engine-params.org

EP Parameters

1 Configuring the Engine

Engine parameters may be specified using the -e option to memcached. These parameters control various aspects of the behavior of the engine.

For example, if you would like to store your database in /data/base and prevent it from having objects larger than 1MB, you would run memcached like this:

memcached -E ep.so -e 'dbfile=/data/base;max_item_size=1048576'

2 Parameters for the EP Engine

key	type	descr
config_file	string	Path to additional parameters.
dbname	string	Path to on-disk storage.
ht_locks	int	Number of locks per hash table.
ht_size	int	Number of buckets per hash table.
max_item_size	int	Maximum number of bytes allowed for
		an item.
max_size	int	Max cumulative item size in bytes.
max_txn_size	int	Max number of disk mutations per
		transaction.
mem_high_wat	int	Automatically evict when exceeding
		this size.
mem_low_wat	int	Low water mark to aim for when evicting.
queue_age_cap	int	Maximum queue time before forcing persist.
couch_response_timeout	int	The maximum time to wait for couch to
		respond to a persistence request before
		resetting the connection (milliseconds)
tap_backlog_limit	int	Max number of items allowed in a
		tap backfill
tap_noop_interval	int	Number of seconds between a noop is sent
		on an idle connection
tap_keepalive	int	Seconds to hold open named tap connections
tap_bg_max_pending	int	Maximum number of pending bg fetch
		operations
		a tap queue may issue (before it must wait
		for responses to appear.
tap_backoff_period	float	Number of seconds the tap connection
		should back off after receiving ETMPFAIL
vb0	bool	If true, start with an active vbucket 0
waitforwarmup	bool	Whether to block server start during
		warmup.
warmup	bool	Whether to load existing data at startup.
expiry_window	int	expiry window to not persist an object
		that is expired (or will be soon)
exp_pager_stime	int	Sleep time for the pager that purges
		expired objects from memory and disk
failpartialwarmup	bool	If false, continue running after failing
		to load some records.
max_vbuckets	int	Maximum number of vbuckets expected (1024)
concurrentDB	bool	True (default) if concurrent DB reads are
		permitted where possible.
chk_remover_stime	int	Interval for the checkpoint remover that
		purges closed unreferenced checkpoints.
chk_max_items	int	Number of max items allowed in a
		checkpoint
chk_period	int	Time bound (in sec.) on a checkpoint
max_checkpoints	int	Number of max checkpoints allowed per
		vbucket
inconsistent_slave_chk	bool	True if we allow a “downstream” master to
		receive checkpoint begin/end messages
item_num_based_new_chk	bool	Enable a new checkpoint creation if the
		number of items in a checkpoint is greater
		than the max number allowed
		along with normal get/set operations.
tap_backfill_resident	float	Resident item threshold for only memory
		backfill to be kicked off
keep_closed_chks	bool	True if we want to keep closed checkpoints
		in memory if the current memory usage is
		below high water mark
bf_resident_threshold	float	Resident item threshold for only memory
		backfill to be kicked off
getl_default_timeout	int	The default timeout for a getl lock in (s)
getl_max_timeout	int	The maximum timeout for a getl lock in (s)
mutation_mem_threshold	float	Memory threshold on the current bucket
		quota for accepting a new mutation
tap_throttle_queue_cap	int	The maximum size of the disk write queue
		to throttle down tap-based replication. -1
		means don’t throttle.
tap_throttle_threshold	float	Percentage of memory in use before we
		throttle tap streams
tap_throttle_cap_pcnt	int	Percentage of total items in write queue
		to throttle tap input. 0 means use fixed
		throttle queue cap.
klog_path	string	Path to the mutation key log.
klog_block_size	int	Mutation key log block size.
klog_flush	string	When to force buffer flushes during
		klog (off, commit1, commit2, full)
klog_sync	string	When to fsync during klog.
flushall_enabled	bool	True if we enable flush_all command; The
		default value is False.
data_traffic_enabled	bool	True if we want to enable data traffic
		immediately after warmup completion
alog_sleep_time	int	Interval of access scanner task in (min)
alog_task_time	int	Hour (0~23) in GMT time at which access
		scanner will be scheduled to run.
pager_active_vb_pcnt	int	Percentage of active vbucket items among
		all evicted items by item pager.
warmup_min_memory_threshold	int	Memory threshold (%) during warmup to
		enable traffic.
warmup_min_items_threshold	int	Item num threshold (%) during warmup to
		enable traffic.
conflict_resolution_type	string	Specifies the type of xdcr conflict
		resolution to use