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Settings.js: support configuration via environment variables. 

All the configuration values can be read from environment variables using the
syntax "${ENV_VAR_NAME}".
This is useful, for example, when running in a Docker container.

EXAMPLE:
   "port":     "${PORT}"
   "minify":   "${MINIFY}"
   "skinName": "${SKIN_NAME}"

Would read the configuration values for those items from the environment
variables PORT, MINIFY and SKIN_NAME.

REMARKS:
Please note that a variable substitution always needs to be quoted.
   "port":   9001,          <-- Literal values. When not using substitution,
   "minify": false              only strings must be quoted: booleans and
   "skin":   "colibris"         numbers must not.

   "port":   ${PORT}        <-- ERROR: this is not valid json
   "minify": ${MINIFY}
   "skin":   ${SKIN_NAME}

   "port":   "${PORT}"      <-- CORRECT: if you want to use a variable
   "minify": "${MINIFY}"        substitution, put quotes around its name,
   "skin":   "${SKIN_NAME}"     even if the required value is a number or a
                                boolean.
                                Etherpad will take care of rewriting it to
                                the proper type if necessary.

Resolves #3543
This commit is contained in:
muxator 2019-03-09 23:01:21 +01:00 committed by muxator
parent f96e139b17
commit 6d400050a3
3 changed files with 147 additions and 1 deletions
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2
docker/README.md
View File

@ -14,6 +14,8 @@ cp ../settings.json.template settings.json
[ further edit your settings.json as needed]
```
**Each configuration parameter can also be set via an environment variable**, using the syntax `"${ENV_VAR_NAME}"`. For details, refer to `settings.json.template`.
Build the version you prefer:
```bash
# builds latest development version

33
settings.json.template
View File

@ -5,6 +5,39 @@
*
* Please note that starting from Etherpad 1.6.0 you can store DB credentials in
* a separate file (credentials.json).
*
*
* ENVIRONMENT VARIABLE SUBSTITUTION
* =================================
*
* All the configuration values can be read from environment variables using the
* syntax "${ENV_VAR_NAME}".
* This is useful, for example, when running in a Docker container.
*
* EXAMPLE:
* "port": "${PORT}"
* "minify": "${MINIFY}"
* "skinName": "${SKIN_NAME}"
*
* Would read the configuration values for those items from the environment
* variables PORT, MINIFY and SKIN_NAME.
*
* REMARKS:
* Please note that a variable substitution always needs to be quoted.
* "port": 9001, <-- Literal values. When not using substitution,
* "minify": false only strings must be quoted: booleans and
* "skin": "colibris" numbers must not.
*
* "port": ${PORT} <-- ERROR: this is not valid json
* "minify": ${MINIFY}
* "skin": ${SKIN_NAME}
*
* "port": "${PORT}" <-- CORRECT: if you want to use a variable
* "minify": "${MINIFY}" substitution, put quotes around its name,
* "skin": "${SKIN_NAME}" even if the required value is a number or a
* boolean.
* Etherpad will take care of rewriting it to
* the proper type if necessary.
*/
{
/*

113
src/node/utils/Settings.js
View File

@ -370,9 +370,118 @@ function storeSettings(settingsObj) {
}
}
/**
* Takes a javascript object containing Etherpad's configuration, and returns
* another object, in which all the string properties whose name is of the form
* "${ENV_VAR}", got their value replaced with the value of the given
* environment variable.
*
* An environment variable's value is always a string. However, the code base
* makes use of the various json types. To maintain compatiblity, some
* heuristics is applied:
*
* - if ENV_VAR does not exist in the environment, null is returned;
* - if ENV_VAR's value is "true" or "false", it is converted to the js boolean
* values true or false;
* - if ENV_VAR's value looks like a number, it is converted to a js number
* (details in the code).
*
* Variable substitution is performed doing a round trip conversion to/from
* json, using a custom replacer parameter in JSON.stringify(), and parsing the
* JSON back again. This ensures that environment variable replacement is
* performed even on nested objects.
*
* see: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify#The_replacer_parameter
*/
function lookupEnvironmentVariables(obj) {
const stringifiedAndReplaced = JSON.stringify(obj, (key, value) => {
/*
* the first invocation of replacer() is with an empty key. Just go on, or
* we would zap the entire object.
*/
if (key === '') {
return value;
}
/*
* If we received from the configuration file a number, a boolean or
* something that is not a string, we can be sure that it was a literal
* value. No need to perform any variable substitution.
*
* The environment variable expansion syntax "${ENV_VAR}" is just a string
* of specific form, after all.
*/
if (typeof value !== 'string') {
return value;
}
/*
* Let's check if the string value looks like a variable expansion (e.g.:
* "${ENV_VAR}")
*/
const match = value.match(/^\$\{(.*)\}$/);
if (match === null) {
// no match: use the value literally, without any substitution
return value;
}
// we found the name of an environment variable. Let's read its value.
const envVarName = match[1];
const envVarValue = process.env[envVarName];
if (envVarValue === undefined) {
console.warn(`Configuration key ${key} tried to read its value from environment variable ${envVarName}, but no value was found. Returning null. Please check your configuration and environment settings.`);
/*
* We have to return null, because if we just returned undefined, the
* configuration item "key" would be stripped from the returned object.
*/
return null;
}
// envVarName contained some value.
/*
* For numeric and boolean strings let's convert it to proper types before
* returning it, in order to maintain backward compatibility.
*/
// cooked from https://stackoverflow.com/questions/175739/built-in-way-in-javascript-to-check-if-a-string-is-a-valid-number
const isNumeric = !isNaN(envVarValue) && !isNaN(parseFloat(envVarValue) && isFinite(envVarValue));
if (isNumeric) {
console.debug(`Configuration key "${key}" will be read from environment variable ${envVarName}. Detected numeric string, that will be coerced to a number`);
return +envVarValue;
}
// the boolean literal case is easy.
if (envVarValue === "true" || envVarValue === "false") {
console.debug(`Configuration key "${key}" will be read from environment variable ${envVarName}. Detected boolean string, that will be coerced to a boolean`);
return (envVarValue === "true");
}
/*
* The only remaining case is that envVarValue is a string with no special
* meaning, and we just return it as-is.
*/
console.debug(`Configuration key "${key}" will be read from environment variable ${envVarName}`);
return envVarValue;
});
const newSettings = JSON.parse(stringifiedAndReplaced);
return newSettings;
}
/**
* - reads the JSON configuration file settingsFilename from disk
* - strips the comments
* - replaces environment variables calling lookupEnvironmentVariables()
* - returns a parsed Javascript object
*
* The isSettings variable only controls the error logging.
@ -409,7 +518,9 @@ function parseSettings(settingsFilename, isSettings) {
console.info(`${settingsType} loaded from: ${settingsFilename}`);
return settings;
const replacedSettings = lookupEnvironmentVariables(settings);
return replacedSettings;
} catch(e) {
console.error(`There was an error processing your ${settingsType} file from ${settingsFilename}: ${e.message}`);