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I have found just one blog entry that claims that when using status=+H

BalancerMember http://1.2.3.4:1234 status=+H

"When the default service is back on-line mod_proxy_balancer will pick that up within about 60 seconds or so and revert back to forwarding all requests to it."

But I can't find any mention of this in the documentation (and if there is any way to affect the time period).

Can anyone provide some documentation that supports this claim?

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1 Answer 1

up vote 2 down vote accepted

It's mentioned numerous times in the Apache documentation for mod_proxy

Key=retry Default=60
Connection pool worker retry timeout in seconds. If the connection pool worker to the backend server is in the error state, Apache will not forward any requests to that server until the timeout expires. This enables to shut down the backend server for maintenance, and bring it back online later. A value of 0 means always retry workers in an error state with no timeout.

BalanceMember inherits all keys provided by ProxyPass, so you can use

#Retry balance members every 60 seconds
BalanceMember http://app1/ retry=60

However the status=+H implys a balance member will be a 'hot standby'. So with the config

BalanceMember http://app1/ retry=30
BalanceMember http://app1-backup/ retry=60 status=+H

When app1 goes down, the hot standby will be used instead. After 30 seconds Apache will retry with app1, if it fails it will switch back over to the hot standby. 5 seconds later, app1 comes back online, but Apache will still use app1-backup until the timeout has expired, then after another 30 seconds when Apache retrys the main server it will succeed. Under normal usage, app1-backup will never be used.

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