prepare 6.0.0 release

[LaunchDarklyCI]

[6.0.0] - 2020-10-07

For more details on changes related to configuration, read the configuration documentation.

Added:

• The Relay Proxy now supports a new mode named "automatic configuration" which is available to customers on LaunchDarkly's Enterprise plan. This mode allows environments and their credentials can be configured dynamically rather than having to be manually configured ahead of time. To learn more, read the online documentation.
• Secure mode can be enabled for an environment by setting SecureMode = true for that environment in the configuration file, or LD_SECURE_MODE_MyEnvName if using environment variables. This is separate from the setting for secure mode on the LaunchDarkly dashboard, which the Relay Proxy is not able to access.
• The new DisconnectedStatusTime configuration property controls how long the Relay Proxy will tolerate a stream connection being interrupted before reporting a "disconnected"/"degraded" status in the status resource.
• The Consul integration now supports ACL tokens with the Token and TokenFile configuration properties.
• The new DisableInternalUsageMetrics configuration property allows turning off the internal analytics that the Relay Proxy normally sends to LaunchDarkly.
• The /status endpoint now includes more information about the LaunchDarkly connection status, database connection status (if applicable) and database configuration (if applicable). To learn more, read Service endpoints. (#104)

Changed (breaking changes in configuration):

• Relay will now print an error and refuse to start if there is any property name or section name in a configuration file that it does not recognize. Previously, it would print a warning but then continue. This change was made because otherwise it is easy to misspell a property and not notice that the value is not being used.
• All configuration settings that represent a time duration must now be specified in a format that includes units, such as 3s for 3 seconds or 5m for 5 minutes. The affected settings include [Main] HeartbeatInterval (HEARTBEAT_INTERVAL), [Events] FlushInterval (EVENTS_FLUSH_INTERVAL), [any database] LocalTTL (CACHE_TTL), and [any environment] TTL (LD_TTL_envname).
• Previously, environment variables that have a true/false value were assumed to be false if the value was anything other than true or 1. Now, any value other than true, false, 0, or 1 is an error.
• All configuration settings that represent port numbers now cause an error if you set them to zero or a negative number. The same is true of the event capacity setting.
• The environment variable name LD_TTL_MINUTES_envname is no longer supported. Use LD_TTL_envname instead.
• The environment variable name REDIS_TTL is no longer supported. Use CACHE_TTL instead.
• The setting [Events] SamplingInterval (SAMPLING_INTERVAL) is no longer supported.

Changed (breaking changes when building the Relay Proxy):

• When building the Relay Proxy, you must use Go 1.14 or higher and Go modules.
• The build command is now just go build, rather than go build ./cmd/ld-relay.

Changed (breaking changes when using the Relay Proxy as a library):

• When using the Relay Proxy as a library, you must use Go 1.14 or higher and Go modules.
• The base import path is now github.com/launchdarkly/ld-relay/v6 instead of gopkg.in/launchdarkly/ld-relay.v5.
• The import path for the Relay type is now github.com/launchdarkly/ld-relay/v6/relay.
• The Config structs are now in a config subpackage. The types of many fields have changed to types that prevent creating a configuration with invalid values (for instance, OptURLAbsolute for URL fields instead of string).
• There is no longer a DefaultConfig. Instead, Relay automatically uses the appropriate default values for any configuration fields that are not set.

Changed (other):

• The prebuilt binaries for Relay Proxy releases no longer include a 32-bit Darwin/MacOS version; current versions of Go only support 64-bit for Darwin. The Linux binaries still include both 32-bit and 64-bit.
• The documentation in the source code repository has been reorganized into multiple files for clarity, so README.md is now only a summary with links to the other files.

Removed:

• The undocumented InsecureSkipVerify configuration property has been removed.