Metrics for MemoryDB - Amazon MemoryDB for Redis
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Metrics for MemoryDB

The Amazon/MemoryDB namespace includes the following Redis metrics.

With the exception of ReplicationLag and EngineCPUUtilization, these metrics are derived from the Redis info command. Each metric is calculated at the node level.

For complete documentation of the Redis info command, see http://redis.io/commands/info.

See Also

Metric Description Unit
ActiveDefragHits The number of value reallocations per minute performed by the active defragmentation process. This is derived from active_defrag_hits statistic at Redis INFO. Number
AuthenticationFailures The total number of failed attempts to authenticate to Redis using the AUTH command. You can find more information about individual authentication failures using the ACL LOG command. We suggest setting an alarm on this to detect unauthorized access attempts. Count
BytesUsedForMemoryDB The total number of bytes allocated by MemoryDB for all purposes, including the dataset, buffers, and so on. Bytes
Dimension: Tier=SSD for clusters using Data tiering: The total number of bytes used by SSD. Bytes
Dimension: Tier=Memory for clusters using Data tiering: The total number of bytes used by memory. This is the value of used_memory statistic at Redis INFO. Bytes
BytesReadFromDisk The total number of bytes read from disk per minute. Supported only for clusters using Data tiering. Bytes
BytesWrittenToDisk The total number of bytes written to disk per minute. Supported only for clusters using Data tiering. Bytes
CommandAuthorizationFailures The total number of failed attempts by users to run commands they don’t have permission to call. You can find more information about individual authentication failures using the ACL LOG command. We suggest setting an alarm on this to detect unauthorized access attempts. Count
CurrConnections The number of client connections, excluding connections from read replicas. MemoryDB uses two to four of the connections to monitor the cluster in each case. This is derived from the connected_clients statistic at Redis INFO. Count
CurrItems The number of items in the cache. This is derived from the Redis keyspace statistic, summing all of the keys in the entire keyspace. Count
Dimension: Tier=Memory for clusters using Data tiering. The number of items in memory. Count
Dimension: Tier=SSD (solid state drives) for clusters using Data tiering. The number of items in SSD. Count
DatabaseMemoryUsagePercentage Percentage of the memory available for the cluster that is in use. This is calculated using used_memory/maxmemory from Redis INFO. Percent
DB0AverageTTL Exposes avg_ttl of DBO from the keyspace statistic of Redis INFO command. Milliseconds
EngineCPUUtilization

Provides CPU utilization of the Redis engine thread. Because Redis is single-threaded, you can use this metric to analyze the load of the Redis process itself. The EngineCPUUtilization metric provides a more precise visibility of the Redis process. You can use it in conjunction with the CPUUtilization metric. CPUUtilization exposes CPU utilization for the server instance as a whole, including other operating system and management processes. For larger node types with four vCPUs or more, use the EngineCPUUtilization metric to monitor and set thresholds for scaling.

Note

On a MemoryDB host, background processes monitor the host to provide a managed database experience. These background processes can take up a significant portion of the CPU workload. This is not significant on larger hosts with more than two vCPUs. But it can affect smaller hosts with 2vCPUs or fewer. If you only monitor the EngineCPUUtilization metric, you will be unaware of situations where the host is overloaded with both high CPU usage from Redis and high CPU usage from the background monitoring processes. Therefore, we recommend monitoring the CPUUtilization metric for hosts with two vCPUs or less.

Percent
Evictions The number of keys that have been evicted due to the maxmemory limit. This is derived from the evicted_keys statistic at Redis INFO. Count
IsPrimary Indicates whether the node is primary node of current shard. The metric can be either 0 (not primary) or 1 (primary). Count
KeyAuthorizationFailures The total number of failed attempts by users to access keys they don’t have permission to access. You can find more information about individual authentication failures using the ACL LOG command. We suggest setting an alarm on this to detect unauthorized access attempts. Count
KeyspaceHits The number of successful read-only key lookups in the main dictionary. This is derived from keyspace_hits statistic at Redis INFO. Count
KeyspaceMisses The number of unsuccessful read-only key lookups in the main dictionary. This is derived from keyspace_misses statistic at Redis INFO. Count
KeysTracked The number of keys being tracked by Redis key tracking as a percentage of tracking-table-max-keys. Key tracking is used to aid client-side caching and notifies clients when keys are modified. Count
MaxReplicationThroughput The maximum observed replication throughput during the last measurement cycle. Bytes per second
MemoryFragmentationRatio Indicates the efficiency in the allocation of memory of the Redis engine. Certain thresholds signify different behaviors. The recommended value is to have fragmentation above 1.0. This is calculated from the mem_fragmentation_ratio statistic of Redis INFO. Number
NewConnections The total number of connections that have been accepted by the server during this period. This is derived from the total_connections_received statistic at Redis INFO. Count
NumItemsReadFromDisk The total number of items retrieved from disk per minute. Supported only for clusters using Data tiering. Count
NumItemsWrittenToDisk The total number of items written to disk per minute. Supported only for clusters using Data tiering. Count
PrimaryLinkHealthStatus This status has two values: 0 or 1. The value 0 indicates that data in the MemoryDB primary node is not in sync with Redis on EC2. The value of 1 indicates that the data is in sync. Boolean
Reclaimed The total number of key expiration events. This is derived from the expired_keys statistic at Redis INFO. Count
ReplicationBytes For nodes in a replicated configuration, ReplicationBytes reports the number of bytes that the primary is sending to all of its replicas. This metric is representative of the write load on the cluster. This is derived from the master_repl_offset statistic at Redis INFO. Bytes
ReplicationDelayedWriteCommands Number of commands that were delayed due to exceeding the maximum replication throughput. Count
ReplicationLag This metric is only applicable for a node running as a read replica. It represents how far behind, in seconds, the replica is in applying changes from the primary node. Seconds

The following are aggregations of certain kinds of commands, derived from info commandstats. The commandstats section provides statistics based on the command type, including the number of calls.

For a full list of available commands, see redis commands in the Redis documentation.

Metric Description Unit
EvalBasedCmds The total number of commands for eval-based commands. This is derived from the Redis commandstats statistic. This is derived from the Redis commandstats statistic by summing eval, evalsha. Count
GeoSpatialBasedCmds The total number of commands for geospatial-based commands. This is derived from the Redis commandstats statistic. It's derived by summing all of the geo type of commands: geoadd, geodist, geohash, geopos, georadius, and georadiusbymember. Count
GetTypeCmds The total number of read-only type commands. This is derived from the Redis commandstats statistic by summing all of the read-only type commands (get, hget, scard, lrange, and so on.) Count
HashBasedCmds The total number of commands that are hash-based. This is derived from the Redis commandstats statistic by summing all of the commands that act upon one or more hashes (hget, hkeys, hvals, hdel, and so on). Count
HyperLogLogBasedCmds The total number of HyperLogLog-based commands. This is derived from the Redis commandstats statistic by summing all of the pf type of commands (pfadd, pfcount, pfmerge, and so on.). Count
JsonBasedCmds The total number of commands that are JSON-based. This is derived from the Redis commandstats statistics by summing all of the commands that act upon one or more JSON document objects. Count
KeyBasedCmds The total number of commands that are key-based. This is derived from the Redis commandstats statistic by summing all of the commands that act upon one or more keys across multiple data structures (del, expire, rename, and so on.). Count
ListBasedCmds The total number of commands that are list-based. This is derived from the Redis commandstats statistic by summing all of the commands that act upon one or more lists (lindex, lrange, lpush, ltrim, and so on). Count
PubSubBasedCmds The total number of commands for pub/sub functionality. This is derived from the Redis commandstatsstatistics by summing all of the commands used for pub/sub functionality: psubscribe, publish, pubsub, punsubscribe, subscribe, and unsubscribe. Count
SetBasedCmds The total number of commands that are set-based. This is derived from the Redis commandstats statistic by summing all of the commands that act upon one or more sets (scard, sdiff, sadd, sunion, and so on). Count
SetTypeCmds The total number of write types of commands. This is derived from the Redis commandstats statistic by summing all of the mutative types of commands that operate on data (set, hset, sadd, lpop, and so on.) Count
SortedSetBasedCmds The total number of commands that are sorted set-based. This is derived from the Redis commandstats statistic by summing all of the commands that act upon one or more sorted sets (zcount, zrange, zrank, zadd, and so on). Count
StringBasedCmds The total number of commands that are string-based. This is derived from the Redis commandstats statistic by summing all of the commands that act upon one or more strings (strlen, setex, setrange, and so on). Count
StreamBasedCmds The total number of commands that are stream-based. This is derived from the Redis commandstats statistic by summing all of the commands that act upon one or more streams data types (xrange, xlen, xadd, xdel, and so on). Count