open-consul/website/source/docs/upgrade-specific.html.md

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docs	Upgrading Specific Versions	docs-upgrading-specific	Specific versions of Consul may have additional information about the upgrade process beyond the standard flow.

Upgrading Specific Versions

The upgrading page covers the details of doing a standard upgrade. However, specific versions of Consul may have more details provided for their upgrades as a result of new features or changed behavior. This page is used to document those details separately from the standard upgrade flow.

Consul 0.9.0

Script Checks Are Now Opt-In

A new enable_script_checks configuration option was added, and defaults to false, meaning that in order to allow an agent to run health checks that execute scripts, this will need to be configured and set to true. This provides a safer out-of-the-box configuration for Consul where operators must opt-in to allow script-based health checks.

If your cluster uses script health checks please be sure to set this to true as part of upgrading agents. If this is set to true, you should also enable ACLs to provide control over which users are allowed to register health checks that could potentially execute scripts on the agent machines.

Web UI Is No Longer Released Separately

Consul releases will no longer include a web_ui.zip file with the compiled web assets. These have been built in to the Consul binary since the 0.7.x series and can be enabled with the -ui configuration option. These built-in web assets have always been identical to the contents of the web_ui.zip file for each release. The -ui-dir option is still available for hosting customized versions of the web assets, but the vast majority of Consul users can just use the built in web assets.

Consul 0.8.0

Upgrade Current Cluster Leader Last

We identified a potential issue with Consul 0.8 that requires the current cluster leader to be upgraded last when updating multiple servers. Please see this issue for more details.

Command-Line Interface RPC Deprecation

The RPC client interface has been removed. All CLI commands that used RPC and the -rpc-addr flag to communicate with Consul have been converted to use the HTTP API and the appropriate flags for it, and the rpc field has been removed from the port and address binding configs. You will need to remove these fields from your config files and update any scripts that passed a custom -rpc-addr to the following commands:

• force-leave
• info
• join
• keyring
• leave
• members
• monitor
• reload

Version 8 ACLs Are Now Opt-Out

The acl_enforce_version_8 configuration now defaults to true to enable full version 8 ACL support by default. If you are upgrading an existing cluster with ACLs enabled, you will need to set this to false during the upgrade on both Consul agents and Consul servers. Version 8 ACLs were also changed so that acl_datacenter must be set on agents in order to enable the agent-side enforcement of ACLs. This makes for a smoother experience in clusters where ACLs aren't enabled at all, but where the agents would have to wait to contact a Consul server before learning that.

Remote Exec Is Now Opt-In

The default for disable_remote_exec was changed to "true", so now operators need to opt-in to having agents support running commands remotely via consul exec.

Raft Protocol Version Compatibility

When upgrading to Consul 0.8.0 from a version lower than 0.7.0, users will need to set the -raft-protocol option to 1 in order to maintain backwards compatibility with the old servers during the upgrade. After the servers have been migrated to version 0.8.0, -raft-protocol can be moved up to 2 and the servers restarted to match the default.

The Raft protocol must be stepped up in this way; only adjacent version numbers are compatible (for example, version 1 cannot talk to version 3). Here is a table of the Raft Protocol versions supported by each Consul version:

Version	Supported Raft Protocols
0.6 and earlier	0
0.7	1
0.8	1, 2, 3

In order to enable all Autopilot features, all servers in a Consul cluster must be running with Raft protocol version 3 or later.

Consul 0.7.1

Child Process Reaping

Child process reaping support has been removed, along with the reap configuration option. Reaping is also done via dumb-init in the Consul Docker image, so removing it from Consul itself simplifies the code and eases future maintenance for Consul. If you are running Consul as PID 1 in a container you will need to arrange for a wrapper process to reap child processes.

DNS Resiliency Defaults

The default for max_stale has been increased from 5 seconds to a near-indefinite threshold (10 years) to allow DNS queries to continue to be served in the event of a long outage with no leader. A new telemetry counter was added at consul.dns.stale_queries to track when agents serve DNS queries that are stale by more than 5 seconds.

Consul 0.7

Consul version 0.7 is a very large release with many important changes. Changes to be aware of during an upgrade are categorized below.

Performance Timing Defaults and Tuning

Consul 0.7 now defaults the DNS configuration to allow for stale queries by defaulting allow_stale to true for better utilization of available servers. If you want to retain the previous behavior, set the following configuration:

{
  "dns_config": {
    "allow_stale": false
  }
}

Consul also 0.7 introduced support for tuning Raft performance using a new performance configuration block. Also, the default Raft timing is set to a lower-performance mode suitable for minimal Consul servers.

To continue to use the high-performance settings that were the default prior to Consul 0.7 (recommended for production servers), add the following configuration to all Consul servers when upgrading:

{
  "performance": {
    "raft_multiplier": 1
  }
}

See the Server Performance guide for more details.

Leave-Related Configuration Defaults

The default behavior of leave_on_terminate and skip_leave_on_interrupt are now dependent on whether or not the agent is acting as a server or client:

• For servers, leave_on_terminate defaults to "false" and skip_leave_on_interrupt defaults to "true".

• For clients, leave_on_terminate defaults to "true" and skip_leave_on_interrupt defaults to "false".

These defaults are designed to be safer for servers so that you must explicitly configure them to leave the cluster. This also results in a better experience for clients, especially in cloud environments where they may be created and destroyed often and users prefer not to wait for the 72 hour reap time for cleanup.

Dropped Support for Protocol Version 1

Consul version 0.7 dropped support for protocol version 1, which means it is no longer compatible with versions of Consul prior to 0.3. You will need to upgrade all agents to a newer version of Consul before upgrading to Consul 0.7.

Prepared Query Changes

Consul version 0.7 adds a feature which allows prepared queries to store a Near parameter in the query definition itself. This feature enables using the distance sorting features of prepared queries without explicitly providing the node to sort near in requests, but requires the agent servicing a request to send additional information about itself to the Consul servers when executing the prepared query. Agents prior to 0.7 do not send this information, which means they are unable to properly execute prepared queries configured with a Near parameter. Similarly, any server nodes prior to version 0.7 are unable to store the Near parameter, making them unable to properly serve requests for prepared queries using the feature. It is recommended that all agents be running version 0.7 prior to using this feature.

WAN Address Translation in HTTP Endpoints

Consul version 0.7 added support for translating WAN addresses in certain HTTP endpoints. The servers and the agents need to be running version 0.7 or later in order to use this feature.

These translated addresses could break HTTP endpoint consumers that are expecting local addresses, so a new X-Consul-Translate-Addresses header was added to allow clients to detect if translation is enabled for HTTP responses. A "lan" tag was added to TaggedAddresses for clients that need the local address regardless of translation.

Outage Recovery and peers.json Changes

The peers.json file is no longer present by default and is only used when performing recovery. This file will be deleted after Consul starts and ingests the file. Consul 0.7 also uses a new, automatically-created raft/peers.info file to avoid ingesting the peers.json file on the first start after upgrading (the peers.json file is simply deleted on the first start after upgrading).

Please be sure to review the Outage Recovery Guide before upgrading for more details.

Consul 0.6.4

Consul 0.6.4 made some substantial changes to how ACLs work with prepared queries. Existing queries will execute with no changes, but there are important differences to understand about how prepared queries are managed before you upgrade. In particular, prepared queries with no Name defined will no longer require any ACL to manage them, and prepared queries with a Name defined are now governed by a new query ACL policy that will need to be configured after the upgrade.

See the ACL Guide for more details about the new behavior and how it compares to previous versions of Consul.

Consul 0.6

Consul version 0.6 is a very large release with many enhancements and optimizations. Changes to be aware of during an upgrade are categorized below.

Data Store Changes

Consul changed the format used to store data on the server nodes in version 0.5 (see 0.5.1 notes below for details). Previously, Consul would automatically detect data directories using the old LMDB format, and convert them to the newer BoltDB format. This automatic upgrade has been removed for Consul 0.6, and instead a safeguard has been put in place which will prevent Consul from booting if the old directory format is detected.

It is still possible to migrate from a 0.5.x version of Consul to 0.6+ using the consul-migrate CLI utility. This is the same tool that was previously embedded into Consul. See the releases page for downloadable versions of the tool.

Also, in this release Consul switched from LMDB to a fully in-memory database for the state store. Because LMDB is a disk-based backing store, it was able to store more data than could fit in RAM in some cases (though this is not a recommended configuration for Consul). If you have an extremely large data set that won't fit into RAM, you may encounter issues upgrading to Consul 0.6.0 and later. Consul should be provisioned with physical memory approximately 2X the data set size to allow for bursty allocations and subsequent garbage collection.

ACL Enhancements

Consul 0.6 introduces enhancements to the ACL system which may require special handling:

• Service ACLs are enforced during service discovery (REST + DNS)

Previously, service discovery was wide open, and any client could query information about any service without providing a token. Consul now requires read-level access at a minimum when ACLs are enabled to return service information over the REST or DNS interfaces. If clients depend on an open service discovery system, then the following should be added to all ACL tokens which require it:

# Enable discovery of all services
service "" {
    policy = "read"
}

When the DNS interface is queried, the agent's acl_token is used, so be sure that token has sufficient privileges to return the DNS records you expect to retrieve from it.

• Event and keyring ACLs

Similar to service discovery, the new event and keyring ACLs will block access to these operations if the acl_default_policy is set to deny. If clients depend on open access to these, then the following should be added to all ACL tokens which require them:

event "" {
  policy = "write"
}

keyring = "write"

Unfortunately, these are new ACLs for Consul 0.6, so they must be added after the upgrade is complete.

Prepared Queries

Prepared queries introduce a new Raft log entry type that isn't supported on older versions of Consul. It's important to not use the prepared query features of Consul until all servers in a cluster have been upgraded to version 0.6.0.

Single Private IP Enforcement

Consul will refuse to start if there are multiple private IPs available, so if this is the case you will need to configure Consul's advertise or bind addresses before upgrading.

New Web UI File Layout

The release .zip file for Consul's web UI no longer contains a dist sub-folder; everything has been moved up one level. If you have any automated scripts that expect the old layout you may need to update them.

Consul 0.5.1

Consul version 0.5.1 uses a different backend store for persisting the Raft log. Because of this change, a data migration is necessary to move the log entries out of LMDB and into the newer backend, BoltDB.

Consul version 0.5.1+ makes this transition seamless and easy. As a user, there are no special steps you need to take. When Consul starts, it checks for presence of the legacy LMDB data files, and migrates them automatically if any are found. You will see a log emitted when Raft data is migrated, like this:

==> Successfully migrated raft data in 5.839642ms

This automatic upgrade will only exist in Consul 0.5.1+ and it will be removed starting with Consul 0.6.0+. It will still be possible to upgrade directly from pre-0.5.1 versions by using the consul-migrate utility, which is available on the Consul Tools page.

Consul 0.5

Consul version 0.5 adds two features that complicate the upgrade process:

• ACL system includes service discovery and registration
• Internal use of tombstones to fix behavior of blocking queries in certain edge cases.

Users of the ACL system need to be aware that deploying Consul 0.5 will cause service registration to be enforced. This means if an agent attempts to register a service without proper privileges it will be denied. If the acl_default_policy is "allow" then clients will continue to work without an updated policy. If the policy is "deny", then all clients will begin to have their registration rejected causing issues.

To avoid this situation, all the ACL policies should be updated to add something like this:

# Enable all services to be registered
service "" {
    policy = "write"
}

This will set the service policy to write level for all services. The blank service name is the catch-all value. A more specific service can also be specified:

# Enable only the API service to be registered
service "api" {
    policy = "write"
}

The ACL policy can be updated while running 0.4, and enforcement will being with the upgrade to 0.5. The policy updates will ensure the availability of the cluster.

The second major change is the new internal command used for tombstones. The details of the change are not important, however to function the leader node will replicate a new command to its followers. Consul is designed defensively, and when a command that is not recognized is received, the server will panic. This is a purposeful design decision to avoid the possibility of data loss, inconsistensies, or security issues caused by future incompatibility.

In practice, this means if a Consul 0.5 node is the leader, all of its followers must also be running 0.5. There are a number of ways to do this to ensure cluster availability:

• Add new 0.5 nodes, then remove the old servers. This will add the new nodes as followers, and once the old servers are removed, one of the 0.5 nodes will become leader.

• Upgrade the followers first, then the leader last. Using consul info, you can determine which nodes are followers. Do an in-place upgrade on them first, and finally upgrade the leader last.

• Upgrade them in any order, but ensure all are done within 15 minutes. Even if the leader is upgraded to 0.5 first, as long as all of the followers are running 0.5 within 15 minutes there will be no issues.

Finally, even if any of the methods above are not possible or the process fails for some reason, it is not fatal. The older version of the server will simply panic and stop. At that point, you can upgrade to the new version and restart the agent. There will be no data loss and the cluster will resume operations.