node-epics-ca is lightweight EPICS Channel Access client library for Node.js, it is a FFI (Foreign Function Interface) implementation that talks to the existing EPICS Channel Access shared libraries using a third-party Node.js FFI package called koffi.
This project borrows ideas, implementations and the shared libraries from the following projects,
https://github.com/RobbieClarken/node-epics
https://github.com/onichandame/epics-ioc-connection
https://github.com/pyepics/pyepics
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Node.js 12.22.12
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Node.js 14.21.3
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Node.js 15.14.0
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Node.js 16.19.0
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Node.js 17.9.1
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Node.js 18.13.0
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Windows x86_64
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Linux x86_64
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macOS x86_64
npm install node-epics-caNODE_EPICS_CA_LIBCA, NODE_EPICS_CA_PEND_IO_DELAY or NODE_EPICS_CA_PEND_EVENT_DELAY can be set optionally, for example,
export NODE_EPICS_CA_LIBCA=/home/debian/epics/base-3.15.9/lib/linux-x86_64/libca.so
export NODE_EPICS_CA_PEND_IO_DELAY=1
export NODE_EPICS_CA_PEND_EVENT_DELAY=0.1If NODE_EPICS_CA_LIBCA is not specified, the os-specific shared libraries in the clibs directory will be used, and which one to use depends on the operating system.
const CA = require('node-epics-ca');
(async () => {
try {
console.log(await CA.get('calcExample'));
} catch (error) {
console.error(`get failed due to ${error}`)
}
})()const CA = require('node-epics-ca');
(async () => {
try {
console.log(await CA.get('calcExample'));
await CA.put("calcExample", 10);
console.log(await CA.get('calcExample'));
} catch (error) {
console.error(`put failed due to ${error}`)
}
})()const CA = require('node-epics-ca');
(async () => {
let pv = await CA.monitor('calcExample');
pv.on('value', function(data) {
console.log('Current:', data);
});
// Test purpose only, prevent the node.js main thread from exiting
setTimeout(function() {
console.log("Done!!!");
}, 3600 * 1000);
})()simpler way for monitor
const CA = require('node-epics-ca');
(async () => {
CA.monitor('calcExample', function(data) {
console.log('Current:', data);
});
setTimeout(function() {
console.log("Done!!!");
}, 3600 * 1000);
})()const CA = require('node-epics-ca');
(async () => {
try {
let result = await CA.info('calcExample');
console.log(`name: ${result.name}`);
console.log(`state: ${result.state}`);
console.log(`host: ${result.host}`);
console.log(`readAccess: ${result.readAccess}`);
console.log(`writeAccess: ${result.writeAccess}`);
console.log(`fieldType: ${result.fieldType}`);
console.log(`elementCount: ${result.elementCount}`);
} catch (error) {
console.log(error);
}
})()const CA = require('node-epics-ca');
let pv = new CA.Channel('calcExample');
(async () => {
try {
await pv.connect();
let value = await pv.get();
console.log(value);
await pv.disconnect()
} catch (error) {
console.log(error);
}
})()const CA = require('node-epics-ca');
(async () => {
try {
let value;
const pv = new CA.Channel('calcExample');
await pv.connect();
value = await pv.get();
console.log(value);
await pv.put(10);
value = await pv.get();
console.log(value);
await pv.disconnect()
} catch (error) {
console.log(error);
}
})()const CA = require('node-epics-ca');
let pv = new CA.Channel('calcExample');
pv.create();
pv.on('monitor', function() {
pv.monitor();
});
pv.on('value', function(data) {
console.log('Current:', data);
});
// Test purpose only, prevent the node.js main thread from exiting
setTimeout(function() {
console.log("Done!!!");
}, 3600 * 1000);const CA = require('node-epics-ca');
let pv = new CA.Channel('calcExample');
(async () => {
try {
await pv.connect();
let result = pv.info();
console.log(`name: ${result.name}`);
console.log(`state: ${result.state}`);
console.log(`host: ${result.host}`);
console.log(`readAccess: ${result.readAccess}`);
console.log(`writeAccess: ${result.writeAccess}`);
console.log(`fieldType: ${result.fieldType}`);
console.log(`elementCount: ${result.elementCount}`);
await pv.disconnect()
} catch (error) {
console.log(error);
}
})()const CA = require('node-epics-ca');
(async () => {
try {
console.log(await CA.get('calcExample', true));
} catch (error) {
console.error(`get failed due to ${error}`);
}
})()const CA = require('node-epics-ca');
(async () => {
try {
console.log(await CA.get('calcExample'));
await CA.put("calcExample", 'One', true);
console.log(await CA.get('calcExample'));
} catch (error) {
console.error(`put failed due to ${error}`);
}
})()const CA = require('node-epics-ca');
(async () => {
CA.monitor('calcExample', function(data) {
console.log('Current:', data);
}, true);
// Test purpose only, prevent the node.js main thread from exiting
setTimeout(function() {
console.log("Done!!!");
}, 3600 * 1000);
})()| Number of PVs | caget (seconds) | caput (seconds) | cainfo(seconds) | camonitor (seconds) |
|---|---|---|---|---|
| 1 | 0.045 | 0.048 | 0.037 | 0.001 |
| 10 | 0.279 | 0.286 | 0.282 | 0.001 |
| 50 | 1.367 | 1.366 | 1.363 | 0.003 |
| 100 | 2.724 | 2.730 | 2.719 | 0.004 |
| 200 | 5.446 | 5.443 | 5.439 | 0.007 |
| 500 | 13.611 | 13.588 | 13.582 | 0.014 |
| Measurement for caget | Time in seconds |
|---|---|
| create() | 0 |
| connect() | 0.033 |
| get() | 0.005 |
| disconnect() | 0.003 |
The test environment is as follows, the client and IOC are in different virtual machines and different subsets.
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Debian Linux 10 (buster)
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Intel Core Processor (Haswell), 4-core, 2.4GHz
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8GB memory
koffi package has limitation for callback count, the maximum is 1024 in version 2.3.20 and increases to 8192 in version 2.3.21-beta.2.
In order to monitor one PV, two callbacks are needed, they are connection state change callback and value change callback, which means only 512 PVs can be monitored at the same if maximum callback is 1024 and 4096 PVs if maximum is 8192.
MIT license