|Alex Williams 770ff519a8||1 month ago|
|.github/workflows||2 months ago|
|diagrams||2 months ago|
|test||2 months ago|
|.gitignore||5 months ago|
|CHANGELOG.md||1 month ago|
|COMMANDS.md||2 months ago|
|LICENSE||7 months ago|
|Makefile||2 months ago|
|README.md||2 months ago|
|client.l||1 month ago|
|clihelpers.l||5 months ago|
|libkv.l||2 months ago|
|libkvclient.l||4 months ago|
|module.l||1 month ago|
|server.l||5 months ago|
|test.l||4 months ago|
Note: This library DOES NOT use the RESP protocol and thus cannot work with the
redis-clior other Redis clients/servers.
client.l can be used to send and receive “Redis-like” commands over TCP or UNIX named pipess.
This library is written in pure PicoLisp and contains no external dependencies.
To ensure everything works on your system, run the tests first:
./server.l --pass <yourpass> --verbose
./client.l --pass <yourpass> INFO
That should return some interesting info about your server. See below for more examples.
(setq *KV_pass "yourpass")
(setq *KV_pass "yourpass")
(kv-send-data '("INFO" "server"))
Received data will be returned as-is (list, integer, string, etc). Wrap the result like:
(kv-print Result) to send the output to
: (load "libkvclient.l") -> kv-start-client : (setq *KV_pass "yourpass") -> "yourpass" : (kv-start-client) -> T : (kv-send-data '("set" "mykey" 12345)) -> "OK" : (kv-send-data '("get" "mykey")) -> 12345 : (kv-send-data '("set" "yourkey" "12345")) -> "OK" : (kv-send-data '("get" "yourkey")) -> "12345"
Feel free to observe the example code in client.l.
(kv-send-data)will send the data to the server and automatically block the client while waiting for a response.
This section describes usage information for the CLI tools
The server listens in the foreground for TCP connections on port
6378 by default. Only the
verbosity are configurable, and a
password is required:
# server.l Usage: ./server.l --pass <pass> [options] Example: ./server.l --pass foobared --port 6378 --verbose --persist 60 Options: --help Show this help message and exit --binary Store data in binary format instead of text (default: plaintext) --pass <password> Password used by clients to access the server (required) --persist <seconds> Number of seconds between database persists to disk (default: disabled) --port <port> TCP listen port for communication with clients (default: 6378) --verbose Verbose flag (default: False)
./server.l --pass yourpass --verbose Parent PID: 38867 [sibling]=38874 [child]=38873 [parent]=38867 [msg] from client: (pid: 38873) ::ffff:127.0.0.1 ("IDENT" ("id" . "3F21CC32") ("hostname" . "meta.lan")) [msg] from child : (pid: 38873) ("message" 38873 ("IDENT" ("id" . "3F21CC32") ("hostname" . "meta.lan"))) [msg] to client: "OK 3F21CC32" [msg] from client: (pid: 38873) ::ffff:127.0.0.1 ("INFO" "server") [msg] from child : (pid: 38873) ("message" 38873 ("INFO" "server")) [msg] to client: "^J# Server^Japp_version:0.11.0^Jos:Linux 4.19.34-tinycore64 x86_64^Jarch_bits:64^Jprocess_id:38874^Jtcp_port:6378^Juptime_in_seconds:1^Juptime_in_days:0^Jexecutable:/usr/bin/picolisp^J" [child]=38873 exiting [msg] from child : (pid: 38873) ("done" 38873 NIL)
The client handles authentication, identification, and sending of “Redis-like” commands to the server. It then prints the result to
STDOUT and can be parsed by standard *NIX tools. The client receives PLIO data over a TCP socket, or named pipe (if client/server are on the same system).
# client.l Usage: ./client.l --pass <pass> COMMAND [arguments] Example: ./client.l --pass foobared --encrypt SET mysecret -- <(echo 'mypass') Options: --help Show this help message and exit --commands Show the full list of commands and exit --decrypt Enable decryption of values using a GPG public key (default: disabled) --encrypt Enable encryption of values using a GPG public key (default: disabled) --name <name> Easily identifiable client name (default: randomly generated) --host <host> Hostname or IP of the key/value server (default: localhost) --pass <data> Password used to access the server (required) --poll <seconds> Number of seconds for polling the key/value server (default: don't poll) --port <port> TCP port of the key/value server (default: 6378) -- STDIN Reads an argument from STDIN COMMAND LIST Commands are case-insensitive and don't always require arguments APPEND key value Append a value to a key BGSAVE Asynchronously save the dataset to disk CLIENT ID Returns the client ID for the current connection CLIENT KILL ID id [id ..] Kill the connection of a client CLIENT LIST Get the list of client connections CONVERT Convert a plaintext database to binary or vice-versa DEL key [key ..] Delete a key EXISTS key [key ..] Determine if a key exists GET key Get the value of a key GETSET key value Set the string value of a key and return its old value HDEL key field [field ..] Delete one or more hash fields HEXISTS key field Determine if a hash field exists HFIND key substring Find a substring in a hash key's field HGET key field Get the value of a hash field HGETALL key Get all the fields and values in a hash HKEYS key Get all the fields in a hash HLEN key Get the number of fields in a hash HMGET key field [field ..] Get the values of all the given hash fields HSET key field value [field value ..] Set the string value of a hash field HSTRLEN key field Get the length of the value of a hash field HVALS key Get all the values in a hash INFO [section] Get information and statistics about the server LINDEX key index Get an element from a list by its index LLEN key Get the length of a list LPOP key Remove and get the first element in a list LPOPRPUSH source destination Remove the first element in a list, append it to another list and return it LPUSH key element [element ..] Prepend one or multiple elements to a list LRANGE key start stop Get a range of elements from a list LREM key count element Remove elements from a list LSET key index element Set the value of an element in a list by its index LTRIM key start stop Trim a list to the specified range MGET key [key ..] Get the values of all the given keys MSET key value [key value ..] Set multiple keys to multiple values PING [message] Ping the server RPOP key Remove and get the last element in a list RPOLRPUSH source destination Remove the last element in a list, prepend it to another list and return it RPUSH key element [element ..] Append one or multiple elements to a list SAVE Synchronously save the dataset to disk SET key value Set the string value of a key STRLEN key Get the length of the value stored in a key
This section will explain some important technical details about the code, and limitations on what this library can and can’t do.
*KV/mykeys. This prefix is hardcoded everywhere and shouldn’t be changed.
*KV/%stats%/prefix and are read-only by external clients.
7672FDB2-4D29-4F10-BA7C-8EAD0E29626Eis used during the handshake sequence between all clients and servers. For compatibility with future tools, please do not change it.
(prinl), so a result
2will both appear the same. Lists are concatenated with a
,comma and also output using
(prinl). Error messages are sent to
STDERRand the client exits with error code
(tmp)directory of the server’s parent process, and will be removed when the parent exits cleanly. Please do not kill the parent process with
kill -KILL) as it will leave an unresponsive zombie sibling with the TCP socket still open, and the named pipes will not be removed.
OKif the key was set. Not all responses are absolutely identical to Redis though. Please remember this library isn’t designed to be a perfect clone of Redis (see Limitations below).
redis-clior other Redis clients.
client.lon the command-line, all values are stored as strings. Please use the TCP socket or named pipe directly to store integers and lists.
For the server, everything starts with the
(kv-listen) function, which is where the TCP server is started:
+------------+ +---------------------+ +----------------+ | TCP client | | (parent) | | (sibling) | +-----+---+--+ | +-------------+ | | +------------+ | ^ | | | TCP server | | | | Key/Value | | | +---------> | (kv-listen) | | | | in-memory | | | | +-------------+ | | | DB | | | | | | +------------+ | +-----+-------------> pipe_sibling +------> | | | | | +-+-+-+----------+ | +--------+ | | | | | +--+ child1 | <-----+ pipe_child_1 <----------+ | | | +--------+ | | | | | | | | | | +--------+ | | | | +--+ child2 | <-----+ pipe_child_2 <------------+ | | +--------+ | | | | | | | | +--------+ | | | +--+ child3 | <-----+ pipe_child_3 <--------------+ +--------+ | | +---------------------+
(kv-listen) is running, a TCP socket is opened on the configured port. An infinite loop begins and listens for incoming connections, giving each new TCP client its own forked child process for handling the request.
A named pipe called
pipe_sibling, is created in a temporary directory of the top-level parent process. This pipe will be used to communicate with other child processes, leaving the parent process to continue serving new TCP requests.
The parent process then forks another process, which we’ll call the sibling - an older sister if you prefer - and the sibling waits on the
pipe_sibling named pipe, listening for COMMANDS from the child processes.
The forked child processes will each create their own named pipe, called
pipe_child_<pid>, also in a temporary directory of the top-level parent process. The child process will listen on its own named pipe for messages sent by its older sister, the sibling. Once a message is received by the child, the response is sent back to the client over the TCP connection.
The idea is to have the sibling be the holder of all the keys. Every “Redis-like” command will have their data and statistics stored in the memory of the sibling process, and the sibling will handle receiving and sending its memory contents (keys/values) through named pipes to the respective child processes.
Similar to Redis, this database implements “snapshotting” (full memory dump to disk) and “AOF” (append-only log file), however both features are tightly coupled, which makes for a much better experience.
--persist Nparameter, where
Nis the number of seconds between each
BGSAVE(background save to disk).
--binaryparameter. Binary format (PLIO) loads and saves much quicker than plaintext, but it becomes difficult to debug a corrupt entry.
BGSAVE, so it technically shouldn’t grow too large or unmanageable.
BGSAVEcommands can still be sent even if persistence is disabled. This will dump the in-memory data to disk as if persistence was enabled.
Here we’ll assume persistence was previously enabled and data has already been written and saved to disk.
BGSAVE(non-blocking) command is received, a temporay copy of the AOF is made, the current AOF is wiped, and a background process is forked to save the DB to disk
kv.aof.tmp. It’s best not to modify or delete those files while the server is running. They can be safely removed while the server is stopped.
The AOF is stored by default in the
kv.aof file as defined by
Here are two separate entries in a typical AOF:
("1596099036.281142829" 54042 ("RPUSH" "mytestlist" ("four" "five" "six"))) ("1596099059.683596840" 57240 ("RPUSH" "yourtestlist" ("seven" "eight" "nine")))
Each line is a PicoLisp list with only 3 items:
StringUnix timestamp with nanoseconds for when the entry was created
IntegerNon-cryptographically secure hash (CRC) of the command and its arguments
ListCommand name, first argument, and subsequent arguments
When replaying the AOF, the server will ensure the hash of command and arguments match, to guarantee the data is intact. Replaying an AOF can be slow, depending on the number of keys/values.
Note: Manually modifying the AOF will require recomputing and replacing the hash with the result from
(hash '("RPUSH" "mytestlist" ("four" "five" "zero"))) -> 61453
The DB is stored by default in the
kv.db file as defined by
*KV_db. When backed up, the new filename contains the suffix
Here are two separate entries in a typical DB:
("smalldata" ("test1" "test2" "test3" "test4" "test5" "test6")) ("fooh_1000" "test data 1000")
Each line is a PicoLisp list with the key in the
(car), and values in the
(cadr). They are quickly replayed and stored in memory with a simple
BGSAVE. Since the AOF is always enabled, it’s not necessary to “save after N changes”, so the config is much simpler.
BGSAVE, but even then the AOF is wiped when a
BGSAVEis initiated (and restored/rewritten if there was an error).
AOF, because such a concept doesn’t even exist.
This library comes with a large suite of unit and integration tests. To run the tests, type:
(native)) should conditionally check for OS support.
Copyright (c) 2020 Alexander Williams, On-Prem firstname.lastname@example.org