snap file rework by @sklassen (#27)

snap improvements;

* Split the DATA directory into log and etc; added vm.args; coded snap configuration hook for name and setcookie; bumped version number to 2.2; and added a description how to install and set options

* Moved snap.ini into local.d; configure now can manage both vm.args and (small subset of) local.d/*.ini; snap does not touch local.ini, so as not to interfer with web configuration interface; Reverted root README.md and added snap/README.md

* Removed the log directory as default writer=stderr is best

* Removed unrequired home plug in for hooks

* Empty rather than Nil plug-ins

* Renamed common subdirectory 2.x

* Removed hooks from snacraft.yaml: no special plugs needed

* Update README.md

* Single data directory suffices

* Unified data and index directory

* Removed user name from snap name

* Expanded the Snap Configuration

* Removed erlang from snapcraft; snap now 70M smaller

* prepare and build have been replaced by single override-build

* Added back explicit essential packages; excluded share/doc

* Added a HOWTO file

* Tidy up the md

* Added new line

.gitignore

@@ -16,7 +16,7 @@ repo/dists
 repo/pool
 pkgs/
 couchdb/
-couchdb_2.0_amd64.snap
+couchdb_*.snap
 parts/
 prime/
 snap/.snapcraft/

README.md

@@ -55,3 +55,4 @@ with issue reporting or contributing to the upkeep of this project.
 [1]: http://mail-archives.apache.org/mod_mbox/couchdb-user/
 [2]: http://mail-archives.apache.org/mod_mbox/couchdb-dev/
 [3]: https://github.com/apache/couchdb/blob/master/CONTRIBUTING.md
+

snap/HOWTO.md

@@ -0,0 +1,109 @@
+# HOW TO install a cluster using snap
+
+# Create three machines
+
+In the instruction below, we are going to set up a three -- the miniumn number needed to gain performace improvement -- Couch cluster database. In this potted example we will be using LXD.
+
+We launch a new container and install couchdb on one machine
+
+1. localhost> `lxc launch ubuntu:18.04 couchdb-c1`
+1. localhost> `lxc exec couchdb-c1 bash`
+1. couchdb-c1> `apt update`
+1. couchdb-c1> `snap install couchdb`
+1. couchdb-c1> `logout`
+
+Here we use LXD copy function to speed up the test
+```
+lxc copy couchdb-c1 couchdb-c2
+lxc copy couchdb-c1 couchdb-c3
+lxc copy couchdb-c1 cdb-backup
+lxc start couchdb-c2
+lxc start couchdb-c3
+lxc start cdb-backup
+```
+
+# Configure CouchDB (using the snap tool)
+
+We are going to need the IP addresses. You can find them here.
+```
+lxc list
+```
+
+Now lets use the snap configuration tool to set the configuration files.
+```
+lxc exec couchdb-c1 snap set couchdb name=couchdb@10.210.199.199 setcookie=monster admin=password bind-address=0.0.0.0
+lxc exec couchdb-c2 snap set couchdb name=couchdb@10.210.199.254 setcookie=monster admin=password bind-address=0.0.0.0
+lxc exec couchdb-c3 snap set couchdb name=couchdb@10.210.199.24 setcookie=monster admin=password bind-address=0.0.0.0
+```
+The backup machine we will leave as a single instance and no sharding. 
+```
+lxc exec cdb-backup snap set couchdb name=couchdb@127.0.0.1 setcookie=monster admin=password bind-address=0.0.0.0 n=1 q=1
+```
+
+The snap must be restarted for the new configurations to take affect. 
+```
+lxc exec couchdb-c1 snap restart couchdb
+lxc exec couchdb-c2 snap restart couchdb
+lxc exec couchdb-c3 snap restart couchdb
+lxc exec cdb-backup snap restart couchdb
+```
+The configuration files are stored here.
+```
+lxc exec cdb-backup cat /var/snap/couchdb/current/etc/vm.args
+lxc exec cdb-backup cat /var/snap/couchdb/current/etc/local.d/*
+```
+Any changes to couchdb from the http configutation tool are made here
+```
+lxc exec cdb-backup cat /var/snap/couchdb/current/etc/local.d/local.ini
+```
+
+# Configure CouchDB Cluster (using the http interface)
+
+Now we set up the cluster via the http front-end. This only needs to be run once on the first machine. The last command syncs with the other nodes and creates the standard databases.
+```
+curl -X POST -H "Content-Type: application/json" http://admin:password@10.210.199.199:5984/_cluster_setup -d '{"action": "add_node", "host":"10.210.199.254", "port": "5984", "username": "admin", "password":"password"}'
+curl -X POST -H "Content-Type: application/json" http://admin:password@10.210.199.199:5984/_cluster_setup -d '{"action": "add_node", "host":"10.210.199.24", "port": "5984", "username": "admin", "password":"password"}'
+curl -X POST -H "Content-Type: application/json" http://admin:password@10.210.199.199:5984/_cluster_setup -d '{"action": "finish_cluster"}'
+```
+Now we have a functioning three node cluster. 
+
+# An Example Database
+
+Let's create an example database ...
+```
+curl -X PUT http://admin:password@10.210.199.199:5984/example
+curl -X PUT http://admin:password@10.210.199.199:5984/example/aaa -d '{"test":1}' -H "Content-Type: application/json"
+curl -X PUT http://admin:password@10.210.199.199:5984/example/aab -d '{"test":2}' -H "Content-Type: application/json"
+curl -X PUT http://admin:password@10.210.199.199:5984/example/aac -d '{"test":3}' -H "Content-Type: application/json"
+```
+... And see that it is sync'd accross the three nodes.
+```
+curl -X GET http://admin:password@10.210.199.199:5984/example/_all_docs
+curl -X GET http://admin:password@10.210.199.254:5984/example/_all_docs
+curl -X GET http://admin:password@10.210.199.24:5984/example/_all_docs
+```
+# Backing Up CouchDB
+
+Our back up server is on 10.210.199.242. We will manually replicate this from one (anyone) of the nodes.
+```
+curl -X POST http://admin:password@10.210.199.242:5984/_replicate -d '{"source":"http://10.210.199.199:5984/example", "target":"example", "continuous":false,"create_target":true}' -H "Content-Type: application/json"
+curl -X GET http://admin:password@10.210.199.242:5984/example/_all_docs
+```
+The data store for the clusters nodes are sharded 
+```
+lxc exec couchdb-c1 ls /var/snap/couchdb/common/2.x/data/shards/
+```
+
+The backup database is a single file.
+```
+lxc exec cdb-backup ls /var/snap/couchdb/common/2.x/data/shards/00000000-ffffffff/
+```
+
+# Monitoring CouchDB 
+
+The logs, by default, are captured by journald
+```
+lxc exec couchdb-c1 bash
+journalctl -u snap.couchdb -f
+```
+

snap/README.md

@@ -0,0 +1,61 @@
+# Building snaps
+
+## Prerequisites
+
+CouchDB requires Ubuntu 16.04. If building on 18.04, then LXD might be useful. 
+
+1. `lxc launch ubuntu:16.04 couchdb-pkg`
+1. `lxc exec couchdb-pkg bash`
+1. `sudo apt update`
+1. `sudo apt install snapd snapcraft`
+
+1. `git clone https://github.com/couchdb/couchdb-pkg.git`
+1. `cd couchdb-pkg`
+
+## How to do it
+
+1. Edit `snap/snapcraft.yaml` to point to the correct tag (e.g. `2.2.0`)
+1. `snapcraft`
+
+# Snap Instalation
+
+You may need to pull the LXD file to the host system.
+
+    $ lxc file pull couchdb-pkg/root/couchdb-pkg/couchdb_2.2.0_amd64.snap /tmp/couchdb_2.2.0_amd64.snap
+
+The self crafted snap will need to be installed in devmode
+
+    $ sudo snap install /tmp/couchdb_2.2.0_amd64.snap --devmode 
+
+# Snap Configuration
+
+There are two levels of erlang and couchdb configuration hierarchy. 
+
+The default layer is stored in /snap/couchdb/current/rel/couchdb/etc/ and is read only. 
+The user override layer, is stored in /var/snap/couchdb/current/etc/ and is writable. 
+Within this second layer, configurations are set with the local.d directory (one file 
+per section) or the local.ini (co-mingled). The "snap set" command works with the 
+former (local.d) and couchdb http configuration overwrites the latter (local.ini). 
+Entries in local.ini supersede those in the local.d directory.
+
+The name of the erlang process and the security cookie used is set in vm.args file.
+This can be set through the snap native configuration. For example, when setting up 
+a cluster over several machines the convention is to set the erlang 
+name to couchdb@your.ip.address. Both erlang and couchdb configuration changes can be 
+made at the same time.
+
+    $ sudo snap set couchdb name=couchdb@216.3.128.12 setcookie=cutter admin=Be1stDB bind-address=0.0.0.0
+
+Snap set variable can not contain underscore character, but any dashes are converted to underscore when
+writing to file. Wrap double quotes around any bracets and avoid spaces.
+
+    $ sudo snap set couchdb delayed-commits=true erlang="{couch_native_process,start_link,[]}"
+
+Snap Native Configuration changes only come into effect after a restart
+
+    $ sudo snap restart couchdb
+
+# Example Cluster
+
+See the HOWTO.md file to see an example of a three node cluster.
+

snap/couchdb.ini

@@ -0,0 +1,3 @@
+[couchdb]
+database_dir = /var/snap/couchdb/common/data
+view_index_dir = /var/snap/couchdb/common/data

snap/meta/hooks/configure

@@ -0,0 +1,178 @@
+#!/bin/sh 
+
+set -e
+
+VM_ARGS=$SNAP_DATA/etc/vm.args
+LOCAL_DIR=$SNAP_DATA/etc/local.d
+
+
+## add or replace for the vm.arg file
+_modify_vm_args() {
+  opt=$1
+  value="$2"
+  replace_line="-$opt $value"
+  if $(grep -q "^-$opt " $VM_ARGS); then
+    sed "s/^-$opt .*/$replace_line/" $VM_ARGS 2>/dev/null >${VM_ARGS}.new
+    mv -f ${VM_ARGS}.new $VM_ARGS 2>/dev/null
+  else
+    echo $replace_line >> $VM_ARGS
+  fi
+}
+
+_modify_ini_file() {
+  section=$1
+  opt=`echo $2 | tr "-" "_"`
+  value="$3"
+  config_file=${LOCAL_DIR}/${section}.ini
+  if [ ! -e ${config_file} ]; then
+    echo "[${section}]" > $config_file
+  fi
+  replace_line="$opt=$value"
+  if $(grep -q "^$opt=" $config_file); then
+    sed "s/^$opt=.*/$replace_line/" $config_file 2>/dev/null >${config_file}.new
+    mv -f ${config_file}.new ${config_file} 2>/dev/null
+  else
+    echo $replace_line >> $config_file
+  fi
+}
+
+# The vm_args file can only be changed from the filesystem
+# configutaion vm.args file
+
+VM_ARGS_OPTIONS="name setcookie"
+for key in $VM_ARGS_OPTIONS
+do
+  val=$(snapctl get $key)
+  if [ ! -z "$val" ]; then
+    _modify_vm_args $key $val
+    sleep 0.125
+  fi
+done
+
+# The following list is either those fields that are whitelisted but 
+# useful to modifiy before first run; or those fields blacklisted
+# The snap set command modifies the files in local.d; any changes 
+# via the URL are reflected in local.ini
+
+# Special Cases
+
+# local.d/admins.ini
+passwd=$(snapctl get admin)
+if [ ! -z "$passwd" ]; then
+   _modify_ini_file admins admin $passwd
+   chmod 600 $SNAP_DATA/etc/local.d/admins.ini
+   sleep 0.125
+fi
+
+# local.d/ssl.ini
+port=$(snapctl get ssl-port)
+if [ ! -z "$port" ]; then
+   _modify_ini_file ssl port $port
+   sleep 0.125
+fi
+
+# local.d/httpd.ini
+port=$(snapctl get httpd-port)
+if [ ! -z "$port" ]; then
+   _modify_ini_file httpd port $port
+   sleep 0.125
+fi
+
+# local.d/chttpd.ini
+port=$(snapctl get chttpd-port)
+if [ ! -z "$port" ]; then
+   _modify_ini_file chttpd port $port
+   sleep 0.125
+fi
+
+# Generic Cases
+
+# local.d/chttpd.ini
+CHTTPD_OPTIONS="port bind-address require-valid-user"
+for key in $CHTTPD_OPTIONS
+do
+  val=$(snapctl get $key)
+  if [ ! -z "$val" ]; then
+    _modify_ini_file chttpd $key $val
+    sleep 0.125
+  fi
+done
+
+# local.d/cluster.ini
+CLUSTER_OPTIONS="n q"
+for key in $CLUSTER_OPTIONS
+do
+  val=$(snapctl get $key)
+  if [ ! -z "$val" ]; then
+    _modify_ini_file cluster $key $val
+    sleep 0.125
+  fi
+done
+
+# local.d/compaction_daemon.ini
+COMPACTION_DAEMON_OPTIONS="check-interval"
+for key in $COMPACTION_DAEMON_OPTIONS
+do
+  val=$(snapctl get $key)
+  if [ ! -z "$val" ]; then
+    _modify_ini_file compaction_daemon $key $val
+    sleep 0.125
+  fi
+done
+
+# local.d/couchdb.ini
+COUCHDB_OPTIONS="database-dir view-index-dir delayed-commits"
+for key in $COUCHDB_OPTIONS
+do
+  val=$(snapctl get $key)
+  if [ ! -z "$val" ]; then
+    _modify_ini_file couchdb $key $val
+    sleep 0.125
+  fi
+done
+
+# local.d/log.ini
+LOG_OPTIONS="writer file level"
+for key in $LOG_OPTIONS
+do
+  val=$(snapctl get $key)
+  if [ ! -z "$val" ]; then
+    _modify_ini_file log $key $val
+    sleep 0.125
+  fi
+done
+
+# local.d/native_query_servers.ini
+NATIVE_QUERY_SERVERS_OPTIONS="query erlang"
+for key in $NATIVE_QUERY_SERVERS_OPTIONS
+do
+  val=$(snapctl get $key)
+  if [ ! -z "$val" ]; then
+    _modify_ini_file native_query_servers $key $val
+    sleep 0.125
+  fi
+done
+
+# local.d/couch_peruser.ini
+COUCH_PERUSER_OPTIONS="database-prefix delete-dbs enable"
+for key in $COUCH_PERUSER_OPTIONS
+do
+  val=$(snapctl get $key)
+  if [ ! -z "$val" ]; then
+    _modify_ini_file couch_peruser $key $val
+    sleep 0.125
+  fi
+done
+
+# local.d/uuids.ini
+UUIDS_OPTIONS="algorithm max-count"
+for key in $UUIDS_OPTIONS
+do
+  val=$(snapctl get $key)
+  if [ ! -z "$val" ]; then
+    _modify_ini_file uuids $key $val
+    sleep 0.125
+  fi
+done
+
+

snap/meta/hooks/install

@@ -0,0 +1,9 @@
+#!/bin/sh 
+
+mkdir -p ${SNAP_DATA}/etc/local.d 
+
+cp ${SNAP}/rel/couchdb/etc/vm.args ${SNAP_DATA}/etc/vm.args
+
+cp ${SNAP}/rel/couchdb/etc/local.d/*.ini ${SNAP_DATA}/etc/local.d
+
+