MySql is used here with remote network connections, and after a reboot of the server these connections started taking 20-30 seconds to connect causing timeouts. Connections used to be nearly instant. Adding skip-name-resolve fixes the delay as remote connections address the database by its IP address, however, this MySql server also hosts an email login database for an internal email server. The skip-name-resolve fix breaks all email logins from clients and servers. The email server is a Postfix/Dovecot stack and using IMAP RoundCube Server and Thunderbird clients. I cannot figure out where in the email stack that addresses MySql configuration needs to be changed. It seems the root of the problems would be a DNS issue, maybe an expired domain name in the configs somewhere. I spent hours looking and need some advice on tackling this. I'd rather solve the root DNS issue, if that's the problem - like track down an expired domain name or fault in the DNS addressing.

We are managing our SQL Always On listeners records in 2 active directory servers (they are syncing each other) and we came across an issue which we couldn't pinpoint the cause for.We are testing MSSQL failovers on our windows DB servers and after the failover we check the DNS manager to see that the IP for the relevant listener changed (our DB servers are on multiple subnets). In some cases (once every few failovers) we see that the listener record duplicates ,meaning we have 2 records for the same listener pointing to different DB servers and not 1 pointing to the primary DB as it should be. We have checked the availability group parameters which might affect this : PublishPTRRecords is set to true for all availability groups and for the cluster. HostRecordTTL is set to 15 seconds. RegisterAllProvidersIP is set to 0 to assure that only a single IP will be available for each listener. I would like to ask your opinion regarding possible causes for this issue or a way to monitor the DNS records change process which might allow me to debug . Thanks

Is there a best practice on what the owner should be for the DNS-record of the Always On Listener? At our location this is sometimes the cluster but sometimes it's the listener object itself so it's unclear for us which one should be best.

I have an onpremise SQL database server, to which, many applications connect to. Created CNAME record for the server and instructed users to change it in their app connection string too. Most of them will, but there will be some who don't, and will pose an issue. Therefor I wish to monitor the network if there is any app that's still try to connect to the SQL server via hostname, and not with the CNAME record. What is the best tool to monitor such traffic? -SQL profiler and extended event seems to have no knowledge about that information. -Wireshark can resolve IPs to DNS names, but not sure how it will know what connection string did the application use. -Monitor DNS queries on DNS servers maybe the most promising. All in all. What are the best tools to capture this information?

Lets say I am setting up AlwaysOn Availability Groups and following are the nodes: Primary 192.168.1.10 Secondary 192.168.1.11 I try to create a DNS entry for availability group listener called AvailabilityListener to which client applications will connect. My question is, which IP address shall I define for this listener? Will it be primary IP or secondary IP or some other machine IP where this listener will be running?

I have a MS SQL Server S hosting a MS SQL Server instance I. I would like another machine M to be able to connect to that instance remotely via the TCP port P. I created an alias A = S\I,P on both S and M using the C:\Windows\SysWOW64\cliconfg.exe tool. S and M can both use the alias A properly. If I wanted another machine M2 to be able to connect to that MS SQL Server instance too, I would need to create an alias on M2 like I did on machines S and M. Is there a way to do it in the DNS server (Microsoft DNS Manager)? I don't see how it could be done because basically: - I would need the DNS server to register the fact that A is an alias for S\I,P - and when a client machine C on the network uses A, I would need the DNS server to "resolve" that alias for C. If it cannot be done using a DNS server, is there a way to do it in a centralized way (that is to say: having some sort of service on the network that "translates" A into S\I,P when a client machine asks for it) ?

We run two SQL server at primary site in AlwaysOn High Availability Group on subnet 10.10.0.0/24 A third SQL server is running on secondary site in a different subnet 10.10.1.0/24 We have had third server as part of a cluster for some time until faced issue from this question . It was then decided to remove the third server from the cluster and all of the resources that it presented. Right off the bat DNS registration for 10.10.1.0/24 subnet had to be removed, but it is now being registered every 24 hours. Whenever it is registered, all clients start to use and fail to connect. This occurred even when all three servers were running and syncing properly, and some clients would just drop live connection just to connect to ip on a different subnet which would fail. Where can I find this 10.10.1.0/24 subet IP address that is still being registered with DNS server? SQL Management studio group listener lists only one IP in correct subnet. Fail-over cluster lists single network IP address too. The third server has since been powered off, but it is irrelevant Get-ClusterGroup SQLHA | Get-ClusterResource | Where-Object {$_ .ResourceType -match "Network Name*"} | Update-ClusterNetworkNameResource -Verbose After running this command DNS server is updated, but yet again two records are created.

**Overview** We're running a sharded MongoDB cluster, using community edition v4.4. The primary mongod in one of the data shards ('shardX' for short) has hit active sessions in cache limit of 1M and new sessions cannot be connected. The secondary mongod in 'shardX' also have a high number of stale config issues that caused all read requests blocked, the mitigation was to hide the secondaries. **Current Situation** Right now all the secondary mongod in 'shardX' are hidden. Only the primary mongod is serving the traffic. We meet two problems. Unhiding the secondary mongod or move chunk will cause secondary mongod cannot find mongo config servers, get stale config errors, and bring the site down. Stale config log: "ok":0,"errMsg":"epoch mismatch detected for collection-xxx","errName":"StaleConfig","errCode":13388, Cannot find config servers log: {"t":{"$date":"2023-12-22T22:17:08.689-08:00"},"s":"I", "c":"SH_REFR", "id":24100, "ctx":"ShardServerCatalogCacheLoader-19","msg":"Error refreshing cached database entry","attr":{"db":"sweeper","durationMillis":20000,"error":"FailedToSatisfyReadPreference: Could not find host matching read preference { mode: \"nearest\" } for set main-config-server"}} Once we unhide a secondary mongod and let it serve traffic, this secondary mongod cannot find mongo config servers, and thus throw stale config errors. All the queries (including scatter and gather queries) hit this secondary mongod will fail. As a result, the site is down. cached active sessions in primary Mongod reach the upper limit: 1 million, and cannot accept any new session. To connect to this shard, we need to connect to it by disableImplicitSessions: mongosh primary-host-of-shardX --quiet --tls --tlsCertificateKeyFile /etc/mongo_secrets/mongocleaner_keystore.pem --tlsCAFile /etc/mongo_secrets/root_ca.crt --authenticationMechanism 'MONGODB-X509' --authenticationDatabase '$external' --disableImplicitSessions All the connections without disabling implicit sessions are rejected. **Further Plan and Help** Since this is a critical production system, we're very concerned if stepDown the primary or restart primary node would cause the whole data shard get offline (e.g. not able to connect config server would result in election failures, etc). Has anyone meet such issues before? Does anyone have any comments or advice for us to isolate the issue or on the next steps? Any comments/advice are much appreciated! **Solutions We tried** The solutions we have tried: - Add 2 new replicas to the 'shardX' shard. - Rolling restart all the mongos. - Restart all the config servers. - Add 2 new mongo config servers. - Remove the backup node for 'shardX' shard - Movechunk - Kill all sessions for all the replicas in the topeka shard. - Update outdated config server address in admin.system.version on the primary instance But none of the above seemed to work. **Supplementary Info** when looking at the mongod.log of the primary mongod, we found many warnings: {"t":{"$date":"2023-12-27T19:07:09.352-08:00"},"s":"W", "c":"NETWORK", "id":23019, "ctx":"ReplicaSetMonitor-TaskExecutor","msg":"DNS resolution while connecting to peer was slow","attr":{"peer":"hostname-of-shardY:27017","durationMillis":563392569}} we verified on the primary node of 'shardX': DNS service should be OK -- by using nslookup and dig of 'hostname-of-shardY' and 'hostname-of-main-config-server'; AND We can do mongosh to connect to 'shardY' and 'main-config-server'.

After SQL Server 2019 Availability Group failover, I need to wait half hour to connect database by available listener ip from client. There are the following servers in this case: - node1, node2, AD-server (same subnet) - client (different subnet) - node1 and node2 are always on nodes which uses AD user as login The case happens when failover - node1 can connect to the database by available listener ip - node2 can connect to the database by available listener ip - AD-server can connect to the database by available listener ip - client can't connect to the database by available listener ip (also can't telnet) After half hour, client can connect database by available listener ip (also can telnet) I suspect the case is caused by DNS. Anyone have the same experience? There are some solution I tested but didn't solve the problem: - I tested MultiSubnetFailover=True and RegisterAllProvidersIP=0. - Recreate dna A record for both the available listener and cluster with “Allow any authenticated user to update DNS record with the same owner name". - https://www.pythian.com/blog/availability-group-delay-with-listener-connectivity-after-failover

I'm not really sure if this is the right place to post this but I happened across a peculiar behaviour yesterday. Historically, when debugging locally, our application's first connection to a given database (foo.local) has taken quite a long time (i.e. ~5s). I discovered yesterday that changing the Hosts file from this:

127.0.0.1 localhost
127.0.0.1 foo.local

to

127.0.0.1 localhost foo.local

Has completely removed this delay - now our application initialises almost instantly. The issue appears to have been some failed DNS lookup, but I can't really figure out exactly what was happening. Was hoping someone could shed some light on this. I know that postgres has log_hostname which (I believe) tries to perform a reverse lookup to identify the hostname, and to my knowledge this is not supported in the Hosts file. However this connection delay occurred regardless of whether log_hostname was on or off. ¯\_(ツ)_/¯ Not an urgent question since the issue has more or less been resolved, but my curiosity has the better of me. If anyone has any ideas I'd be very appreciative! Extra info:
Postgres: PostgreSQL 14.6 on aarch64-apple-darwin20.6.0, compiled by Apple clang version 12.0.5 (clang-1205.0.22.9), 64-bit
Npgsql: 6.0.8 (but also reproduced in 7.0.6)
Platform: Mac Sonoma 14.1.1

I have 2 node setup 10.1.0.7 - mongodb-1.com (primary) 10.1.0.8 - mongodb-2.com (secondary) here is my mongod.conf net: port: 27017 bindIp: 0.0.0.0 tls: mode: allowTLS certificateKeyFile: /etc/mongodb/certificates/mongodb.pem security: authorization: enabled keyFile: /home/dbuser/repset replication: replSetName: "repset" here is my rs.conf() { _id: 'repset', version: 4, term: 3, members: [ { _id: 0, host: '10.1.0.7:27017', arbiterOnly: false, buildIndexes: true, hidden: false, priority: 1, tags: {}, secondaryDelaySecs: Long("0"), votes: 1 }, { _id: 1, host: '10.1.0.8:27017', arbiterOnly: false, buildIndexes: true, hidden: false, priority: 1, tags: {}, secondaryDelaySecs: Long("0"), votes: 1 } ], protocolVersion: Long("1"), writeConcernMajorityJournalDefault: true, settings: { chainingAllowed: true, heartbeatIntervalMillis: 2000, heartbeatTimeoutSecs: 10, electionTimeoutMillis: 10000, catchUpTimeoutMillis: -1, catchUpTakeoverDelayMillis: 30000, getLastErrorModes: {}, getLastErrorDefaults: { w: 1, wtimeout: 0 }, replicaSetId: ObjectId("641aebeb4623f6fd0e700cf2") } } Now my proposed setup would be there are 2 application servers that will connect to this replica set. 1 is via private IP and the other is via DNS name. Now when I connect via private IP. it is working fine. I cant do the same when connecting via DNS name. is that possible? I am connecting to this via this script below (via Private IP that's working) mongodb://username:password@10.1.0.7:27017,10.1.0.8:27017/?authSource=admin&replicaSet=repset The script below is the one that could not connect (via DNS) mongodb://username:password@mongodb-1.com:27017,mongodb-2.com:27017/?authSource=admin&replicaSet=repset UPDATE: I do not know why this works but when I try to add each domain name as replicaset members. rs.add('mongodb-1.com:27017') rs.add('mongodb-2.com:27017') I am now able to connect publicly via this command mongodb://username:password@mongodb-1.com:27017,mongodb-2.com:27017/?authSource=admin&replicaSet=repset

We have always on availability group that spans across different data centers. Our network team has decommissioned some DNS servers and those servers will need to be updated with the active ones on all the nodes that is on the availability group. My question is whether is there any thing to watch out , all the nodes are set to RegisterAllProvidersIP 0.

I have a site running on Amazon EC2 , which runs fast and contains some reasonably complex MySQL queries. Part of that site is an API which serves out data to another site. These queries are very simple (one is literally returning one row from a table containing only that row). Making these API calls from the external domain results in a 10-20 second delay. The data always returns fine, no errors are thrown. Nothing is shown in the logs. Running any of these queries locally in PHPMyAdmin , they complete in around 0.007 seconds . CPU load is 20%-30%. RAM usage is about 60%. My problem is similar to: This I've added 'skip_name_resolve' to my my.cnf. This made no difference. There is a lot of talk about MySQL and DNS , but the docs around that didn't really help me. This seems like a problem with a simple solution , but I cannot work out what it is. **EDIT1.** To clarify , my MySQL queries are very very basic. One of them is literally just SELECT * FROM aboutPage Where aboutPage contains 1 row and 5 columns of tiny data. This runs lightning quick as expected in PHPMyAdmin locally , but has a slow load when accessed remotely. The main app that runs the API also runs fast . Its literally just when trying to access data from another IP/DNS that its slow.

**Questions**: how can I get my availability group to be registered as ag-ewgtest.sql.company.com given that my server thinks of itself as server.company.com. **Setup:** my SQL Server 2012 availability group is on multiple subnets, similar to what's described at in this MSDN blog article . When I go into Failover Cluster Manager, it shows that name resolution is not yet available: I then right-click "Name: ag-ewgtest" and choose properties. I check off "Publish PTR records" and it shows me that the full name is ag-ewgtest.company.com. The problem I have is that I'm only being allowed to update the DNS zone sql.company.com. If I change the DNS name to be ag-ewgtest.sql.company.com then the full name becomes ag-ewgtest.sql.company.com.company.com. I've tried updating my NIC as: But hasn't made a difference. How can I change the subdomain that my availability group tries to register itself in?

I'm wondering if anyone knows if there is a way to return the name that was used to connect to the SQL server rather than the actual server's name. For instance I typically connect to the server via a DNS CName. But if I run this .. select @@SERVERNAME ... I get the actual server name. I'm looking to find a way to get the CName with which I connected if it is even possible. Thoughts?

Setup: Windows server 2016 standard edition. SQL server 2016 standard edition. 2 nodes configured in a cluster without witness quorum. all member of the same Active Directory domain. 1 Availability group for 1 Database only. 1 listener. Creation went well, and any manual SQL or Cluster fail-over are working properly. - dns domain: mydom.local - Node1 machine Name: Mynode1 - Node2 machine Name: Mynode2 - Cluster name: mycluster - Listener name: mySQLlistener - Availability Group: MySQLAG But since then I have regularly this error message in my Cluster logs: Source: Microsoft-Windows-FailoverClustering Event ID: 1257

Cluster network name resource failed registration of one or more associated DNS names(s) because the access to update the secure DNS Zone was denied.

Cluster Network name: 'MySQLAG_mySQLlistener'
DNS Zone: 'mydom.local'

Ensure that cluster name object (CNO) is granted permissions to the Secure DNS Zone.

I found this ressource and this ressource which propose to recreate the CNO DNS record, but in the error message it is not the CNO for which it raise an error it is a Network name I don't use at all… Built with the Availability Group + ListenerName. Which is even more strange is that this network name is created with an "_" which is not "legal" for host names as per my understanding . so I'm wondering if I'm not having another issue… Any idea why it raise this error would be much appreciated.

Somehow on the same DEV server we have two Linked Servers to the same PROD server. While that, in and of itself, is not an issue; we have noted something we can't explain and we wonder of anyone else has experienced something similar. One of the Linked Servers is named using the actual machine name (ProductionSQLServerData) and the second is named using the DNS alias (ProdData) for that machine. In a command window from any machine both names ping to the same IP address. We have checked the source and the target machines and there are no entries in the host files that would misdirect the queries. We are stumped and wonder ir anyone else has experienced this type of behavior and was able to track down the reason for it. Thanks in advance for any response.

A connection string for SQL Server can contain MultiSubnetFailover=true, to handle multiple DNS A records, letting the client try to connect to every IP address of a domain (or subdomain) name, to access the current master (of Always On availability groups). Does this work with other DBMSes, like MySQL? If not, is there an equivalent?

When a DBMS fails over after a failure, if it fails over to a server in a different and unrelated data center, then the IP address of the subdomain name of that database will need to be changed in that name's DNS server, and due to DNS propagation delays, it could be days before all the DNS servers of the world have the IP address for the new master, during which time some clients would still be trying to access to old master. What can be done to deal with this, other than changing the client software to fetch the IP address of the master from somewhere, or is that the only option? Thanks.

I have a fail-over cluster set between two Windows Server 2016 machines, and I'm seeing errors regarding the DNS record, both for the cluster itself and for any listener I try to add in SQL high availability. > Cluster network name resource 'Cluster Name' failed registration of one or more associated DNS name(s) for the following reason: DNS server failure. > Ensure that the network adapters associated with dependent IP address resources are configured with at least one accessible DNS server. I've looked through this link and I do see the 8.8.8.8 DNS on my machines, after the records for the domain DNS - these DNS settings are automatically pushed from our DC and I'm not sure I can change them. Has anyone experienced this? Is there another solution?