Squid configuration directive store_id_children

Available in: 4   3.5   3.4  

History:

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:

	The maximum number of StoreID helper processes to spawn. If you limit
	it too few Squid will have to wait for them to process a backlog of
	requests, slowing it down. If you allow too many they will use RAM
	and other system resources noticably.
	
	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. 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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