Squid configuration directive store_id_children

Available in: 4   3.5   3.4  

History:

Changes to store_id_children in Squid-4:

New parameter queue-size= to set the maximum number of queued requests.

New parameter on-persistent-overload= to set the action taken when the helper queue is overloaded.

Changes to store_id_children in Squid-3.4:

Controls the number of StoreID helper processes.

Options startup=N, idle=N, concurrency=N

  • startup=N allow finer tuning of how many helpers are started initially.
  • idle=N allow fine tuning of how many helper to retain as buffer against sudden traffic loads.
  • concurrency=N was previously called url_rewrite_concurrency as a distinct directive.

This directive is not available in the 3.3 version of Squid.

For older versions than 3.3 see the linked pages above

Configuration Details:

Option Name:store_id_children
Replaces:storeurl_rewrite_children
Requires:
Default Value:store_id_children 20 startup=0 idle=1 concurrency=0
Suggested Config:

	Specifies the maximum number of StoreID helper processes that Squid
	may spawn (numberofchildren) and several related options. Using
	too few of these helper processes (a.k.a. "helpers") creates request
	queues. Using too many helpers wastes your system resources.

	Usage: numberofchildren [option]...
	
	The startup= and idle= options allow some measure of skew in your
	tuning.
	
		startup=
	
	Sets a minimum of how many processes are to be spawned when Squid
	starts or reconfigures. When set to zero the first request will
	cause spawning of the first child process to handle it.
	
	Starting too few will cause an initial slowdown in traffic as Squid
	attempts to simultaneously spawn enough processes to cope.
	
		idle=
	
	Sets a minimum of how many processes Squid is to try and keep available
	at all times. When traffic begins to rise above what the existing
	processes can handle this many more will be spawned up to the maximum
	configured. A minimum setting of 1 is required.

		concurrency=

	The number of requests each storeID helper can handle in
	parallel. Defaults to 0 which indicates the helper
	is a old-style single threaded program.

	When this directive is set to a value >= 1 then the protocol
	used to communicate with the helper is modified to include
	an ID in front of the request/response. The ID from the request
	must be echoed back with the response to that request.

		queue-size=N

	Sets the maximum number of queued requests to N. A request is queued
	when no existing child can accept it due to concurrency limit and no
	new child can be started due to numberofchildren limit. The default
	maximum is 2*numberofchildren. If the queued requests exceed queue
	size and redirector_bypass configuration option is set, then
	redirector is bypassed. Otherwise, Squid is allowed to temporarily
	exceed the configured maximum, marking the affected helper as
	"overloaded". If the helper overload lasts more than 3 minutes, the
	action prescribed by the on-persistent-overload option applies.

		on-persistent-overload=action

	Specifies Squid reaction to a new helper request arriving when the helper
	has been overloaded for more that 3 minutes already. The number of queued
	requests determines whether the helper is overloaded (see the queue-size
	option).

	Two actions are supported:

	  die	Squid worker quits. This is the default behavior.

	  ERR	Squid treats the helper request as if it was
		immediately submitted, and the helper immediately
		replied with an ERR response. This action has no effect
		on the already queued and in-progress helper requests.

 

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