be8958552e
Add retry behavior on startup and point to RFC 5936 Signed-off-by: Miek Gieben <miek@miek.nl>
73 lines
1.8 KiB
Markdown
73 lines
1.8 KiB
Markdown
# secondary
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## Name
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*secondary* - enables serving a zone retrieved from a primary server.
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## Description
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With *secondary* you can transfer (via AXFR) a zone from another server. The retrieved zone is
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*not committed* to disk (a violation of the RFC). This means restarting CoreDNS will cause it to
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retrieve all secondary zones.
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If the primary server(s) don't respond when CoreDNS is starting up, the AXFR will be retried
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indefinitely every 10s.
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## Syntax
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~~~
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secondary [ZONES...]
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~~~
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* **ZONES** zones it should be authoritative for. If empty, the zones from the configuration block
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are used. Note that without a remote address to *get* the zone from, the above is not that useful.
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A working syntax would be:
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~~~
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secondary [zones...] {
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transfer from ADDRESS [ADDRESS...]
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}
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~~~
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* `transfer from` specifies from which **ADDRESS** to fetch the zone. It can be specified multiple
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times; if one does not work, another will be tried. Transferring this zone outwards again can be
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done by enabling the *transfer* plugin.
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When a zone is due to be refreshed (refresh timer fires) a random jitter of 5 seconds is applied,
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before fetching. In the case of retry this will be 2 seconds. If there are any errors during the
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transfer in, the transfer fails; this will be logged.
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## Examples
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Transfer `example.org` from 10.0.1.1, and if that fails try 10.1.2.1.
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~~~ corefile
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example.org {
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secondary {
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transfer from 10.0.1.1 10.1.2.1
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}
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}
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~~~
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Or re-export the retrieved zone to other secondaries.
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~~~ corefile
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example.net {
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secondary {
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transfer from 10.1.2.1
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}
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transfer {
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to *
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}
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}
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~~~
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## Bugs
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Only AXFR is supported and the retrieved zone is not committed to disk.
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## See Also
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See the *transfer* plugin to enable zone transfers _to_ other servers.
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And RFC 5936 detailing the AXFR protocol.
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