defmodule DBConnection.Stream do
defstruct [:conn, :query, :params, :opts]
@type t :: %__MODULE__{conn: DBConnection.conn(), query: any, params: any, opts: Keyword.t()}
end
defimpl Enumerable, for: DBConnection.Stream do
def count(_), do: {:error, __MODULE__}
def member?(_, _), do: {:error, __MODULE__}
def slice(_), do: {:error, __MODULE__}
def reduce(stream, acc, fun), do: DBConnection.reduce(stream, acc, fun)
end
defmodule DBConnection.PrepareStream do
defstruct [:conn, :query, :params, :opts]
@type t :: %__MODULE__{conn: DBConnection.conn(), query: any, params: any, opts: Keyword.t()}
end
defimpl Enumerable, for: DBConnection.PrepareStream do
def count(_), do: {:error, __MODULE__}
def member?(_, _), do: {:error, __MODULE__}
def slice(_), do: {:error, __MODULE__}
def reduce(stream, acc, fun), do: DBConnection.reduce(stream, acc, fun)
end
defmodule DBConnection do
@moduledoc """
A behaviour module for implementing efficient database connection
client processes, pools and transactions.
`DBConnection` handles callbacks differently to most behaviours. Some
callbacks will be called in the calling process, with the state
copied to and from the calling process. This is useful when the data
for a request is large and means that a calling process can interact
with a socket directly.
A side effect of this is that query handling can be written in a
simple blocking fashion, while the connection process itself will
remain responsive to OTP messages and can enqueue and cancel queued
requests.
If a request or series of requests takes too long to handle in the
client process a timeout will trigger and the socket can be cleanly
disconnected by the connection process.
If a calling process waits too long to start its request it will
timeout and its request will be cancelled. This prevents requests
building up when the database can not keep up.
If no requests are received for an idle interval, the pool will
ping all stale connections which can then ping the database to keep
the connection alive.
Should the connection be lost, attempts will be made to reconnect with
(configurable) exponential random backoff to reconnect. All state is
lost when a connection disconnects but the process is reused.
The `DBConnection.Query` protocol provide utility functions so that
queries can be encoded and decoded without blocking the connection or pool.
## Connection pools
DBConnection connections support using different pools via the `:pool` option
passed to `start_link/1`. The default pool is `DBConnection.ConnectionPool`.
Another supported pool that is commonly used for tests is `DBConnection.Ownership`.
For now, using *custom* pools is not supported since the API for pools is not
public.
## Errors
Most functions in this module raise a `DBConnection.ConnectionError` exception
when failing to check out a connection from the pool.
"""
require Logger
alias DBConnection.Holder
require Holder
defstruct [:pool_ref, :conn_ref, :conn_mode]
defmodule EncodeError do
defexception [:message]
end
defmodule TransactionError do
defexception [:status, :message]
def exception(:idle),
do: %__MODULE__{status: :idle, message: "transaction is not started"}
def exception(:transaction),
do: %__MODULE__{status: :transaction, message: "transaction is already started"}
def exception(:error),
do: %__MODULE__{status: :error, message: "transaction is aborted"}
end
@typedoc """
Run or transaction connection reference.
"""
@type t :: %__MODULE__{pool_ref: any, conn_ref: reference}
@type conn :: GenServer.server() | t
@type query :: DBConnection.Query.t()
@type params :: any
@type result :: any
@type cursor :: any
@type status :: :idle | :transaction | :error
@type start_option ::
{:after_connect, (t -> any) | {module, atom, [any]} | nil}
| {:after_connect_timeout, timeout}
| {:connection_listeners, list(Process.dest()) | nil}
| {:backoff_max, non_neg_integer}
| {:backoff_min, non_neg_integer}
| {:backoff_type, :stop | :exp | :rand | :rand_exp}
| {:configure, (keyword -> keyword) | {module, atom, [any]} | nil}
| {:idle_interval, non_neg_integer}
| {:idle_limit, non_neg_integer}
| {:max_restarts, non_neg_integer}
| {:max_seconds, pos_integer}
| {:name, GenServer.name()}
| {:pool, module}
| {:pool_size, pos_integer}
| {:queue_interval, non_neg_integer}
| {:queue_target, non_neg_integer}
| {:show_sensitive_data_on_connection_error, boolean}
@type option ::
{:log, (DBConnection.LogEntry.t() -> any) | {module, atom, [any]} | nil}
| {:queue, boolean}
| {:timeout, timeout}
| {:deadline, integer | nil}
@doc """
Connect to the database. Return `{:ok, state}` on success or
`{:error, exception}` on failure.
If an error is returned it will be logged and another
connection attempt will be made after a backoff interval.
This callback is called in the connection process.
"""
@callback connect(opts :: Keyword.t()) ::
{:ok, state :: any} | {:error, Exception.t()}
@doc """
Checkouts the state from the connection process. Return `{:ok, state}`
to allow the checkout or `{:disconnect, exception, state}` to disconnect.
This callback is called immediately after the connection is established
and the state is never effetively checked in again. That's because
DBConnection keeps the connection state in an ETS table that is moved
between the different clients checking out connections. There is no
`checkin` callback. The state is only handed back to the connection
process during pings and (re)connects.
This callback is called in the connection process.
"""
@callback checkout(state :: any) ::
{:ok, new_state :: any} | {:disconnect, Exception.t(), new_state :: any}
@doc """
Called when the connection has been idle for a period of time. Return
`{:ok, state}` to continue or `{:disconnect, exception, state}` to
disconnect.
This callback is called if no callbacks have been called after the
idle timeout and a client process is not using the state. The idle
timeout can be configured by the `:idle_interval` and `:idle_interval`
options. This function can be called whether the connection is checked
in or checked out.
This callback is called in the connection process.
"""
@callback ping(state :: any) ::
{:ok, new_state :: any} | {:disconnect, Exception.t(), new_state :: any}
@doc """
Handle the beginning of a transaction.
Return `{:ok, result, state}` to continue, `{status, state}` to notify caller
that the transaction can not begin due to the transaction status `status`,
or `{:disconnect, exception, state}` to error and disconnect.
A callback implementation should only return `status` if it
can determine the database's transaction status without side effect.
This callback is called in the client process.
"""
@callback handle_begin(opts :: Keyword.t(), state :: any) ::
{:ok, result, new_state :: any}
| {status, new_state :: any}
| {:disconnect, Exception.t(), new_state :: any}
@doc """
Handle committing a transaction. Return `{:ok, result, state}` on successfully
committing transaction, `{status, state}` to notify caller that the
transaction can not commit due to the transaction status `status`,
or `{:disconnect, exception, state}` to error and disconnect.
A callback implementation should only return `status` if it
can determine the database's transaction status without side effect.
This callback is called in the client process.
"""
@callback handle_commit(opts :: Keyword.t(), state :: any) ::
{:ok, result, new_state :: any}
| {status, new_state :: any}
| {:disconnect, Exception.t(), new_state :: any}
@doc """
Handle rolling back a transaction. Return `{:ok, result, state}` on successfully
rolling back transaction, `{status, state}` to notify caller that the
transaction can not rollback due to the transaction status `status` or
`{:disconnect, exception, state}` to error and disconnect.
A callback implementation should only return `status` if it
can determine the database' transaction status without side effect.
This callback is called in the client and connection process.
"""
@callback handle_rollback(opts :: Keyword.t(), state :: any) ::
{:ok, result, new_state :: any}
| {status, new_state :: any}
| {:disconnect, Exception.t(), new_state :: any}
@doc """
Handle getting the transaction status. Return `{:idle, state}` if outside a
transaction, `{:transaction, state}` if inside a transaction,
`{:error, state}` if inside an aborted transaction, or
`{:disconnect, exception, state}` to error and disconnect.
If the callback returns a `:disconnect` tuples then `status/2` will return
`:error`.
"""
@callback handle_status(opts :: Keyword.t(), state :: any) ::
{status, new_state :: any}
| {:disconnect, Exception.t(), new_state :: any}
@doc """
Prepare a query with the database. Return `{:ok, query, state}` where
`query` is a query to pass to `execute/4` or `close/3`,
`{:error, exception, state}` to return an error and continue or
`{:disconnect, exception, state}` to return an error and disconnect.
This callback is intended for cases where the state of a connection is
needed to prepare a query and/or the query can be saved in the
database to call later.
This callback is called in the client process.
"""
@callback handle_prepare(query, opts :: Keyword.t(), state :: any) ::
{:ok, query, new_state :: any}
| {:error | :disconnect, Exception.t(), new_state :: any}
@doc """
Execute a query prepared by `c:handle_prepare/3`. Return
`{:ok, query, result, state}` to return altered query `query` and result
`result` and continue, `{:error, exception, state}` to return an error and
continue or `{:disconnect, exception, state}` to return an error and
disconnect.
This callback is called in the client process.
"""
@callback handle_execute(query, params, opts :: Keyword.t(), state :: any) ::
{:ok, query, result, new_state :: any}
| {:error | :disconnect, Exception.t(), new_state :: any}
@doc """
Close a query prepared by `c:handle_prepare/3` with the database. Return
`{:ok, result, state}` on success and to continue,
`{:error, exception, state}` to return an error and continue, or
`{:disconnect, exception, state}` to return an error and disconnect.
This callback is called in the client process.
"""
@callback handle_close(query, opts :: Keyword.t(), state :: any) ::
{:ok, result, new_state :: any}
| {:error | :disconnect, Exception.t(), new_state :: any}
@doc """
Declare a cursor using a query prepared by `c:handle_prepare/3`. Return
`{:ok, query, cursor, state}` to return altered query `query` and cursor
`cursor` for a stream and continue, `{:error, exception, state}` to return an
error and continue or `{:disconnect, exception, state}` to return an error
and disconnect.
This callback is called in the client process.
"""
@callback handle_declare(query, params, opts :: Keyword.t(), state :: any) ::
{:ok, query, cursor, new_state :: any}
| {:error | :disconnect, Exception.t(), new_state :: any}
@doc """
Fetch the next result from a cursor declared by `c:handle_declare/4`. Return
`{:cont, result, state}` to return the result `result` and continue using
cursor, `{:halt, result, state}` to return the result `result` and close the
cursor, `{:error, exception, state}` to return an error and close the
cursor, `{:disconnect, exception, state}` to return an error and disconnect.
This callback is called in the client process.
"""
@callback handle_fetch(query, cursor, opts :: Keyword.t(), state :: any) ::
{:cont | :halt, result, new_state :: any}
| {:error | :disconnect, Exception.t(), new_state :: any}
@doc """
Deallocate a cursor declared by `c:handle_declare/4` with the database. Return
`{:ok, result, state}` on success and to continue,
`{:error, exception, state}` to return an error and continue, or
`{:disconnect, exception, state}` to return an error and disconnect.
This callback is called in the client process.
"""
@callback handle_deallocate(query, cursor, opts :: Keyword.t(), state :: any) ::
{:ok, result, new_state :: any}
| {:error | :disconnect, Exception.t(), new_state :: any}
@doc """
Disconnect from the database. Return `:ok`.
The exception as first argument is the exception from a `:disconnect`
3-tuple returned by a previous callback.
If the state is controlled by a client and it exits or takes too long
to process a request the state will be last known state. In these
cases the exception will be a `DBConnection.ConnectionError`.
This callback is called in the connection process.
"""
@callback disconnect(err :: Exception.t(), state :: any) :: :ok
@connection_module_key :connection_module
@doc """
Use `DBConnection` to set the behaviour.
"""
defmacro __using__(_) do
quote location: :keep do
@behaviour DBConnection
end
end
@doc """
Starts and links to a database connection process.
By default the `DBConnection` starts a pool with a single connection.
The size of the pool can be increased with `:pool_size`. A separate
pool can be given with the `:pool` option.
### Options
* `:backoff_min` - The minimum backoff interval (default: `1_000`)
* `:backoff_max` - The maximum backoff interval (default: `30_000`)
* `:backoff_type` - The backoff strategy, `:stop` for no backoff and
to stop, `:exp` for exponential, `:rand` for random and `:rand_exp` for
random exponential (default: `:rand_exp`)
* `:configure` - A function to run before every connect attempt to
dynamically configure the options, either a 1-arity fun,
`{module, function, args}` with options prepended to `args` or `nil` where
only returned options are passed to connect callback (default: `nil`). This
function is called *in the connection process*.
* `:after_connect` - A function to run on connect using `run/3`, either
a 1-arity fun, `{module, function, args}` with `t:DBConnection.t/0` prepended
to `args` or `nil` (default: `nil`)
* `:after_connect_timeout` - The maximum time allowed to perform
function specified by `:after_connect` option (default: `15_000`)
* `:connection_listeners` - A list of process destinations to send
notification messages whenever a connection is connected or disconnected.
See "Connection listeners" below
* `:name` - A name to register the started process (see the `:name` option
in `GenServer.start_link/3`)
* `:pool` - Chooses the pool to be started (default: `DBConnection.ConnectionPool`). See
["Connection pools"](#module-connection-pools).
* `:pool_size` - Chooses the size of the pool (default: `1`)
* `:idle_interval` - Controls the frequency we check for idle connections
in the pool. We then notify each idle connection to ping the database.
In practice, the ping happens within `idle_interval <= ping < 2 * idle_interval`.
Defaults to 1000ms.
* `:idle_limit` - The number of connections to ping on each `:idle_interval`.
Defaults to the pool size (all connections).
* `:queue_target` and `:queue_interval` - See "Queue config" below
* `:max_restarts` and `:max_seconds` - Configures the `:max_restarts` and
`:max_seconds` for the connection pool supervisor (see the `Supervisor` docs).
Typically speaking the connection process doesn't terminate, except due to
faults in DBConnection. However, if backoff has been disabled, then they
also terminate whenever a connection is disconnected (for instance, due to
client or server errors)
* `:show_sensitive_data_on_connection_error` - By default, `DBConnection`
hides all information during connection errors to avoid leaking credentials
or other sensitive information. You can set this option if you wish to
see complete errors and stacktraces during connection errors
### Example
{:ok, conn} = DBConnection.start_link(mod, [idle_interval: 5_000])
## Queue config
Handling requests is done through a queue. When DBConnection is
started, there are two relevant options to control the queue:
* `:queue_target` in milliseconds, defaults to 50ms
* `:queue_interval` in milliseconds, defaults to 1000ms
Our goal is to wait at most `:queue_target` for a connection.
If all connections checked out during a `:queue_interval` takes
more than `:queue_target`, then we double the `:queue_target`.
If checking out connections take longer than the new target,
then we start dropping messages.
For example, by default our target is 50ms. If all connections
checkouts take longer than 50ms for a whole second, we double
the target to 100ms and we start dropping messages if the
time to checkout goes above the new limit.
This allows us to better plan for overloads as we can refuse
requests before they are sent to the database, which would
otherwise increase the burden on the database, making the
overload worse.
## Connection listeners
The `:connection_listeners` option allows one or more processes to be notified
whenever a connection is connected or disconnected. A listener may be a remote
or local PID, a locally registered name, or a tuple in the form of
`{registered_name, node}` for a registered name at another node.
Each listener process may receive the following messages where `pid`
identifies the connection process:
* `{:connected, pid}`
* `{:disconnected, pid}`
Note the disconnected messages is not guaranteed to be delivered if the
`pid` for connection crashes. So it is recommended to monitor the connected
`pid` if you want to track all disconnections.
Here is an example of a `connection_listener` implementation:
defmodule DBConnectionListener do
use GenServer
def start_link(opts) do
GenServer.start_link(__MODULE__, [], opts)
end
def get_notifications(pid) do
GenServer.call(pid, :read_state)
end
@impl true
def init(stack) when is_list(stack) do
{:ok, stack}
end
@impl true
def handle_call(:read_state, _from, state) do
{:reply, state, state}
end
@impl true
def handle_info({:connected, _pid} = msg, state) do
{:noreply, [msg | state]}
end
@impl true
def handle_info({_other_states, _pid} = msg, state) do
{:noreply, [msg | state]}
end
end
You can then start it, pass it into a `DBConnection.start_link/1` and when needed
can query the notifications:
{:ok, pid} = DBConnectionListener.start_link([])
{:ok, _conn} = DBConnection.start_link(SomeModule, [connection_listeners: [connection_listener]])
notifications = DBConnectionListener.get_notifications(pid)
## Telemetry
A `[:db_connection, :connection_error]` event is published whenever a
connection checkout receives a `%DBConnection.ConnectionError{}`.
Measurements:
* `:count` - A fixed-value measurement which always measures 1.
Metadata
* `:error` - The `DBConnection.ConnectionError` struct which triggered the event.
* `:opts` - All options given to the pool operation
"""
@spec start_link(module, opts :: Keyword.t()) :: GenServer.on_start()
def start_link(conn_mod, opts) do
case child_spec(conn_mod, opts) do
{_, {m, f, args}, _, _, _, _} -> apply(m, f, args)
%{start: {m, f, args}} -> apply(m, f, args)
end
end
@doc """
Creates a supervisor child specification for a pool of connections.
See `start_link/2` for options.
"""
@spec child_spec(module, opts :: Keyword.t()) :: :supervisor.child_spec()
def child_spec(conn_mod, opts) do
pool = Keyword.get(opts, :pool, DBConnection.ConnectionPool)
pool.child_spec({conn_mod, opts})
end
@doc """
Forces all connections in the pool to disconnect within the given interval
in milliseconds.
Once this function is called, the pool will disconnect all of its connections
as they are checked in or as they are pinged. Checked in connections will be
randomly disconnected within the given time interval. Pinged connections are
immediately disconnected - as they are idle (according to `:idle_interval`).
If the connection has a backoff configured (which is the case by default),
disconnecting means an attempt at a new connection will be done immediately
after, without starting a new process for each connection. However, if backoff
has been disabled, the connection process will terminate. In such cases,
disconnecting all connections may cause the pool supervisor to restart
depending on the max_restarts/max_seconds configuration of the pool,
so you will want to set those carefully.
"""
@spec disconnect_all(conn, non_neg_integer, opts :: Keyword.t()) :: :ok
def disconnect_all(conn, interval, opts \\ []) when interval >= 0 do
pool = Keyword.get(opts, :pool, DBConnection.ConnectionPool)
pool.disconnect_all(conn, interval, opts)
end
@doc """
Prepare a query with a database connection for later execution.
It returns `{:ok, query}` on success or `{:error, exception}` if there was
an error.
The returned `query` can then be passed to `execute/4` and/or `close/3`
### Options
* `:queue` - Whether to block waiting in an internal queue for the
connection's state (boolean, default: `true`). See "Queue config" in
`start_link/2` docs
* `:timeout` - The maximum time that the caller is allowed to perform
this operation (default: `15_000`)
* `:deadline` - If set, overrides `:timeout` option and specifies absolute
monotonic time in milliseconds by which caller must perform operation.
See `System` module documentation for more information on monotonic time
(default: `nil`)
* `:log` - A function to log information about a call, either
a 1-arity fun, `{module, function, args}` with `t:DBConnection.LogEntry.t/0`
prepended to `args` or `nil`. See `DBConnection.LogEntry` (default: `nil`)
The pool and connection module may support other options. All options
are passed to `c:handle_prepare/3`.
### Example
DBConnection.transaction(pool, fn conn ->
query = %Query{statement: "SELECT * FROM table"}
query = DBConnection.prepare!(conn, query)
try do
DBConnection.execute!(conn, query, [])
after
DBConnection.close(conn, query)
end
end)
"""
@spec prepare(conn, query, opts :: Keyword.t()) ::
{:ok, query} | {:error, Exception.t()}
def prepare(conn, query, opts \\ []) do
meter = meter(opts)
result =
with {:ok, query, meter} <- parse(query, meter, opts) do
run(conn, &run_prepare/4, query, meter, opts)
end
log(result, :prepare, query, nil)
end
@doc """
Prepare a query with a database connection and return the prepared
query. An exception is raised on error.
See `prepare/3`.
"""
@spec prepare!(conn, query, opts :: Keyword.t()) :: query
def prepare!(conn, query, opts \\ []) do
case prepare(conn, query, opts) do
{:ok, result} -> result
{:error, err} -> raise err
end
end
@doc """
Prepare a query and execute it with a database connection and return both the
prepared query and the result, `{:ok, query, result}` on success or
`{:error, exception}` if there was an error.
The returned `query` can be passed to `execute/4` and `close/3`.
### Options
* `:queue` - Whether to block waiting in an internal queue for the
connection's state (boolean, default: `true`). See "Queue config" in
`start_link/2` docs
* `:timeout` - The maximum time that the caller is allowed to perform
this operation (default: `15_000`)
* `:deadline` - If set, overrides `:timeout` option and specifies absolute
monotonic time in milliseconds by which caller must perform operation.
See `System` module documentation for more information on monotonic time
(default: `nil`)
* `:log` - A function to log information about a call, either
a 1-arity fun, `{module, function, args}` with `t:DBConnection.LogEntry.t/0`
prepended to `args` or `nil`. See `DBConnection.LogEntry` (default: `nil`)
### Example
query = %Query{statement: "SELECT id FROM table WHERE id=$1"}
{:ok, query, result} = DBConnection.prepare_execute(conn, query, [1])
{:ok, result2} = DBConnection.execute(conn, query, [2])
:ok = DBConnection.close(conn, query)
"""
@spec prepare_execute(conn, query, params, Keyword.t()) ::
{:ok, query, result}
| {:error, Exception.t()}
def prepare_execute(conn, query, params, opts \\ []) do
result =
with {:ok, query, meter} <- parse(query, meter(opts), opts) do
parsed_prepare_execute(conn, query, params, meter, opts)
end
log(result, :prepare_execute, query, params)
end
defp parsed_prepare_execute(conn, query, params, meter, opts) do
with {:ok, query, result, meter} <-
run(conn, &run_prepare_execute/5, query, params, meter, opts),
{:ok, result, meter} <- decode(query, result, meter, opts) do
{:ok, query, result, meter}
end
end
@doc """
Prepare a query and execute it with a database connection and return both the
prepared query and result. An exception is raised on error.
See `prepare_execute/4`.
"""
@spec prepare_execute!(conn, query, Keyword.t()) :: {query, result}
def prepare_execute!(conn, query, params, opts \\ []) do
case prepare_execute(conn, query, params, opts) do
{:ok, query, result} -> {query, result}
{:error, err} -> raise err
end
end
@doc """
Execute a prepared query with a database connection and return
`{:ok, query, result}` on success or `{:error, exception}` if there was an error.
If the query is not prepared on the connection an attempt may be made to
prepare it and then execute again.
### Options
* `:queue` - Whether to block waiting in an internal queue for the
connection's state (boolean, default: `true`). See "Queue config" in
`start_link/2` docs
* `:timeout` - The maximum time that the caller is allowed to perform
this operation (default: `15_000`)
* `:deadline` - If set, overrides `:timeout` option and specifies absolute
monotonic time in milliseconds by which caller must perform operation.
See `System` module documentation for more information on monotonic time
(default: `nil`)
* `:log` - A function to log information about a call, either
a 1-arity fun, `{module, function, args}` with `t:DBConnection.LogEntry.t/0`
prepended to `args` or `nil`. See `DBConnection.LogEntry` (default: `nil`)
The pool and connection module may support other options. All options
are passed to `handle_execute/4`.
See `prepare/3`.
"""
@spec execute(conn, query, params, opts :: Keyword.t()) ::
{:ok, query, result} | {:error, Exception.t()}
def execute(conn, query, params, opts \\ []) do
result =
case maybe_encode(query, params, meter(opts), opts) do
{:prepare, meter} ->
parsed_prepare_execute(conn, query, params, meter, opts)
{:ok, params, meter} ->
with {:ok, query, result, meter} <-
run(conn, &run_execute/5, query, params, meter, opts),
{:ok, result, meter} <- decode(query, result, meter, opts) do
{:ok, query, result, meter}
end
{_, _, _, _} = error ->
error
end
log(result, :execute, query, params)
end
@doc """
Execute a prepared query with a database connection and return the
result. Raises an exception on error.
See `execute/4`
"""
@spec execute!(conn, query, params, opts :: Keyword.t()) :: result
def execute!(conn, query, params, opts \\ []) do
case execute(conn, query, params, opts) do
{:ok, _query, result} -> result
{:error, err} -> raise err
end
end
@doc """
Close a prepared query on a database connection and return `{:ok, result}` on
success or `{:error, exception}` on error.
This function should be used to free resources held by the connection
process and/or the database server.
## Options
* `:queue` - Whether to block waiting in an internal queue for the
connection's state (boolean, default: `true`). See "Queue config" in
`start_link/2` docs
* `:timeout` - The maximum time that the caller is allowed to perform
this operation (default: `15_000`)
* `:deadline` - If set, overrides `:timeout` option and specifies absolute
monotonic time in milliseconds by which caller must perform operation.
See `System` module documentation for more information on monotonic time
(default: `nil`)
* `:log` - A function to log information about a call, either
a 1-arity fun, `{module, function, args}` with `t:DBConnection.LogEntry.t/0`
prepended to `args` or `nil`. See `DBConnection.LogEntry` (default: `nil`)
The pool and connection module may support other options. All options
are passed to `c:handle_close/3`.
See `prepare/3`.
"""
@spec close(conn, query, opts :: Keyword.t()) ::
{:ok, result} | {:error, Exception.t()}
def close(conn, query, opts \\ []) do
conn
|> run_cleanup(&run_close/4, [query], meter(opts), opts)
|> log(:close, query, nil)
end
@doc """
Close a prepared query on a database connection and return the result. Raises
an exception on error.
See `close/3`.
"""
@spec close!(conn, query, opts :: Keyword.t()) :: result
def close!(conn, query, opts \\ []) do
case close(conn, query, opts) do
{:ok, result} -> result
{:error, err} -> raise err
end
end
@doc """
Acquire a lock on a connection and run a series of requests on it.
The return value of this function is the return value of `fun`.
To use the locked connection call the request with the connection
reference passed as the single argument to the `fun`. If the
connection disconnects all future calls using that connection
reference will fail.
`run/3` and `transaction/3` can be nested multiple times but a
`transaction/3` call inside another `transaction/3` will be treated
the same as `run/3`.
> #### Checkout failures {: .warning}
>
> If we cannot check out a connection from the pool, this function raises a
> `DBConnection.ConnectionError` exception.
> If you want to handle these cases, you should rescue
> `DBConnection.ConnectionError` exceptions when using `run/3`.
## Options
* `:queue` - Whether to block waiting in an internal queue for the
connection's state (boolean, default: `true`). See "Queue config" in
`start_link/2` docs
* `:timeout` - The maximum time that the caller is allowed to perform
this operation (default: `15_000`)
* `:deadline` - If set, overrides `:timeout` option and specifies absolute
monotonic time in milliseconds by which caller must perform operation.
See `System` module documentation for more information on monotonic time
(default: `nil`)
The pool may support other options.
## Example
{:ok, res} = DBConnection.run(conn, fn conn ->
DBConnection.execute!(conn, query, [])
end)
"""
@spec run(conn, (t -> result), opts :: Keyword.t()) :: result when result: var
def run(conn, fun, opts \\ [])
def run(%DBConnection{} = conn, fun, _) do
fun.(conn)
end
def run(pool, fun, opts) do
case checkout(pool, nil, opts) do
{:ok, conn, _} ->
old_status = status(conn, opts)
try do
result = fun.(conn)
{result, run(conn, &run_status/3, nil, opts)}
catch
kind, error ->
checkin(conn)
:erlang.raise(kind, error, __STACKTRACE__)
else
{result, {:error, _, _}} ->
checkin(conn)
result
{result, {^old_status, _meter}} ->
checkin(conn)
result
{_result, {new_status, _meter}} ->
err =
DBConnection.ConnectionError.exception(
"connection was checked out with status #{inspect(old_status)} " <>
"but it was checked in with status #{inspect(new_status)}"
)
disconnect(conn, err)
raise err
{_result, {kind, reason, stack, _meter}} ->
:erlang.raise(kind, reason, stack)
end
{:error, err, _} ->
raise err
{kind, reason, stack, _} ->
:erlang.raise(kind, reason, stack)
end
end
@doc """
Acquire a lock on a connection and run a series of requests inside a
transaction. The result of the transaction fun is return inside an `:ok`
tuple: `{:ok, result}`.
To use the locked connection call the request with the connection
reference passed as the single argument to the `fun`. If the
connection disconnects all future calls using that connection
reference will fail.
`run/3` and `transaction/3` can be nested multiple times. If a transaction is
rolled back or a nested transaction `fun` raises the transaction is marked as
failed. All calls except `run/3`, `transaction/3`, `rollback/2`, `close/3` and
`close!/3` will raise an exception inside a failed transaction until the outer
transaction call returns. All `transaction/3` calls will return
`{:error, :rollback}` if the transaction failed or connection closed and
`rollback/2` is not called for that `transaction/3`.
### Options
* `:queue` - Whether to block waiting in an internal queue for the
connection's state (boolean, default: `true`). See "Queue config" in
`start_link/2` docs
* `:timeout` - The maximum time that the caller is allowed to perform
this operation (default: `15_000`)
* `:deadline` - If set, overrides `:timeout` option and specifies absolute
monotonic time in milliseconds by which caller must perform operation.
See `System` module documentation for more information on monotonic time
(default: `nil`)
* `:log` - A function to log information about begin, commit and rollback
calls made as part of the transaction, either a 1-arity fun,
`{module, function, args}` with `t:DBConnection.LogEntry.t/0` prepended to
`args` or `nil`. See `DBConnection.LogEntry` (default: `nil`)
The pool and connection module may support other options. All options
are passed to `c:handle_begin/2`, `c:handle_commit/2` and
`c:handle_rollback/2`.
### Example
{:ok, res} = DBConnection.transaction(conn, fn conn ->
DBConnection.execute!(conn, query, [])
end)
"""
@spec transaction(conn, (t -> result), opts :: Keyword.t()) ::
{:ok, result} | {:error, reason :: any}
when result: var
def transaction(conn, fun, opts \\ [])
def transaction(%DBConnection{conn_mode: :transaction} = conn, fun, _opts) do
%DBConnection{conn_ref: conn_ref} = conn
try do
result = fun.(conn)
conclude(conn, result)
catch
:throw, {__MODULE__, ^conn_ref, reason} ->
fail(conn)
{:error, reason}
kind, reason ->
stack = __STACKTRACE__
fail(conn)
:erlang.raise(kind, reason, stack)
else
result ->
{:ok, result}
end
end
def transaction(%DBConnection{} = conn, fun, opts) do
case begin(conn, &run/4, opts) do
{:ok, _} ->
run_transaction(conn, fun, &run/4, opts)
{:error, %DBConnection.TransactionError{}} ->
{:error, :rollback}
{:error, err} ->
raise err
end
end
def transaction(pool, fun, opts) do
case begin(pool, &checkout/4, opts) do
{:ok, conn, _} ->
run_transaction(conn, fun, &checkin/4, opts)
{:error, %DBConnection.TransactionError{}} ->
{:error, :rollback}
{:error, err} ->
raise err
end
end
@doc """
Rollback a database transaction and release lock on connection.
When inside of a `transaction/3` call does a non-local return, using a
`throw/1` to cause the transaction to enter a failed state and the
`transaction/3` call returns `{:error, reason}`. If `transaction/3` calls are
nested the connection is marked as failed until the outermost transaction call
does the database rollback.
### Example
{:error, :oops} = DBConnection.transaction(pool, fun(conn) ->
DBConnection.rollback(conn, :oops)
end)
"""
@spec rollback(t, reason :: any) :: no_return
def rollback(conn, reason)
def rollback(%DBConnection{conn_mode: :transaction} = conn, reason) do
%DBConnection{conn_ref: conn_ref} = conn
throw({__MODULE__, conn_ref, reason})
end
def rollback(%DBConnection{} = _conn, _reason) do
raise "not inside transaction"
end
@doc """
Return the transaction status of a connection.
The callback implementation should return the transaction status according to
the database, and not make assumptions based on client-side state.
This function will raise a `DBConnection.ConnectionError` when called inside a
deprecated `transaction/3`.
### Options
See module documentation. The pool and connection module may support other
options. All options are passed to `c:handle_status/2`.
### Example
# outside of the transaction, the status is `:idle`
DBConnection.status(conn) #=> :idle
DBConnection.transaction(conn, fn conn ->
DBConnection.status(conn) #=> :transaction
# run a query that will cause the transaction to rollback, e.g.
# uniqueness constraint violation
DBConnection.execute(conn, bad_query, [])
DBConnection.status(conn) #=> :error
end)
DBConnection.status(conn) #=> :idle
"""
@spec status(conn, opts :: Keyword.t()) :: status
def status(conn, opts \\ []) do
case run(conn, &run_status/3, nil, opts) do
{status, _meter} ->
status
{:error, _err, _meter} ->
:error
{kind, reason, stack, _meter} ->
:erlang.raise(kind, reason, stack)
end
end
@doc """
Create a stream that will prepare a query, execute it and stream results
using a cursor.
### Options
* `:queue` - Whether to block waiting in an internal queue for the
connection's state (boolean, default: `true`). See "Queue config" in
`start_link/2` docs
* `:timeout` - The maximum time that the caller is allowed to perform
this operation (default: `15_000`)
* `:deadline` - If set, overrides `:timeout` option and specifies absolute
monotonic time in milliseconds by which caller must perform operation.
See `System` module documentation for more information on monotonic time
(default: `nil`)
* `:log` - A function to log information about a call, either
a 1-arity fun, `{module, function, args}` with `t:DBConnection.LogEntry.t/0`
prepended to `args` or `nil`. See `DBConnection.LogEntry` (default: `nil`)
The pool and connection module may support other options. All options
are passed to `c:handle_prepare/3`, `c:handle_close/3`, `c:handle_declare/4`,
and `c:handle_deallocate/4`.
### Example
{:ok, results} = DBConnection.transaction(conn, fn conn ->
query = %Query{statement: "SELECT id FROM table"}
stream = DBConnection.prepare_stream(conn, query, [])
Enum.to_list(stream)
end)
"""
@spec prepare_stream(t, query, params, opts :: Keyword.t()) ::
DBConnection.PrepareStream.t()
def prepare_stream(%DBConnection{} = conn, query, params, opts \\ []) do
%DBConnection.PrepareStream{conn: conn, query: query, params: params, opts: opts}
end
@doc """
Create a stream that will execute a prepared query and stream results using a
cursor.
### Options
* `:queue` - Whether to block waiting in an internal queue for the
connection's state (boolean, default: `true`). See "Queue config" in
`start_link/2` docs
* `:timeout` - The maximum time that the caller is allowed to perform
this operation (default: `15_000`)
* `:deadline` - If set, overrides `:timeout` option and specifies absolute
monotonic time in milliseconds by which caller must perform operation.
See `System` module documentation for more information on monotonic time
(default: `nil`)
* `:log` - A function to log information about a call, either
a 1-arity fun, `{module, function, args}` with `t:DBConnection.LogEntry.t/0`
prepended to `args` or `nil`. See `DBConnection.LogEntry` (default: `nil`)
The pool and connection module may support other options. All options
are passed to `c:handle_declare/4` and `c:handle_deallocate/4`.
### Example
DBConnection.transaction(pool, fn conn ->
query = %Query{statement: "SELECT id FROM table"}
query = DBConnection.prepare!(conn, query)
try do
stream = DBConnection.stream(conn, query, [])
Enum.to_list(stream)
after
# Make sure query is closed!
DBConnection.close(conn, query)
end
end)
"""
@spec stream(t, query, params, opts :: Keyword.t()) :: DBConnection.Stream.t()
def stream(%DBConnection{} = conn, query, params, opts \\ []) do
%DBConnection.Stream{conn: conn, query: query, params: params, opts: opts}
end
@doc """
Reduces a previously built stream or prepared stream.
"""
def reduce(%DBConnection.PrepareStream{} = stream, acc, fun) do
%DBConnection.PrepareStream{conn: conn, query: query, params: params, opts: opts} = stream
declare = fn conn, opts ->
{query, cursor} = prepare_declare!(conn, query, params, opts)
{:cont, query, cursor}
end
enum = resource(conn, declare, &stream_fetch/3, &stream_deallocate/3, opts)
enum.(acc, fun)
end
def reduce(%DBConnection.Stream{} = stream, acc, fun) do
%DBConnection.Stream{conn: conn, query: query, params: params, opts: opts} = stream
declare = fn conn, opts ->
case declare(conn, query, params, opts) do
{:ok, query, cursor} ->
{:cont, query, cursor}
{:ok, cursor} ->
{:cont, query, cursor}
{:error, err} ->
raise err
end
end
enum = resource(conn, declare, &stream_fetch/3, &stream_deallocate/3, opts)
enum.(acc, fun)
end
@doc false
def register_as_pool(conn_module) do
Process.put(@connection_module_key, conn_module)
end
@doc """
Returns connection module used by the given connection pool.
When given a process that is not a connection pool, returns an `:error`.
"""
@spec connection_module(conn) :: {:ok, module} | :error
def connection_module(conn) do
with pid when pid != nil <- pool_pid(conn),
{:dictionary, dictionary} <- Process.info(pid, :dictionary),
{:ok, module} <- fetch_from_dictionary(dictionary, @connection_module_key),
do: {:ok, module},
else: (_ -> :error)
end
defp pool_pid(%DBConnection{pool_ref: Holder.pool_ref(pool: pid)}), do: pid
defp pool_pid(conn), do: GenServer.whereis(conn)
defp fetch_from_dictionary(dictionary, key) do
Enum.find_value(dictionary, :error, fn
{^key, value} -> {:ok, value}
_pair -> nil
end)
end
## Helpers
defp checkout(pool, meter, opts) do
checkout = System.monotonic_time()
pool_mod = Keyword.get(opts, :pool, DBConnection.ConnectionPool)
caller = Keyword.get(opts, :caller, self())
callers = [caller | Process.get(:"$callers") || []]
try do
pool_mod.checkout(pool, callers, opts)
catch
kind, reason ->
stack = __STACKTRACE__
{kind, reason, stack, past_event(meter, :checkout, checkout)}
else
{:ok, pool_ref, _conn_mod, checkin, _conn_state} ->
conn = %DBConnection{pool_ref: pool_ref, conn_ref: make_ref()}
meter = meter |> past_event(:checkin, checkin) |> past_event(:checkout, checkout)
{:ok, conn, meter}
{:error, err} ->
{:error, err, past_event(meter, :checkout, checkout)}
end
end
defp checkout(%DBConnection{} = conn, fun, meter, opts) do
with {:ok, result, meter} <- fun.(conn, meter, opts) do
{:ok, conn, result, meter}
end
end
defp checkout(pool, fun, meter, opts) do
with {:ok, conn, meter} <- checkout(pool, meter, opts) do
case fun.(conn, meter, opts) do
{:ok, result, meter} ->
{:ok, conn, result, meter}
error ->
checkin(conn)
error
end
end
end
defp checkin(%DBConnection{pool_ref: pool_ref}) do
Holder.checkin(pool_ref)
end
defp checkin(%DBConnection{} = conn, fun, meter, opts) do
return = fun.(conn, meter, opts)
checkin(conn)
return
end
defp checkin(pool, fun, meter, opts) do
run(pool, fun, meter, opts)
end
defp disconnect(%DBConnection{pool_ref: pool_ref}, err) do
_ = Holder.disconnect(pool_ref, err)
:ok
end
defp stop(%DBConnection{pool_ref: pool_ref}, kind, reason, stack) do
msg = "client #{inspect(self())} stopped: " <> Exception.format(kind, reason, stack)
exception = DBConnection.ConnectionError.exception(msg)
_ = Holder.stop(pool_ref, exception)
:ok
end
defp handle_common_result(return, conn, meter) do
case return do
{:ok, result, _conn_state} ->
{:ok, result, meter}
{:error, err, _conn_state} ->
{:error, err, meter}
{:disconnect, err, _conn_state} ->
disconnect(conn, err)
{:error, err, meter}
{:catch, kind, reason, stack} ->
stop(conn, kind, reason, stack)
{kind, reason, stack, meter}
other ->
bad_return!(other, conn, meter)
end
end
@compile {:inline, bad_return!: 3}
defp bad_return!(other, conn, meter) do
try do
raise DBConnection.ConnectionError, "bad return value: #{inspect(other)}"
catch
:error, reason ->
stack = __STACKTRACE__
stop(conn, :error, reason, stack)
{:error, reason, stack, meter}
end
end
defp parse(query, meter, opts) do
try do
DBConnection.Query.parse(query, opts)
catch
kind, reason ->
stack = __STACKTRACE__
{kind, reason, stack, meter}
else
query ->
{:ok, query, meter}
end
end
defp describe(conn, query, meter, opts) do
try do
DBConnection.Query.describe(query, opts)
catch
kind, reason ->
stack = __STACKTRACE__
raised_close(conn, query, meter, opts, kind, reason, stack)
else
query ->
{:ok, query, meter}
end
end
defp encode(conn, query, params, meter, opts) do
try do
DBConnection.Query.encode(query, params, opts)
catch
kind, reason ->
stack = __STACKTRACE__
raised_close(conn, query, meter, opts, kind, reason, stack)
else
params ->
{:ok, params, meter}
end
end
defp maybe_encode(query, params, meter, opts) do
try do
DBConnection.Query.encode(query, params, opts)
rescue
DBConnection.EncodeError -> {:prepare, meter}
catch
kind, reason ->
stack = __STACKTRACE__
{kind, reason, stack, meter}
else
params ->
{:ok, params, meter}
end
end
defp decode(query, result, meter, opts) do
meter = event(meter, :decode)
try do
DBConnection.Query.decode(query, result, opts)
catch
kind, reason ->
stack = __STACKTRACE__
{kind, reason, stack, meter}
else
result ->
{:ok, result, meter}
end
end
defp prepare_declare(conn, query, params, opts) do
result =
with {:ok, query, meter} <- parse(query, meter(opts), opts) do
parsed_prepare_declare(conn, query, params, meter, opts)
end
log(result, :prepare_declare, query, params)
end
defp parsed_prepare_declare(conn, query, params, meter, opts) do
run(conn, &run_prepare_declare/5, query, params, meter, opts)
end
defp prepare_declare!(conn, query, params, opts) do
case prepare_declare(conn, query, params, opts) do
{:ok, query, cursor} ->
{query, cursor}
{:error, err} ->
raise err
end
end
defp declare(conn, query, params, opts) do
result =
case maybe_encode(query, params, meter(opts), opts) do
{:prepare, meter} ->
parsed_prepare_declare(conn, query, params, meter, opts)
{:ok, params, meter} ->
run(conn, &run_declare/5, query, params, meter, opts)
{_, _, _, _} = error ->
error
end
log(result, :declare, query, params)
end
defp deallocate(conn, query, cursor, opts) do
conn
|> run_cleanup(&run_deallocate/4, [query, cursor], meter(opts), opts)
|> log(:deallocate, query, cursor)
end
defp run_prepare(conn, query, meter, opts) do
with {:ok, query, meter} <- prepare(conn, query, meter, opts) do
describe(conn, query, meter, opts)
end
end
defp prepare(%DBConnection{pool_ref: pool_ref} = conn, query, meter, opts) do
pool_ref
|> Holder.handle(:handle_prepare, [query], opts)
|> handle_common_result(conn, event(meter, :prepare))
end
defp run_prepare_execute(conn, query, params, meter, opts) do
with {:ok, query, meter} <- run_prepare(conn, query, meter, opts),
{:ok, params, meter} <- encode(conn, query, params, meter, opts) do
run_execute(conn, query, params, meter, opts)
end
end
defp run_execute(conn, query, params, meter, opts) do
%DBConnection{pool_ref: pool_ref} = conn
meter = event(meter, :execute)
case Holder.handle(pool_ref, :handle_execute, [query, params], opts) do
{:ok, query, result, _conn_state} ->
{:ok, query, result, meter}
{:ok, _, _} = other ->
bad_return!(other, conn, meter)
other ->
handle_common_result(other, conn, meter)
end
end
defp raised_close(conn, query, meter, opts, kind, reason, stack) do
with {:ok, _, meter} <- run_close(conn, [query], meter, opts) do
{kind, reason, stack, meter}
end
end
defp run_close(conn, args, meter, opts) do
meter = event(meter, :close)
cleanup(conn, :handle_close, args, meter, opts)
end
defp run_cleanup(%DBConnection{} = conn, fun, args, meter, opts) do
fun.(conn, args, meter, opts)
end
defp run_cleanup(pool, fun, args, meter, opts) do
with {:ok, conn, meter} <- checkout(pool, meter, opts) do
try do
fun.(conn, args, meter, opts)
after
checkin(conn)
end
end
end
defp cleanup(conn, fun, args, meter, opts) do
%DBConnection{pool_ref: pool_ref} = conn
case Holder.cleanup(pool_ref, fun, args, opts) do
{:ok, result, _conn_state} ->
{:ok, result, meter}
{:error, err, _conn_state} ->
{:error, err, meter}
{:disconnect, err, _conn_state} ->
disconnect(conn, err)
{:error, err, meter}
{:catch, kind, reason, stack} ->
stop(conn, kind, reason, stack)
{kind, reason, stack, meter}
other ->
bad_return!(other, conn, meter)
end
end
defp run(%DBConnection{} = conn, fun, meter, opts) do
fun.(conn, meter, opts)
end
defp run(pool, fun, meter, opts) do
with {:ok, conn, meter} <- checkout(pool, meter, opts) do
try do
fun.(conn, meter, opts)
after
checkin(conn)
end
end
end
defp run(%DBConnection{} = conn, fun, arg, meter, opts) do
fun.(conn, arg, meter, opts)
end
defp run(pool, fun, arg, meter, opts) do
with {:ok, conn, meter} <- checkout(pool, meter, opts) do
try do
fun.(conn, arg, meter, opts)
after
checkin(conn)
end
end
end
defp run(%DBConnection{} = conn, fun, arg1, arg2, meter, opts) do
fun.(conn, arg1, arg2, meter, opts)
end
defp run(pool, fun, arg1, arg2, meter, opts) do
with {:ok, conn, meter} <- checkout(pool, meter, opts) do
try do
fun.(conn, arg1, arg2, meter, opts)
after
checkin(conn)
end
end
end
defp meter(opts) do
case Keyword.get(opts, :log) do
nil -> nil
log -> {log, []}
end
end
defp event(nil, _),
do: nil
defp event({log, events}, event),
do: {log, [{event, System.monotonic_time()} | events]}
defp past_event(nil, _, _),
do: nil
defp past_event(log_events, _, nil),
do: log_events
defp past_event({log, events}, event, time),
do: {log, [{event, time} | events]}
defp log({:ok, res, meter}, call, query, params),
do: log(meter, call, query, params, {:ok, res})
defp log({:ok, res1, res2, meter}, call, query, params),
do: log(meter, call, query, params, {:ok, res1, res2})
defp log({ok, res, meter}, call, query, cursor) when ok in [:cont, :halt],
do: log(meter, call, query, cursor, {ok, res})
defp log({:error, err, meter}, call, query, params),
do: log(meter, call, query, params, {:error, err})
defp log({kind, reason, stack, meter}, call, query, params),
do: log(meter, call, query, params, {kind, reason, stack})
defp log(nil, _, _, _, result),
do: log_result(result)
defp log({log, times}, call, query, params, result) do
entry = DBConnection.LogEntry.new(call, query, params, times, entry_result(result))
try do
log(log, entry)
catch
kind, reason ->
stack = __STACKTRACE__
log_raised(entry, kind, reason, stack)
end
log_result(result)
end
defp entry_result({kind, reason, stack})
when kind in [:error, :exit, :throw] do
msg = "an exception was raised: " <> Exception.format(kind, reason, stack)
{:error, %DBConnection.ConnectionError{message: msg}}
end
defp entry_result({ok, res}) when ok in [:cont, :halt],
do: {:ok, res}
defp entry_result(other), do: other
defp log({mod, fun, args}, entry), do: apply(mod, fun, [entry | args])
defp log(fun, entry), do: fun.(entry)
defp log_result({kind, reason, stack}) when kind in [:error, :exit, :throw] do
:erlang.raise(kind, reason, stack)
end
defp log_result(other), do: other
defp log_raised(entry, kind, reason, stack) do
reason = Exception.normalize(kind, reason, stack)
Logger.error(
fn ->
"an exception was raised logging #{inspect(entry)}: " <>
Exception.format(kind, reason, stack)
end,
crash_reason: {crash_reason(kind, reason), stack}
)
catch
_, _ ->
:ok
end
defp crash_reason(:throw, value), do: {:nocatch, value}
defp crash_reason(_, value), do: value
defp run_transaction(conn, fun, run, opts) do
%DBConnection{conn_ref: conn_ref} = conn
try do
result = fun.(%{conn | conn_mode: :transaction})
conclude(conn, result)
catch
:throw, {__MODULE__, ^conn_ref, reason} ->
reset(conn)
case rollback(conn, run, opts) do
{:ok, _} ->
{:error, reason}
{:error, %DBConnection.TransactionError{}} ->
{:error, reason}
{:error, %DBConnection.ConnectionError{}} ->
{:error, reason}
{:error, err} ->
raise err
end
kind, reason ->
stack = __STACKTRACE__
reset(conn)
_ = rollback(conn, run, opts)
:erlang.raise(kind, reason, stack)
else
result ->
case commit(conn, run, opts) do
{:ok, _} ->
{:ok, result}
{:error, %DBConnection.TransactionError{}} ->
{:error, :rollback}
{:error, err} ->
raise err
end
after
reset(conn)
end
end
defp fail(%DBConnection{pool_ref: pool_ref}) do
case Holder.status?(pool_ref, :ok) do
true -> Holder.put_status(pool_ref, :aborted)
false -> :ok
end
end
defp conclude(%DBConnection{pool_ref: pool_ref, conn_ref: conn_ref}, result) do
case Holder.status?(pool_ref, :ok) do
true -> result
false -> throw({__MODULE__, conn_ref, :rollback})
end
end
defp reset(%DBConnection{pool_ref: pool_ref}) do
case Holder.status?(pool_ref, :aborted) do
true -> Holder.put_status(pool_ref, :ok)
false -> :ok
end
end
defp begin(conn, run, opts) do
conn
|> run.(&run_begin/3, meter(opts), opts)
|> log(:begin, :begin, nil)
end
defp run_begin(conn, meter, opts) do
%DBConnection{pool_ref: pool_ref} = conn
meter = event(meter, :begin)
case Holder.handle(pool_ref, :handle_begin, [], opts) do
{status, _conn_state} when status in [:idle, :transaction, :error] ->
status_disconnect(conn, status, meter)
other ->
handle_common_result(other, conn, meter)
end
end
defp rollback(conn, run, opts) do
conn
|> run.(&run_rollback/3, meter(opts), opts)
|> log(:rollback, :rollback, nil)
end
defp run_rollback(conn, meter, opts) do
%DBConnection{pool_ref: pool_ref} = conn
meter = event(meter, :rollback)
case Holder.handle(pool_ref, :handle_rollback, [], opts) do
{status, _conn_state} when status in [:idle, :transaction, :error] ->
status_disconnect(conn, status, meter)
other ->
handle_common_result(other, conn, meter)
end
end
defp commit(conn, run, opts) do
case run.(conn, &run_commit/3, meter(opts), opts) do
{:rollback, {:ok, result, meter}} ->
log(meter, :commit, :rollback, nil, {:ok, result})
err = DBConnection.TransactionError.exception(:error)
{:error, err}
{query, other} ->
log(other, :commit, query, nil)
{:error, err, meter} ->
log(meter, :commit, :commit, nil, {:error, err})
{kind, reason, stack, meter} ->
log(meter, :commit, :commit, nil, {kind, reason, stack})
end
end
defp run_commit(conn, meter, opts) do
%DBConnection{pool_ref: pool_ref} = conn
meter = event(meter, :commit)
case Holder.handle(pool_ref, :handle_commit, [], opts) do
{:error, _conn_state} ->
{:rollback, run_rollback(conn, meter, opts)}
{status, _conn_state} when status in [:idle, :transaction] ->
{:commit, status_disconnect(conn, status, meter)}
other ->
{:commit, handle_common_result(other, conn, meter)}
end
end
defp status_disconnect(conn, status, meter) do
err = DBConnection.TransactionError.exception(status)
disconnect(conn, err)
{:error, err, meter}
end
defp run_status(conn, meter, opts) do
%DBConnection{pool_ref: pool_ref} = conn
case Holder.handle(pool_ref, :handle_status, [], opts) do
{status, _conn_state} when status in [:idle, :transaction, :error] ->
{status, meter}
{:disconnect, err, _conn_state} ->
disconnect(conn, err)
{:error, err, meter}
{:catch, kind, reason, stack} ->
stop(conn, kind, reason, stack)
{kind, reason, stack, meter}
other ->
bad_return!(other, conn, meter)
end
end
defp run_prepare_declare(conn, query, params, meter, opts) do
with {:ok, query, meter} <- prepare(conn, query, meter, opts),
{:ok, query, meter} <- describe(conn, query, meter, opts),
{:ok, params, meter} <- encode(conn, query, params, meter, opts),
{:ok, query, cursor, meter} <- run_declare(conn, query, params, meter, opts) do
{:ok, query, cursor, meter}
end
end
defp run_declare(conn, query, params, meter, opts) do
%DBConnection{pool_ref: pool_ref} = conn
meter = event(meter, :declare)
case Holder.handle(pool_ref, :handle_declare, [query, params], opts) do
{:ok, query, result, _conn_state} ->
{:ok, query, result, meter}
{:ok, _, _} = other ->
bad_return!(other, conn, meter)
other ->
handle_common_result(other, conn, meter)
end
end
defp stream_fetch(conn, {:cont, query, cursor}, opts) do
conn
|> run(&run_stream_fetch/4, [query, cursor], meter(opts), opts)
|> log(:fetch, query, cursor)
|> case do
{ok, result} when ok in [:cont, :halt] ->
{[result], {ok, query, cursor}}
{:error, err} ->
raise err
end
end
defp stream_fetch(_, {:halt, _, _} = state, _) do
{:halt, state}
end
defp run_stream_fetch(conn, args, meter, opts) do
[query, _] = args
with {ok, result, meter} when ok in [:cont, :halt] <- run_fetch(conn, args, meter, opts),
{:ok, result, meter} <- decode(query, result, meter, opts) do
{ok, result, meter}
end
end
defp run_fetch(conn, args, meter, opts) do
%DBConnection{pool_ref: pool_ref} = conn
meter = event(meter, :fetch)
case Holder.handle(pool_ref, :handle_fetch, args, opts) do
{:cont, result, _conn_state} ->
{:cont, result, meter}
{:halt, result, _conn_state} ->
{:halt, result, meter}
other ->
handle_common_result(other, conn, meter)
end
end
defp stream_deallocate(conn, {_status, query, cursor}, opts),
do: deallocate(conn, query, cursor, opts)
defp run_deallocate(conn, args, meter, opts) do
meter = event(meter, :deallocate)
cleanup(conn, :handle_deallocate, args, meter, opts)
end
defp resource(%DBConnection{} = conn, start, next, stop, opts) do
start = fn -> start.(conn, opts) end
next = fn state -> next.(conn, state, opts) end
stop = fn state -> stop.(conn, state, opts) end
Stream.resource(start, next, stop)
end
end
