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41 lines
1.6 KiB
ReStructuredText
41 lines
1.6 KiB
ReStructuredText
ScyllaDB Manager: connection to sshd server is slow or timing out
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===================================================================
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This troubleshooting guide describes what to do if you experience slow ScyllaDB
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Manager behavior or when connections to ScyllaDB nodes over SSH are timing out.
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Phenomenon
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^^^^^^^^^^
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This might affect users of the ScyllaDB Manager when determining REST API status
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of the managed clusters. ScyllaDB Manager Client might report certain nodes as
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being down even if they are accessible.
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Background
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^^^^^^^^^^
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ScyllaDB Manager manages the ScyllaDB nodes over the HTTP API. Communication
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between ScyllaDB Manager server and ScyllaDB nodes is encrypted by tunneling HTTP
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traffic over an SSH connection.
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Establishing an SSH tunnel requires that ScyllaDB nodes have a running sshd
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server and optionally the sshd server can be configured to do reverse DNS
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for resolving client IPs.
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When resolving takes a long time or it stalls for some reason then connections
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and interaction with the sshd server can be impaired.
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Solution
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^^^^^^^^
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There are two options for solving this.
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One option is to improve your DNS setup on the ScyllaDB node by changing to a
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better DNS resolver. It is recommended to use static nameserver IPs from
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`Cloudflare <https://www.cloudflare.com/learning/dns/what-is-1.1.1.1/>`_
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or `Google <https://developers.google.com/speed/public-dns/>`_.
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Another option is to disable reverse DNS usage for the sshd server. This can
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be done by navigating to the sshd configuration file (located in
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/etc/ssh/sshd_config on Unix based systems) and setting the UseDNS
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configuration option to off.
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