shm-typed-array
v0.1.1
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IPC shared memory for NodeJs. Use as Buffer or TypedArray.
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IPC shared memory for Node.js
Use as Buffer
or TypedArray
Supports System V and POSIX shared memory
Install
$ npm install shm-typed-array
Windows is not supported.
System V vs POSIX
Versions 0.0.* support only System V memory segments.
Starting from version 0.1.0 POSIX memory objects are also supported.
System V is the classic way to use shared memory, stores IPC objects internally in the kernel.
POSIX is newer, but not fully supported in MacOS, uses the file system interface.
To create POSIX memory objects, use string parameter key
in API.
Eg. shm.create(100, 'Buffer', '/test')
will create virtual file /dev/shm/test
in tmpfs for Linix.
To create System V memory segment, use numeric parameter key
in API.
Eg. shm.create(100, 'Buffer', 1234)
or shm.create(100)
to autogenerate key.
API
shm.create (count, typeKey, key?, perm?)
Create shared memory segment/object.count
- number of elements (not bytes),typeKey
- type of elements ('Buffer'
by default, see list below),key
- integer/null to create System V memory segment, or string to create POSIX memory object,perm
- permissions flag (default is 660
).
Returns shared memory Buffer
or descendant of TypedArray
object, class depends on param typeKey
.
Or returns null
if shm already exists with provided key.
For System V: returned object has property key
- integer key of created System V shared memory segment, to use in shm.get(key)
.
For POSIX: shared memory objects are not automatically destroyed. You should call shm.destroy(key)
manually on process cleanup or if you don't need the object anymore.
shm.get (key, typeKey)
Get created shared memory segment/object by key.
Returns null
if shm not exists with provided key.
shm.detach (key, forceDestroy?)
Detach shared memory segment/object.
For System V: If there are no other attaches for a segment, it will be destroyed automatically (even if forceDestroy
is not true).
For POSIX: Unlike System V segments, POSIX object will not be destroyed automatically. You need to destroy it manually by providing true to forceDestroy
argument or using shm.destroy(key)
.
shm.destroy (key)
Destroy shared memory segment/object.
Same as shm.detach(key, true)
shm.detachAll ()
Detach all created shared memory segments and objects.
Will be automatically called on process exit, see Cleanup.
shm.getTotalSize()
Get total size of all used (mapped) shared memory in bytes.
shm.getTotalCreatedSize()
Get total size of all created shared memory in bytes.
shm.LengthMax
Max length of shared memory segment (count of elements, not bytes)
2^31 for 64bit, 2^30 for 32bit
Types:
shm.BufferType = {
'Buffer': shm.SHMBT_BUFFER,
'Int8Array': shm.SHMBT_INT8,
'Uint8Array': shm.SHMBT_UINT8,
'Uint8ClampedArray': shm.SHMBT_UINT8CLAMPED,
'Int16Array': shm.SHMBT_INT16,
'Uint16Array': shm.SHMBT_UINT16,
'Int32Array': shm.SHMBT_INT32,
'Uint32Array': shm.SHMBT_UINT32,
'Float32Array': shm.SHMBT_FLOAT32,
'Float64Array': shm.SHMBT_FLOAT64,
};
Cleanup
This library does cleanup of created SHM segments/objects only on normal exit of process, see exit
event.
If you want to do cleanup on terminate signals like SIGINT
, SIGTERM
, please use node-cleanup / node-death and add code to exit handlers:
shm.detachAll();
Also note that POSIX shared memory objects are not automatically destroyed.
You should call shm.destroy('/your_name')
manually if you don't need it anymore.
Usage
See example.js
Usage of memory segments:
const cluster = require('cluster');
const shm = require('shm-typed-array');
var buf, arr;
if (cluster.isMaster) {
buf = shm.create(4096); //4KB
arr = shm.create(1000000*100, 'Float32Array'); //100M floats
buf[0] = 1;
arr[0] = 10.0;
console.log('[Master] Typeof buf:', buf.constructor.name,
'Typeof arr:', arr.constructor.name);
var worker = cluster.fork();
worker.on('online', function() {
this.send({ msg: 'shm', bufKey: buf.key, arrKey: arr.key });
var i = 0;
setInterval(function() {
buf[0] += 1;
arr[0] /= 2;
console.log(i + ' [Master] Set buf[0]=', buf[0],
' arr[0]=', arr ? arr[0] : null);
i++;
if (i == 5) {
groupSuicide();
}
}, 500);
});
} else {
process.on('message', function(data) {
var msg = data.msg;
if (msg == 'shm') {
buf = shm.get(data.bufKey);
arr = shm.get(data.arrKey, 'Float32Array');
console.log('[Worker] Typeof buf:', buf.constructor.name,
'Typeof arr:', arr.constructor.name);
var i = 0;
setInterval(function() {
console.log(i + ' [Worker] Get buf[0]=', buf[0],
' arr[0]=', arr ? arr[0] : null);
i++;
if (i == 2) {
shm.detach(data.arrKey);
arr = null; //otherwise process will drop
}
}, 500);
} else if (msg == 'exit') {
process.exit();
}
});
}
function groupSuicide() {
if (cluster.isMaster) {
for (var id in cluster.workers) {
cluster.workers[id].send({ msg: 'exit'});
cluster.workers[id].destroy();
}
process.exit();
}
}
Output:
[Master] Typeof buf: Buffer Typeof arr: Float32Array
[Worker] Typeof buf: Buffer Typeof arr: Float32Array
0 [Master] Set buf[0]= 2 arr[0]= 5
0 [Worker] Get buf[0]= 2 arr[0]= 5
1 [Master] Set buf[0]= 3 arr[0]= 2.5
1 [Worker] Get buf[0]= 3 arr[0]= 2.5
2 [Master] Set buf[0]= 4 arr[0]= 1.25
2 [Worker] Get buf[0]= 4 arr[0]= null
3 [Master] Set buf[0]= 5 arr[0]= 0.625
3 [Worker] Get buf[0]= 5 arr[0]= null
4 [Master] Set buf[0]= 6 arr[0]= 0.3125
shm segments destroyed: 2