Memcached Exporter for Prometheus

镜像概述和主要用途

Memcached Exporter是Prometheus的官方导出器，用于从Memcached服务器收集性能指标并以Prometheus兼容格式暴露，以便进行监控和告警。该导出器能够采集Memcached的连接状态、命令执行情况、内存使用、LRU缓存行为等关键指标，并通过HTTP接口提供给Prometheus抓取。

核心功能和特性

• 全面的指标收集：涵盖连接状态、命令统计、内存使用、LRU缓存管理、slab类信息等多维度指标
• 多目标支持：通过/scrape端点支持多Memcached实例监控，适合大规模部署
• 安全特性：支持TLS加密和基本认证，保障指标传输安全
• 进程指标采集：可选采集Memcached进程自身的资源使用情况（CPU、内存、文件描述符等）
• 灵活配置：支持自定义Memcached连接地址、监听端口及TLS参数

使用场景和适用范围

适用于所有需要监控Memcached服务器运行状态的场景，包括：

• 生产环境中Memcached缓存服务的性能监控
• 多Memcached实例集群的集中监控
• 需要对缓存命中率、内存使用率、连接数等指标进行告警的场景
• 与Prometheus、Grafana等工具集成构建监控dashboard

使用方法和配置说明

基本运行

通过Docker运行Memcached Exporter，默认监听9150端口，暴露/metrics端点：

docker run -p 9150:9150 quay.io/prometheus/memcached-exporter:latest

连接到指定Memcached服务器

默认连接localhost:11211，可通过--memcached.address参数指定目标Memcached地址：

docker run -p 9150:9150 quay.io/prometheus/memcached-exporter:latest --memcached.address=memcached-host:11211

多目标采集模式

支持通过/scrape端点采集多个Memcached实例指标，需指定target参数：

curl http://localhost:9150/scrape?target=memcached-host.company.com:11211

启动多目标模式时，建议设置--memcached.address=""避免默认连接：

./memcached-exporter --memcached.address=""

Prometheus集成示例（多目标）

结合服务发现工具（如prometheus-elasticache-sd）的Prometheus配置示例：

scrape_configs:
  - job_name: "memcached_exporter_targets"
    file_sd_configs:
      - files:
          - /path/to/elasticache.json  # 服务发现生成的目标文件
    metrics_path: /scrape
    relabel_configs:
      # 仅保留Memcached实例
      - source_labels: [__meta_elasticache_engine]
        regex: memcached
        action: keep
      # 构建目标参数
      - source_labels: [__meta_elasticache_endpoint_address, __meta_elasticache_endpoint_port]
        separator: ':'
        target_label: __param_target
      # 设置instance标签
      - source_labels: [__param_target]
        target_label: instance
      # 导出器地址
      - target_label: __address__
        replacement: memcached-exporter-service.company.com:9151

TLS和基本认证

导出器自身的TLS和认证

通过--web.config.file参数指定配置文件启用TLS和基本认证，配置文件格式详见exporter-toolkit文档。

与Memcached的TLS连接

使用--memcached.tls.*系列参数配置与Memcached的TLS连接，具体参数可通过memcached_exporter --help查看。

进程指标采集

通过--memcached.pid-file <path>参数指定Memcached进程PID文件，可额外采集进程资源使用指标（需导出器进程有权限读取/proc信息），包括CPU时间、内存使用、文件描述符等。

收集的指标

导出器采集以下Memcached指标（按类型分类）：

连接和状态指标

# HELP memcached_accepting_conns The Memcached server is currently accepting new connections.
# TYPE memcached_accepting_conns gauge
# HELP memcached_connections_listener_disabled_total Number of times that memcached has hit its connections limit and disabled its listener.
# TYPE memcached_connections_listener_disabled_total counter
# HELP memcached_connections_total Total number of connections opened since the server started running.
# TYPE memcached_connections_total counter
# HELP memcached_connections_yielded_total Total number of connections yielded running due to hitting the memcached's -R limit.
# TYPE memcached_connections_yielded_total counter
# HELP memcached_current_connections Current number of open connections.
# TYPE memcached_current_connections gauge
# HELP memcached_max_connections Maximum number of clients allowed.
# TYPE memcached_max_connections gauge

命令和请求指标

# HELP memcached_commands_total Total number of all requests broken down by command (get, set, etc.) and status.
# TYPE memcached_commands_total counter

内存和存储指标

# HELP memcached_current_bytes Current number of bytes used to store items.
# TYPE memcached_current_bytes gauge
# HELP memcached_current_items Current number of items stored by this instance.
# TYPE memcached_current_items gauge
# HELP memcached_items_total Total number of items stored during the life of this instance.
# TYPE memcached_items_total counter
# HELP memcached_limit_bytes Number of bytes this server is allowed to use for storage.
# TYPE memcached_limit_bytes gauge
# HELP memcached_malloced_bytes Number of bytes of memory allocated to slab pages.
# TYPE memcached_malloced_bytes gauge

LRU缓存管理指标

# HELP memcached_direct_reclaims_total Times worker threads had to directly reclaim or evict items.
# TYPE memcached_direct_reclaims_total counter
# HELP memcached_items_evicted_total Total number of valid items removed from cache to free memory for new items.
# TYPE memcached_items_evicted_total counter
# HELP memcached_items_reclaimed_total Total number of times an entry was stored using memory from an expired entry.
# TYPE memcached_items_reclaimed_total counter
# HELP memcached_lru_crawler_enabled Whether the LRU crawler is enabled.
# TYPE memcached_lru_crawler_enabled gauge
# HELP memcached_lru_crawler_hot_max_factor Set idle age of HOT LRU to COLD age * this
# TYPE memcached_lru_crawler_hot_max_factor gauge
# HELP memcached_lru_crawler_hot_percent Percent of slab memory reserved for HOT LRU.
# TYPE memcached_lru_crawler_hot_percent gauge
# HELP memcached_lru_crawler_items_checked_total Total items examined by LRU Crawler.
# TYPE memcached_lru_crawler_items_checked_total counter
# HELP memcached_lru_crawler_maintainer_thread Split LRU mode and background threads.
# TYPE memcached_lru_crawler_maintainer_thread gauge
# HELP memcached_lru_crawler_moves_to_cold_total Total number of items moved from HOT/WARM to COLD LRU's.
# TYPE memcached_lru_crawler_moves_to_cold_total counter
# HELP memcached_lru_crawler_moves_to_warm_total Total number of items moved from COLD to WARM LRU.
# TYPE memcached_lru_crawler_moves_to_warm_total counter
# HELP memcached_lru_crawler_moves_within_lru_total Total number of items reshuffled within HOT or WARM LRU's.
# TYPE memcached_lru_crawler_moves_within_lru_total counter
# HELP memcached_lru_crawler_reclaimed_total Total items freed by LRU Crawler.
# TYPE memcached_lru_crawler_reclaimed_total counter
# HELP memcached_lru_crawler_sleep Microseconds to sleep between LRU crawls.
# TYPE memcached_lru_crawler_sleep gauge
# HELP memcached_lru_crawler_starts_total Times an LRU crawler was started.
# TYPE memcached_lru_crawler_starts_total counter
# HELP memcached_lru_crawler_to_crawl Max items to crawl per slab per run.
# TYPE memcached_lru_crawler_to_crawl gauge
# HELP memcached_lru_crawler_warm_max_factor Set idle age of WARM LRU to COLD age * this
# TYPE memcached_lru_crawler_warm_max_factor gauge
# HELP memcached_lru_crawler_warm_percent Percent of slab memory reserved for WARM LRU.
# TYPE memcached_lru_crawler_warm_percent gauge

数据传输指标

# HELP memcached_read_bytes_total Total number of bytes read by this server from network.
# TYPE memcached_read_bytes_total counter
# HELP memcached_written_bytes_total Total number of bytes sent by this server to network.
# TYPE memcached_written_bytes_total counter

服务器信息指标

# HELP memcached_time_seconds current UNIX time according to the server.
# TYPE memcached_time_seconds gauge
# HELP memcached_up Could the memcached server be reached.
# TYPE memcached_up gauge
# HELP memcached_uptime_seconds Number of seconds since the server started.
# TYPE memcached_uptime_seconds counter
# HELP memcached_version The version of this memcached server.
# TYPE memcached_version gauge

Slab类指标

# HELP memcached_slab_chunk_size_bytes Number of bytes allocated to each chunk within this slab class.
# TYPE memcached_slab_chunk_size_bytes gauge
# HELP memcached_slab_chunks_free Number of chunks not yet allocated items.
# TYPE memcached_slab_chunks_free gauge
# HELP memcached_slab_chunks_free_end Number of free chunks at the end of the last allocated page.
# TYPE memcached_slab_chunks_free_end gauge
# HELP memcached_slab_chunks_per_page Number of chunks within a single page for this slab class.
# TYPE memcached_slab_chunks_per_page gauge
# HELP memcached_slab_chunks_used Number of chunks allocated to an item.
# TYPE memcached_slab_chunks_used gauge
# HELP memcached_slab_cold_items Number of items presently stored in the COLD LRU.
# TYPE memcached_slab_cold_items gauge
# HELP memcached_slab_commands_total Total number of all requests broken down by command (get, set, etc.) and status per slab.
# TYPE memcached_slab_commands_total counter
# HELP memcached_slab_current_chunks Number of chunks allocated to this slab class.
# TYPE memcached_slab_current_chunks gauge
# HELP memcached_slab_current_items Number of items currently stored in this slab class.
# TYPE memcached_slab_current_items gauge
# HELP memcached_slab_current_pages Number of pages allocated to this slab class.
# TYPE memcached_slab_current_pages gauge
# HELP memcached_slab_hot_age_seconds Age of the oldest item in HOT LRU.
# TYPE memcached_slab_hot_age_seconds gauge
# HELP memcached_slab_hot_items Number of items presently stored in the HOT LRU.
# TYPE memcached_slab_hot_items gauge
# HELP memcached_slab_items_age_seconds Number of seconds the oldest item has been in the slab class.
# TYPE memcached_slab_items_age_seconds gauge
# HELP memcached_slab_items_crawler_reclaimed_total Number of items freed by the LRU Crawler.
# TYPE memcached_slab_items_crawler_reclaimed_total counter
# HELP memcached_slab_items_evicted_nonzero_total Total number of times an item which had an explicit expire time set had to be evicted from the LRU before it expired.
# TYPE memcached_slab_items_evicted_nonzero_total counter
# HELP memcached_slab_items_evicted_time_seconds Seconds since the last access for the most recent item evicted from this class.
# TYPE memcached_slab_items_evicted_time_seconds counter
# HELP memcached_slab_items_evicted_total Total number of times an item had to be evicted from the LRU before it expired.
# TYPE memcached_slab_items_evicted_total counter
# HELP memcached_slab_items_evicted_unfetched_total Total nmber of items evicted and never fetched.
# TYPE memcached_slab_items_evicted_unfetched_total counter
# HELP memcached_slab_items_expired_unfetched_total Total number of valid items evicted from the LRU which were never touched after being set.
# TYPE memcached_slab_items_expired_unfetched_total counter
# HELP memcached_slab_items_moves_to_cold Number of items moved from HOT or WARM into COLD.
# TYPE memcached_slab_items_moves_to_cold counter
# HELP memcached_slab_items_moves_to_warm Number of items moves from COLD into WARM.
# TYPE memcached_slab_items_moves_to_warm counter
# HELP memcached_slab_items_moves_within_lru Number of times active items were bumped within HOT or WARM.
# TYPE memcached_slab_items_moves_within_lru counter
# HELP memcached_slab_items_outofmemory_total Total number of items for this slab class that have triggered an out of memory error.
# TYPE memcached_slab_items_outofmemory_total counter
# HELP memcached_slab_items_reclaimed_total Total number of items reclaimed.
# TYPE memcached_slab_items_reclaimed_total counter
# HELP memcached_slab_items_tailrepairs_total Total number of times the entries for a particular ID need repairing.
# TYPE memcached_slab_items_tailrepairs_total counter
# HELP memcached_slab_lru_hits_total Number of get_hits to the LRU.
# TYPE memcached_slab_lru_hits_total counter
# HELP memcached_slab_mem_requested_bytes Number of bytes of memory actual items take up within a slab.
# TYPE memcached_slab_mem_requested_bytes counter
# HELP memcached_slab_warm_age_seconds Age of the oldest item in HOT LRU.
# TYPE memcached_slab_warm_age_seconds gauge
# HELP memcached_slab_warm_items Number of items presently stored in the WARM LRU.
# TYPE memcached_slab_warm_items gauge

进程指标（可选）

# HELP memcached_process_cpu_seconds_total Total user and system CPU time spent in seconds.
# TYPE memcached_process_cpu_seconds_total counter
# HELP memcached_process_max_fds Maximum number of open file descriptors.
# TYPE memcached_process_max_fds gauge
# HELP memcached_process_open_fds Number of open file descriptors.
# TYPE memcached_process_open_fds gauge
# HELP memcached_process_resident_memory_bytes Resident memory size in bytes.
# TYPE memcached_process_resident_memory_bytes gauge
# HELP memcached_process_start_time_seconds Start time of the process since unix epoch in seconds.
# TYPE memcached_process_start_time_seconds gauge
# HELP memcached_process_virtual_memory_bytes Virtual memory size in bytes.
# TYPE memcached_process_virtual_memory_bytes gauge