Change Details

Our Varnish config [current retries 503 responses a fixed number of times](https://github.com/wikimedia/operations-puppet/blob/30a155fcf9d279af360b586fd2573ac56c35e14f/modules/varnish/templates/vcl/wikimedia.vcl.erb#L385), between [1 (text, bits)](https://github.com/wikimedia/operations-puppet/blob/79fdeb017728a5ade491b50c870f00f84400e8ce/modules/role/manifests/cache/text.pp#L66) and [4 (Parsoid)](https://github.com/wikimedia/operations-puppet/blob/5593f10cba4a48ab5f72cf4d803521f88eaca94c/modules/role/manifests/cache/parsoid.pp#L36) times. To avoid exacerbating overload situations, we should only retry 503s if a `Retry-After` header signals that this is permissible.

Our Varnish config [current retries 503 responses a fixed number of times](https://github.com/wikimedia/operations-puppet/blob/30a155fcf9d279af360b586fd2573ac56c35e14f/modules/varnish/templates/vcl/wikimedia.vcl.erb#L385), between [1 (text)](https://github.com/wikimedia/operations-puppet/blob/79fdeb017728a5ade491b50c870f00f84400e8ce/modules/role/manifests/cache/text.pp#L66) and [4 (Parsoid,](https://github.com/wikimedia/operations-puppet/blob/5593f10cba4a48ab5f72cf4d803521f88eaca94c/modules/role/manifests/cache/parsoid.pp#L36)[bits](https://github.com/wikimedia/operations-puppet/blob/5593f10cba4a48ab5f72cf4d803521f88eaca94c/modules/role/manifests/cache/bits.pp#L67)) times. To avoid exacerbating overload situations, we should only retry 503s if a `Retry-After` header signals that this is permissible.

Our Varnish config [current retries 503 responses a fixed number of times](https://github.com/wikimedia/operations-puppet/blob/30a155fcf9d279af360b586fd2573ac56c35e14f/modules/varnish/templates/vcl/wikimedia.vcl.erb#L385), between [1 (text, bits)](https://github.com/wikimedia/operations-puppet/blob/79fdeb017728a5ade491b50c870f00f84400e8ce/modules/role/manifests/cache/text.pp#L66) and [4 (Parsoid)](https://github.com/wikimedia/operations-puppet/blob/5593f10cba4a48ab5f72cf4d803521f88eaca94c/modules/role/manifests/cache/parsoid.pp#L36)](https://github.com/wikimedia/operations-puppet/blob/79fdeb017728a5ade491b50c870f00f84400e8ce/modules/role/manifests/cache/text.pp#L66) and [4 (Parsoid,](https://github.com/wikimedia/operations-puppet/blob/5593f10cba4a48ab5f72cf4d803521f88eaca94c/modules/role/manifests/cache/parsoid.pp#L36)[bits](https://github.com/wikimedia/operations-puppet/blob/5593f10cba4a48ab5f72cf4d803521f88eaca94c/modules/role/manifests/cache/bits.pp#L67)) times. To avoid exacerbating overload situations, we should only retry 503s if a `Retry-After` header signals that this is permissible.