The sum of all three values is 100, so will be used 60% of the time. The first three records share a priority of 10, so the weight field's value will be used by clients to determine which server (host and port combination) to contact. TTL class SRV priority weight port target. In the following example, both the priority and weight fields are used to provide a combination of load balancing and backup service. If a service has multiple SRV records with the same priority value, clients should load balance them in proportion to the values of their weight fields. Clients should use the SRV records with the lowest-numbered priority value first, and fall back to records of higher value if the connection fails. The priority field determines the precedence of use of the record's data. Provisioning for high service availability Pointing to a hostname with a CNAME record is not a valid configuration. The priority given here is 0, and the weight is 5.Īs in MX records, the target in SRV records must point to hostname with an address record ( A or AAAA record). This points to a server named listening on TCP port 5060 for Session Initiation Protocol (SIP) protocol services. target: the canonical hostname of the machine providing the service, ending in a dot.Īn example SRV record in textual form that might be found in a zone file might be the following:.port: the TCP or UDP port on which the service is to be found.weight: A relative weight for records with the same priority, higher value means higher chance of getting picked.priority: the priority of the target host, lower value means more preferred.SRV: Type of Record (this is always SRV).IN: standard DNS class field (this is always IN).name: the domain name for which this record is valid, ending in a dot.proto: the transport protocol of the desired service this is usually either TCP or UDP.service: the symbolic name of the desired service.Some Internet protocols such as the Session Initiation Protocol (SIP) and the Extensible Messaging and Presence Protocol (XMPP) often require SRV support by network elements. It is defined in RFC 2782, and its type code is 33. So driver queries SRV records for the host name in connection string and then TXT record and combines them to connect to cluster.Type of resource record in the Domain Name SystemĪ Service record ( SRV record) is a specification of data in the Domain Name System defining the location, i.e., the hostname and port number, of servers for specified services. "authSource=admin&replicaSet=atlas-uovfn7-shard-0" Important thing is to add _mongodb._tcp as prefix. You can see the svr hostname field have 3 different sever names which are part of the replica set. Instead, a single SRV record identifies all the nodes associated with the cluster (and their port numbers) and an associated TXT record defines the options for the URI.Īll the above answers specify SRV and TXT records in context of mongo conn string correctly!! Just want to add if we need to see these SRV or TXT records we can use below commands(Windws cmd i have used):įor SRV records: nslookup -q=SRV _mongodb._.netĪbove command will give you result like Non-authoritative answer: The use of SRV records eliminates the requirement for every client to pass in a complete set of state information for the cluster. With the 3.4 or earlier driver, we have to specify all the options on the command line using the MongoDB URI syntax. We also have to specify the ssl and replicaSet options Note that without the SRV record configuration we must list several nodes (in the case of Atlas we always include all the cluster members, though this is not required). You can see an example of this URL on a 2.2.12 or later connection string This allows a client to connect to a replica set even if one of the nodes that the client specifies is unavailable You will recall from using replica sets with MongoDB that the client must specify at least one replica set member (and may specify several of them) when connecting. In MongoDB 3.6 is introduced the concept of a seed list that is specified using DNS records, specifically SRV and TXT records.
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