Interprocess shared memory cache for Node.JS

It supports auto memory-management and fast object serialization. It uses a hashmap and LRU cache internally to maintain its contents.

• 1.7.3 Account isolation
• 1.7.2 Fix hash find
• 1.7.1 Support Node.JS 14
• 1.7.0 Only Support Node.JS 12+
• 1.6.2
  • Add exchange method which can be used as atomic lock as well as increase
  • Add fastGet method which does not touch the LRU sequence
• 1.6.1 Update nan requirement to 2.4.0
• 1.6.0 Add support for Win32 (#7). Thanks to @matthias-christen@dancrumb

You can install it with npm. Just type npm i node-shared-cache will do it.

You can also download and install it manually, but you need to install Node.JS and node-gyp first.

git clone https://github.com/kyriosli/node-shared-cache.git cd node-shared-cache node-gyp rebuild 

This software (source code and its binary builds) is absolutely copy free and any download or modification is permitted except for unprohibited commercial use.

But due to the complexity of this software, any bugs or runtime exceptions could happen when programs which includeed it run into an unexpected situation, which in most cases should be harmless but also have the chance to cause:

• program crash
• system down
• software damage
• hardware damage

which would lead to data corruption or even economic losses.

So when you are using this software, DO

• check the data
• double check the data
• avoid undefined behavior to happen

To avoid data crupption, we use a read-write lock to ensure that data modification is exclusive. But when a program is writting data when something bad, for example, a SIGKILL, happens that crashes the program before the write operation is complete and lock is released, other processes may not be able to enter the exclusive region again. I do not use an auto recovery lock such as flock, which will automatically release when process exits, just in case that wrong data is returned when performing a reading operation, or even, causing a segment fault.

// create cache instancevarcache=require("node-shared-cache");varobj=newcache.Cache("test",557056);// setting propertyobj.foo="bar";// getting propertyconsole.log(obj.foo);// enumerating propertiesfor(varkinobj);Object.keys(obj);// deleting propertydeleteobj.foo;// writing objects is also supportedobj.foo={foo: "bar"};// but original object reference is not savedvartest=(obj.foo={foo: "bar"});test===obj.foo;// false// circular reference is supported.test.self=test;obj.foo=test;// and saved result is also circulartest=obj.foo;test.self===test;// true// increase a keycache.increase(obj,"foo");cache.increase(obj,"foo",3);// exchange current key with new value, the old value is returnedcache.set(obj,"foo",123);cache.exchange(obj,"foo",456);// 123obj.foo;// 456// release memory regioncache.release("test");// dump current cachevarvalues=cache.dump(obj);// dump current cache by key prefixvalues=cache.dump(obj,"foo_");

functionCache(name,size,optionalblock_size)

name represents a file name in shared memory, size represents memory size in bytes to be used. block_size denotes the size of the unit of the memory block.

block_size can be any of:

• cache.SIZE_64 (6): 64 bytes (default)
• cache.SIZE_128 (7): 128 bytes
• cache.SIZE_256 (8): 256 bytes
• cache.SIZE_512 (9): 512 bytes
• cache.SIZE_1K (10): 1KB
• cache.SIZE_2K (11): 2KB
• ...
• cache.SIZE_16K (14): 16KB

Note that:

• size should not be smaller than 524288 (512KB)
• block count is 32-aligned
• key length should not be greater than (block_size - 32) / 2, for example, when block size is 64 bytes, maximum key length is 16 chars.
• key length should also not be greater than 256

So when block_size is set to default, the maximum memory size that can be used is 128M, and the maximum keys that can be stored is 2088960 (8192 blocks is used for data structure)

set(name,value);

functionrelease(name)

The shared memory named name will be released. Throws error if shared memory is not found. Note that this method simply calls shm_unlink and does not check whether the memory region is really initiated by this module.

Don't call this method when the cache is still used by some process, may cause memory leak

function clear(instance) 

Clears a cache

functionincrease(instance,name,optionalincrease_by)

Increase a key in the cache by an integer (default to 1). If the key is absent, or not an integer, the key will be set to increase_by.

functionexchange(instance,name,new_value)

Update a key in the cache with a new value, the old value is returned.

functionfastGet(instance,name)

Get the value of a key without touching the LRU sequence. This method is usually faster than instance[name] because it uses different lock mechanism to ensure shared reading across processes.

functiondump(instance,optionalprefix)

Dump keys and values

Tests are run under a virtual machine with one processor:

$ node -v v0.12.4 $ cat /proc/cpuinfo processor : 0 vendor_id : GenuineIntel cpu family : 6 model : 45 model name : Intel(R) Xeon(R) CPU E5-2630 0 @ 2.30GHz stepping : 7 microcode : 0x70d cpu MHz : 2300.090 cache size : 15360 KB ...

Block size is set to 64 and 1MB of memory is used.

When setting property 100w times:

// test plain objectvarplain={};console.time("plain obj");for(vari=0;i<1000000;i++){plain["test"+(i&127)]=i;}console.timeEnd("plain obj");// test shared cachevarobj=newbinding.Cache("test",1048576);console.time("shared cache");for(vari=0;i<1000000;i++){obj["test"+(i&127)]=i;}console.timeEnd("shared cache");

The result is:

plain obj: 227ms shared cache: 492ms (1:2.17) 

When trying to read existing key:

console.time("read plain obj");for(vari=0;i<1000000;i++){plain["test"+(i&127)];}console.timeEnd("read plain obj");console.time("read shared cache");for(vari=0;i<1000000;i++){obj["test"+(i&127)];}console.timeEnd("read shared cache");

The result is:

read plain obj: 138ms read shared cache: 524ms (1:3.80) 

When trying to read keys that are not existed:

console.time("read plain obj with key absent");for(vari=0;i<1000000;i++){plain["oops"+(i&127)];}console.timeEnd("read plain obj with key absent");console.time("read shared cache with key absent");for(vari=0;i<1000000;i++){obj["oops"+(i&127)];}console.timeEnd("read shared cache with key absent");

The result is:

read plain obj with key absent: 265ms read shared cache with key absent: 595ms (1:2.24) 

When enumerating all the keys:

console.time("enumerate plain obj");for(vari=0;i<100000;i++){Object.keys(plain);}console.timeEnd("enumerate plain obj");console.time("enumerate shared cache");for(vari=0;i<100000;i++){Object.keys(obj);}console.timeEnd("enumerate shared cache");

The result is:

enumerate plain obj: 1201ms enumerate shared cache: 4262ms (1:3.55) 

Warn: Because the shared memory can be modified at any time even the current Node.js process is running, depending on keys enumeration result to determine whether a key is cached is unwise. On the other hand, it takes so long a time to build strings from memory slice, as well as putting them into an array, so DO NOT USE IT unless you know that what you are doing.

We choose a c-style binary serialization method rather than JSON.stringify, in two concepts:

• Performance serializing and unserializing
• Support for circular reference

Tests code list:

varinput={env: process.env,arr: [process.env,process.env]};console.time("JSON.stringify");for(vari=0;i<100000;i++){JSON.stringify(input);}console.timeEnd("JSON.stringify");console.time("binary serialization");for(vari=0;i<100000;i++){obj.test=input;}console.timeEnd("binary serialization");// test object unserializationinput=JSON.stringify(input);console.time("JSON.parse");for(vari=0;i<100000;i++){JSON.parse(input);}console.timeEnd("JSON.parse");console.time("binary unserialization");for(vari=0;i<100000;i++){obj.test;}console.timeEnd("binary unserialization");

The result is:

JSON.stringify: 5876ms binary serialization: 2523ms (2.33:1) JSON.parse: 2042ms binary unserialization: 2098ms (1:1.03)