Changelog

4.1.0 - 2026-08-14

Changes

• Report missing or invalid configuration as a LoggerTelegramBackend.ConfigError with a message explaining how to fix it, instead of a bare {:missing_config, key} tuple. attach/1 and configure/1 now return the exception struct, so code matching on {:missing_config, key} needs updating
• Validate :level, :metadata and :metadata_filter when the backend is attached or reconfigured, rather than accepting them and crashing on the first event. :token must be a string. Setting an option to nil still means "use the default"
• Filter and render events by the level the caller actually used. LoggerBackends collapses the eight Logger levels into four before a backend sees them, so level: :critical used to discard everything, including Logger.emergency/1. All eight levels now work as expected, and the tag in the message shows the level the caller logged with
• Accept the deprecated level: :warn as :warning instead of emitting a deprecation warning for every event
• Keep the bot token out of crash reports, :sys.get_state/1 and failure messages written to stderr
• Bound the inspect output of individual metadata values, so one large term (:crash_reason under metadata: :all, for example) no longer uses up the whole message
• Document every configuration option, message filtering and the caveats of logging to Telegram in the README, which is now also the module documentation
• Test compatibility with Elixir 1.20 and OTP 29

Bug fixes

• Keep the backend attached when the configured HTTP client raises, throws or exits

4.0.0 - 2026-06-08

Breaking Changes

• Require Elixir 1.15 or later
• Validate required configuration during backend initialization and return an error when :token or :chat_id is missing

Changes

• Require finch 0.22 or later when using the built-in HTTP client
• Require logger_backends 1.0 or later
• Test compatibility with Elixir 1.18 and OTP 27

Bug fixes

• Fix message truncation to respect Telegram's 4096-character message limit after HTML parsing
• Preserve part of the message budget when truncating large metadata payloads
• Avoid rendering an empty <pre> block when no metadata is included
• Log send failures to stderr without emitting warning stacktrace noise
• Fix the HTTP client test filename typo
• Fix README and documentation typos

3.0.0 - 2023-08-12

Breaking Changes

• Migrate built-in HTTP from hackney to Finch
• Replace the:adapter with the :client option
• Remove the :proxy option

Changes

• Log a warning if sending fails
• Allow messages to be filtered by a metadata key

Bug fixes

• Escape metadata fields when sending messages
• Fix deprecation warnings on Elixir 1.15

Upgrade Instructions

Dependencies

Add :finch to your list of dependencies in mix.exs:

def deps do
  [
    {:logger_telegram_backend, "~> 3.0"},
    {:finch, "~> 0.16"},
  ]
end

Adding the backend

1. In your Application.start/2 callback, add the LoggerTelegramBackend backend:

   def start(_type, _args) do
   +  LoggerTelegramBackend.attach()

2. Remove the :backends configuration from :logger:

   config :logger,
   - backends: [LoggerTelegramBackend, :console]

Config

Configuration is now done via the LoggerTelegramBackend key:

- config :logger, :telegram,
+ config :logger, LoggerTelegramBackend,
    # ...

HTTP client (optional)

1. Remove the :adapter configuration and

2. Add the :client option and pass your own module that implements the LoggerTelegramBackend.HTTPClient behaviour

   config :logger, LoggerTelegramBackend,
   -  adapter: {Tesla.Adapter.Gun, []}
   +  client: MyGunAdapter

   See the documentation for LoggerTelegramBackend.HTTPClient for more information.

Proxy (optional)

1. Remove the :proxy configuration

2. Add the :client_pool_opts configuration

   config :logger, LoggerTelegramBackend,
   -  proxy: "socks5://127.0.0.1:9050"
   +  client_pool_opts: [conn_opts: [proxy: {:http, "127.0.0.1", 9050, []}]]

   See Pool Configuration Options for further information.

2.0.1 - 2021-05-02

Fixed

• Don't crash if sending an event does not succeed

2.0.0 - 2020-12-22

Changed

• Use tesla to make the underlying HTTP client configurable

Breaking Changes

• Make hackney an optional dependency. To use the default hackney based adapter, add it to the list of dependencies:

  def deps do
    [
      {:logger_telegram_backend, "~> 2.0.0"},
      {:hackney, "~> 1.17"}
    ]
  end

1.3.0 - 2019-07-22

Changed

• Respect maximum message length to avoid MESSAGE_TOO_LONG errors
• Bump ex_doc from 0.20.2 to 0.21.1

1.2.1 - 2019-05-27

Changed

• Bump httpoison from 1.4.0 to 1.5.1
• Bump ex_doc from 0.19.1 to 0.20.2

1.2.0 - 2018-11-28

Added

• Add proxy support (from @mvalitov)

1.1.0 - 2018-11-26

Changed

• Remove dependency on Poison: the success of a request is now solely determined by the HTTP status code.
• Remove GenStage and simplify the overall event handling logic
• Update dependencies

1.0.3 - 2018-05-25

Added

• Add @impl attributes

Changed

• Update dependencies
• Format code

Fixed

• Fix typo in README

1.0.2 - 2018-03-01

Changed

• Update httpoison to 1.0

1.0.1 - 2018-02-10

Changed

• Update Dependencies

1.0.0 - 2018-01-14