Non-blocking Redis client with focus on performance and robustness.
This fork is the official continuation of wooga/eredis
.
It includes several improvements, such as
TLS support, Sentinel support and TCP error handling corrections.
See CHANGELOG.md for details.
Note: This client connects to a standalone Redis node, optionally using Sentinel. For Redis Cluster, you need eredis_cluster or ecredis.
Supported Redis features:
- Any command, through
eredis:q/2,3
- Transactions
- Pipelining
- Authentication & multiple DBs
- Pubsub
- TLS
- Sentinel support
Generated API documentation: doc/eredis.md
Published documentation can also be found on hexdocs.
If you have Redis running on localhost with default settings, like:
docker run --rm --net=host redis:latest
you may copy and paste the following into a shell to try out Eredis:
git clone https://github.com/Nordix/eredis.git
cd eredis
rebar3 shell
{ok, C} = eredis:start_link().
{ok, <<"OK">>} = eredis:q(C, ["SET", "foo", "bar"]).
{ok, <<"bar">>} = eredis:q(C, ["GET", "foo"]).
To connect to a Redis instance listening on a Unix domain socket:
{ok, C1} = eredis:start_link({local, "/var/run/redis.sock"}, 0).
To connect to a Redis instance using TLS:
Options = [{tls, [{cacertfile, "ca.crt"},
{certfile, "client.crt"},
{keyfile, "client.key"}]}],
{ok, C2} = eredis:start_link("127.0.0.1", ?TLS_PORT, Options),
To connect to a Redis sentinel cluster:
SentinelOptions = [{master_group, mymaster},
{endpoints, [{"127.0.0.1", 26379}]}],
{ok, C1} = eredis:start_link([{sentinel, SentinelOptions}]).
MSET and MGET:
KeyValuePairs = ["key1", "value1", "key2", "value2", "key3", "value3"].
{ok, <<"OK">>} = eredis:q(C, ["MSET" | KeyValuePairs]).
{ok, Values} = eredis:q(C, ["MGET" | ["key1", "key2", "key3"]]).
HASH
HashObj = ["id", "objectId", "message", "message", "receiver", "receiver", "status", "read"].
{ok, <<"OK">>} = eredis:q(C, ["HMSET", "key" | HashObj]).
{ok, Values} = eredis:q(C, ["HGETALL", "key"]).
LIST
eredis:q(C, ["LPUSH", "keylist", "value"]).
eredis:q(C, ["RPUSH", "keylist", "value"]).
eredis:q(C, ["LRANGE", "keylist", 0, -1]).
Transactions:
{ok, <<"OK">>} = eredis:q(C, ["MULTI"]).
{ok, <<"QUEUED">>} = eredis:q(C, ["SET", "foo", "bar"]).
{ok, <<"QUEUED">>} = eredis:q(C, ["SET", "bar", "baz"]).
{ok, [<<"OK">>, <<"OK">>]} = eredis:q(C, ["EXEC"]).
Pipelining:
P1 = [["SET", a, "1"],
["LPUSH", b, "3"],
["LPUSH", b, "2"]].
[{ok, <<"OK">>}, {ok, <<"1">>}, {ok, <<"2">>}] = eredis:qp(C, P1).
Pubsub:
1> eredis_sub:sub_example().
received {subscribed,<<"foo">>,<0.34.0>}
{<0.34.0>,<0.37.0>}
2> eredis_sub:pub_example().
received {message,<<"foo">>,<<"bar">>,<0.34.0>}
ok
3>
Pattern Subscribe:
1> eredis_sub:psub_example().
received {subscribed,<<"foo*">>,<0.33.0>}
{<0.33.0>,<0.36.0>}
2> eredis_sub:ppub_example().
received {pmessage,<<"foo*">>,<<"foo123">>,<<"bar">>,<0.33.0>}
ok
3>
Query: qp/2,3
Eredis has one main function to interact with redis, which is
eredis:q(Client::pid(), Command::iolist())
. The response will either
be {ok, Value::binary() | [binary()]}
or {error, Message::binary()}
. The value is always the exact value returned by
Redis, without any type conversion. If Redis returns a list of values,
this list is returned in the exact same order without any type
conversion.
Pipelined query: qp/2,3
To send multiple requests to redis in a batch, aka. pipelining
requests, you may use eredis:qp(Client::pid(), [Command::iolist()])
. This function returns {ok, [Value::binary()]}
where the values are the redis responses in the same order as the
commands you provided.
Connect a client: start_link/1
To start the client, use start_link/1
or one of its variants. start_link/1
takes the following options (proplist):
host
: DNS name or IP address as string; or unix domain socket as{local, Path}
(available in OTP 19+)port
: integer, default is 6379database
: integer or 0 for default database, default: 0username
: string, default: no usernamepassword
: string, default: no passwordreconnect_sleep
: integer of milliseconds to sleep between reconnect attempts, default: 100connect_timeout
: timeout value in milliseconds to use in the connect, default: 5000socket_options
: proplist of gen_tcp options used when connecting the socket, default is?SOCKET_OPTS
. It's possible to specify{active, N}
or{active, true}
. Activeonce
andfalse
are not supported. The default is N = 10.tls
: enable TLS by providing a list of options used when establishing the TLS connection, default is off. It's possible to specify{active, N}
or{active, true}
in TLS options. Activeonce
andfalse
are not supported. The default is N = 10. Note that{active, N}
with TLS requires OTP 21.3 or later.
Commands are pipelined automatically so multiple processes can share the same
Eredis connection instance. Although q/2,3
and qp/2,3
are blocking until the
response is returned, Eredis is not blocked.
Process A Process B Eredis TCP/TLS socket
| | | (Redis server)
| q(Pid, Command1) | | |
|------------------------------------>|---------------->|
| | q(Pid, Command2) | |
| |----------------->|---------------->|
| | | |
... ... ... ...
| | | |
| | | Response 1 |
|<------------------------------------|<----------------|
| | | Response 2 |
| |<-----------------|<----------------|
When Eredis for some reason loses the connection to Redis, Eredis
will keep trying to reconnect until a connection is successfully
established, which includes the AUTH
and SELECT
calls. The sleep
time between attempts to reconnect can be set in the
eredis:start_link/1
call.
As long as the connection is down, Eredis will respond to any request
immediately with {error, no_connection}
without actually trying to
connect. This serves as a kind of circuit breaker and prevents a
stampede of clients just waiting for a failed connection attempt or
gen_server:call
timeout.
Note: If Eredis is starting up and cannot connect, it will fail
immediately with {connection_error, Reason}
.
Thanks to Dave Peticolas (jdavisp3), eredis supports
pubsub. eredis_sub
offers a separate client that will forward
channel messages from Redis to an Erlang process in an "active-once"
pattern similar to gen_tcp sockets. After every message received, the
controlling process must acknowledge receipt using
eredis_sub:ack_message/1
.
If the controlling process does not process messages fast enough, eredis will queue the messages up to a certain queue size controlled by configuration. When the max size is reached, eredis will either drop messages or crash, also based on configuration.
Subscriptions are managed using eredis_sub:subscribe/2
and
eredis_sub:unsubscribe/2
. When Redis acknowledges the change in
subscription, a message is sent to the controlling process for each
channel. Then, eredis sends a message on the form {subscribed, Channel, ClientPid}
to the controlling process, which must be acked using
eredis_sub:ack_message/1
.
eredis also supports Pattern Subscribe using eredis_sub:psubscribe/2
and eredis_sub:punsubscribe/2
. As with normal subscriptions, a message
is sent to the controlling process for each channel and eredis sends a
message on the form {subscribed, Channel, ClientPid}
to the
controlling process, which must be acked using eredis_sub:ack_message/1
.
The controlling process is also notified in case of reconnection attempts or
failures. See test/eredis_pubsub_SUITE.erl
for examples.
Starting with version 1.5, eredis automatically resubscribes after reconnect.
Then, the controlling process will receive {subscribed, Channel, ClientPid}
messages again for every channel and pattern subscribed to. These must also be
acked.
Here is a list of all the messages that are sent to the controlling process. Some messages don't need to be acked, but it does not harm doing so.
-
{eredis_connected, Pid}
when the socket to Redis is established and authenticated. Doesn't need to be acked. -
{eredis_disconnected, Pid}
when the connection to Redis has been lost. Doesn't need to be acked. -
{eredis_reconnect_attempt, Pid}
at every reconnect attempt, when the connection to Redis has been lost. Doesn't need to be acked. -
{eredis_reconnect_failed, Pid, {error, {connection_error, Reason}}}
after every failed reconnect attempt. Doesn't need to be acked. -
{message, Channel, Message, Pid}
for every incoming message on subscribed channels. Needs to be acked usingeredis_sub:ack_message/1
. -
{pmessage, Pattern, Channel, Message, Pid}
for every incoming message on channels subscribed to by pattern, using usingeredis_sub:psubscribe/2
. Needs to be acked usingeredis_sub:ack_message/1
. -
{subscribed, Channel, Pid}
when a subscription has been confirmed by Redis. Channel is either a channel (subscribe) or a pattern (psubscribe). Needs to be acked usingeredis_sub:ack_message/1
. -
{unsubscribed, Channel, Pid}
when a subscription has been removed from Redis. Channel is either a channel (unsubscribe) or a pattern (punsubscribe). Needs to be acked usingeredis_sub:ack_message/1
.
Eredis also implements the AUTH and SELECT calls for you. When the
client is started with something else than default values for password
and database, it will issue the AUTH
and SELECT
commands
appropriately, even when reconnecting after a timeout.
Using lasp-bench you may
benchmark Eredis on your own hardware using the provided config and
driver. See priv/basho_bench_driver_eredis.config
and
src/basho_bench_driver_eredis.erl
.
Testcase summary from our daily runs:
The eredis-benchmark repo runs
a daily job that produces above graphs. It also contains the script
run-tests.sh
that might help you with the needed steps when setting up the
benchmark testing on your own.
Eredis uses the same queueing mechanism as Erldis. eredis:q/2
uses
gen_server:call/2
to do a blocking call to the client
gen_server. The client will immediately send the request to Redis, add
the caller to the queue and reply with noreply
. This frees the
gen_server up to accept new requests and parse responses as they come
on the socket.
When data is received on the socket, we call eredis_parser:parse/2
until it returns a value, we then use gen_server:reply/2
to reply to
the first process waiting in the queue.
This queueing mechanism works because Redis guarantees that the response will be in the same order as the requests.
The socket is set to {active, N}
with N = 10 by default. This is configurable
by including {active, N}
in socket options or TLS options (if TLS is used). N
must be an integer or true
. Active once
and false
are not supported.
The response parser is capable of parsing partial data and continuing when more data arrives on the socket.
EUnit tests currently require a locally running instance of Redis.
rebar3 eunit
Xref, dialyzer and elvis should result in no errors.
rebar3 xref
rebar3 dialyzer
elvis rock
When the parser is accumulating data, a new binary is generated for
every call to parse/2
. This might create binaries that will be
reference counted. This could be improved by replacing it with an
iolist.
When parsing bulk replies, the parser knows the size of the bulk. If the
bulk is big and would come in many chunks, this could be improved by
having the client explicitly use gen_tcp:recv/2
to fetch the entire
bulk at once.
This is a fork of the original Eredis. Eredis was created by Knut Nesheim, with inspiration from the earlier Erldis.
Although this project is almost a complete rewrite, many patterns are the same as you find in Erldis, most notably the queueing of requests.
create_multibulk/1
and to_binary/1
were taken verbatim from Erldis.