DigitalOceanMigrationGuide

A guide to moving your services to our new virtual infrastructure at DigitalOcean.

Contents

  1. Changes Requiring Action
  2. Important Dates
  3. Service Impacts During Migration
    1. Email
    2. Databases
  4. Overview of New Machines
    1. New Features
      1. Networking Change: IPv6 is Supported
        1. IPv6 Limitations
      2. Web Server
  5. Using the New Shell Server
    1. Using Cron: Permissions No Longer Needed
  6. Moving Web Sites
    1. PHP
    2. Low-level domain users
    3. Proxied Servers
  7. Changes to Databases
    1. Postgresql
    2. MySQL
  8. Changes to XMPP
  9. Features Coming After Migration

1. Changes Requiring Action

If you...

...you will need to take some manual actions during the migration or your services may break.

Migration should be otherwise transparent.

2. Important Dates

TBD

3. Service Impacts During Migration

The migration should have minimal impact for most members. However, there will be some impact during a few phases.

3.1. Email

While we are moving mail volumes, IMAP PUSH may not function correctly and result in delays in your client notifying you of new mail. This is due to multiple mail delivery servers writing to your email volume; when the mail delivery agent and imap server are on separate machines, FAM notifications are not delivered to the imap server so it can't see that a new message was delivered without explicitly polling the directory. Mail access will still work generally, and IMAP PUSH notifications should only behave oddly for a few hours.

Spam detection may also be affected during a brief window -- the new mail server does not share the SpamAssassin bayes database with the current mail server, so for the window when both mail servers are active spam detection may be impaired slightly.

3.2. Databases

There will be up to ~2h of downtime for databases to ensure that no data is lost when moving data to the new servers. We will be disabling Mysql and Postgres separately, so each will be down for a shorter period during the window.

4. Overview of New Machines

The new machines that members will directly interact with are:

For a full list of servers at the new host and their purposes, see Hardware#Digital_Ocean

All servers are now running Debian Stretch (the latest stable release). Packages that were requested through the members portal on both bog and navajos have been installed on marsh and shelob so if your software works now, it ought to work on the new servers. If you are using compiled binaries that link against system libraries you might need to recompile.

4.1. New Features

4.1.1. Networking Change: IPv6 is Supported

Core HCoop services (ssh, email, dns, ...) are now IPv6 enabled. Members with native IPv6 are encouraged to test the new services and report any problems.

By default, domtool will not generate AAAA (IPv6) DNS records for your domains, but this will be enabled for the dom type after all sites are migrated.

4.1.1.1. IPv6 Limitations

Unfortunately, DigitalOcean's IPv6 implementation has one annoying (and undocumented!) limitation: they block several outgoing mail ports, so you will not be able to connect over IPv6 to the following services / ports:

Note that IMAPS (993) and POP3S (995) are accessible. This does somewhat complicate mail usage on our servers as the ports are blocked even from our servers to our servers, so we have set up mail-ipv4.hcoop.net, which you should use for now if you need to connect directly to IMAP or SMTP. If you are just using sendmail (or the php mail() function), that has been configured already to use the ipv4 only address. We are working on a better workaround that will be transparent (local caching nameserver that will filter AAAA record lookups for our mail server so that we can keep IPv6 enabled for offsite uses).

4.1.2. Web Server

All sites are now using mod_fcgid based php 5.6, which should provide a significant improvement in performance.

The new webserver has the latest Apache 2.4.x release, so the sslCertificateChainFile directive will no longer be required for https -- the certificates can contain the full chain now.

5. Using the New Shell Server

The new shell server may be accessed using ssh marsh.hcoop.net. Thanks to openafs, both the old and new infrastructure share the same volumes and you can access your data from either.

5.1. Using Cron: Permissions No Longer Needed

All members have cron enabled by default on the new login server and no longer need to specially request permissions.

Members with crontabs on bog will need to re-create the crontab on marsh. This should just be a matter of copying the crontab contents to marsh, and removing it from bog afterward.

6. Moving Web Sites

We are upgrading from apache 2.2 to 2.4, but have a configuration that should behave identically the one currently used on ServerNavajos. We are currently using mod_access_compat (Allow/Deny/Satisfy directives) instead of the newer Require access framework so that existing configurations do not need to be updated. At some point in the future we will update domtool and convert member configurations to the new access control directives.

If you are using the dom type, the move should be transparent; we will update DefaultWebNode to the new web server and reconfigure all domains on the date scheduled for transitioning to the new servers. If you would like to migrate your domains early, you may set the environment variable DefaultWebNode = "shelob"; in your configuration to force the domain to be configured on the new webserver.

6.1. PHP

The new webserver is running php 5.6, with a configuration matching the existing production configuration.

We have supported a simple fastcgi based php for a while now, but have not widely deployed it. Our current method of supporting php-cgi based php (suphp) has been removed from debian stretch, and shelob only supports fastcgi based php.

All domains have been automatically upgraded to fastcgi based php, and plain cgi php support has been removed from domtool.

After we migrate all domains, we will be able to enable php 7.2 with minimal effort (due to domtool limitations, it's not feasible to support it while ServerNavajos is in production).

(fastcgi php is mandatory now)

6.2. Low-level domain users

You're on your own, possibly ;-)

If you use vhost or vhostDefault to configure your websites, you will need to set the WebPlaces environment variable to host them on shelob: 

domain "yourdomain"
with
  vhostDefault where
    WebPlaces = [web_place_default "shelob"];
  with
    ...
  end;
end;

Any dnsIP or dnsDefault records pointing toward navajos_ip or "69.90.123.70" need to be changed to point to shelob: 

domain "yourdomain"
with
  ...
  dnsDefault shelob_ip;
end;

You may have webAt directives that need fixing up: 

webAt "shelob" "www" with
  ...
end;

Proxies and reverse proxies are similar: switch from bog to marsh. 

web "www" with
  proxyPass "/" "http://marsh:50000/";
  proxyPassReverse "/" "http://marsh:50000/";
  ...
end;

6.3. Proxied Servers

Will need to be moved to marsh, but will still work when connecting from the new webserver to bog. Connections will be going unencrypted over the Internet however!

todo: example of proxied server config and update.

7. Changes to Databases

7.1. Postgresql

Postgres users must take action! Due to our usage of gssapi and ident for authentication, we cannot set up a simple stunnel for secure connections between the datacenters. To ensure the security of your data, connections from one datacenter to the other will require ssl be enabled in postgres. Applications based on libpq ought to negotiate ssl automatically, but php applications using the PDO library will not automatically negotiate, and require sslmode=require be added to the connection string.

Postgresql is also being upgraded to 9.6 as 9.1 is not longer supported. There should be no major compatibility issues, and all databases will be automatically migrated. Postgres will still listen on port 5433; some time after migration is complete we will enable postgresql 11 on port 5432.

dbtool commands for postgres will now use version postgres-9 instead of postgres-9.1.

7.2. MySQL

The MySQL migration should be transparent. We are staying on Percona MySQL 5.6, and are using an stunnel to transparently/securely proxy connections between the datacenters during migration.

8. Changes to XMPP

We are now using ejabberd 18.06, which brings ...

9. Features Coming After Migration

Once migration is completed, a few features will be implemented as soon as feasible:

CategoryMemberManual

DigitalOceanMigrationGuide (last edited 2018-12-09 22:30:35 by ClintonEbadi)