(POOLER-107) Add configuration API endpoint

This commit adds a configuration endpoint to the vmpooler API. Pool
size, and pool template, can be adjusted for pools that are configured
at vmpooler application start time. Pool template changes trigger a pool
refresh, and the new template has delta disks created automatically by
vmpooler.

Additionally, the capability to create template delta disks is added to
the vsphere provider, and this is implemented to ensure that templates
have delta disks created at application start time.

The mechanism used to find template VM objects is simplified to make the flow of logic easier to understand. As an additional benefit, performance of this lookup is improved by using FindByInventoryPath.

A table of contents is added to API.md to ease navigation. Without this change API.md has no table of contents and is difficult to navigate.

Add mutex object for managing pool configuration updates

This commit adds a mutex object for ensuring that pool configuration changes are synchronized across multiple running threads, removing the possibility of two threads attempting to update something at once, without relying on redis data. Without this change this is managed crudely by specifying in redis that a configuration update is taking place. This redis data is left so the REPOPULATE section of _check_pool can still identify when a configuration change is in progress, and prevent a pool from repopulating at that time.

Add wake up event for pool template changes

This commit adds a wake up event to detect pool template changes.
Additionally, GET /config has a template_ready section added to the
output for each pool, which makes clear when a pool is ready to populate
itself.

lib/vmpooler/api/v1.rb

@@ -120,6 +120,74 @@ module Vmpooler
       result
     end
 
+    def update_pool_size(payload)
+      result = { 'ok' => false }
+
+      pool_index = pool_index(pools)
+      pools_updated = 0
+      sync_pool_sizes
+
+      payload.each do |poolname, size|
+        unless pools[pool_index[poolname]]['size'] == size.to_i
+          pools[pool_index[poolname]]['size'] = size.to_i
+          backend.hset('vmpooler__config__poolsize', poolname, size)
+          pools_updated += 1
+          status 201
+        end
+      end
+      status 200 unless pools_updated > 0
+      result['ok'] = true
+      result
+    end
+
+    def update_pool_template(payload)
+      result = { 'ok' => false }
+
+      pool_index = pool_index(pools)
+      pools_updated = 0
+      sync_pool_templates
+
+      payload.each do |poolname, template|
+        unless pools[pool_index[poolname]]['template'] == template
+          pools[pool_index[poolname]]['template'] = template
+          backend.hset('vmpooler__config__template', poolname, template)
+          pools_updated += 1
+          status 201
+        end
+      end
+      status 200 unless pools_updated > 0
+      result['ok'] = true
+      result
+    end
+
+    def sync_pool_templates
+      pool_index = pool_index(pools)
+      template_configs = backend.hgetall('vmpooler__config__template')
+      unless template_configs.nil?
+        template_configs.each do |poolname, template|
+          if pool_index.include? poolname
+            unless pools[pool_index[poolname]]['template'] == template
+              pools[pool_index[poolname]]['template'] = template
+            end
+          end
+        end
+      end
+    end
+
+    def sync_pool_sizes
+      pool_index = pool_index(pools)
+      poolsize_configs = backend.hgetall('vmpooler__config__poolsize')
+      unless poolsize_configs.nil?
+        poolsize_configs.each do |poolname, size|
+          if pool_index.include? poolname
+            unless pools[pool_index[poolname]]['size'] == size.to_i
+              pools[pool_index[poolname]]['size'] == size.to_i
+            end
+          end
+        end
+      end
+    end
+
     # Provide run-time statistics
     #
     # Example:
@@ -196,6 +264,8 @@ module Vmpooler
         }
       }
 
+      sync_pool_sizes
+
       result[:capacity] = get_capacity_metrics(pools, backend) unless views and not views.include?("capacity")
       result[:queue] = get_queue_metrics(pools, backend) unless views and not views.include?("queue")
       result[:clone] = get_task_metrics(backend, 'clone', Date.today.to_s) unless views and not views.include?("clone")
@@ -502,6 +572,30 @@ module Vmpooler
       invalid
     end
 
+    def invalid_template_or_size(payload)
+      invalid = []
+      payload.each do |pool, size|
+        invalid << pool unless pool_exists?(pool)
+        unless is_integer?(size)
+          invalid << pool
+          next
+        end
+        invalid << pool unless Integer(size) >= 0
+      end
+      invalid
+    end
+
+    def invalid_template_or_path(payload)
+      invalid = []
+      payload.each do |pool, template|
+        invalid << pool unless pool_exists?(pool)
+        invalid << pool unless template.include? '/'
+        invalid << pool if template[0] == '/'
+        invalid << pool if template[-1] == '/'
+      end
+      invalid
+    end
+
     post "#{api_prefix}/vm/:template/?" do
       content_type :json
       result = { 'ok' => false }
@@ -747,6 +841,95 @@ module Vmpooler
 
       JSON.pretty_generate(result)
     end
+
+    post "#{api_prefix}/config/poolsize/?" do
+      content_type :json
+      result = { 'ok' => false }
+
+      if config['experimental_features']
+        need_token! if Vmpooler::API.settings.config[:auth]
+
+        payload = JSON.parse(request.body.read)
+
+        if payload
+          invalid = invalid_template_or_size(payload)
+          if invalid.empty?
+            result = update_pool_size(payload)
+          else
+            invalid.each do |bad_template|
+              metrics.increment("config.invalid.#{bad_template}")
+            end
+            result[:bad_templates] = invalid
+            status 400
+          end
+        else
+          metrics.increment('config.invalid.unknown')
+          status 404
+        end
+      else
+        status 405
+      end
+
+      JSON.pretty_generate(result)
+    end
+
+    post "#{api_prefix}/config/pooltemplate/?" do
+      content_type :json
+      result = { 'ok' => false }
+
+      if config['experimental_features']
+        need_token! if Vmpooler::API.settings.config[:auth]
+
+        payload = JSON.parse(request.body.read)
+
+        if payload
+          invalid = invalid_template_or_path(payload)
+          if invalid.empty?
+            result = update_pool_template(payload)
+          else
+            invalid.each do |bad_template|
+              metrics.increment("config.invalid.#{bad_template}")
+            end
+            result[:bad_templates] = invalid
+            status 400
+          end
+        else
+          metrics.increment('config.invalid.unknown')
+          status 404
+        end
+      else
+        status 405
+      end
+
+      JSON.pretty_generate(result)
+    end
+
+    get "#{api_prefix}/config/?" do
+      content_type :json
+      result = { 'ok' => false }
+      status 404
+
+      if pools
+        sync_pool_sizes
+        sync_pool_templates
+
+        pool_configuration = []
+        pools.each do |pool|
+          pool['template_ready'] = template_ready?(pool, backend)
+          pool_configuration << pool
+        end
+
+        result = {
+          pool_configuration: pool_configuration,
+          status: {
+            ok: true
+          }
+        }
+
+        status 200
+      end
+      JSON.pretty_generate(result)
+    end
   end
   end
 end