docs: update instructions for shared exception store in cluster setup

docs/admin/tuning-scale-horizontally-cluster.rst

@@ -1,383 +1,395 b''
 .. _scale-horizontal-cluster:
 
 
 Scale Horizontally / RhodeCode Cluster
 --------------------------------------
 
 |RCE| is built in a way it support horizontal scaling across multiple machines.
 There are three main pre-requisites for that:
 
 - Shared storage that each machine can access. Using NFS or other shared storage system.
 - Shared DB connection across machines. Using `MySQL`/`PostgreSQL` that each node can access.
 - |RCE| user sessions and caches need to use a shared storage (e.g `Redis`_/`Memcached`)
 
 
 Horizontal scaling means adding more machines or workers into your pool of
 resources. Horizontally scaling |RCE| gives a huge performance increase,
 especially under large traffic scenarios with a high number of requests.
 This is very beneficial when |RCE| is serving many users simultaneously,
 or if continuous integration servers are automatically pulling and pushing code.
 It also adds High-Availability to your running system.
 
 
 Cluster Overview
 ^^^^^^^^^^^^^^^^
 
 Below we'll present a configuration example that will use two separate nodes to serve
 |RCE| in a load-balanced environment. The 3rd node will act as a shared storage/cache
 and handle load-balancing. In addition 3rd node will be used as shared database instance.
 
 This setup can be used both in Docker based configuration or with individual
 physical/virtual machines. Using the 3rd node for Storage/Redis/PostgreSQL/Nginx is
 optional. All those components can be installed on one of the two nodes used for |RCE|.
 We'll use following naming for our nodes:
 
  - `rc-node-1` (NFS, DB, Cache node)
  - `rc-node-2` (Worker node1)
  - `rc-node-3` (Worker node2)
 
 Our shares NFS storage in the example is located on `/home/rcdev/storage` and
 it's RW accessible on **each** node.
 
 In this example we used certain recommended components, however many
 of those can be replaced by other, in case your organization already uses them, for example:
 
 - `MySQL`/`PostgreSQL`: Aren't replaceable and are the two only supported databases.
 - `Nginx`_ on `rc-node-1` can be replaced by: `Hardware Load Balancer (F5)`, `Apache`_, `HA-Proxy` etc.
 - `Nginx`_ on rc-node-2/3 acts as a reverse proxy and can be replaced by other HTTP server
   acting as reverse proxy such as `Apache`_.
 - `Redis`_ on `rc-node-1` can be replaced by: `Memcached`
 
 
 Here's an overview what components should be installed/setup on each server in our example:
 
 - **rc-node-1**:
 
  - main storage acting as NFS host.
  - `nginx` acting as a load-balancer.
  - `postgresql-server` used for database and sessions.
  - `redis-server` used for storing shared caches.
  - optionally `rabbitmq-server` for `Celery` if used.
  - optionally if `Celery` is used Enterprise/Community instance + VCSServer.
  - optionally mailserver that can be shared by other instances.
  - optionally channelstream server to handle live communication for all instances.
 
 
 - **rc-node-2/3**:
 
  - `nginx` acting as a reverse proxy to handle requests to |RCE|.
  - 1x RhodeCode Enterprise/Community instance.
  - 1x VCSServer instance.
  - optionally for testing connection: postgresql-client, redis-client (redis-tools).
 
 
 Before we start here are few assumptions that should be fulfilled:
 
 - make sure each node can access each other.
 - make sure `Redis`_/`MySQL`/`PostgreSQL`/`RabbitMQ`_ are running on `rc-node-1`
 - make sure both `rc-node-2`/`3` can access NFS storage with RW access
 - make sure rc-node-2/3 can access `Redis`_/`PostgreSQL`, `MySQL` database on `rc-node-1`.
 - make sure `Redis`_/Database/`RabbitMQ`_ are password protected and accessible only from rc-node-2/3.
 
 
 
 Setup rc-node-2/3
 ^^^^^^^^^^^^^^^^^
 
 Initially before `rc-node-1` we'll configure both nodes 2 and 3 to operate as standalone
 nodes with their own hostnames. Use a default installation settings, and use
 the default local addresses (127.0.0.1) to configure VCSServer and Community/Enterprise instances.
 All external connectivity will be handled by the reverse proxy (`Nginx`_ in our example).
 
 This way we can ensure each individual host works,
 accepts connections, or do some operations explicitly on chosen node.
 
 In addition this would allow use to explicitly direct certain traffic to a node, e.g
 CI server will only call directly `rc-node-3`. This should be done similar to normal
 installation so check out `Nginx`_/`Apache`_ configuration example to configure each host.
 Each one should already connect to shared database during installation.
 
 
 1) Assuming our final url will be http://rc-node-1, Configure `instances_id`, `app.base_url`
 
 a) On **rc-node-2** find the following settings and edit :file:`/home/{user}/.rccontrol/{instance-id}/rhodecode.ini`
 
 .. code-block:: ini
 
     ## required format is: *NAME-
     instance_id = *rc-node-2-
     app.base_url = http://rc-node-1
 
 
 b) On **rc-node-3** find the following settings and edit :file:`/home/{user}/.rccontrol/{instance-id}/rhodecode.ini`
 
 .. code-block:: ini
 
     ## required format is: *NAME-
     instance_id = *rc-node-3-
     app.base_url = http://rc-node-1
 
 
 
 2) Configure `User Session` to use a shared database. Example config that should be
-   changed on both node 2 and 3. Edit :file:`/home/{user}/.rccontrol/{instance-id}/rhodecode.ini`
+   changed on both **rc-node-2** and **rc-node-3** .
+   Edit :file:`/home/{user}/.rccontrol/{instance-id}/rhodecode.ini`
 
 .. code-block:: ini
 
     ####################################
     ###       BEAKER SESSION        ####
     ####################################
 
     ## Disable the default `file` sessions
     #beaker.session.type = file
     #beaker.session.data_dir = %(here)s/data/sessions
 
     ## use shared db based session, fast, and allows easy management over logged in users
     beaker.session.type = ext:database
     beaker.session.table_name = db_session
     # use our rc-node-1 here
     beaker.session.sa.url = postgresql://postgres:qweqwe@rc-node-1/rhodecode
     beaker.session.sa.pool_recycle = 3600
     beaker.session.sa.echo = false
 
 In addition make sure both instances use the same `session.secret` so users have
 persistent sessions across nodes. Please generate other one then in this example.
 
 .. code-block:: ini
 
     # use an unique generated long string
     beaker.session.secret = 70e116cae2274656ba7265fd860aebbd
 
 3) Configure stored cached/archive cache to our shared NFS `rc-node-1`
 
 .. code-block:: ini
 
     # note the `_` prefix that allows using a directory without
     # remap and rescan checking for vcs inside it.
     cache_dir = /home/rcdev/storage/_cache_dir/data
     # note archive cache dir is disabled by default, however if you enable
     # it also needs to be shared
     #archive_cache_dir = /home/rcdev/storage/_tarball_cache_dir
 
 
-4) Change cache backends to use `Redis`_ based caches. Below full example config
+4) Use shared exception store. Example config that should be
+   changed on both **rc-node-2** and **rc-node-3**, and also for VCSServer.
+   Edit :file:`/home/{user}/.rccontrol/{instance-id}/rhodecode.ini` and
+   :file:`/home/{user}/.rccontrol/{vcsserver-instance-id}/vcsserver.ini`
+   and add/change following setting.
+
+.. code-block:: ini
+
+    exception_tracker.store_path = /home/rcdev/storage/_exception_store_data
+
+
+5) Change cache backends to use `Redis`_ based caches. Below full example config
    that replaces default file-based cache to shared `Redis`_ with Distributed Lock.
 
 
 .. code-block:: ini
 
     #####################################
     ###         DOGPILE CACHE        ####
     #####################################
 
     ## `cache_perms` cache settings for permission tree, auth TTL.
     #rc_cache.cache_perms.backend = dogpile.cache.rc.file_namespace
     #rc_cache.cache_perms.expiration_time = 300
 
     ## alternative `cache_perms` redis backend with distributed lock
     rc_cache.cache_perms.backend = dogpile.cache.rc.redis
     rc_cache.cache_perms.expiration_time = 300
     ## redis_expiration_time needs to be greater then expiration_time
     rc_cache.cache_perms.arguments.redis_expiration_time = 7200
     rc_cache.cache_perms.arguments.socket_timeout = 30
     rc_cache.cache_perms.arguments.host = rc-node-1
     rc_cache.cache_perms.arguments.password = qweqwe
     rc_cache.cache_perms.arguments.port = 6379
     rc_cache.cache_perms.arguments.db = 0
     rc_cache.cache_perms.arguments.distributed_lock = true
 
     ## `cache_repo` cache settings for FileTree, Readme, RSS FEEDS
     #rc_cache.cache_repo.backend = dogpile.cache.rc.file_namespace
     #rc_cache.cache_repo.expiration_time = 2592000
 
     ## alternative `cache_repo` redis backend with distributed lock
     rc_cache.cache_repo.backend = dogpile.cache.rc.redis
     rc_cache.cache_repo.expiration_time = 2592000
     ## redis_expiration_time needs to be greater then expiration_time
     rc_cache.cache_repo.arguments.redis_expiration_time = 2678400
     rc_cache.cache_repo.arguments.socket_timeout = 30
     rc_cache.cache_repo.arguments.host = rc-node-1
     rc_cache.cache_repo.arguments.password = qweqwe
     rc_cache.cache_repo.arguments.port = 6379
     rc_cache.cache_repo.arguments.db = 1
     rc_cache.cache_repo.arguments.distributed_lock = true
 
     ## cache settings for SQL queries, this needs to use memory type backend
     rc_cache.sql_cache_short.backend = dogpile.cache.rc.memory_lru
     rc_cache.sql_cache_short.expiration_time = 30
 
     ## `cache_repo_longterm` cache for repo object instances, this needs to use memory
     ## type backend as the objects kept are not pickle serializable
     rc_cache.cache_repo_longterm.backend = dogpile.cache.rc.memory_lru
     ## by default we use 96H, this is using invalidation on push anyway
     rc_cache.cache_repo_longterm.expiration_time = 345600
     ## max items in LRU cache, reduce this number to save memory, and expire last used
     ## cached objects
     rc_cache.cache_repo_longterm.max_size = 10000
 
 
-4) Configure `Nginx`_ as reverse proxy on `rc-node-2/3`:
+6) Configure `Nginx`_ as reverse proxy on `rc-node-2/3`:
    Minimal `Nginx`_ config used:
 
 
 .. code-block:: nginx
 
     ## rate limiter for certain pages to prevent brute force attacks
     limit_req_zone  $binary_remote_addr  zone=req_limit:10m   rate=1r/s;
 
     ## custom log format
     log_format log_custom '$remote_addr - $remote_user [$time_local] '
                           '"$request" $status $body_bytes_sent '
                           '"$http_referer" "$http_user_agent" '
                           '$request_time $upstream_response_time $pipe';
 
     server {
         listen          80;
         server_name     rc-node-2;
         #server_name     rc-node-3;
 
         access_log   /var/log/nginx/rhodecode.access.log log_custom;
         error_log    /var/log/nginx/rhodecode.error.log;
 
         # example of proxy.conf can be found in our docs.
         include     /etc/nginx/proxy.conf;
 
         ## serve static files by Nginx, recommended for performance
         location /_static/rhodecode {
             gzip on;
             gzip_min_length  500;
             gzip_proxied     any;
             gzip_comp_level 4;
             gzip_types  text/css text/javascript text/xml text/plain text/x-component application/javascript application/json application/xml application/rss+xml font/truetype font/opentype application/vnd.ms-fontobject image/svg+xml;
             gzip_vary on;
             gzip_disable     "msie6";
             #alias /home/rcdev/.rccontrol/community-1/static;
             alias /home/rcdev/.rccontrol/enterprise-1/static;
         }
 
 
         location /_admin/login {
             limit_req  zone=req_limit  burst=10  nodelay;
             try_files $uri @rhode;
         }
 
         location / {
             try_files $uri @rhode;
         }
 
         location @rhode {
             # Url to running RhodeCode instance.
             # This is shown as `- URL: <host>` in output from rccontrol status.
             proxy_pass      http://127.0.0.1:10020;
         }
 
         ## custom 502 error page. Will be displayed while RhodeCode server
         ## is turned off
         error_page 502 /502.html;
         location = /502.html {
            #root  /home/rcdev/.rccontrol/community-1/static;
            root  /home/rcdev/.rccontrol/enterprise-1/static;
         }
     }
 
 
-5) Optional: Full text search, in case you use `Whoosh` full text search we also need a
+7) Optional: Full text search, in case you use `Whoosh` full text search we also need a
    shared storage for the index. In our example our NFS is mounted at `/home/rcdev/storage`
    which represents out storage so we can use the following:
 
 .. code-block:: ini
 
     # note the `_` prefix that allows using a directory without
     # remap and rescan checking for vcs inside it.
     search.location = /home/rcdev/storage/_index_data/index
 
 
 .. note::
 
     If you use ElasticSearch it's by default shared, and simply running ES node is
     by default cluster compatible.
 
 
-6) Optional: If you intend to use mailing all instances need to use either a shared
-   mailing node, or each will use individual local mailagent. Simply put node-1/2/3 needs
-   to use same mailing configuration.
+8) Optional: If you intend to use mailing all instances need to use either a shared
+   mailing node, or each will use individual local mail agent. Simply put node-1/2/3
+   needs to use same mailing configuration.
 
 
 
 Setup rc-node-1
 ^^^^^^^^^^^^^^^
 
 
 Configure `Nginx`_ as Load Balancer to rc-node-2/3.
 Minimal `Nginx`_ example below:
 
 .. code-block:: nginx
 
     ## define rc-cluster which contains a pool of our instances to connect to
     upstream rc-cluster {
         # rc-node-2/3 are stored in /etc/hosts with correct IP addresses
         server rc-node-2:80;
         server rc-node-3:80;
     }
 
     server {
         listen          80;
         server_name     rc-node-1;
 
         location / {
             proxy_pass http://rc-cluster;
         }
     }
 
 
 .. note::
 
    You should configure your load balancing accordingly. We recommend writing
    load balancing rules that will separate regular user traffic from
    automated process traffic like continuous servers or build bots. Sticky sessions
    are not required.
 
 
 Show which instance handles a request
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 You can easily check if load-balancing is working as expected. Visit our main node
 `rc-node-1` URL which at that point should already handle incoming requests and balance
 it across node-2/3.
 
 Add a special GET param `?showrcid=1` to show current instance handling your request.
 
 For example: visiting url `http://rc-node-1/?showrcid=1` will show, in the bottom
 of the screen` cluster instance info.
 e.g: `RhodeCode instance id: rc-node-3-rc-node-3-3246`
 which is generated from::
 
     <NODE_HOSTNAME>-<INSTANCE_ID>-<WORKER_PID>
 
 
 Using Celery with cluster
 ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 
 If `Celery` is used we recommend setting also an instance of Enterprise/Community+VCSserver
 on the node that is running `RabbitMQ`_. Those instances will be used to executed async
 tasks on the `rc-node-1`. This is the most efficient setup. `Celery` usually
 handles tasks such as sending emails, forking repositories, importing
 repositories from external location etc. Using workers on instance that has
 the direct access to disks used by NFS as well as email server gives noticeable
 performance boost. Running local workers to the NFS storage results in faster
 execution of forking large repositories or sending lots of emails.
 
 Those instances need to be configured in the same way as for other nodes.
 The instance in rc-node-1 can be added to the cluser, but we don't recommend doing it.
 For best results let it be isolated to only executing `Celery` tasks in the cluster setup.
 
 
 .. _Gunicorn: http://gunicorn.org/
 .. _Whoosh: https://pypi.python.org/pypi/Whoosh/
 .. _Elasticsearch: https://www.elastic.co/..
 .. _RabbitMQ: http://www.rabbitmq.com/
 .. _Nginx: http://nginx.io
 .. _Apache: http://nginx.io
 .. _Redis: http://redis.io