurement1 = read_and_parse_sys_stat(&Path::new("fixtures/linux/sys/fs/cgroup/cpuacct_1/")).unwrap();
+        measurement1.precise_time_ns = 375953965125920;
+        let mut measurement2 = read_and_parse_sys_stat(&Path::new("fixtures/linux/sys/fs/cgroup/cpuacct_2/")).unwrap();
+        measurement2.precise_time_ns = 376013815302920;
+
+        let stat = measurement1.calculate_per_minute(&measurement2).unwrap();
+        let in_percentages = stat.in_percentages();
+
+        // Rounding in the floating point calculations can vary, so check if this
+        // is in the correct range.
+        assert!(in_percentages.total_usage > 49.70);
+        assert!(in_percentages.total_usage < 49.71);
+
+        assert!(in_percentages.user > 47.60);
+        assert!(in_percentages.user < 47.61);
+
+        assert!(in_percentages.system > 0.38);
+        assert!(in_percentages.system < 0.39);
+    }
+}

src/cpu/mod.rs

@@ -0,0 +1,2 @@
+pub mod proc;
+pub mod cgroup;