kjnilsson

Name of RabbitMQ header	App	Type	Purpose
x-received-from	Federation	internal	record hop information for cycle detection
x-death	Dead lettering	internal	record dead lettering information (somewhat compacted)
x-stream-offset	Streams	outgoing annotation	include the offset for a given message consumed using AMQP
x-delivery-count	Quorum	outgoing annotation	include the number of delivery attemps for messages consumed from a quorum queue
x-stream-filter	Streams	incoming annotation	include a message filter string used for stream filtering feature
CC, BCC	Routing	incoming annotation	used for including additional routes, not evaluated beyond routing, really ought to be x- headers
x-first-death-reason	DLX	outgoing annotation	dead lettering info
x-first-death-queue	DLX	outgoing annotation	dead lettering queue name

kjnilsson

Introduction

There are two types of consumer processing failures:

1. Poison messages. Messages that are badly formatted and either cause the consuming application to crash or otherwise fail to process the message.

2. Downstream dependency failures. I.e. when a message is valid but a downstream dependency such as a database isn't available. This category can further be subdived into:

   a. All messages on the queue are destined to the same unavailable downstream.

b. The downstream dependencies may be different depending on the message. (e.g. different databases or integration endpoints).

kjnilsson

10 RabbitMQ tips you didn't know

1. Don't retry publishes to Quorum Queues or Streams if the channel is still live.

   Normally we recommend to retry a publish operation if a publisher confirm isn't received within some timeframe. This isn't actually necessary if you know you are only publishing to quorum queues and/or streams and the channel used for publishing is still live. These queue types have their own reliability/resend protocol between the channel and the queue and will ensure publish operations get there once the situation that caused the delay resolves itself (e.g. a temporary unavailability

kjnilsson

using System;
using System.Threading.Tasks;
using RabbitMQ.Client;
using RabbitMQ.Client.Events;

namespace ConsoleApplication
{
    public class Program
    {
        public static void Main(string[] args)

kjnilsson

add two fields to append_entries_rpc:

read_index :: non_neg_integer()
echo :: boolean()

and one field to append_entries_reply:

read_index :: non_neg_integer()

kjnilsson

//invaluable for all those Choice<'a, exn> flows
let exnf f = Printf.ksprintf (fun s -> exn s) f

//combine paths
let (</>) x y = System.IO.Path.Combine(x, y)

//allows you to pattern match on values in the current scope rather than just literals
let (|Eq|_|) expected value =
    if expected = value then Some ()
    else None

kjnilsson

module type GenServerType =
  type State
  val init : ErlangTerm list -> State
  ...
  
  
  
module MyGenServer : GenServerType =
  type State = {Name : string}
  let init args =

kjnilsson

-module(ra_thw).

-export([
         % new/1, % size,
         new/2, % size, distance
         append/3,
         to_list/1,
         get/2, % kv lookup
         truncate/2 % state, first entry to keep
        ]).

kjnilsson

  Checking whether the PLT /Users/knilsson/code/rabbitmq/rabbitmq-public-umbrella-master/deps/rabbit_common/.rabbit_common.plt is up-to-date... yes
  Proceeding with analysis...
app_utils.erl:44: The created fun only terminates with explicit exception
app_utils.erl:50: The created fun only terminates with explicit exception
file_handle_cache.erl:1015: The pattern {MemUse, MemLimit} can never match since previous clauses completely covered the type {non_neg_integer(),'infinity'}
file_handle_cache.erl:1016: The pattern {MemUse, MemLimit} can never match since previous clauses completely covered the type {non_neg_integer(),'infinity'}
file_handle_cache.erl:1021: Function reduce_read_cache/2 will never be called
file_handle_cache.erl:1029: Guard test Freed::any() >= MemToFree::none() can never succeed
file_handle_cache_stats.erl:33: Expression produces a value of type atom() | ets:tid(), but this value is unmatched
file_handle_cache_stats.erl:44: Expression produces a value of type [integer()] | integer(), but th

kjnilsson

module xmas

open Fez.Core

let greet who =
    sprintf "Hi %s" who

type Tid = Tid

// this is simply to create an atom