DockerAvailability (DockerAvailability v1.0.0)

Detects whether Docker is installed and usable on the host system.

This module provides a small probe for Docker availability. It checks both the Docker client executable and the Docker daemon because a host may have the docker command installed while the daemon is stopped, unreachable, or inaccessible to the current user.

executable/0 only checks whether the docker executable can be found in PATH. check/0 performs the full availability check by running Docker version commands and collecting the client and server versions. available?/0 is a boolean convenience wrapper around check/0.

The functions in this module do not install Docker, start the Docker daemon, or modify Docker state.

Summary

Types

check_result()

reason()

Functions

available?()

Returns whether Docker is installed and usable.

check()

Checks whether Docker is installed and usable.

executable()

Returns the path to the Docker executable.

Types

check_result()

@type check_result() ::
  {:ok,
   %{
     executable: Path.t(),
     client_version: String.t() | nil,
     server_version: String.t() | nil
   }}
  | {:error, reason()}

reason()

@type reason() ::
  :docker_not_found
  | {:docker_command_failed, non_neg_integer(), String.t()}
  | {:docker_unavailable, non_neg_integer(), String.t()}

Functions

available?()

@spec available?() :: boolean()

Returns whether Docker is installed and usable.

This is a boolean convenience wrapper around check/0.

Returns true only when all of the following conditions are satisfied:

the docker executable is found in PATH
the Docker client version can be queried
the Docker server version can be queried, which implies that the Docker daemon is reachable by the current process

Returns false for all error cases, including a missing executable, a failed Docker client command, or an unreachable Docker daemon.

Use check/0 instead when the caller needs diagnostic details.

check()

@spec check() :: check_result()

Checks whether Docker is installed and usable.

This function performs the full Docker probe. It first locates the Docker executable with executable/0, then runs Docker version commands to obtain both the client and server versions.

Returns {:ok, info} when Docker is usable. The returned map contains:

:executable - the resolved path to the Docker executable
:client_version - the Docker client version reported by the executable
:server_version - the Docker server version reported by the daemon

Returns one of the following error tuples:

{:error, :docker_not_found} when the docker executable cannot be found in PATH
{:error, {:docker_command_failed, status, output}} when a Docker client command fails before daemon availability is established
{:error, {:docker_unavailable, status, output}} when the Docker server version cannot be queried, typically because the Docker daemon is stopped, unreachable, or inaccessible to the current user

status is the command exit status and output is the trimmed combined standard output and standard error from the Docker command.

executable()

@spec executable() :: {:ok, Path.t()} | {:error, :docker_not_found}

Returns the path to the Docker executable.

This function searches for docker in the current process PATH by using System.find_executable/1.

Returns {:ok, path} when the executable is found.

Returns {:error, :docker_not_found} when the executable is not available in PATH.

This function does not check whether the Docker daemon is running. Use check/0 or available?/0 when daemon connectivity also matters.