feat: add longFieldMaxLength config option, deprecate `errorMessage…

…MaxLength` (#2193)

This config option will truncate some transaction, span, and error fields
that can be longer at the configured number of JavaScript characters per
https://github.com/elastic/apm/blob/master/specs/agents/field-limits.md#long_field_max_length-configuration

Notably truncation is now based on a count of JavaScript *characters*
rather than in UTF-8 encoded bytes.

This also deprecates the errorMessageMaxLength config option. It now
defaults to the longFieldMaxLength value if not specified. Otherwise
errorMessageMaxLength is still supported.

Fixes: #1921

CHANGELOG.asciidoc

@@ -37,6 +37,31 @@ Notes:
 [float]
 ===== Features
 
+* Add the `longFieldMaxLength` integer configuration option (default `10000`).
+  Specific transaction/span/error fields (see the list below) will be truncated
+  at this number of unicode characters. ({pull}2193[#2193], {issues}1921[#1921])
++
+  The `errorMessageMaxLength` configuration option is now *deprecated*, but
+  still supported. Users should switch to using `longFieldMaxLength. If
+  `errorMessageMaxLength` is not specified, truncation of error messages will
+  now use the `longFieldMaxLength` value.
++
+  Note that ultimately the maximum length of any tracing field is limited by the
+  {apm-server-ref-v}/configuration-process.html#max_event_size[`max_event_size`]
+  configured for the receiving APM server.
++
+  The fields affected by `longFieldMaxLength` are:
++
+** `transaction.context.request.body`, `error.context.request.body` - Before
+   this change these fields were not truncated.
+** `transaction.context.message.body`, `span.context.message.body`,
+   `error.context.message.body` - Before this change these fields were not
+   truncated.
+** `span.context.db.statement` - Before this change this field was truncated
+   at 10000 *bytes*. Truncation is now a number of unicode characters.
+** `error.exception.message`, `error.log.message` - Before this change, the
+   default 2kB `errorMessageMaxLength` would apply.
+
 * Improve the TypeScript types by exporting more of interfaces:
   `AgentConfigOptions`, `Transaction`, `Span`, `TransactionOptions`,
   `SpanOptions`. ({issues}2118[#2118])

docs/configuration.asciidoc

@@ -671,16 +671,20 @@ The default value `0` means that no source code will be collected for span libra
 ==== `errorMessageMaxLength`
 
 * *Type:* String
-* *Default:* `2kb`
+* *Default:* `"2kb"`
 * *Env:* `ELASTIC_APM_ERROR_MESSAGE_MAX_LENGTH`
 
+This option is **deprecated** -- use <<long-field-max-length,`longFieldMaxLength`>> instead.
+
 The maximum length allowed for error messages.
 It is expressed in bytes or includes a size suffix such as `2kb`.
 Size suffixes are case-insensitive and include `b`,
 `kb`,
 `mb`,
 and `gb`.
 Messages above this length will be truncated before being sent to the APM Server.
+Note that while the configuration option accepts a number of *bytes*, truncation
+is based on a number of unicode characters, not bytes.
 
 Set to `-1` do disable truncation.
 
@@ -689,6 +693,31 @@ This applies to the following properties:
 - `error.exception.message`
 - `error.log.message`
 
+
+[[long-field-max-length]]
+==== `longFieldMaxLength`
+
+* *Type:* Integer
+* *Default:* 10000
+* *Env:* `ELASTIC_APM_LONG_FIELD_MAX_LENGTH`
+
+The following transaction, span, and error fields will be truncated at this
+number of unicode characters before being sent to APM server:
+
+- `transaction.context.request.body`, `error.context.request.body`
+- `transaction.context.message.body`, `span.context.message.body`,
+  `error.context.message.body`
+- `span.context.db.statement`
+- `error.exception.message`, `error.log.message` - If
+  <<error-message-max-length,`errorMessageMaxLength`>> is specified, then that
+  value takes precedence for these error message fields.
+
+Note that tracing data is limited at the upstream APM server to
+{apm-server-ref-v}/configuration-process.html#max_event_size[`max_event_size`],
+which defaults to 300kB. If you configure `longFieldMaxLength` too large, it
+could result in transactions, spans, or errors that are rejected by APM server.
+
+
 [[stack-trace-limit]]
 ==== `stackTraceLimit`
 

index.d.ts

@@ -218,7 +218,7 @@ declare namespace apm {
     disableInstrumentations?: string | string[];
     disableSend?: boolean;
     environment?: string;
-    errorMessageMaxLength?: string; // Also support `number`, but as we're removing this functionality soon, there's no need to advertise it
+    errorMessageMaxLength?: string; // DEPRECATED: use `longFieldMaxLength`.
     errorOnAbortedRequests?: boolean;
     filterHttpHeaders?: boolean;
     frameworkName?: string;
@@ -237,6 +237,7 @@ declare namespace apm {
     logLevel?: LogLevel;
     logUncaughtExceptions?: boolean;
     logger?: PinoLogger | Logger;
+    longFieldMaxLength?: number;
     maxQueueSize?: number;
     metricsInterval?: string; // Also support `number`, but as we're removing this functionality soon, there's no need to advertise it
     metricsLimit?: number;

lib/config.js

@@ -56,7 +56,6 @@ var DEFAULTS = {
   disableInstrumentations: [],
   disableSend: false,
   environment: process.env.NODE_ENV || 'development',
-  errorMessageMaxLength: '2kb',
   errorOnAbortedRequests: false,
   filterHttpHeaders: true,
   globalLabels: undefined,
@@ -71,6 +70,7 @@ var DEFAULTS = {
   logUncaughtExceptions: false, // TODO: Change to `true` in the v4.0.0
   // Rough equivalent of the Java Agent's max_queue_size:
   // https://www.elastic.co/guide/en/apm/agent/java/current/config-reporter.html#config-max-queue-size
+  longFieldMaxLength: 10000,
   maxQueueSize: 1024,
   metricsInterval: '30s',
   metricsLimit: 1000,
@@ -130,6 +130,7 @@ var ENV_TABLE = {
   kubernetesPodUID: ['ELASTIC_APM_KUBERNETES_POD_UID', 'KUBERNETES_POD_UID'],
   logLevel: 'ELASTIC_APM_LOG_LEVEL',
   logUncaughtExceptions: 'ELASTIC_APM_LOG_UNCAUGHT_EXCEPTIONS',
+  longFieldMaxLength: 'ELASTIC_APM_LONG_FIELD_MAX_LENGTH',
   maxQueueSize: 'ELASTIC_APM_MAX_QUEUE_SIZE',
   metricsInterval: 'ELASTIC_APM_METRICS_INTERVAL',
   metricsLimit: 'ELASTIC_APM_METRICS_LIMIT',
@@ -185,6 +186,7 @@ var BOOL_OPTS = [
 ]
 
 var NUM_OPTS = [
+  'longFieldMaxLength',
   'maxQueueSize',
   'metricsLimit',
   'sourceLinesErrorAppFrames',
@@ -571,6 +573,7 @@ function truncateOptions (opts) {
   if (opts.hostname) opts.hostname = truncate(String(opts.hostname), INTAKE_STRING_MAX_SIZE)
 }
 
+// Translate a string byte size, e.g. '10kb', into an integer number of bytes.
 function bytes (input) {
   const matches = input.match(/^(\d+)(b|kb|mb|gb)$/i)
   if (!matches) return Number(input)
@@ -677,7 +680,8 @@ function getBaseClientConfig (conf, agent) {
   if (isLambdaExecutionEnviornment()) {
     cloudProvider = 'none'
   }
-  return {
+
+  const clientConfig = {
     agentName: 'nodejs',
     agentVersion: version,
     serviceName: conf.serviceName,
@@ -691,7 +695,8 @@ function getBaseClientConfig (conf, agent) {
 
     // Sanitize conf
     truncateKeywordsAt: INTAKE_STRING_MAX_SIZE,
-    truncateErrorMessagesAt: conf.errorMessageMaxLength,
+    truncateLongFieldsAt: conf.longFieldMaxLength,
+    // truncateErrorMessagesAt: see below
 
     // HTTP conf
     secretToken: conf.secretToken,
@@ -724,6 +729,14 @@ function getBaseClientConfig (conf, agent) {
     // Cloud metadata fetching
     cloudMetadataFetcher: (new CloudMetadata(cloudProvider, conf.logger, conf.serviceName))
   }
+
+  if (conf.errorMessageMaxLength !== undefined) {
+    // As of v10 of the http client, truncation of error messages will default
+    // to `truncateLongFieldsAt` if `truncateErrorMessagesAt` is not specified.
+    clientConfig.truncateErrorMessagesAt = conf.errorMessageMaxLength
+  }
+
+  return clientConfig
 }
 
 // Exports.

package.json

@@ -86,7 +86,7 @@
     "basic-auth": "^2.0.1",
     "cookie": "^0.4.0",
     "core-util-is": "^1.0.2",
-    "elastic-apm-http-client": "^9.9.0",
+    "elastic-apm-http-client": "^10.0.0",
     "end-of-stream": "^1.4.4",
     "error-callsites": "^2.0.4",
     "error-stack-parser": "^2.0.6",

test/config.test.js

@@ -60,7 +60,7 @@ var optionFixtures = [
   ['disableSend', 'DISABLE_SEND', false],
   ['disableInstrumentations', 'DISABLE_INSTRUMENTATIONS', []],
   ['environment', 'ENVIRONMENT', 'development'],
-  ['errorMessageMaxLength', 'ERROR_MESSAGE_MAX_LENGTH', 2048],
+  ['errorMessageMaxLength', 'ERROR_MESSAGE_MAX_LENGTH', undefined],
   ['errorOnAbortedRequests', 'ERROR_ON_ABORTED_REQUESTS', false],
   ['filterHttpHeaders', 'FILTER_HTTP_HEADERS', true],
   ['frameworkName', 'FRAMEWORK_NAME'],
@@ -74,6 +74,7 @@ var optionFixtures = [
   ['kubernetesPodUID', 'KUBERNETES_POD_UID'],
   ['logLevel', 'LOG_LEVEL', 'info'],
   ['logUncaughtExceptions', 'LOG_UNCAUGHT_EXCEPTIONS', false],
+  ['longFieldMaxLength', 'LONG_FIELD_MAX_LENGTH', 10000],
   ['maxQueueSize', 'MAX_QUEUE_SIZE', 1024],
   ['metricsInterval', 'METRICS_INTERVAL', 30],
   ['metricsLimit', 'METRICS_LIMIT', 1000],
@@ -109,7 +110,7 @@ optionFixtures.forEach(function (fixture) {
     } else if (fixture[0] === 'serverCaCertFile') {
       // special case for files, so a temp file can be written
       type = 'file'
-    } else if (typeof fixture[2] === 'number') {
+    } else if (typeof fixture[2] === 'number' || fixture[0] === 'errorMessageMaxLength') {
       type = 'number'
     } else if (Array.isArray(fixture[2])) {
       type = 'array'