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// Copyright 2023 Greptime Team
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use common_telemetry::error;
use lazy_static::lazy_static;
use once_cell::sync::Lazy;
use prometheus::*;
use snafu::ResultExt;
use tikv_jemalloc_ctl::stats::{allocated_mib, resident_mib};
use tikv_jemalloc_ctl::{epoch, epoch_mib, stats};

use crate::error::UpdateJemallocMetricsSnafu;

lazy_static! {
    pub static ref SYS_JEMALLOC_RESIDEN: IntGauge = register_int_gauge!(
        "sys_jemalloc_resident",
        "Total number of bytes allocated by the application."
    )
    .unwrap();
    pub static ref SYS_JEMALLOC_ALLOCATED: IntGauge = register_int_gauge!(
        "sys_jemalloc_allocated",
        "Total number of bytes in physically resident data pages mapped by the allocator."
    )
    .unwrap();
}

pub(crate) static JEMALLOC_COLLECTOR: Lazy<Option<JemallocCollector>> = Lazy::new(|| {
    let collector = JemallocCollector::try_new()
        .map_err(|e| {
            error!(e; "Failed to retrieve jemalloc metrics");
            e
        })
        .ok();
    collector.inspect(|c| {
        if let Err(e) = c.update() {
            error!(e; "Failed to update jemalloc metrics");
        };
    })
});

pub(crate) struct JemallocCollector {
    epoch: epoch_mib,
    allocated: allocated_mib,
    resident: resident_mib,
}

impl JemallocCollector {
    pub(crate) fn try_new() -> crate::error::Result<Self> {
        let e = epoch::mib().context(UpdateJemallocMetricsSnafu)?;
        let allocated = stats::allocated::mib().context(UpdateJemallocMetricsSnafu)?;
        let resident = stats::resident::mib().context(UpdateJemallocMetricsSnafu)?;
        Ok(Self {
            epoch: e,
            allocated,
            resident,
        })
    }

    pub(crate) fn update(&self) -> crate::error::Result<()> {
        let _ = self.epoch.advance().context(UpdateJemallocMetricsSnafu)?;
        let allocated = self.allocated.read().context(UpdateJemallocMetricsSnafu)?;
        let resident = self.resident.read().context(UpdateJemallocMetricsSnafu)?;
        SYS_JEMALLOC_RESIDEN.set(allocated as i64);
        SYS_JEMALLOC_ALLOCATED.set(resident as i64);
        Ok(())
    }
}