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PgError.js is an error class for Node.js that parses PostgreSQL's ErrorResponse format and names its fields with human readable properties. It's most useful when combined with Brian Carlson's Node.js PostgreSQL client library to get structured and identifiable PostgreSQL errors. Supports all fields returned by PostgreSQL up to v9.4.
The PostgreSQL client library does return an Error
object with some fields
set, but it's not a dedicated object for easy instanceof
identification nor
does it yet support all field types. I've found it immensely useful to be
strict and classify errors beforehand when building fault tolerant systems. That
helps programmatically decide whether to wrap, escalate or handle a particular
error.
npm install pg-error
PgError.js follows semantic versioning, so feel free to
depend on its major version with something like >= 1.0.0 < 2
(a.k.a ^1.0.0
).
var PgError = require("pg-error")
var error = new PgError({
M: "null value in column \"name\" violates not-null constraint",
S: "ERROR",
C: "23502"
})
error instanceof PgError // => true
error instanceof Error // => true
error.message // => "null value in column \"name\" violates not-null constraint"
error.severity // => "ERROR"
error.code // => 23502
Parsing PostgreSQL's ErrorResponse
var msg = new Buffer("MWash your teeth!\0SWARNING\0\0")
var error = PgError.parse(msg)
error.message // => "Wash your teeth!"
error.severity // => "WARNING"
Using with Node.js PostgreSQL client library
The client does its error and notice parsing on the Pg.Connection
object.
You can get an active instance of it after connecting from Pg.Client
:
var Pg = require("pg")
var pg = new Pg.Client({host: "/tmp", database: "pg_error_test"})
var connection = pg.connection
You'll have to swap out two functions, Pg.Connection.prototype.parseE
and
Pg.Connection.prototype.parseN
, for parsing errors and notices respectively:
connection.parseE = PgError.parse
connection.parseN = PgError.parse
If you want every connection instance to parse errors to PgError
, set them on the Pg.Connection
prototype:
Pg.Connection.prototype.parseE = PgError.parse
Pg.Connection.prototype.parseN = PgError.parse
However, the way the client is built, it will start emitting those errors and
notices under the PgError
event name. Until that's improved in the
Pg.Connection
class, you'll need to re-emit those under the correct error
and notice
events:
function emitPgError(err) {
switch (err.severity) {
case "ERROR":
case "FATAL":
case "PANIC": return this.emit("error", err)
default: return this.emit("notice", err)
}
}
connection.on("PgError", emitPgError)
That's it. Your Pg query errors should now be instances of PgError
and with
all the human readable field names.
Using with Knex.js
Using PgError.js with Knex.js is similar to using it with the plain Node.js PostgreSQL client library described above. Because Knex.js has a connection pool, you'll have to hook PgError.js in on every newly created connection:
var Knex = require("knex")
Knex({
pool: {
min: 1,
max: 10,
afterCreate: function(connection, done) {
connection.connection.parseE = PgError.parse
connection.connection.parseN = PgError.parse
connection.connection.on("PgError", emitPgError)
done()
}
}
})
The emitPgError
function is listed above.
For descriptions of the properties, please see PostgreSQL's Error and Notice Message Fields.
Property | Field | Description |
---|---|---|
severity | S | |
code | C | |
condition | Code name in lowercase according to errcodes.txt. | |
detail | D | |
hint | H | |
position | P | Position parsed to a Number . |
internalPosition | p | Internal position parsed to a Number . |
internalQuery | q | |
where | W | |
schema | s | |
table | t | |
column | c | |
dataType | d | |
constraint | n | |
file | F | |
line | L | Line parsed to a Number . |
routine | R |
PgError.js is released under a Lesser GNU Affero General Public License, which in summary means:
- You can use this program for no cost.
- You can use this program for both personal and commercial reasons.
- You do not have to share your own program's code which uses this program.
- You have to share modifications (e.g. bug-fixes) you've made to this program.
For more convoluted language, see the LICENSE
file.
Andri Möll typed this and the code.
Monday Calendar supported the engineering work.
If you find PgError.js needs improving, please don't hesitate to type to me now at andri@dot.ee or create an issue online.