netdata/netdata

// SPDX-License-Identifier: GPL-3.0-or-later

package couchdb

import (
    "bytes"
    "encoding/json"
    "errors"
    "fmt"
    "io"
    "math"
    "net/http"
    "strings"
    "sync"

    "github.com/netdata/netdata/go/go.d.plugin/pkg/stm"
    "github.com/netdata/netdata/go/go.d.plugin/pkg/web"
)

const (
    urlPathActiveTasks   = "/_active_tasks"
    urlPathOverviewStats = "/_node/%s/_stats"
    urlPathSystemStats   = "/_node/%s/_system"
    urlPathDatabases     = "/_dbs_info"

    httpStatusCodePrefix    = "couchdb_httpd_status_codes_"
    httpStatusCodePrefixLen = len(httpStatusCodePrefix)
)

func (cdb *CouchDB) collect() (map[string]int64, error) {
    ms := cdb.scrapeCouchDB()
    if ms.empty() {
        return nil, nil
    }

    collected := make(map[string]int64)
    cdb.collectNodeStats(collected, ms)
    cdb.collectSystemStats(collected, ms)
    cdb.collectActiveTasks(collected, ms)
    cdb.collectDBStats(collected, ms)

    return collected, nil
}

func (cdb *CouchDB) collectNodeStats(collected map[string]int64, ms *cdbMetrics) {
    if !ms.hasNodeStats() {
        return
    }

    for metric, value := range stm.ToMap(ms.NodeStats) {
        collected[metric] = value
        if strings.HasPrefix(metric, httpStatusCodePrefix) {
            code := metric[httpStatusCodePrefixLen:]
            collected["couchdb_httpd_status_codes_"+string(code[0])+"xx"] += value
        }
    }
}

func (cdb *CouchDB) collectSystemStats(collected map[string]int64, ms *cdbMetrics) {
    if !ms.hasNodeSystem() {
        return
    }

    for metric, value := range stm.ToMap(ms.NodeSystem) {
        collected[metric] = value
    }

    collected["peak_msg_queue"] = findMaxMQSize(ms.NodeSystem.MessageQueues)
}

func (cdb *CouchDB) collectActiveTasks(collected map[string]int64, ms *cdbMetrics) {
    collected["active_tasks_indexer"] = 0
    collected["active_tasks_database_compaction"] = 0
    collected["active_tasks_replication"] = 0
    collected["active_tasks_view_compaction"] = 0

    if !ms.hasActiveTasks() {
        return
    }

    for _, task := range ms.ActiveTasks {
        collected["active_tasks_"+task.Type]++
    }
}

func (cdb *CouchDB) collectDBStats(collected map[string]int64, ms *cdbMetrics) {
    if !ms.hasDBStats() {
        return
    }

    for _, dbStats := range ms.DBStats {
        if dbStats.Error != "" {
            cdb.Warning("database '", dbStats.Key, "' doesn't exist")
            continue
        }
        merge(collected, stm.ToMap(dbStats.Info), "db_"+dbStats.Key)
    }
}

func (cdb *CouchDB) scrapeCouchDB() *cdbMetrics {
    ms := &cdbMetrics{}
    wg := &sync.WaitGroup{}

    wg.Add(1)
    go func() { defer wg.Done(); cdb.scrapeNodeStats(ms) }()

    wg.Add(1)
    go func() { defer wg.Done(); cdb.scrapeSystemStats(ms) }()

    wg.Add(1)
    go func() { defer wg.Done(); cdb.scrapeActiveTasks(ms) }()

    if len(cdb.databases) > 0 {
        wg.Add(1)
        go func() { defer wg.Done(); cdb.scrapeDBStats(ms) }()
    }

    wg.Wait()
    return ms
}

func (cdb *CouchDB) scrapeNodeStats(ms *cdbMetrics) {
    req, _ := web.NewHTTPRequest(cdb.Request)
    req.URL.Path = fmt.Sprintf(urlPathOverviewStats, cdb.Config.Node)

    var stats cdbNodeStats
    if err := cdb.doOKDecode(req, &stats); err != nil {
        cdb.Warning(err)
        return
    }
    ms.NodeStats = &stats
}

func (cdb *CouchDB) scrapeSystemStats(ms *cdbMetrics) {
    req, _ := web.NewHTTPRequest(cdb.Request)
    req.URL.Path = fmt.Sprintf(urlPathSystemStats, cdb.Config.Node)

    var stats cdbNodeSystem
    if err := cdb.doOKDecode(req, &stats); err != nil {
        cdb.Warning(err)
        return
    }
    ms.NodeSystem = &stats
}

func (cdb *CouchDB) scrapeActiveTasks(ms *cdbMetrics) {
    req, _ := web.NewHTTPRequest(cdb.Request)
    req.URL.Path = urlPathActiveTasks

    var stats []cdbActiveTask
    if err := cdb.doOKDecode(req, &stats); err != nil {
        cdb.Warning(err)
        return
    }
    ms.ActiveTasks = stats
}

func (cdb *CouchDB) scrapeDBStats(ms *cdbMetrics) {
    req, _ := web.NewHTTPRequest(cdb.Request)
    req.URL.Path = urlPathDatabases
    req.Method = http.MethodPost
    req.Header.Add("Accept", "application/json")
    req.Header.Add("Content-Type", "application/json")

    var q struct {
        Keys []string `json:"keys"`
    }
    q.Keys = cdb.databases
    body, err := json.Marshal(q)
    if err != nil {
        cdb.Error(err)
        return
    }
    req.Body = io.NopCloser(bytes.NewReader(body))

    var stats []cdbDBStats
    if err := cdb.doOKDecode(req, &stats); err != nil {
        cdb.Warning(err)
        return
    }
    ms.DBStats = stats
}

func findMaxMQSize(MessageQueues map[string]interface{}) int64 {
    var max float64
    for _, mq := range MessageQueues {
        switch mqSize := mq.(type) {
        case float64:
            max = math.Max(max, mqSize)
        case map[string]interface{}:
            if v, ok := mqSize["count"].(float64); ok {
                max = math.Max(max, v)
            }
        }
    }
    return int64(max)
}

func (cdb *CouchDB) pingCouchDB() error {
    req, _ := web.NewHTTPRequest(cdb.Request)

    var info struct{ Couchdb string }
    if err := cdb.doOKDecode(req, &info); err != nil {
        return err
    }

    if info.Couchdb != "Welcome" {
        return errors.New("not a CouchDB endpoint")
    }

    return nil
}

func (cdb *CouchDB) doOKDecode(req *http.Request, in interface{}) error {
    resp, err := cdb.httpClient.Do(req)
    if err != nil {
        return fmt.Errorf("error on HTTP request '%s': %v", req.URL, err)
    }
    defer closeBody(resp)

    // TODO: read resp body, it contains reason
    // ex.: {"error":"bad_request","reason":"`keys` member must exist."} (400)
    if resp.StatusCode != http.StatusOK {
        return fmt.Errorf("'%s' returned HTTP status code: %d", req.URL, resp.StatusCode)
    }

    if err := json.NewDecoder(resp.Body).Decode(in); err != nil {
        return fmt.Errorf("error on decoding response from '%s': %v", req.URL, err)
    }
    return nil
}

func closeBody(resp *http.Response) {
    if resp != nil && resp.Body != nil {
        _, _ = io.Copy(io.Discard, resp.Body)
        _ = resp.Body.Close()
    }
}

func merge(dst, src map[string]int64, prefix string) {
    for k, v := range src {
        dst[prefix+"_"+k] = v
    }
}