CouchDB 1.6.1 <--> 3.1.2 replication

0. Define environment variables to hold dummy user/pass and remote host name
$ USERPASS=cmst1:passwd
$ REMOTEHOST=alanblah.blah.ch

1. Checking status of remote CouchDB (running with Erlang R16B03)
$ curl -ks --cert $X509_USER_CERT --key $X509_USER_KEY "https://$REMOTEHOST/couchdb/"
{"couchdb":"Welcome","uuid":"50f495ef9a2090ec6dcb8f1543cab70d","version":"1.6.1","vendor":{"version":"1.6.1","name":"The Apache Software Foundation"}}

2. Checking status of local CouchDB (running with Erlang 22.3.4.19)
$ curl http://localhost:5984/
{"couchdb":"Welcome","version":"3.1.2","git_sha":"572b68e72","uuid":"652fb71bc6c32121e0752325a4973eb3","features":["access-ready","partitioned","pluggable-storage-engines","reshard","scheduler"],"vendor":{"name":"The Apache Software Foundation"}}

2.a. and documents in the _replicator db
$ curl http://$USERPASS@localhost:5984/_replicator/_all_docs
{"total_rows":1,"offset":0,"rows":[
{"id":"_design/_replicator","key":"_design/_replicator","value":{"rev":"1-85a961d0d9b235b7b4f07baed1a38fda"}}
]}

2.b. and output of _scheduler/docs API
curl http://$USERPASS@localhost:5984/_scheduler/docs
{"total_rows":0,"offset":0,"docs":[

]}

3. Now checking source and target database
$ curl -ks --cert $X509_USER_CERT --key $X509_USER_KEY "https://$REMOTEHOST/couchdb/workqueue/_all_docs"
{"total_rows":2,"offset":0,"rows":[
{"id":"_design/WorkQueue","key":"_design/WorkQueue","value":{"rev":"1-cecd66584cf99f7b7e536f42b9c75d09"}},
{"id":"task_activity","key":"task_activity","value":{"rev":"4-3975ecf173f7f5b3776ccc2df2fbb4c8"}}
]}

$ curl http://$USERPASS@localhost:5984/workqueue_inbox/_all_docs
{"total_rows":1,"offset":0,"rows":[
{"id":"_design/WorkQueue","key":"_design/WorkQueue","value":{"rev":"1-46bfe3e5277b1eaa409511fb80ce16fd"}}
]}

4. Setting up a continuous and permanent replication:
$ curl -X POST http://$USERPASS@localhost:5984/_replicator -d '{"source":"http://$USERPASS@localhost:5984/workqueue_inbox/", "target":"https://$REMOTEHOST/couchdb/workqueue/", "continuous":true}' -H "Content-Type: application/json"
{"ok":true,"id":"5dfd894db86cbb4a52913705f2000aed","rev":"1-95994b3bd17dff6b8748af0cb0e9b7ea"}

5. Checking replication status
$ curl http://$USERPASS@localhost:5984/_replicator/5dfd894db86cbb4a52913705f2000aed
{"_id":"5dfd894db86cbb4a52913705f2000aed","_rev":"2-ccad0c419045c032c447cb3b64a8663f","source":"http://****:****@localhost:5984/workqueue_inbox/","target":"https://$REMOTEHOST/couchdb/workqueue/","continuous":true,"owner":"cmst1","_replication_state":"failed","_replication_state_time":"2022-02-26T20:57:58Z","_replication_state_reason":"{error,undef}"}

$ curl http://$USERPASS@localhost:5984/_scheduler/docs
{"total_rows":1,"offset":0,"docs":[
{"database":"_replicator","doc_id":"5dfd894db86cbb4a52913705f2000aed","id":null,"source":"http://cmst1:*****@localhost:5984/workqueue_inbox/","target":null,"state":"failed","error_count":1,"info":{"error":"{error,undef}"},"start_time":"2022-02-26T20:57:58Z","last_updated":"2022-02-26T20:57:58Z"}
]}

6. Create a dummy document in the source database
$ curl -X PUT http://$USERPASS@localhost:5984/workqueue_inbox/dummy_doc01 -d '{"name":"Alan", "age":"1"}' -H "Content-Type: application/json"
{"ok":true,"id":"dummy_doc01","rev":"1-51ba96b578089e025eaf6c3c97ff5ca1"}

7. Check again the source and remote databases
$ curl -ks --cert $X509_USER_CERT --key $X509_USER_KEY "https://$REMOTEHOST/couchdb/workqueue/_all_docs"
{"total_rows":2,"offset":0,"rows":[
{"id":"_design/WorkQueue","key":"_design/WorkQueue","value":{"rev":"1-cecd66584cf99f7b7e536f42b9c75d09"}},
{"id":"task_activity","key":"task_activity","value":{"rev":"9-b308c957d8b168a79367ae5777305cac"}}
]}

$ curl http://$USERPASS@localhost:5984/workqueue_inbox/_all_docs
{"total_rows":2,"offset":0,"rows":[
{"id":"_design/WorkQueue","key":"_design/WorkQueue","value":{"rev":"1-46bfe3e5277b1eaa409511fb80ce16fd"}},
{"id":"dummy_doc01","key":"dummy_doc01","value":{"rev":"1-51ba96b578089e025eaf6c3c97ff5ca1"}}
]}