Querying Sequins

Sequins has a single interface for fetching values, HTTP GET:

$ http localhost:9599/mydata/<key>
HTTP/1.1 200 OK
Accept-Ranges: bytes
Content-Length: 7
Date: Mon, 01 Aug 2016 11:57:53 GMT
Last-Modified: Mon, 01 Aug 2016 11:56:27 GMT
X-Sequins-Version: version0


For this reason, Sequins has no client library; you can use whatever HTTP client is available in your language.

Response and Request Headers

Sequins supports a couple advanced HTTP features and customizations:

  • Last-Modified is set to the time that the database was last updated or created.

  • Content-Length is set on responses, and you should ensure that your HTTP client verifies that the response body is the correct length.

  • X-Sequins-Version is set on responses, and holds the current version of the database.

  • If the request was proxied to a peer in a distributed cluster, 'X-Sequins-Proxied-to' will hold the hostname of the peer.

Response Codes

Sequins will sometimes return non-200 response codes:

  • 400 Bad Request: This is returned for requests with an HTTP method other than GET, and for requests with only a single path component (and therefore no key), like GET /foo.

  • 404 Not Found: This indicates that either the key or database does not exist. If you need to differentiate, check for the presence of an X-Sequins-Version header; if one is set, then you have reached a valid database, but the key is not present in it.

  • 502 Bad Gateway: This indicates that the node attempted to proxy the request to a peer in a distributed cluster, but that no peers were available for the given partition. This could be the case if the cluster is partially down.

  • 504 Gateway Timeout: Like a 502, this indicates that the node attempted to proxy the request to a peer or peers in a distributed cluster, but that all peers timed out.

If sequins responds with an HTTP status code not listed here, please file an issue.

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