graphql-prom-metrics

MetricsClient for @dreamit/graphql-server using prom-client library.

Installation

npm install --save @dreamit/graphql-prom-metrics

TypeScript declarations are provided within the project.

Compatibility

graphql-prom-metrics is compatible with @dreamit/graphql-server version ^3.2.1 and prom-client version ^14.0.1.

Features

• Provides out-of-the-box metrics for GraphQLServer
• Provides 3 custom as well as NodeJS related metrics.
• Uses only 2 peerDependencies: @dreamit/graphql-server version 3 and prom-client version 14 (no other production dependencies)

Metrics

The PromMetricsClient uses prom-client library to provide NodeJS metrics like cpu and memory usage as well as GraphQLServer related metrics.

Warning!: If you are using PromMetricsClient you should avoid creating multiple GraphQLServer instances that all use the PromMetricsClient. Because of the usage of a global object in the prom-client library this might result in unexpected behaviour or malfunction. You can set another metrics client like SimpleMetricsClient by calling GraphQLServer setOptions() or GraphQLServer setMetricsClient().

The PromMetricsClient provides three custom metrics for the GraphQL server:

• graphql_server_availability: Availability gauge with status 0 (unavailable) and 1 (available)
• graphql_server_request_throughput: The number of incoming requests
• graphql_server_errors: The number of errors that are encountered while running the GraphQLServer. The counter uses the errorName field as label so errors could be differentiated. At the moment the following labels are available and initialized with 0:
  • FetchError
  • GraphQLError
  • SchemaValidationError
  • MethodNotAllowedError
  • InvalidSchemaError
  • MissingQueryParameterError
  • ValidationError
  • SyntaxError
  • IntrospectionDisabledError

A simple metrics endpoint can be created by using getMetricsContentType and getMetrics functions from the GraphQLServer instance. In the example below a second route is used to return metrics data.

const graphQLServerPort = 3592
const graphQLServerExpress = express()
const customGraphQLServer = new GraphQLServer({
    schema: someExampleSchema,
    metricsClient: new PromMetricsClient(),
})
graphQLServerExpress.use(bodyParser.text({ type: '*/*' }))
graphQLServerExpress.all('/graphql', (req, res) => {
    return customGraphQLServer.handleRequestAndSendResponse(req, res)
})
graphQLServerExpress.get('/metrics', async (req, res) => {
    return res
        .contentType(customGraphQLServer.getMetricsContentType())
        .send(await customGraphQLServer.getMetrics())
})
graphQLServerExpress.listen({ port: graphQLServerPort })
console.info(`Starting GraphQL server on port ${graphQLServerPort}`)

Contact

If you have questions or issues please visit our Issue page and open a new issue if there are no fitting issues for your topic yet.

License

graphql-server is under MIT-License.