Squid configuration directive store_id_children
- 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
|Default Value:||store_id_children 20 startup=0 idle=1 concurrency=0|
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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