RabbitMQ發送端channel->basic_publish()阻塞問題

背景

公司測試服務器上裝了一個rabbitmq，$this->channel->basic_publish($msg, '', $queue); 調用這個方法會被阻塞， 可是在以前本地，預發佈，生產服務器都是能夠正常運行（基本是一把梭，並未遇到相似的坑），在網上也沒有找到解決此問題的好方法，各類折騰總算解決了，因而總結下但願對其餘人有所幫助。

踩坑記

因爲公司測試服務器配置低，系統環境複雜，並且磁盤也快滿了，說實話用着很扎心，很早就放棄用線上測試環境，全部測試基本在本地搞定。因爲和Android 端對接 websocket 服務接口，對方要求給他搞個線上穩定的環境，同時爲了方便他回家調試，因而就把線上環境弄起來。

剛開始覺得是安裝方式出了問題，因而又換編譯安裝，裝完後仍是如此，各類折騰.......

問題緣由

我安裝的版本：RabbitMQ 3.1.5，Erlang R14B04，在RabbitMQ Web管理面板中，發現了端倪，出現了一個紅色的報警，截圖以下：

該問題是因爲官方機制的帶來的，當可用磁盤空間降至配置的限制（默認爲50 MB）如下時，將觸發警報，全部生產者將被阻止。目的是避免填滿整個磁盤，這將致使節點上的全部寫操做失敗並可能致使RabbitMQ終止。

官網上有該問題解決方法：https://www.rabbitmq.com/disk-alarms.html

解決方法

修改rabbitmq配置文件，設置下 disk_free_limit 磁盤限制。因爲不一樣的版本配置文件有點差別，能夠參考官方文檔說明。

配置文件位置

在RabbitMQ 3.7.0以前，RabbitMQ配置文件名爲rabbitmq.config並使用了Erlang術語配置格式。 新版仍然支持該格式以實現向後兼容性。 建議運行3.7.0或更高版本的用戶考慮新的sysctl格式

rabbitmq的系統配置文件老版本通常是 rabbitmq.config ，新版本通常是 rabbitmq.conf，能夠登陸後臺查看它的路徑，默認狀況下在

Generic UNIX - $RABBITMQ_HOME/etc/rabbitmq/
Debian - /etc/rabbitmq/
RPM - /etc/rabbitmq/
Mac OSX (Homebrew) - ${install_prefix}/etc/rabbitmq/, the Homebrew prefix is usually /usr/local
Windows - %APPDATA%\RabbitMQ\

配置文件內容

若是你是源碼安裝，最初這個文件是沒有的，須要手動建立

vim /etc/rabbitmq/rabbitmq.config

%% -*- mode: erlang -*-
%% ----------------------------------------------------------------------------
%% RabbitMQ Sample Configuration File.
%%
%% See http://www.rabbitmq.com/configure.html for details.
%% ----------------------------------------------------------------------------
[
 {rabbit,
  [%%
   %% Network Connectivity
   %% ====================
   %%

   %% By default, RabbitMQ will listen on all interfaces, using
   %% the standard (reserved) AMQP port.
   %%
   %% {tcp_listeners, [5672]},

   %% To listen on a specific interface, provide a tuple of {IpAddress, Port}.
   %% For example, to listen only on localhost for both IPv4 and IPv6:
   %%
   %% {tcp_listeners, [{"127.0.0.1", 5672},
   %%                  {"::1",       5672}]},

   %% SSL listeners are configured in the same fashion as TCP listeners,
   %% including the option to control the choice of interface.
   %%
   %% {ssl_listeners, [5671]},

   %% Number of Erlang processes that will accept connections for the TCP
   %% and SSL listeners.
   %%
   %% {num_tcp_acceptors, 10},
   %% {num_ssl_acceptors, 1},

   %% Maximum time for AMQP 0-8/0-9/0-9-1 handshake (after socket connection
   %% and SSL handshake), in milliseconds.
   %%
   %% {handshake_timeout, 10000},

   %% Log levels (currently just used for connection logging).
   %% One of 'debug', 'info', 'warning', 'error' or 'none', in decreasing
   %% order of verbosity. Defaults to 'info'.
   %%
  {log_levels, [{connection, error}, {channel, error}]}

   %% Set to 'true' to perform reverse DNS lookups when accepting a
   %% connection. Hostnames will then be shown instead of IP addresses
   %% in rabbitmqctl and the management plugin.
   %%
   %% {reverse_dns_lookups, true},

   %%
   %% Security / AAA
   %% ==============
   %%

   %% The default "guest" user is only permitted to access the server
   %% via a loopback interface (e.g. localhost).
   %% {loopback_users, [<<"guest">>]},
   %%
   %% Uncomment the following line if you want to allow access to the
   %% guest user from anywhere on the network.
   %% {loopback_users, []},

   %% Configuring SSL.
   %% See http://www.rabbitmq.com/ssl.html for full documentation.
   %%
   %% {ssl_options, [{cacertfile,           "/path/to/testca/cacert.pem"},
   %%                {certfile,             "/path/to/server/cert.pem"},
   %%                {keyfile,              "/path/to/server/key.pem"},
   %%                {verify,               verify_peer},
   %%                {fail_if_no_peer_cert, false}]},

   %% Choose the available SASL mechanism(s) to expose.
   %% The two default (built in) mechanisms are 'PLAIN' and
   %% 'AMQPLAIN'. Additional mechanisms can be added via
   %% plugins.
   %%
   %% See http://www.rabbitmq.com/authentication.html for more details.
   %%
   %% {auth_mechanisms, ['PLAIN', 'AMQPLAIN']},

   %% Select an authentication database to use. RabbitMQ comes bundled
   %% with a built-in auth-database, based on mnesia.
   %%
   %% {auth_backends, [rabbit_auth_backend_internal]},

   %% Configurations supporting the rabbitmq_auth_mechanism_ssl and
   %% rabbitmq_auth_backend_ldap plugins.
   %%
   %% NB: These options require that the relevant plugin is enabled.
   %% See http://www.rabbitmq.com/plugins.html for further details.

   %% The RabbitMQ-auth-mechanism-ssl plugin makes it possible to
   %% authenticate a user based on the client's SSL certificate.
   %%
   %% To use auth-mechanism-ssl, add to or replace the auth_mechanisms
   %% list with the entry 'EXTERNAL'.
   %%
   %% {auth_mechanisms, ['EXTERNAL']},

   %% The rabbitmq_auth_backend_ldap plugin allows the broker to
   %% perform authentication and authorisation by deferring to an
   %% external LDAP server.
   %%
   %% For more information about configuring the LDAP backend, see
   %% http://www.rabbitmq.com/ldap.html.
   %%
   %% Enable the LDAP auth backend by adding to or replacing the
   %% auth_backends entry:
   %%
   %% {auth_backends, [rabbit_auth_backend_ldap]},

   %% This pertains to both the rabbitmq_auth_mechanism_ssl plugin and
   %% STOMP ssl_cert_login configurations. See the rabbitmq_stomp
   %% configuration section later in this file and the README in
   %% https://github.com/rabbitmq/rabbitmq-auth-mechanism-ssl for further
   %% details.
   %%
   %% To use the SSL cert's CN instead of its DN as the username
   %%
   %% {ssl_cert_login_from, common_name},

   %% SSL handshake timeout, in milliseconds.
   %%
   %% {ssl_handshake_timeout, 5000},

   %% Password hashing implementation. Will only affect newly
   %% created users. To recalculate hash for an existing user
   %% it's necessary to update her password.
   %%
   %% {password_hashing_module, rabbit_password_hashing_sha256},

   %% Configuration entry encryption.
   %% See http://www.rabbitmq.com/configure.html#configuration-encryption
   %%
   %% To specify the passphrase in the configuration file:
   %%
   %% {config_entry_decoder, [{passphrase, <<"mypassphrase">>}]}
   %%
   %% To specify the passphrase in an external file:
   %%
   %% {config_entry_decoder, [{passphrase, {file, "/path/to/passphrase/file"}}]}
   %%
   %% To make the broker request the passphrase when it starts:
   %%
   %% {config_entry_decoder, [{passphrase, prompt}]}
   %%
   %% To change encryption settings:
   %%
   %% {config_entry_decoder, [{cipher,     aes_cbc256},
   %%                         {hash,       sha512},
   %%                         {iterations, 1000}]}

   %%
   %% Default User / VHost
   %% ====================
   %%

   %% On first start RabbitMQ will create a vhost and a user. These
   %% config items control what gets created. See
   %% http://www.rabbitmq.com/access-control.html for further
   %% information about vhosts and access control.
   %%
   %% {default_vhost,       <<"/">>},
   %% {default_user,        <<"guest">>},
   %% {default_pass,        <<"guest">>},
   %% {default_permissions, [<<".*">>, <<".*">>, <<".*">>]},

   %% Tags for default user
   %%
   %% For more details about tags, see the documentation for the
   %% Management Plugin at http://www.rabbitmq.com/management.html.
   %%
   %% {default_user_tags, [administrator]},

   %%
   %% Additional network and protocol related configuration
   %% =====================================================
   %%

   %% Set the default AMQP heartbeat delay (in seconds).
   %%
   %% {heartbeat, 60},

   %% Set the max permissible size of an AMQP frame (in bytes).
   %%
   %% {frame_max, 131072},

   %% Set the max frame size the server will accept before connection
   %% tuning occurs
   %%
   %% {initial_frame_max, 4096},

   %% Set the max permissible number of channels per connection.
   %% 0 means "no limit".
   %%
   %% {channel_max, 128},

   %% Customising Socket Options.
   %%
   %% See (http://www.erlang.org/doc/man/inet.html#setopts-2) for
   %% further documentation.
   %%
   %% {tcp_listen_options, [{backlog,       128},
   %%                       {nodelay,       true},
   %%                       {exit_on_close, false}]},

   %%
   %% Resource Limits & Flow Control
   %% ==============================
   %%
   %% See http://www.rabbitmq.com/memory.html for full details.

   %% Memory-based Flow Control threshold.
   %%
   %% {vm_memory_high_watermark, 0.4},

   %% Alternatively, we can set a limit (in bytes) of RAM used by the node.
   %%
   %% {vm_memory_high_watermark, {absolute, 1073741824}},
   %%
   %% Or you can set absolute value using memory units.
   %%
   %% {vm_memory_high_watermark, {absolute, "1024M"}},
   %%
   %% Supported units suffixes:
   %%
   %% k, kiB: kibibytes (2^10 bytes)
   %% M, MiB: mebibytes (2^20)
   %% G, GiB: gibibytes (2^30)
   %% kB: kilobytes (10^3)
   %% MB: megabytes (10^6)
   %% GB: gigabytes (10^9)

   %% Fraction of the high watermark limit at which queues start to
   %% page message out to disc in order to free up memory.
   %%
   %% Values greater than 0.9 can be dangerous and should be used carefully.
   %%
   %% {vm_memory_high_watermark_paging_ratio, 0.5},

   %% Interval (in milliseconds) at which we perform the check of the memory
   %% levels against the watermarks.
   %%
   %% {memory_monitor_interval, 2500},

   %% Set disk free limit (in bytes). Once free disk space reaches this
   %% lower bound, a disk alarm will be set - see the documentation
   %% listed above for more details.
   %%
   %% {disk_free_limit, 50000000},
   %%
   %% Or you can set it using memory units (same as in vm_memory_high_watermark)
   %% {disk_free_limit, "50MB"},
   %% {disk_free_limit, "50000kB"},
   %% {disk_free_limit, "2GB"},

   %% Alternatively, we can set a limit relative to total available RAM.
   %%
   %% Values lower than 1.0 can be dangerous and should be used carefully.
   %% {disk_free_limit, {mem_relative, 2.0}},

   %%
   %% Misc/Advanced Options
   %% =====================
   %%
   %% NB: Change these only if you understand what you are doing!
   %%

   %% To announce custom properties to clients on connection:
   %%
   %% {server_properties, []},

   %% How to respond to cluster partitions.
   %% See http://www.rabbitmq.com/partitions.html for further details.
   %%
   %% {cluster_partition_handling, ignore},

   %% Make clustering happen *automatically* at startup - only applied
   %% to nodes that have just been reset or started for the first time.
   %% See http://www.rabbitmq.com/clustering.html#auto-config for
   %% further details.
   %%
   %% {cluster_nodes, {['rabbit@my.host.com'], disc}},

   %% Interval (in milliseconds) at which we send keepalive messages
   %% to other cluster members. Note that this is not the same thing
   %% as net_ticktime; missed keepalive messages will not cause nodes
   %% to be considered down.
   %%
   %% {cluster_keepalive_interval, 10000},

   %% Set (internal) statistics collection granularity.
   %%
   %% {collect_statistics, none},

   %% Statistics collection interval (in milliseconds).
   %%
   %% {collect_statistics_interval, 5000},

   %% Explicitly enable/disable hipe compilation.
   %%
   %% {hipe_compile, true},

   %% Timeout used when waiting for Mnesia tables in a cluster to
   %% become available.
   %%
   %% {mnesia_table_loading_timeout, 30000},

   %% Size in bytes below which to embed messages in the queue index. See
   %% http://www.rabbitmq.com/persistence-conf.html
   %%
   %% {queue_index_embed_msgs_below, 4096}

  ]},

 %% ----------------------------------------------------------------------------
 %% Advanced Erlang Networking/Clustering Options.
 %%
 %% See http://www.rabbitmq.com/clustering.html for details
 %% ----------------------------------------------------------------------------
 {kernel,
  [%% Sets the net_kernel tick time.
   %% Please see http://erlang.org/doc/man/kernel_app.html and
   %% http://www.rabbitmq.com/nettick.html for further details.
   %%
   %% {net_ticktime, 60}
  ]},

 %% ----------------------------------------------------------------------------
 %% RabbitMQ Management Plugin
 %%
 %% See http://www.rabbitmq.com/management.html for details
 %% ----------------------------------------------------------------------------

 {rabbitmq_management,
  [%% Pre-Load schema definitions from the following JSON file. See
   %% http://www.rabbitmq.com/management.html#load-definitions
   %%
   %% {load_definitions, "/path/to/schema.json"},

   %% Log all requests to the management HTTP API to a file.
   %%
   %% {http_log_dir, "/path/to/access.log"},

   %% Change the port on which the HTTP listener listens,
   %% specifying an interface for the web server to bind to.
   %% Also set the listener to use SSL and provide SSL options.
   %%
   %% {listener, [{port,     12345},
   %%             {ip,       "127.0.0.1"},
   %%             {ssl,      true},
   %%             {ssl_opts, [{cacertfile, "/path/to/cacert.pem"},
   %%                         {certfile,   "/path/to/cert.pem"},
   %%                         {keyfile,    "/path/to/key.pem"}]}]},

   %% One of 'basic', 'detailed' or 'none'. See
   %% http://www.rabbitmq.com/management.html#fine-stats for more details.
   %% {rates_mode, basic},

   %% Configure how long aggregated data (such as message rates and queue
   %% lengths) is retained. Please read the plugin's documentation in
   %% http://www.rabbitmq.com/management.html#configuration for more
   %% details.
   %%
   %% {sample_retention_policies,
   %%  [{global,   [{60, 5}, {3600, 60}, {86400, 1200}]},
   %%   {basic,    [{60, 5}, {3600, 60}]},
   %%   {detailed, [{10, 5}]}]}
  ]},

 %% ----------------------------------------------------------------------------
 %% RabbitMQ Shovel Plugin
 %%
 %% See http://www.rabbitmq.com/shovel.html for details
 %% ----------------------------------------------------------------------------

 {rabbitmq_shovel,
  [{shovels,
    [%% A named shovel worker.
     %% {my_first_shovel,
     %%  [

     %% List the source broker(s) from which to consume.
     %%
     %%   {sources,
     %%    [%% URI(s) and pre-declarations for all source broker(s).
     %%     {brokers, ["amqp://user:password@host.domain/my_vhost"]},
     %%     {declarations, []}
     %%    ]},

     %% List the destination broker(s) to publish to.
     %%   {destinations,
     %%    [%% A singular version of the 'brokers' element.
     %%     {broker, "amqp://"},
     %%     {declarations, []}
     %%    ]},

     %% Name of the queue to shovel messages from.
     %%
     %% {queue, <<"your-queue-name-goes-here">>},

     %% Optional prefetch count.
     %%
     %% {prefetch_count, 10},

     %% when to acknowledge messages:
     %% - no_ack: never (auto)
     %% - on_publish: after each message is republished
     %% - on_confirm: when the destination broker confirms receipt
     %%
     %% {ack_mode, on_confirm},

     %% Overwrite fields of the outbound basic.publish.
     %%
     %% {publish_fields, [{exchange,    <<"my_exchange">>},
     %%                   {routing_key, <<"from_shovel">>}]},

     %% Static list of basic.properties to set on re-publication.
     %%
     %% {publish_properties, [{delivery_mode, 2}]},

     %% The number of seconds to wait before attempting to
     %% reconnect in the event of a connection failure.
     %%
     %% {reconnect_delay, 2.5}

     %% ]} %% End of my_first_shovel
    ]}
   %% Rather than specifying some values per-shovel, you can specify
   %% them for all shovels here.
   %%
   %% {defaults, [{prefetch_count,     0},
   %%             {ack_mode,           on_confirm},
   %%             {publish_fields,     []},
   %%             {publish_properties, [{delivery_mode, 2}]},
   %%             {reconnect_delay,    2.5}]}
  ]},

 %% ----------------------------------------------------------------------------
 %% RabbitMQ Stomp Adapter
 %%
 %% See http://www.rabbitmq.com/stomp.html for details
 %% ----------------------------------------------------------------------------

 {rabbitmq_stomp,
  [%% Network Configuration - the format is generally the same as for the broker

   %% Listen only on localhost (ipv4 & ipv6) on a specific port.
   %% {tcp_listeners, [{"127.0.0.1", 61613},
   %%                  {"::1",       61613}]},

   %% Listen for SSL connections on a specific port.
   %% {ssl_listeners, [61614]},

   %% Number of Erlang processes that will accept connections for the TCP
   %% and SSL listeners.
   %%
   %% {num_tcp_acceptors, 10},
   %% {num_ssl_acceptors, 1},

   %% Additional SSL options

   %% Extract a name from the client's certificate when using SSL.
   %%
   %% {ssl_cert_login, true},

   %% Set a default user name and password. This is used as the default login
   %% whenever a CONNECT frame omits the login and passcode headers.
   %%
   %% Please note that setting this will allow clients to connect without
   %% authenticating!
   %%
   %% {default_user, [{login,    "guest"},
   %%                 {passcode, "guest"}]},

   %% If a default user is configured, or you have configured use SSL client
   %% certificate based authentication, you can choose to allow clients to
   %% omit the CONNECT frame entirely. If set to true, the client is
   %% automatically connected as the default user or user supplied in the
   %% SSL certificate whenever the first frame sent on a session is not a
   %% CONNECT frame.
   %%
   %% {implicit_connect, true}
  ]},

 %% ----------------------------------------------------------------------------
 %% RabbitMQ MQTT Adapter
 %%
 %% See https://github.com/rabbitmq/rabbitmq-mqtt/blob/stable/README.md
 %% for details
 %% ----------------------------------------------------------------------------

 {rabbitmq_mqtt,
  [%% Set the default user name and password. Will be used as the default login
   %% if a connecting client provides no other login details.
   %%
   %% Please note that setting this will allow clients to connect without
   %% authenticating!
   %%
   %% {default_user, <<"guest">>},
   %% {default_pass, <<"guest">>},

   %% Enable anonymous access. If this is set to false, clients MUST provide
   %% login information in order to connect. See the default_user/default_pass
   %% configuration elements for managing logins without authentication.
   %%
   %% {allow_anonymous, true},

   %% If you have multiple chosts, specify the one to which the
   %% adapter connects.
   %%
   %% {vhost, <<"/">>},

   %% Specify the exchange to which messages from MQTT clients are published.
   %%
   %% {exchange, <<"amq.topic">>},

   %% Specify TTL (time to live) to control the lifetime of non-clean sessions.
   %%
   %% {subscription_ttl, 1800000},

   %% Set the prefetch count (governing the maximum number of unacknowledged
   %% messages that will be delivered).
   %%
   %% {prefetch, 10},

   %% TCP/SSL Configuration (as per the broker configuration).
   %%
   %% {tcp_listeners, [1883]},
   %% {ssl_listeners, []},

   %% Number of Erlang processes that will accept connections for the TCP
   %% and SSL listeners.
   %%
   %% {num_tcp_acceptors, 10},
   %% {num_ssl_acceptors, 1},

   %% TCP/Socket options (as per the broker configuration).
   %%
   %% {tcp_listen_options, [{backlog,   128},
   %%                       {nodelay,   true}]}
  ]},

 %% ----------------------------------------------------------------------------
 %% RabbitMQ AMQP 1.0 Support
 %%
 %% See https://github.com/rabbitmq/rabbitmq-amqp1.0/blob/stable/README.md
 %% for details
 %% ----------------------------------------------------------------------------

 {rabbitmq_amqp1_0,
  [%% Connections that are not authenticated with SASL will connect as this
   %% account. See the README for more information.
   %%
   %% Please note that setting this will allow clients to connect without
   %% authenticating!
   %%
   %% {default_user, "guest"},

   %% Enable protocol strict mode. See the README for more information.
   %%
   %% {protocol_strict_mode, false}
  ]},

 %% ----------------------------------------------------------------------------
 %% RabbitMQ LDAP Plugin
 %%
 %% See http://www.rabbitmq.com/ldap.html for details.
 %%
 %% ----------------------------------------------------------------------------

 {rabbitmq_auth_backend_ldap,
  [%%
   %% Connecting to the LDAP server(s)
   %% ================================
   %%

   %% Specify servers to bind to. You *must* set this in order for the plugin
   %% to work properly.
   %%
   %% {servers, ["your-server-name-goes-here"]},

   %% Connect to the LDAP server using SSL
   %%
   %% {use_ssl, false},

   %% Specify the LDAP port to connect to
   %%
   %% {port, 389},

   %% LDAP connection timeout, in milliseconds or 'infinity'
   %%
   %% {timeout, infinity},

   %% Enable logging of LDAP queries.
   %% One of
   %%   - false (no logging is performed)
   %%   - true (verbose logging of the logic used by the plugin)
   %%   - network (as true, but additionally logs LDAP network traffic)
   %%
   %% Defaults to false.
   %%
   %% {log, false},

   %%
   %% Authentication
   %% ==============
   %%

   %% Pattern to convert the username given through AMQP to a DN before
   %% binding
   %%
   %% {user_dn_pattern, "cn=${username},ou=People,dc=example,dc=com"},

   %% Alternatively, you can convert a username to a Distinguished
   %% Name via an LDAP lookup after binding. See the documentation for
   %% full details.

   %% When converting a username to a dn via a lookup, set these to
   %% the name of the attribute that represents the user name, and the
   %% base DN for the lookup query.
   %%
   %% {dn_lookup_attribute,   "userPrincipalName"},
   %% {dn_lookup_base,        "DC=gopivotal,DC=com"},

   %% Controls how to bind for authorisation queries and also to
   %% retrieve the details of users logging in without presenting a
   %% password (e.g., SASL EXTERNAL).
   %% One of
   %%  - as_user (to bind as the authenticated user - requires a password)
   %%  - anon    (to bind anonymously)
   %%  - {UserDN, Password} (to bind with a specified user name and password)
   %%
   %% Defaults to 'as_user'.
   %%
   %% {other_bind, as_user},

   %%
   %% Authorisation
   %% =============
   %%

   %% The LDAP plugin can perform a variety of queries against your
   %% LDAP server to determine questions of authorisation. See
   %% http://www.rabbitmq.com/ldap.html#authorisation for more
   %% information.

   %% Set the query to use when determining vhost access
   %%
   %% {vhost_access_query, {in_group,
   %%                       "ou=${vhost}-users,ou=vhosts,dc=example,dc=com"}},

   %% Set the query to use when determining resource (e.g., queue) access
   %%
   %% {resource_access_query, {constant, true}},

   %% Set queries to determine which tags a user has
   %%
   %% {tag_queries, []}
  ]}
].

注意

• 註釋採用%%
• 取消註釋後，注意下每行後的 英文逗號 取捨，不然重啓時會報錯，語法錯誤

修改配置（重點）

去掉 disk_free_limit 前的註釋便可，或者設置合適的大小值，也可參照官網的修改方法

保存並重啓

重啓後若是系統不能識別， 試試在/etc/rabbitmq下面增長rabbitmq-env.conf, 內容以下：

CONFIG_FILE=/etc/rabbitmq/rabbitmq

重啓後查看配置文件是否生效，若是沒有，在RabbitMQ的啓動log裏面會有config file(s) : (none) 信息：

rabbitmqctl environment

cat /var/log/rabbitmq/rabbit@VM\_233\_220\_centos.log

Starting RabbitMQ 3.7.7 on Erlang 21.0
 Copyright (C) 2007-2018 Pivotal Software, Inc.
 Licensed under the MPL.  See http://www.rabbitmq.com/
2018-08-12 16:40:14.671 [info] <0.1409.0>
 node           : rabbit@iZuf6cdovpqjj6q2xqxrjlZ
 home dir       : /var/lib/rabbitmq
 config file(s) : (none)
 cookie hash    : Q3TjDnUThEMjV/iOuMOw0w==
 log(s)         : /var/log/rabbitmq/rabbit@iZuf6cdovpqjj6q2xqxrjlZ.log
                : /var/log/rabbitmq/rabbit@iZuf6cdovpqjj6q2xqxrjlZ_upgrade.log
 database dir   : /var/lib/rabbitmq/mnesia/rabbit@iZuf6cdovpqjj6q2xqxrjlZ

其它阻塞的場景

內存大小
最快的解決方案時將vm_memory_high_watermark值上調，若是短期內上調不了，能夠選擇直接升級服務器內存。

可是這樣治標不治本，若是隊列繼續堆積，內存佔用率仍是會變大，最終的解決方案，應該要平衡消費者和生產者，讓消息隊列儘可能不要堆積致使內存過大阻塞。

消息積壓
在RabbitMQ中，消息可能被存儲在多個不一樣的隊列，消息越早被消費，那麼消息通過的隊列層次越少，則平均每一個消息處理的開銷就越小。但若發佈消息的速率過快，MQ來不及處理，這些消息就可能進入很深層次的隊列，大大增長平均每一個消息的處理開銷，進一步使得處理新消息和發送舊消息的能力減弱，更多的消息會進入很深的隊列，循環往復，整個系統的性能就會極大的下降。

另外若接收消息的速率過快還會實現某些進程的mailbox過大，可能會產生很嚴重的後果。爲此程序中必須有一個合理的生產和消費流控機制。