X-Git-Url: https://git.arvados.org/arvados.git/blobdiff_plain/0df7a1c38affbc50a9c7d8834f9822e398860d91..a25971cae157b6bc40037e391db226da36dc9b30:/services/api/lib/eventbus.rb

diff --git a/services/api/lib/eventbus.rb b/services/api/lib/eventbus.rb
index 0b8cae2439..ac53876122 100644
--- a/services/api/lib/eventbus.rb
+++ b/services/api/lib/eventbus.rb
@@ -1,3 +1,7 @@
+# If any threads raise an unhandled exception, make them all die.
+# We trust a supervisor like runit to restart the server in this case.
+Thread.abort_on_exception = true
+
 require 'eventmachine'
 require 'oj'
 require 'faye/websocket'
@@ -49,61 +53,121 @@ class EventBus
   end
 
   # Push out any pending events to the connection +ws+
-  # +id+  the id of the most recent row in the log table, may be nil
-  def push_events ws, id = nil
-      begin
-        # Must have at least one filter set up to receive events
-        if ws.filters.length > 0
-          # Start with log rows readable by user, sorted in ascending order
-          logs = Log.readable_by(ws.user).order("id asc")
-
-          if ws.last_log_id
-            # Client is only interested in log rows that are newer than the
-            # last log row seen by the client.
-            logs = logs.where("logs.id > ?", ws.last_log_id)
-          elsif id
-            # No last log id, so only look at the most recently changed row
-            logs = logs.where("logs.id = ?", id.to_i)
-          else
-            return
-          end
+  # +notify_id+  the id of the most recent row in the log table, may be nil
+  #
+  # This accepts a websocket and a notify_id (this is the row id from Postgres
+  # LISTEN/NOTIFY, it may be nil if called from somewhere else)
+  #
+  # It queries the database for log rows that are either
+  #  a) greater than ws.last_log_id, which is the last log id which was a candidate to be sent out
+  #  b) if ws.last_log_id is nil, then it queries rows starting with notify_id
+  #
+  # Regular Arvados permissions are applied using readable_by() and filters using record_filters()
+  # To avoid clogging up the database, queries are limited to batches of 100.  It will schedule a new
+  # push_events call if there are more log rows to send.
+  def push_events ws, notify_id
+    begin
+      if !notify_id.nil? and !ws.last_log_id.nil? and notify_id <= ws.last_log_id
+        # This notify is for a row we've handled already.
+        return
+      end
+
+      # Must have at least one filter set up to receive events
+      if ws.filters.length > 0
+        # Start with log rows readable by user, sorted in ascending order
+        logs = Log.readable_by(ws.user).order("id asc")
 
-          # Now process filters provided by client
-          cond_out = []
-          param_out = []
-          ws.filters.each do |filter|
-            ft = record_filters filter.filters, Log.table_name
-            cond_out += ft[:cond_out]
+        cond_id = nil
+        cond_out = []
+        param_out = []
+
+        if !ws.last_log_id.nil?
+          # Client is only interested in log rows that are newer than the
+          # last log row seen by the client.
+          cond_id = "logs.id > ?"
+          param_out << ws.last_log_id
+        elsif !notify_id.nil?
+          # No last log id, so look at rows starting with notify id
+          cond_id = "logs.id >= ?"
+          param_out << notify_id
+        else
+          # No log id to start from, nothing to do, return
+          return
+        end
+
+        # Now build filters provided by client
+        ws.filters.each do |filter|
+          ft = record_filters filter.filters, Log
+          if ft[:cond_out].any?
+            # Join the clauses within a single subscription filter with AND
+            # so it is consistent with regular queries
+            cond_out << "(#{ft[:cond_out].join ') AND ('})"
             param_out += ft[:param_out]
           end
+        end
 
-          # Add filters to query
-          if cond_out.any?
-            logs = logs.where(cond_out.join(' OR '), *param_out)
-          end
+        # Add filters to query
+        if cond_out.any?
+          # Join subscriptions with OR
+          logs = logs.where(cond_id + " AND ((#{cond_out.join ') OR ('}))", *param_out)
+        else
+          logs = logs.where(cond_id, *param_out)
+        end
+
+        # Execute query and actually send the matching log rows
+        count = 0
+        limit = 10
+
+        logs.limit(limit).each do |l|
+          ws.send(l.as_api_response.to_json)
+          ws.last_log_id = l.id
+          count += 1
+        end
 
-          # Finally execute query and actually send the matching log rows
-          logs.each do |l|
-            ws.send(l.as_api_response.to_json)
-            ws.last_log_id = l.id
+        if count == limit
+          # Number of rows returned was capped by limit(), we need to schedule
+          # another query to get more logs (will start from last_log_id
+          # reported by current query)
+          EventMachine::next_tick do
+            push_events ws, nil
           end
-        elsif id
-          # No filters set up, so just record the sequence number
-          ws.last_log_id = id.to_i
+        elsif !notify_id.nil? and (ws.last_log_id.nil? or notify_id > ws.last_log_id)
+          # Number of rows returned was less than cap, but the notify id is
+          # higher than the last id visible to the client, so update last_log_id
+          ws.last_log_id = notify_id
         end
-      rescue Exception => e
-        puts "Error publishing event: #{$!}"
-        puts "Backtrace:\n\t#{e.backtrace.join("\n\t")}"
-        ws.send ({status: 500, message: 'error'}.to_json)
-        ws.close
+      elsif !notify_id.nil?
+        # No filters set up, so just record the sequence number
+        ws.last_log_id = notify_id
       end
+    rescue ArgumentError => e
+      # There was some kind of user error.
+      Rails.logger.warn "Error publishing event: #{$!}"
+      ws.send ({status: 500, message: $!}.to_json)
+      ws.close
+    rescue => e
+      Rails.logger.warn "Error publishing event: #{$!}"
+      Rails.logger.warn "Backtrace:\n\t#{e.backtrace.join("\n\t")}"
+      ws.send ({status: 500, message: $!}.to_json)
+      ws.close
+      # These exceptions typically indicate serious server trouble:
+      # out of memory issues, database connection problems, etc.  Go ahead and
+      # crash; we expect that a supervisor service like runit will restart us.
+      raise
+    end
   end
 
   # Handle inbound subscribe or unsubscribe message.
   def handle_message ws, event
     begin
-      # Parse event data as JSON
-      p = (Oj.load event.data).symbolize_keys
+      begin
+        # Parse event data as JSON
+        p = (Oj.load event.data).symbolize_keys
+        filter = Filter.new(p)
+      rescue Oj::Error => e
+        ws.send ({status: 400, message: "malformed request"}.to_json)
+        return
+      end
 
       if p[:method] == 'subscribe'
         # Handle subscribe event
@@ -117,11 +181,11 @@ class EventBus
         if ws.filters.length < MAX_FILTERS
           # Add a filter.  This gets the :filters field which is the same
           # format as used for regular index queries.
-          ws.filters << Filter.new(p)
-          ws.send ({status: 200, message: 'subscribe ok'}.to_json)
+          ws.filters << filter
+          ws.send ({status: 200, message: 'subscribe ok', filter: p}.to_json)
 
           # Send any pending events
-          push_events ws
+          push_events ws, nil
         else
           ws.send ({status: 403, message: "maximum of #{MAX_FILTERS} filters allowed per connection"}.to_json)
         end
@@ -140,11 +204,9 @@ class EventBus
       else
         ws.send ({status: 400, message: "missing or unrecognized method"}.to_json)
       end
-    rescue Oj::Error => e
-      ws.send ({status: 400, message: "malformed request"}.to_json)
-    rescue Exception => e
-      puts "Error handling message: #{$!}"
-      puts "Backtrace:\n\t#{e.backtrace.join("\n\t")}"
+    rescue => e
+      Rails.logger.warn "Error handling message: #{$!}"
+      Rails.logger.warn "Backtrace:\n\t#{e.backtrace.join("\n\t")}"
       ws.send ({status: 500, message: 'error'}.to_json)
       ws.close
     end
@@ -204,7 +266,7 @@ class EventBus
                 # channel and calls #push_events to actually dispatch the
                 # events to the client.
                 conn.wait_for_notify do |channel, pid, payload|
-                  @channel.push payload
+                  @channel.push payload.to_i
                 end
               end
             ensure