Queueing requestors with an external api #34
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| take_member_from_pool_queued(Pool0 = #pool{queue_max = QMax, queued_requestors = Requestors}, CPid, From, Timeout) -> | ||
| case {take_member_from_pool(Pool0, CPid), queue:len(Requestors)} of | ||
| {{error_no_members, Pool1}, QMax} -> | ||
| {error_no_members, Pool1}; |
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@seth In a better spot for review. Bookkeeping extracted to helpers, new metrics. |
oferrigni
changed the title
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I think I found the dialyzer issue. Fixes are on sf/queueing branch. I mixed in a bunch of whitespace and formatting changes and some variable name refactor. That was messy of me :( The core of the dialyzer issue was that |
| %% @doc Obtain exclusive access to a member from 'PoolName'. | ||
| %% | ||
| %% If no free members are available, reply is deferred for up to | ||
| %% 5 seconds. During this window, if accept member is called |
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Docs say 5 seconds, but timeout is passed in as an arg and I can't find where it defaults to 5. Is this just an old comment?
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Doc is old, will fix. Timeout is specified by the consumer. A timeout of zero requires a member to be immediately free.
| gen_server:call(PoolName, take_member, infinity). | ||
| gen_server:call(PoolName, {take_member, 0}, infinity). | ||
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| %% @doc Obtain exclusive access to a member from 'PoolName'. |
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Take_member now supports request queueing! This feature allows for consumers to specify a timeout during which a pool member may be returned to a caller. A timeout of zero means that a member or error will be immediately returned. Otherwise, take_member will defer replying to the consumer, setting a timer to the duration of the timeout. When the timer pops, error_no_members will be sent to the consumer. If during the timeout a new member is returned to the pool, the requestor queue will be popped and that requestor will receive the the member.
Queueing requestors with an external api
Take member queuing:
There is a new options to configure a pool:
queue_max: Maximum depth of the requestor queue before returning error_no_members
Semantics are as follows
pooler:take_member/2 makes a blocking request to pooler. The second argument is a timeout after which, the pool will reply with error_no_members. If queue_max has been reached, error_no_members will be returned immediately.
take_member/1 is now an alias to take_member_queued/2 with the timeout set to zero