153 lines
8.4 KiB
Markdown
153 lines
8.4 KiB
Markdown
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# Memcached Input Plugin
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This plugin gathers statistics data from [Memcached][memcached] instances.
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⭐ Telegraf v0.1.2
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🏷️ server
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💻 all
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[memcached]: https://memcached.org/
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## Global configuration options <!-- @/docs/includes/plugin_config.md -->
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In addition to the plugin-specific configuration settings, plugins support
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additional global and plugin configuration settings. These settings are used to
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modify metrics, tags, and field or create aliases and configure ordering, etc.
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See the [CONFIGURATION.md][CONFIGURATION.md] for more details.
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[CONFIGURATION.md]: ../../../docs/CONFIGURATION.md#plugins
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## Configuration
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```toml @sample.conf
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# Read metrics from one or many memcached servers.
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[[inputs.memcached]]
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# An array of address to gather stats about. Specify an ip on hostname
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# with optional port. ie localhost, 10.0.0.1:11211, etc.
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servers = ["localhost:11211"]
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# An array of unix memcached sockets to gather stats about.
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# unix_sockets = ["/var/run/memcached.sock"]
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## Optional TLS Config
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# enable_tls = false
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# tls_ca = "/etc/telegraf/ca.pem"
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# tls_cert = "/etc/telegraf/cert.pem"
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# tls_key = "/etc/telegraf/key.pem"
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## If false, skip chain & host verification
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# insecure_skip_verify = true
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```
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## Metrics
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The fields from this plugin are gathered in the *memcached* measurement.
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Fields:
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* accepting_conns - Whether or not server is accepting conns
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* auth_cmds - Number of authentication commands handled, success or failure
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* auth_errors - Number of failed authentications
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* bytes - Current number of bytes used to store items
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* bytes_read - Total number of bytes read by this server from network
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* bytes_written - Total number of bytes sent by this server to network
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* cas_badval - Number of CAS reqs for which a key was found, but the CAS value
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did not match
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* cas_hits - Number of successful CAS reqs
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* cas_misses - Number of CAS reqs against missing keys
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* cmd_flush - Cumulative number of flush reqs
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* cmd_get - Cumulative number of retrieval reqs
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* cmd_set - Cumulative number of storage reqs
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* cmd_touch - Cumulative number of touch reqs
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* conn_yields - Number of times any connection yielded to another due to
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hitting the -R limit
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* connection_structures - Number of connection structures allocated by the
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server
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* curr_connections - Number of open connections
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* curr_items - Current number of items stored
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* decr_hits - Number of successful decr reqs
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* decr_misses - Number of decr reqs against missing keys
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* delete_hits - Number of deletion reqs resulting in an item being removed
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* delete_misses - Number of deletions reqs for missing keys
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* evicted_active - Items evicted from LRU that had been hit recently but did
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not jump to top of LRU
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* evicted_unfetched - Items evicted from LRU that were never touched by
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get/incr/append/etc
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* evictions - Number of valid items removed from cache to free memory for
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new items
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* expired_unfetched - Items pulled from LRU that were never touched by
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get/incr/append/etc before expiring
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* extstore_compact_lost - The number of objects lost during the compaction process. This happens when objects couldn't be rescued or moved to other pages before they were overwritten or evicted.
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* extstore_compact_rescues - The total number of objects successfully rescued during the compaction process, meaning they were moved to another page instead of being discarded.
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* extstore_compact_resc_cold - The number of cold objects (rarely accessed) rescued during the compaction process.
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* extstore_compact_resc_old - The number of older objects (likely less frequently accessed) rescued during the compaction process.
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* extstore_compact_skipped - The number of compaction operations skipped, often due to the page not requiring compaction or other conditions preventing it.
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* extstore_page_allocs - The total number of pages allocated in the external storage system.
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* extstore_page_evictions - The total number of pages evicted (removed) from external storage, generally to free up space.
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* extstore_page_reclaims - The total number of previously evicted pages that were reclaimed and reused.
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* extstore_pages_free - The number of pages currently free (unallocated) in the external storage.
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* extstore_pages_used - The number of pages currently in use in the external storage system.
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* extstore_objects_evicted - The total number of objects evicted from external storage, typically to free up space.
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* extstore_objects_read - The total number of objects read from external storage.
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* extstore_objects_written - The total number of objects written to external storage.
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* extstore_objects_used - The number of active objects currently in use in the external storage.
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* extstore_bytes_evicted - The total number of bytes evicted from external storage.
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* extstore_bytes_written - The total number of bytes written to external storage.
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* extstore_bytes_read - The total number of bytes read from external storage.
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* extstore_bytes_used - The total number of bytes currently in use in external storage.
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* extstore_bytes_fragmented - The total number of fragmented bytes in external storage, representing space that is allocated but not fully utilized.
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* extstore_limit_maxbytes - The maximum limit of bytes that external storage can use.
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* extstore_io_queue - The current length of the I/O queue, representing pending input/output operations for external storage.
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* get_expired - Number of items that have been requested but had already
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expired
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* get_flushed - Number of items that have been requested but have been flushed
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via flush_all
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* get_hits - Number of keys that have been requested and found present
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* get_misses - Number of items that have been requested and not found
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* hash_bytes - Bytes currently used by hash tables
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* hash_is_expanding - Indicates if the hash table is being grown to a new size
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* hash_power_level - Current size multiplier for hash table
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* incr_hits - Number of successful incr reqs
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* incr_misses - Number of incr reqs against missing keys
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* limit_maxbytes - Number of bytes this server is allowed to use for storage
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* listen_disabled_num - Number of times server has stopped accepting new
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connections (maxconns)
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* max_connections - Max number of simultaneous connections
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* reclaimed - Number of times an entry was stored using memory from an
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expired entry
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* rejected_connections - Conns rejected in maxconns_fast mode
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* store_no_memory - Number of rejected storage requests caused by exhaustion
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of the memory limit when evictions are disabled
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* store_too_large - Number of rejected storage requests caused by attempting
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to write a value larger than the item size limit
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* threads - Number of worker threads requested
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* total_connections - Total number of connections opened since the server
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started running
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* total_items - Total number of items stored since the server started
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* touch_hits - Number of keys that have been touched with a new expiration time
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* touch_misses - Number of items that have been touched and not found
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* uptime - Number of secs since the server started
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Description of gathered fields taken from [memcached protocol docs][protocol].
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[protocol]: https://github.com/memcached/memcached/blob/master/doc/protocol.txt
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## Tags
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* Memcached measurements have the following tags:
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* server (the host name from which metrics are gathered)
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## Sample Queries
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You can use the following query to get the average get hit and miss ratio, as
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well as the total average size of cached items, number of cached items and
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average connection counts per server.
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```sql
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SELECT mean(get_hits) / mean(cmd_get) as get_ratio, mean(get_misses) / mean(cmd_get) as get_misses_ratio, mean(bytes), mean(curr_items), mean(curr_connections) FROM memcached WHERE time > now() - 1h GROUP BY server
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```
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## Example Output
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```text
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memcached,server=localhost:11211 accepting_conns=1i,auth_cmds=0i,auth_errors=0i,bytes=0i,bytes_read=7i,bytes_written=0i,cas_badval=0i,cas_hits=0i,cas_misses=0i,cmd_flush=0i,cmd_get=0i,cmd_set=0i,cmd_touch=0i,conn_yields=0i,connection_structures=3i,curr_connections=2i,curr_items=0i,decr_hits=0i,decr_misses=0i,delete_hits=0i,delete_misses=0i,evicted_active=0i,evicted_unfetched=0i,evictions=0i,expired_unfetched=0i,get_expired=0i,get_flushed=0i,get_hits=0i,get_misses=0i,hash_bytes=524288i,hash_is_expanding=0i,hash_power_level=16i,incr_hits=0i,incr_misses=0i,limit_maxbytes=67108864i,listen_disabled_num=0i,max_connections=1024i,reclaimed=0i,rejected_connections=0i,store_no_memory=0i,store_too_large=0i,threads=4i,total_connections=3i,total_items=0i,touch_hits=0i,touch_misses=0i,uptime=3i 1644771989000000000
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```
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