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Unexpected cluster state for single node config #2557

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gesellix opened this issue Feb 15, 2020 · 7 comments · Fixed by #2581
Closed

Unexpected cluster state for single node config #2557

gesellix opened this issue Feb 15, 2020 · 7 comments · Fixed by #2581
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api beginner-friendly bug need more info patches-welcome

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@gesellix
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gesellix commented Feb 15, 2020 •
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Description

With CouchDB 3.x (#2296) we have the option to setup a node as "single node" via config setting. I expected this to have the same effect like using the Fauxton cluster setup UI from CouchDB 2.x.

Using the new config setting we get the following cluster state at /_cluster_setup:

{"state":"cluster_finished"}

When using the Fauxton based single node setup, the /_cluster_setup endpoint returns:

{"state":"single_node_enabled"}

Steps to Reproduce

git clone https://github.com/apache/couchdb-docker
cd couchdb-docker/
echo -e "\n[couchdb]\nsingle_node = true\n" >> dev/local.ini 
docker build -t couchdb:3 dev
docker run --rm -it --env COUCHDB_USER=admin --env COUCHDB_PASSWORD=password -p 5984:5984 couchdb:3
curl --user admin:password -X GET "https://localhost:5984/_cluster_setup"

Expected Behaviour

GET /_cluster_setup should return single_node_enabled when the new couchdb.single_node=true setting has been used.

Your Environment

  • CouchDB version used: CouchDB/3.0.0-8748310 (Erlang OTP/21)
  • Operating system and version: Docker image based on docker-couchdb (docker build -t couchdb:3 dev)
@janl
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janl commented Feb 19, 2020

Good find! Agreed that this is a little confusing. CouchDB internals don’t really care about cluster vs. single node. A single node just happens to be a cluster of one, hence the confusion. The introduction of the new setting requires one more clause in this function:

couchdb/src/setup/src/setup_httpd.erl

Lines 30 to 54 in 3f64ef2

handle_setup_req(#httpd{method='GET'}=Req) ->
ok = chttpd:verify_is_server_admin(Req),
Dbs = chttpd:qs_json_value(Req, "ensure_dbs_exist", setup:cluster_system_dbs()),
couch_log:notice("Dbs: ~p~n", [Dbs]),
case erlang:list_to_integer(config:get("cluster", "n", undefined)) of
1 ->
case setup:is_single_node_enabled(Dbs) of
false ->
chttpd:send_json(Req, 200, {[{state, single_node_disabled}]});
true ->
chttpd:send_json(Req, 200, {[{state, single_node_enabled}]})
end;
_ ->
case setup:is_cluster_enabled() of
false ->
chttpd:send_json(Req, 200, {[{state, cluster_disabled}]});
true ->
case setup:has_cluster_system_dbs(Dbs) of
false ->
chttpd:send_json(Req, 200, {[{state, cluster_enabled}]});
true ->
chttpd:send_json(Req, 200, {[{state, cluster_finished}]})
end
end
end;

It should be easy enough to add, using config:get_boolean() like here

couchdb/src/setup/src/setup_sup.erl

Line 38 in 3f64ef2

case config:get_boolean("couchdb", "single_node", false) of

@gesellix wanna try a PR?

@gesellix
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wanna try a PR?

Oh yes, the code pointers help a lot. I'll try!

This was referenced Feb 19, 2020
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@gesellix
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Fixed with #2574 - thx @janl!

@gesellix gesellix reopened this Feb 19, 2020
@gesellix
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Not sure if #2574 fixes this issue.

@janl can you confirm that is_single_node_enabled will be called in case of a single_node-configured instance?

I think that it won't be called, because GET /_node/_local/_config yields cluster.n = 3 for me. is_single_node_enabled will only be called in case of cluster.n = 1.

@janl
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janl commented Feb 19, 2020

Ah shoot, you're right! Cc @wohali

This was referenced Feb 19, 2020
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@janl
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janl commented Feb 19, 2020

Thanks @gesellix

@gesellix
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🙏 you're welcome

@janl janl mentioned this issue Feb 19, 2020
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