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require nodecount on setup #4

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Jun 3, 2017
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require nodecount on setup #4

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75a7682
require nodecount on setup
robertkowalski Jul 24, 2015
dd68945
use config:setineger/3
robertkowalski Jul 24, 2015
b107042
fix wording
robertkowalski Jul 24, 2015
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13 changes: 11 additions & 2 deletions src/setup.erl
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,11 @@ require_admins(undefined, {undefined, undefined}) ->
require_admins(_,_) ->
ok.

require_node_count(undefined) ->
throw({error, "Cluster setup requires node_count to be configured"});
require_node_count(_) ->
ok.

error_bind_address() ->
throw({error, "Cluster setup requires bind_addres != 127.0.0.1"}).

Expand Down Expand Up @@ -83,7 +88,8 @@ enable_cluster_http(Options) ->
{<<"username">>, couch_util:get_value(username, Options)},
{<<"password">>, couch_util:get_value(password, Options)},
{<<"bind_address">>, couch_util:get_value(bind_address, Options)},
{<<"port">>, couch_util:get_value(port, Options)}
{<<"port">>, couch_util:get_value(port, Options)},
{<<"node_count">>, couch_util:get_value(node_count, Options)}
]}),

Headers = [
Expand Down Expand Up @@ -134,6 +140,10 @@ enable_cluster_int(Options, no) ->
config:set("httpd", "bind_address", binary_to_list(NewBindAddress))
end,

NodeCount = couch_util:get_value(node_count, Options),
ok = require_node_count(NodeCount),
config:set_integer("cluster", "n", NodeCount),
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@b20n b20n Jul 24, 2015

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N should not be set to the number of nodes in the cluster; those parameters are largely orthogonal.

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@robertkowalski robertkowalski Jul 24, 2015

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@banjiewen can you explain to what we would have to set N instead?

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@robertkowalski robertkowalski Jul 24, 2015

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this is the issue we are trying to fix: https://issues.apache.org/jira/browse/COUCHDB-2594

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@b20n b20n Jul 24, 2015

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Bob's last comment on that ticket sounds right to me. I'd have N set to:

N = case NodeCount of
    1 -> 1;
    NC when NC >= 3 -> 3
end

Wherein bad cluster sizes (2, or < 1) are rejected (but I don't know what the project's stance on 2 node clusters is).

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@kxepal kxepal Jul 24, 2015

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@banjiewen @rnewson what the reasons stands behind magic number 3? Why it shouldn't be bigger? If it really shouldn't, why we allow user to configure it?

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@b20n b20n Jul 24, 2015

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I'm sure larger values haven't been extensively tested, but IIUC they should work fine. N should be odd, of course.

The parameter exists to allow users/operators to manage the fault tolerance of their system, or a database within it. It should be configurable, and 3 is a very good default - it allows ~unimpeded operation of the system when one copy of the data is unavailable. If a user is willing to pay more latency, CPU, and disk space for additional fault tolerance, they can increase it.


Port = proplists:get_value(port, Options),
case Port of
undefined ->
Expand All @@ -142,7 +152,6 @@ enable_cluster_int(Options, no) ->
config:set("httpd", "port", integer_to_list(Port))
end,
couch_log:notice("Enable Cluster: ~p~n", [Options]).
%cluster_state:set(enabled).

maybe_set_admin(Username, Password) ->
case couch_auth_cache:get_admin(Username) of
Expand Down
3 changes: 2 additions & 1 deletion src/setup_httpd.erl
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Expand Up @@ -58,7 +58,8 @@ handle_action("enable_cluster", Setup) ->
{port, <<"port">>},
{remote_node, <<"remote_node">>},
{remote_current_user, <<"remote_current_user">>},
{remote_current_password, <<"remote_current_password">>}
{remote_current_password, <<"remote_current_password">>},
{node_count, <<"node_count">>}
], Setup),
case setup:enable_cluster(Options) of
{error, cluster_enabled} ->
Expand Down
7 changes: 5 additions & 2 deletions test/t-frontend-setup.sh
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Expand Up @@ -16,10 +16,10 @@ HEADERS="-HContent-Type:application/json"
curl a:b@127.0.0.1:15986/_nodes/_all_docs

# Enable Cluster on node A
curl a:b@127.0.0.1:15984/_cluster_setup -d '{"action":"enable_cluster","username":"foo","password":"baz","bind_address":"0.0.0.0"}' $HEADERS
curl a:b@127.0.0.1:15984/_cluster_setup -d '{"action":"enable_cluster","username":"foo","password":"baz","bind_address":"0.0.0.0","node_count":2}' $HEADERS

# Enable Cluster on node B
curl a:b@127.0.0.1:15984/_cluster_setup -d '{"action":"enable_cluster","remote_node":"127.0.0.1","port":"25984","remote_current_user":"a","remote_current_password":"b","username":"foo","password":"baz","bind_address":"0.0.0.0"}' $HEADERS
curl a:b@127.0.0.1:15984/_cluster_setup -d '{"action":"enable_cluster","remote_node":"127.0.0.1","port":"25984","remote_current_user":"a","remote_current_password":"b","username":"foo","password":"baz","bind_address":"0.0.0.0","node_count":2}' $HEADERS

# Add node B on node A
curl a:b@127.0.0.1:15984/_cluster_setup -d '{"action":"add_node","username":"foo","password":"baz","host":"127.0.0.1","port":25984}' $HEADERS
Expand Down Expand Up @@ -57,4 +57,7 @@ curl a:b@127.0.0.1:25984/_replicator
curl a:b@127.0.0.1:25984/_metadata
curl a:b@127.0.0.1:25984/_global_changes

# Number of nodes is set to 2
curl a:b@127.0.0.1:25984/_node/node2@127.0.0.1/_config/cluster/n

echo "YAY ALL GOOD"
7 changes: 5 additions & 2 deletions test/t.sh
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Expand Up @@ -16,10 +16,10 @@ HEADERS="-HContent-Type:application/json"
curl a:b@127.0.0.1:15986/_nodes/_all_docs

# Enable Cluster on node A
curl a:b@127.0.0.1:15984/_cluster_setup -d '{"action":"enable_cluster","username":"foo","password":"baz","bind_address":"0.0.0.0"}' $HEADERS
curl a:b@127.0.0.1:15984/_cluster_setup -d '{"action":"enable_cluster","username":"foo","password":"baz","bind_address":"0.0.0.0","node_count":2}' $HEADERS

# Enable Cluster on node B
curl a:b@127.0.0.1:25984/_cluster_setup -d '{"action":"enable_cluster","username":"foo","password":"baz","bind_address":"0.0.0.0"}' $HEADERS
curl a:b@127.0.0.1:25984/_cluster_setup -d '{"action":"enable_cluster","username":"foo","password":"baz","bind_address":"0.0.0.0","node_count":2}' $HEADERS

# Add node B on node A
curl a:b@127.0.0.1:15984/_cluster_setup -d '{"action":"add_node","username":"foo","password":"baz","host":"127.0.0.1","port":25984}' $HEADERS
Expand Down Expand Up @@ -57,4 +57,7 @@ curl a:b@127.0.0.1:25984/_replicator
curl a:b@127.0.0.1:25984/_metadata
curl a:b@127.0.0.1:25984/_global_changes

# Number of nodes is set to 2
curl a:b@127.0.0.1:25984/_node/node2@127.0.0.1/_config/cluster/n

echo "YAY ALL GOOD"