Have to start some real work. Will complete tests over lunch.

README.md

@@ -12,8 +12,9 @@ This plugin does not bundle any JDBC jar files, and does expect them to be in a
 particular location. Please ensure you read the 4 installation lines below.
 
 ## Headlines
-  - Support for connection pooling added in 0.2.0 [unreleased until #21 is resolved]
-  - Support for unsafe statement handling (allowing dynamic queries) in 0.2.0 [unreleased until #21 is resolved]
+  - Support for connection pooling added in 0.2.0 [unreleased until #10 is resolved]
+  - Support for unsafe statement handling (allowing dynamic queries) in 0.2.0 [unreleased until #10 is resolved]
+  - Altered exception handling to now count sequential flushes with exceptions thrown in 0.2.0 [untested and unreleased until #10 is resolved]
 
 ## Versions
   - See master branch for logstash v2+
@@ -31,20 +32,19 @@ particular location. Please ensure you read the 4 installation lines below.
 
 ## Configuration options
 
-| Option | Type | Description | Required? |
-| ------ | ---- | ----------- | --------- |
-| driver_path | String | File path to jar file containing your JDBC driver. This is optional, and all JDBC jars may be placed in $LOGSTASH_HOME/vendor/jar/jdbc instead. | No |
-| connection_string | String | JDBC connection URL | Yes |
-| username | String | JDBC username - this is optional as it may be included in the connection string, for many drivers | No |
-| password | String | JDBC password - this is optional as it may be included in the connection string, for many drivers | No |
-| statement | Array | An array of strings representing the SQL statement to run. Index 0 is the SQL statement that is prepared, all other array entries are passed in as parameters (in order). A parameter may either be a property of the event (i.e. "@timestamp", or "host") or a formatted string (i.e. "%{host} - %{message}" or "%{message}"). If a key is passed then it will be automatically converted as required for insertion into SQL. If it's a formatted string then it will be passed in verbatim. | Yes | 
-| unsafe_statement | Boolean | If yes, the statement is evaluated for event fields - this allows you to use dynamic table names, etc. **This is highly dangerous** and you should **not** use this unless you are 100% sure that the field(s) you are passing in are 100% safe. Failure to do so will result in possible SQL injections. Please be aware that there is also a potential performance penalty as each event must be evaluated and inserted into SQL one at a time, where as when this is false multiple events are inserted at once. Example statement: [ "insert into %{table_name_field} (column) values(?)", "fieldname" ] | No |
-| max_pool_size | Number | Maximum number of connections to open to the SQL server at any 1 time | No |
-| connection_timeout | Number | Number of seconds before a SQL connection is closed | No |
-| flush_size | Number | Maximum number of entries to buffer before sending to SQL - if this is reached before idle_flush_time | No |
-| idle_flush_time | Number | Number of idle seconds before sending data to SQL - even if the flush_size has not yet been reached | No |
-| max_repeat_exceptions | Number | Number of times the same exception can repeat before we stop logstash. Set to a value less than 1 if you never want it to stop | No |
-| max_repeat_exceptions_time | Number | Maxium number of seconds between exceptions before they're considered "different" exceptions. If you modify idle_flush_time you should consider this value | No |
+| Option | Type | Description | Required? | Default |
+| ------ | ---- | ----------- | --------- | ------- |
+| driver_path | String | File path to jar file containing your JDBC driver. This is optional, and all JDBC jars may be placed in $LOGSTASH_HOME/vendor/jar/jdbc instead. | No | |
+| connection_string | String | JDBC connection URL | Yes | |
+| username | String | JDBC username - this is optional as it may be included in the connection string, for many drivers | No | |
+| password | String | JDBC password - this is optional as it may be included in the connection string, for many drivers | No | |
+| statement | Array | An array of strings representing the SQL statement to run. Index 0 is the SQL statement that is prepared, all other array entries are passed in as parameters (in order). A parameter may either be a property of the event (i.e. "@timestamp", or "host") or a formatted string (i.e. "%{host} - %{message}" or "%{message}"). If a key is passed then it will be automatically converted as required for insertion into SQL. If it's a formatted string then it will be passed in verbatim. | Yes |  |
+| unsafe_statement | Boolean | If yes, the statement is evaluated for event fields - this allows you to use dynamic table names, etc. **This is highly dangerous** and you should **not** use this unless you are 100% sure that the field(s) you are passing in are 100% safe. Failure to do so will result in possible SQL injections. Please be aware that there is also a potential performance penalty as each event must be evaluated and inserted into SQL one at a time, where as when this is false multiple events are inserted at once. Example statement: [ "insert into %{table_name_field} (column) values(?)", "fieldname" ] | No | False |
+| max_pool_size | Number | Maximum number of connections to open to the SQL server at any 1 time | No | 5 |
+| connection_timeout | Number | Number of seconds before a SQL connection is closed | No | 2800 |
+| flush_size | Number | Maximum number of entries to buffer before sending to SQL - if this is reached before idle_flush_time | No | 1000 |
+| idle_flush_time | Number | Number of idle seconds before sending data to SQL - even if the flush_size has not yet been reached | No | 1 |
+| max_flush_exceptions | Number | Number of sequential flushes which cause an exception, before we stop logstash. Set to a value less than 1 if you never want it to stop. This should be carefully configured with relation to idle_flush_time if your SQL instance is not highly available. | No | 0 |
 
 ## Example configurations
 If you have a working sample configuration, for a DB thats not listed, pull requests are welcome.

lib/logstash-output-jdbc_ring-buffer.rb

@@ -0,0 +1,19 @@
+class RingBuffer < Array
+  attr_reader :max_size
+
+  def initialize(max_size, enum = nil)
+    @max_size = max_size
+    enum.each { |e| self << e } if enum
+  end
+
+  def <<(el)
+    if self.size < @max_size || @max_size.nil?
+      super
+    else
+      self.shift
+      self.push(el)
+    end
+  end
+
+  alias :push :<<
+end

lib/logstash/outputs/jdbc.rb

@@ -4,6 +4,7 @@
 require "stud/buffer"
 require "java"
 require "logstash-output-jdbc_jars"
+require "logstash-output-jdbc_ring-buffer"
 
 class LogStash::Outputs::Jdbc < LogStash::Outputs::Base
   # Adds buffer support
@@ -58,17 +59,20 @@ class LogStash::Outputs::Jdbc < LogStash::Outputs::Base
   # a timely manner.
   #
   # If you change this value please ensure that you change
-  # max_repeat_exceptions_time accordingly.
+  # max_flush_exceptions accordingly.
   config :idle_flush_time, :validate => :number, :default => 1
 
-  # Maximum number of repeating (sequential) exceptions, before we stop retrying
+  # Maximum number of sequential flushes which encounter exceptions, before we stop retrying.
   # If set to < 1, then it will infinitely retry.
-  config :max_repeat_exceptions, :validate => :number, :default => 4
+  # 
+  # You should carefully tune this in relation to idle_flush_time if your SQL server
+  # is not highly available.
+  # i.e. If your idle_flush_time is 1, and your max_flush_exceptions is 200, and your SQL server takes
+  # longer than 200 seconds to reboot, then logstash will stop.
+  config :max_flush_exceptions, :validate => :number, :default => 0
 
-  # The max number of seconds since the last exception, before we consider it
-  # a different cause.
-  # This value should be carefully considered in respect to idle_flush_time.
-  config :max_repeat_exceptions_time, :validate => :number, :default => 30
+  config :max_repeat_exceptions, :obsolete => "This has been replaced by max_flush_exceptions - which behaves slightly differently. Please check the documentation."
+  config :max_repeat_exceptions_time, :obsolete => "This is no longer required"
 
   public
   def register
@@ -85,17 +89,12 @@ def register
     @pool.setMaximumPoolSize(@max_pool_size)
     @pool.setConnectionTimeout(@connection_timeout)
 
+    @exceptions_tracker = RingBuffer.new(@max_flush_exceptions)
+
     if (@flush_size > 1000)
       @logger.warn("JDBC - Flush size is set to > 1000")
     end
 
-    @repeat_exception_count = 0
-    @last_exception_time = Time.now
-
-    if (@max_repeat_exceptions > 0) and ((@idle_flush_time * @max_repeat_exceptions) > @max_repeat_exceptions_time)
-      @logger.warn("JDBC - max_repeat_exceptions_time is set such that it may still permit a looping exception. You probably changed idle_flush_time. Considering increasing max_repeat_exceptions_time.")
-    end
-
     buffer_initialize(
       :max_items => @flush_size,
       :max_interval => @idle_flush_time,
@@ -119,21 +118,14 @@ def flush(events, teardown=false)
   end
 
   def on_flush_error(e)
-    return if @max_repeat_exceptions < 1
+    return if @max_flush_exceptions < 1
 
-    if @last_exception == e.to_s
-      @repeat_exception_count += 1
-    else
-      @repeat_exception_count = 0
-    end
+    @exceptions_tracker << e.class
 
-    if (@repeat_exception_count >= @max_repeat_exceptions) and (Time.now - @last_exception_time) < @max_repeat_exceptions_time
-      @logger.error("JDBC - Exception repeated more than the maximum configured", :exception => e, :max_repeat_exceptions => @max_repeat_exceptions, :max_repeat_exceptions_time => @max_repeat_exceptions_time)
+    if @exceptions_tracker.reject { |i| i.nil? }.count >= @max_flush_exceptions
+      @logger.error("JDBC - max_flush_exceptions has been reached")
       raise e
     end
-
-    @last_exception_time = Time.now
-    @last_exception = e.to_s
   end
 
   def teardown
@@ -239,7 +231,11 @@ def add_statement_event_params(statement, event)
       when false
         statement.setBoolean(idx + 1, false)
       else
-        statement.setString(idx + 1, event.sprintf(i))
+        if event[i].nil? and i =~ /%\{/
+          statement.setString(idx + 1, event.sprintf(i))
+        else
+          statement.setString(idx + 1, nil)
+        end
       end
     end
 

logstash-output-jdbc.gemspec

@@ -1,6 +1,6 @@
 Gem::Specification.new do |s|
   s.name = 'logstash-output-jdbc'
-  s.version = "0.2.0.rc3"
+  s.version = "0.2.0.rc4"
   s.licenses = [ "Apache License (2.0)" ]
   s.summary = "This plugin allows you to output to SQL, via JDBC"
   s.description = "This gem is a logstash plugin required to be installed on top of the Logstash core pipeline using $LS_HOME/bin/plugin install gemname. This gem is not a stand-alone program"
@@ -24,4 +24,6 @@ Gem::Specification.new do |s|
   s.add_runtime_dependency "logstash-codec-plain"
 
   s.add_development_dependency "logstash-devutils"
+
+  s.post_install_message = "logstash-output-jdbc 0.2.0 introduces several new features - please ensure you check the documentation in the README file"
 end

spec/outputs/jdbc_spec.rb

@@ -0,0 +1,13 @@
+require "logstash/devutils/rspec/spec_helper"
+require "logstash/outputs/jdbc"
+require "stud/temporary"
+
+describe LogStash::Outputs::Jdbc do
+
+  it "should register without errors" do
+    plugin = LogStash::Plugin.lookup("output", "jdbc").new({})
+    expect { plugin.register }.to_not raise_error
+
+  end
+
+end