dops [DNS Operations]

dops manages DNS operations on a cloud provider to synchronize the needed hostname-target values(records) from multiple sources.

Note: dops is NOT a DNS server

Providers

A provider is a cloud service provider with supported DNS web service like DNS registration and routing. This is where the DNS records are operated. Currently, supported providers are:

1. aws - AWS Route53
2. cloudflare - Cloudflare
3. inmemory - Emulates a provider for testing

More providers can be individually added when required by implementing the provider.Provider{} interface methods.

Sources

A source provides the list of DNS records(endpoints) that must be created/synchronised with a suported provider.

Supported sources:

1. connector - This is a TCP connection source backed by Go native gob decoding. This is a super convenient approach for any other Go program to transmit DNS records via net.Listen("tcp", ":xxxx"). After the connection is established, dops reconciliation loop will query the listening source for endpoints periodically. This design makes dops pluggable with another internal service.

2. dummy - emulates a source by providing randomly generated endpoints for testing.

3. empty - An empty source provides no endpoint; a quick cleanup tool for testing.

More sources can be individually added when required by implementing the source.Source{} interface methods.

Ownership

Multiple instances of dops with different filters/parameteres can be operated on a specific or a set of hosted zones. To facilitate harmonious co-operation, for each endpoint dops injects a TXT record with ownership labels pertaining to the running instance that operates that set of records.

Unlike A type records, CNAME records cannot share hostname with any other type(A, TXT, SRV, etc.) To circumvent this limitation, TXT records are maintained with the user provided prefix. This is transparently handled, users need not fret.

For example:

A source endpoint with hostname try for domain dops2.toppr.systems of type A record will create two entries in the provider's DNS hosted zone. Note that the hostnames are same for both type of records.

pvsb.dops2.toppr.systems

Actual record -> try.dops2.toppr.systems 0 IN A 192.0.2.252

Ownership record -> try.dops2.toppr.systems 0 IN TXT \"origin=dops,dops/owner=test\"

However, the same endpoint of record type CNAME will have an ownership record with a different hostname with prefix.

pvsb.dops2.toppr.systems

Actual record -> try.dops2.toppr.systems 0 IN CNAME ip-10-1-0-80.ap-south-1.compute.internal

Ownership record -> prefix-try.dops2.toppr.systems 0 IN TXT \"origin=dops,dops/owner=test\"

It's not recommended to manually modify dops managed records on the cloud portal, it will leave records in an inconsistent state while synchronising.

CLI

dops takes parameters in effectively two forms - command flags and env variables. Both can be mixed. Parameters marked as required are mandatory.

More information is available with dops --help

$ dops --source=dummy \
--provider=aws \
--fqdn-template="dops2.toppr.systems" \
--txt-owner-id=test \
--aws-zone-type=private \
--aws-zones-cache-duration=2h \
--domain-filter="dops2.toppr.systems" \
--domain-filter="dops.toppr.systems" \
--log-format=json \
--log-level=info

INFO[0000] config: {DefaultTargets:[] Sources:[dummy] FQDNTemplate:dops2.toppr.systems PublishHostIP:false ConnectorSourceServer:localhost:9876 Provider:aws DomainFilter:[dops2.toppr.systems dops.toppr.systems] ExcludeDomains:[] RegexDomainFilter: RegexDomainExclusion: ZoneIDFilter:[] AWSZoneType:private AWSZoneTagFilter:[] AWSAssumeRole: AWSBatchChangeSize:1000 AWSBatchChangeInterval:1s AWSEvaluateTargetHealth:true AWSAPIRetries:3 AWSPreferCNAME:true AWSZoneCacheDuration:2h0m0s CloudflareProxied:false CloudflareZonesPerPage:50 InMemoryZones:[] Policy:sync Registry:txt TXTOwnerID:test TXTPrefix: TXTSuffix: Interval:1m0s MinEventSyncInterval:5s Once:false DryRun:false UpdateEvents:false LogFormat:json MetricsAddress::7979 LogLevel:info TXTCacheInterval:0s TXTWildcardReplacement: ManagedDNSRecordTypes:[A CNAME]}


{"level":"info","msg":"Applying provider record filter for domains: [dops2.toppr.systems. .dops2.toppr.systems. dops.toppr.systems. .dops.toppr.systems.]","time":"2022-01-28T16:26:05+05:30"}
{"level":"info","msg":"Desired change: CREATE dummy-ccod.dops2.toppr.systems A [Id: /hostedzone/Z055666939ELBYE3XXXXX]","time":"2022-01-28T16:26:05+05:30"}
{"level":"info","msg":"Desired change: CREATE dummy-ccod.dops2.toppr.systems TXT [Id: /hostedzone/Z055666939ELBYE3XXXXX]","time":"2022-01-28T16:26:05+05:30"}
{"level":"info","msg":"Desired change: CREATE dummy-cdzs.dops2.toppr.systems A [Id: /hostedzone/Z055666939ELBYE3XXXXX]","time":"2022-01-28T16:26:05+05:30"}
{"level":"info","msg":"Desired change: CREATE dummy-cdzs.dops2.toppr.systems TXT [Id: /hostedzone/Z055666939ELBYE3XXXXX]","time":"2022-01-28T16:26:05+05:30"}
{"level":"info","msg":"Desired change: CREATE dummy-gusp.dops2.toppr.systems A [Id: /hostedzone/Z055666939ELBYE3XXXXX]","time":"2022-01-28T16:26:05+05:30"}
{"level":"info","msg":"Desired change: CREATE dummy-gusp.dops2.toppr.systems TXT [Id: /hostedzone/Z055666939ELBYE3XXXXX]","time":"2022-01-28T16:26:05+05:30"}
{"level":"info","msg":"Desired change: CREATE dummy-gyac.dops2.toppr.systems A [Id: /hostedzone/Z055666939ELBYE3XXXXX]","time":"2022-01-28T16:26:05+05:30"}
{"level":"info","msg":"Desired change: CREATE dummy-gyac.dops2.toppr.systems TXT [Id: /hostedzone/Z055666939ELBYE3XXXXX]","time":"2022-01-28T16:26:05+05:30"}
{"level":"info","msg":"Desired change: CREATE dummy-rfig.dops2.toppr.systems A [Id: /hostedzone/Z055666939ELBYE3XXXXX]","time":"2022-01-28T16:26:05+05:30"}
{"level":"info","msg":"Desired change: CREATE dummy-rfig.dops2.toppr.systems TXT [Id: /hostedzone/Z055666939ELBYE3XXXXX]","time":"2022-01-28T16:26:05+05:30"}
{"level":"info","msg":"10 record(s) in zone dops2.toppr.systems. [Id: /hostedzone/Z055666939ELBYE3XXXXX] were successfully updated","time":"2022-01-28T16:26:06+05:30"}

Contribution

When teams start using dops, it's likely that needs of various other source (perhaps read endpoints from text file? json over http?) and providers will arise. More information about design and how-to contribute documents will be added when interest to contribute is shown in our engienering forum.