Internal Application Load Balancer logging and monitoring

This document provides you with the information that you need to understand logging and monitoring metrics for internal Application Load Balancers. The logging and monitoring metrics for both regional internal Application Load Balancers and cross-region internal Application Load Balancers are the same.

Logging

You can enable logging on a per-backend service basis. A single internal Application Load Balancer's URL map can reference more than one backend service. You might need to enable logging for multiple backend services depending on your configuration.

Logs sampling and collection

The requests (and corresponding responses) handled by load balancer backend virtual machine (VM) instances are sampled. These sampled requests are then processed to generate logs. You control the fraction of the requests that are emitted as log entries according to the logConfig.sampleRate parameter. When logConfig.sampleRate is 1.0 (100%), this means that logs are generated for all of the requests and written to Cloud Logging.

Optional fields

Log records contain required fields and optional fields. The What is logged section lists which fields are optional and which are required. All required fields are always included. You can customize which optional fields you keep.

  • If you select include all optional, all optional fields in the log record format are included in the flow logs. When new optional fields are added to the record format, the flow logs automatically include the new fields.

  • If you select exclude all optional, all optional fields are omitted.

  • If you select custom, you can specify the optional fields that you want to include, such as tls.protocol,tls.cipher.

For instructions about customizing optional fields, see Enable logging on an existing backend service.

Enabling logging on an existing backend service

For regional internal Application Load Balancers, use the following steps:

Console

  1. In the Google Cloud console, go to the Load balancing page.

    Go to Load balancing

  2. Click the name of your load balancer.

  3. Click Edit.

  4. Click Backend Configuration.

  5. Click Edit next to your backend service.

  6. Click Advanced configurations (Session affinity, connection draining timeout).

  7. Click Enable logging.

  8. Set a Sample rate fraction. You can set a number from 0.0 through 1.0, where 0.0 means that no requests are logged and 1.0 means that 100% of the requests are logged. The default value is 1.0.

  9. Optional: To include all the optional fields in the logs, in the Optional fields section, click Include all optional fields.

  10. To finish editing the backend service, click Update.

  11. To finish editing the load balancer, click Update.

gcloud

To update the backend service to enable logging, use the gcloud compute backend-services update command.

gcloud compute backend-services update BACKEND_SERVICE \
    --enable-logging \
    --logging-sample-rate=RATE \
    --region=REGION \
    --logging-optional=LOGGING_OPTIONAL_MODE \
    --logging-optional-fields=OPTIONAL_FIELDS

where

  • --enable-logging enables logging for that backend service.
  • --logging-sample-rate lets you specify a value from 0.0 through 1.0, where 0.0 means no requests are logged and 1.0 means 100% of requests are logged. Only meaningful with the --enable-logging parameter. Enabling logging but setting the sampling rate to 0.0 is equivalent to disabling logging. The default value is 1.0.

  • --logging-optional lets you specify the optional fields that you want to include in the logs:

    • INCLUDE_ALL_OPTIONAL to include all optional fields.

    • EXCLUDE_ALL_OPTIONAL (default) to exclude all optional fields.

    • CUSTOM to include a custom list of optional fields that you specify in OPTIONAL_FIELDS.

  • --logging-optional-fields lets you specify a comma-separated list of optional fields that you want to include in the logs.

    For example, tls.protocol,tls.cipher can only be set if LOGGING_OPTIONAL_MODE is set to CUSTOM.

For cross-region internal Application Load Balancers, use the following steps:

Console

  1. In the Google Cloud console, go to the Load balancing page.

    Go to Load balancing

  2. Click the name of your load balancer.

  3. Click Edit.

  4. Click Backend Configuration.

  5. Click Edit next to your backend service.

  6. Click Advanced configurations (Session affinity, connection draining timeout).

  7. Click Enable logging.

  8. Set a Sample rate fraction. You can set a number from 0.0 through 1.0, where 0.0 means that no requests are logged and 1.0 means that 100% of the requests are logged. The default value is 1.0.

  9. Optional: To include all the optional fields in the logs, in the Optional fields section, click Include all optional fields.

  10. To finish editing the backend service, click Update.

  11. To finish editing the load balancer, click Update.

gcloud

To update the backend service to enable logging, use the gcloud compute backend-services update command.

gcloud compute backend-services update BACKEND_SERVICE \
    --enable-logging \
    --logging-sample-rate=RATE \
    --global \
    --logging-optional=LOGGING_OPTIONAL_MODE \
    --logging-optional-fields=OPTIONAL_FIELDS

where

  • --enable-logging enables logging for that backend service.
  • --logging-sample-rate lets you specify a value from 0.0 through 1.0, where 0.0 means no requests are logged and 1.0 means 100% of requests are logged. Only meaningful with the --enable-logging parameter. Enabling logging but setting the sampling rate to 0.0 is equivalent to disabling logging. The default value is 1.0.

  • --logging-optional lets you specify the optional fields that you want to include in the logs:

    • INCLUDE_ALL_OPTIONAL to include all optional fields.

    • EXCLUDE_ALL_OPTIONAL (default) to exclude all optional fields.

    • CUSTOM to include a custom list of optional fields that you specify in OPTIONAL_FIELDS.

  • --logging-optional-fields lets you specify a comma-separated list of optional fields that you want to include in the logs.

    For example, tls.protocol,tls.cipher can only be set if LOGGING_OPTIONAL_MODE is set to CUSTOM.

After you enable logging on the backend service, each HTTP(S) request is logged by using Cloud Logging.

How to view logs

To view logs, in the Google Cloud console, go to the Logs Explorer page.

Internal Application Load Balancer logs are indexed first by network and then by region.

  • To see logs for all internal Application Load Balancers, in the first pull-down menu, select Internal Application Load Balancer Rule.
  • To see logs for only one network, select Internal Application Load Balancer Rule, and then select the name of a network.
  • To see logs for just one region of the network, select Internal Application Load Balancer Rule > NETWORK > REGION.

Log fields of type boolean typically only appear if they have a value of true. If a boolean field has a value of false, that field is omitted from the log.

UTF-8 encoding is enforced for log fields. Characters that are not UTF-8 characters are replaced with question marks.

You can configure export of logs-based metrics for resource logs (resource.type="internal_http_lb_rule"). The metrics created are based on the "Internal Application Load Balancer Rule" resource, which is available under Cloud Monitoring dashboards:

Go to Monitoring

What is logged

Internal Application Load Balancer log entries contain information useful for monitoring and debugging your HTTP(S) traffic. Log records contain required fields, which are the default fields of every log record, and optional fields that add additional information about your HTTP(S) traffic. Optional fields can be omitted to save storage costs. Log entries contain the following types of information:

  • General information shown in most Google Cloud logs, such as severity, project ID, project number, and timestamp as described in the LogEntry.
  • HttpRequest log fields.

Some log fields are in a multi-field format, with more than one piece of data in a given field. For example, the tls field is of the TlsDetails format, which contains the TLS protocol and TLS cipher in a single field. These multi-field fields are described in the following record format table.

Field Type Field type: Required or Optional Description
logName string Required The resource name of the log to which this log entry belongs.
In the form "projects/PROJECT_ID/logs/requests".
timestamp string Required The time at which the request began.
severity LogSeverity format Required The severity of the log entry. Defaults to LogSeverity.DEFAULT.
httpRequest HttpRequest object Required An HttpRequest proto that describes the HTTP(S) request being logged.
trace string Required The resource name of the trace associated with the log entry, if any. If it contains a relative resource name, the name is assumed to be relative to https://tracing.googleapis.com. Example: projects/PROJECT_ID/traces/06796866738c859f2f19b7cfb3214824.

Internal Application Load Balancers don't support this field.

spanId string Required The span ID within the trace associated with the log entry. For Trace spans, this string has the same format that the Trace API v2 uses: a 16-character hexadecimal encoding of an 8-byte array, such as 000000000000004a.

Internal Application Load Balancers don't support this field.

resource MonitoredResource object Required

The monitored resource that produced this log entry.

The MonitoredResourceDescriptor object describes the schema of a MonitoredResource object by using a type name and a set of labels.

For example, monitored resource descriptors for internal Application Load Balancers have a resource type of internal_http_lb_rule and use resource labels to identify the actual resource and its attributes. For a list of resource labels, see the Resource labels for resource.type="internal_http_lb_rule".
jsonPayload object (Struct format) Required The log entry payload that is expressed as a JSON object. The JSON object contains the following fields:
  • tls
  • proxyStatus
  • backendTargetProjectNumber
  • serviceDirectoryService
  • cloudFitExperiment
  • cloudFitFault
  • serviceExtensionInfo
  • mtls
  • authzPolicyInfo
string Required

The proxyStatus field holds a string that specifies why the internal Application Load Balancer returned the HttpRequest.status. This field is populated only when the proxy returns an error code.

The field is not logged if the value is an empty string. This can happen if the proxy or backend doesn't return an error or the error code that is not 0, 4XX, or 5XX.

The proxyStatus field has two parts:
string Required The backendTargetProjectNumber field holds the project number that identifies the owner of the backend service or backend bucket.
string Required The serviceDirectoryService field holds the name of the Service Directory service on which the Cloud FIT fault was configured.
string Required The cloudFitExperiment field holds the name of the Cloud FIT experiment.
string Required The cloudFitFault field holds the name of the fault injected by a Cloud FIT fault experiment in this request path.
ServiceExtensionInfo Required The serviceExtensionInfo field stores information about the gRPC streams from the load balancer to Service Extensions. For more information, see what is logged for callout extensions.
AuthzPolicyInfo Required The authzPolicyInfo field stores information about the Authorization Policy result. This information is only available for internal Application Load Balancers enabled Authorization Policy. For more information, see what is logged for authorization policy.
TlsDetails Optional The tls field holds the TlsDetails that specifies the TLS metadata for the connection between the client and the internal Application Load Balancer. This field is only available if the client is using TLS/SSL encryption.
MtlsDetails Optional The mtls field holds the MtlsDetails value that specifies the mTLS metadata for the connection between the client and the internal Application Load Balancer. This field is only available if the load balancer uses frontend mutual TLS (mTLS).

TlsDetails field format

Field Field format Field type: Required or Optional Description
protocol string Optional TLS protocol that clients use to establish a connection with the load balancer. Possible values can be TLS 1.0, 1.1, 1.2, 1.3, or QUIC. This value is set to NULL if the client is not using TLS/SSL encryption.
cipher string Optional TLS cipher that clients use to establish a connection with the load balancer. This value is set to NULL if the client is not using HTTP(S) or the client is not using TLS/SSL encryption.

MtlsDetails field format

Field Field format Field type: Required or Optional Description
clientCertPresent bool Optional

true if the client has provided a certificate during the TLS handshake; otherwise, false.
clientCertChainVerified bool Optional

true if the client certificate chain is verified against a configured TrustStore; otherwise, false.
clientCertError string Optional

Predefined strings representing the error conditions. For more information about the error strings, see mTLS client validation modes.
clientCertSha256Fingerprint string Optional

Base64-encoded SHA-256 fingerprint of the client certificate.
clientCertSerialNumber string Optional

The serial number of the client certificate. If the serial number is longer than 50 bytes, the string client_cert_serial_number_exceeded_size_limit is added to client_cert_error, and the serial number is set to an empty string.
clientCertValidStartTime string Optional

Timestamp (RFC 3339 date string format) before which the client certificate is not valid. For example, 2022-07-01T18:05:09+00:00.
clientCertValidEndTime string Optional

Timestamp (RFC 3339 date string format) after which the client certificate is not valid. For example, 2022-07-01T18:05:09+00:00.
clientCertSpiffeId string Optional

The SPIFFE ID from the subject alternative name (SAN) field. If the value is not valid or exceeds 2048 bytes, the SPIFFE ID is set to an empty string.

If the SPIFFE ID is longer than 2048 bytes, the string client_cert_spiffe_id_exceeded_size_limit is added to client_cert_error.
clientCertUriSans string Optional

Comma-separated Base64-encoded list of the SAN extensions of type URI. The SAN extensions are extracted from the client certificate. The SPIFFE ID is not included in the client_cert_uri_sans field.

If the client_cert_uri_sans field is longer than 512 bytes, the string client_cert_uri_sans_exceeded_size_limit is added to client_cert_error, and the comma-separated list is set to an empty string.
clientCertDnsnameSans string Optional

Comma-separated Base64-encoded list of the SAN extensions of type DNSName. The SAN extensions are extracted from the client certificate.

If the client_cert_dnsname_sans field is longer than 512 bytes, the string client_cert_dnsname_sans_exceeded_size_limit is added to client_cert_error, and the comma-separated list is set to an empty string.
clientCertIssuerDn string Optional

Base64-encoded full Issuer field from the certificate.

If the client_cert_issuer_dn field is longer than 512 bytes, the string client_cert_issuer_dn_exceeded_size_limit is added to client_cert_error, and client_cert_issuer_dn is set to an empty string.
clientCertSubjectDn string Optional

Base64-encoded full Subject field from the certificate.

If the client_cert_subject_dn field is longer than 512 bytes, the string client_cert_subject_dn_exceeded_size_limit is added to client_cert_error, and client_cert_subject_dn is set to an empty string.
clientCertLeaf string Optional

The client leaf certificate for an established mTLS connection where the certificate passed validation. Certificate encoding is compliant with RFC 9440: the binary DER certificate is encoded using Base64 (without line breaks, spaces, or other characters outside the Base64 alphabet) and delimited with colons on either side.

If client_cert_leaf exceeds 16 KB unencoded, the string client_cert_validated_leaf_exceeded_size_limit is added to client_cert_error, and client_cert_leaf is set to an empty string.
clientCertChain string Optional

The comma-delimited list of certificates, in standard TLS order, of the client certificate chain for an established mTLS connection where the client certificate passed validation, not including the leaf certificate. Certificate encoding is compliant with RFC 9440.

If the combined size of client_cert_leaf and client_cert_chain before Base64 encoding exceeds 16 KB, the string client_cert_validated_chain_exceeded_size_limit is added to client_cert_error, and client_cert_chain is set to an empty string.

proxyStatus error field

The proxyStatus field contains a string that specifies why the load balancer returned an error. There are two parts in the proxyStatus field, proxyStatus error and proxyStatus details. This section describes the strings that are supported in the proxyStatus error field.

The proxyStatus error field is applicable to the following load balancers:

  • Regional external Application Load Balancer
  • Cross-region internal Application Load Balancer
  • Regional internal Application Load Balancer
proxyStatus error Description Common accompanying response codes
destination_unavailable The load balancer considers the backend to be unavailable. For example, recent attempts to communicate with the backend have failed, or a health check might have resulted in a failure. 500, 503
connection_timeout The load balancer's attempt to open a connection to the backend has timed out. 504
connection_terminated

The load balancer's connection to the backend ended before a complete response is received.

This proxyStatus error is returned during any of the following scenarios:

  • The load balancer's connection to the backend ended before a complete response is received.
  • The TLS connection failed on the SSL handshake, and the client didn't establish a connection with the load balancer.

 0, 502, 503
connection_refused The load balancer's connection to the backend is refused. 502, 503
connection_limit_reached

The load balancer is configured to limit the number of connections it has to the backend, and that limit has been exceeded.

This proxyStatus error is returned during any of the following scenarios:

  • If any backend is in maintenance mode, the traffic can't be routed to the backend.
  • If the request is locally rate limited.
  • Envoy is handling error conditions such as running out of memory.
 502, 503
destination_not_found The load balancer can't determine the appropriate backend to use for this request. For example, the backend might not be configured. 500, 404
dns_error The load balancer encountered a DNS error when trying to find an IP address for the backend hostname. 502, 503
proxy_configuration_error The load balancer encountered an internal configuration error. 500
proxy_internal_error The load balancer encountered an internal error. 0, 500, 502
proxy_internal_response The load balancer generated the response without attempting to connect to the backend. Any response code depending on the type of problem. For example, the 410 response code means that the backend is unavailable due to payment delinquency.
http_response_timeout The load balancer reached a configured backend service timeout limit while waiting for the complete response from the backend. 504, 408
http_request_error The load balancer encountered an HTTP 4xx error, indicating problems with the client request. 400, 403, 405, 406, 408, 411, 413, 414, 415, 416, 417, or 429
http_protocol_error The load balancer encountered an HTTP protocol error while communicating with the backend. 502
tls_protocol_error The load balancer encountered a TLS error during the TLS handshake. 0
tls_certificate_error The load balancer encountered an error at the time of verifying the certificate presented by the server or by the client when mTLS is enabled. 0
tls_alert_received The load balancer encountered a fatal TLS alert during the TLS handshake. 0

proxyStatus details field

The proxyStatus field contains a string that specifies why the load balancer returned an error. There are two parts in the proxyStatus field, proxyStatus error and proxyStatus details. The proxyStatus details field is optional and is shown only when additional information is available. This section describes the strings that are supported in the proxyStatus details field.

The proxyStatus details field is applicable to the following load balancers:

  • Regional external Application Load Balancer
  • Regional internal Application Load Balancer
  • Cross-region internal Application Load Balancer
proxyStatus details Description Common accompanying response codes
client_disconnected_before_any_response The connection to the client was broken before the load balancer sent any response. 0
backend_connection_closed The backend unexpectedly closed its connection to the load balancer. This can happen if the load balancer is sending traffic to another entity such as a third-party application that has a TCP timeout shorter than the 10-minute (600-second) timeout of the load balancer. 502
failed_to_connect_to_backend The load balancer failed to connect to the backend. This failure includes timeouts during the connection phase. 503
failed_to_pick_backend The load balancer failed to pick a healthy backend to handle the request. 502
response_sent_by_backend The HTTP request was proxied successfully to the backend, and the response was returned by the backend. The HTTP response code is set by the software running on the backend.
client_timed_out

The connection between the load balancer and client exceeded the idle timeout.

For more information about regional external Application Load Balancer, see Client HTTP keepalive timeout. For more information about internal Application Load Balancer, see Client HTTP keepalive timeout. 		0, 408
backend_timeout

The backend timed out while generating a response.

 502
http_protocol_error_from_backend_response The backend response contains an HTTP protocol error. 501, 502
http_protocol_error_from_request The client request contains an HTTP protocol error. 400, 503
http_version_not_supported The HTTP protocol version is not supported. Only HTTP 0.9, 1.0, 1.1, and 2.0 are supported. 400
handled_by_identity_aware_proxy This response was generated by Identity-Aware Proxy (IAP) during verifying the identity of the client before allowing access. 200, 302, 400, 401, 403, 500, 502
invalid_request_headers

The HTTP request headers received from a client contain at least one character that isn't allowed under an applicable HTTP specification.

For example, header field names that include a double quotation mark (") or any characters outside of the standard ASCII range (that is, any byte >= 0x80) are invalid.

For more information, see:

 400, 404
ip_detection_failed The original IP address couldn't be detected. Any response code possible depending on the nature of the failure. The value must be from 400 to 599.
request_body_too_large The HTTP request body exceeded the maximum length supported by the load balancer. 413, 507
request_header_timeout The request header timed out because the load balancer didn't receive the complete request within 5 seconds. 408, 504
denied_by_security_policy The load balancer denied this request because of a Google Cloud Armor security policy. 403
throttled_by_security_policy The request was blocked by a Google Cloud Armor throttle rule. 429
client_cert_chain_invalid_eku Either the client certificate or its issuer doesn't have extended key usage that includes clientAuth. For more information, see Logged errors for closed connections. 0
client_cert_chain_max_name_constraints_exceeded An intermediate certificate provided for validation had more than 10 name constraints. For more information, see Logged errors for closed connections. 0
client_cert_invalid_rsa_key_size A client leaf or intermediate certificate had an invalid RSA key size. For more information, see Logged errors for closed connections. 0
client_cert_not_provided The client didn't provide the requested certificate during the handshake. For more information, see Logged errors for closed connections. 0
client_cert_pki_too_large The PKI to be used for validation has more than three intermediate certificates that share the same Subject and Subject Public Key Info. For more information, see Logged errors for closed connections. 0
client_cert_unsupported_elliptic_curve_key A client or intermediate certificate is using an unsupported elliptic curve. For more information, see Logged errors for closed connections. 0
client_cert_unsupported_key_algorithm A client or intermediate certificate is using a non-RSA or non-ECDSA algorithm. For more information, see Logged errors for closed connections. 0
client_cert_validation_failed The client certificate fails validation with the TrustConfig. For more information, see Logged errors for closed connections. 0
client_cert_validation_not_performed You have configured mutual TLS without setting up a TrustConfig. For more information, see Logged errors for closed connections. 0
client_cert_validation_search_limit_exceeded The depth or iteration limit is reached while attempting to validate the certificate chain. For more information, see Logged errors for closed connections. 0
client_cert_validation_timed_out The time limit exceeded (200 ms) while validating the certificate chain. For more information, see Logged errors for closed connections. 0
tls_version_not_supported The TLS protocol version is recognized but not supported. The error results in a closed TLS connection. 0
unknown_psk_identity Servers send this error when PSK key establishment is required, but the client doesn't provide an acceptable PSK identity. The error results in a closed TLS connection. 0
no_application_protocol Sent by servers when a client "application_layer_protocol_negotiation" extension advertises only protocols that the server doesn't support. See TLS application-layer protocol negotiation extension. The error results in a closed TLS connection. 0
no_certificate No certificate was found. The error results in a closed TLS connection. 0
bad_certificate A certificate is invalid, or it contains signatures that couldn't be verified. The error results in a closed TLS connection. 0
unsupported_certificate A certificate is of an unsupported type. The error results in a closed TLS connection. 0
certificate_revoked A certificate was revoked by its signer. The error results in a closed TLS connection. 0
certificate_expired A certificate has expired or it is not valid. The error results in a closed TLS connection. 0
certificate_unknown Some unspecified issues arose while processing the certificate, rendering it unacceptable. The error results in a closed TLS connection. 0
unknown_ca A valid certificate chain or partial chain was received, but the certificate was not accepted because the CA certificate couldn't be located or matched with a known trust anchor. The error results in a closed TLS connection. 0
unexpected_message An inappropriate message, such as a wrong handshake message or premature application data was received. The error results in a closed TLS connection. 0
bad_record_mac A record is received that can't be deprotected. The error results in a closed TLS connection. 0
record_overflow A TLSCiphertext record was received that has a length more than 214+256 bytes, or a record was decrypted to a TLSPlaintext record with more than 214 bytes (or some other negotiated limit). The error results in a closed TLS connection. 0
handshake_failure Unable to negotiate an acceptable set of security parameters given the options available. The error results in a closed TLS connection. 0
illegal_parameter A field in the handshake was incorrect or inconsistent with other fields. The error results in a closed TLS connection. 0
access_denied A valid certificate or PSK was received, but when access control was applied, the client didn't proceed with negotiation. The error results in a closed TLS connection. 0
decode_error A message couldn't be decoded because some fields were out of the specified range, or the length of the message was incorrect. The error results in a closed TLS connection. 0
decrypt_error A handshake (not record layer) cryptographic operation failed, including being unable to correctly verify a signature or validate a finished message or a PSK binder. The error results in a closed TLS connection. 0
insufficient_security A negotiation has failed specifically because the server requires parameters more secure than those supported by the client. The error results in a closed TLS connection. 0
inappropriate_fallback Sent by a server in response to an invalid connection retry attempt from a client. The error results in a closed TLS connection. 0
user_cancelled The user is cancels the handshake for some reason unrelated to a protocol failure. The error results in a closed TLS connection. 0
missing_extension Sent by endpoints that receive a handshake message not containing an extension that is mandatory to send for the offered TLS version or other negotiated parameters. The error results in a closed TLS connection. 0
unsupported_extension Sent by endpoints that receive any handshake message containing an extension known to be prohibited for inclusion in the given handshake message, or including any extensions in ServerHello or Certificate that was not first offered in the corresponding ClientHello or CertificateRequest. The error results in a closed TLS connection. 0
unrecognized_name Sent by servers when no server exists that can be identified by the name provided by the client through the "server_name" extension. See TLS extension definitions. 0
bad_certificate_status_response Sent by clients when an invalid or unacceptable OCSP response is provided by the server through the "status_request" extension. See TLS extension definitions. The error results in a closed TLS connection. 0
load_balancer_configured_resource_limits_reached The load balancer has reached the configured resource limits, such as the maximum number of connections. 400, 500, 503

Failed TLS connection log entries

When the TLS connection between the client and the load balancer fails before any backend is selected, log entries record the errors. You can configure the backend services with different log sample rates. When a TLS connection fails, the failed TLS connection log sample rate is the highest sample rate for any backend service. For example, if you have configured two backend services with logging sample rate as 0.3 and 0.5, the failed TLS connection log sample rate is 0.5.

You can identify failed TLS connections by checking for these log entry details:

  • proxyStatus error type is tls_alert_received, tls_certificate_error, tls_protocol_error, or connection_terminated.
  • There is no backend information.

The following sample shows a failed TLS log entry with the proxyStatus error field:

   json_payload:    {
   @type: "type.googleapis.com/google.cloud.loadbalancing.type.LoadBalancerLogEntry"
   proxyStatus: "error="tls_alert_received"; details="server_to_client: handshake_failure""
   log_name: "projects/529254013417/logs/mockservice.googleapis.com%20name"
   }
   http_request {
    latency {
      nanos: 12412000
    }
    protocol: "HTTP/1.0"
    remote_ip: "127.0.0.2"
   }
  resource {
    type: "mock_internal_http_lb_rule"
    labels {
      backend_name: ""
      backend_scope: ""
      backend_scope_type: "UNKNOWN"
      backend_target_name: ""
      backend_target_type: "UNKNOWN"
      backend_type: "UNKNOWN"
      forwarding_rule_name: "l7-ilb-https-forwarding-rule-dev"
      matched_url_path_rule: "UNKNOWN"
      network_name: "lb-network"
      region: "REGION"
      target_proxy_name: "l7-ilb-https-proxy-dev"
      url_map_name: ""
    }
  }
  timestamp: "2023-08-15T16:49:30.850785Z"

Resource labels

The following table lists the resource labels for resource.type="internal_http_lb_rule".

Field Type Description
network_name string The name of the load balancer's VPC network.
project_id string The identifier of the Google Cloud project associated with this resource.
region string The region in which the load balancer is defined.
url_map_name string The name of the URL map object configured to select a backend service.
forwarding_rule_name string The name of the forwarding rule object.
target_proxy_name string The name of the target proxy object referenced by the forwarding rule.
matched_url_path_rule string The URL map path rule or route rule configured as part of the URL map key. Can be UNMATCHED or UNKNOWN as fallbacks.
  • UNMATCHED refers to a request that matches no URL path rules, so it uses the default path rule.
  • UNKNOWN indicates an internal error.
backend_target_name string The name of the backend selected to handle the request, based on the URL map path rule or route rule that matches the request.
backend_target_type string The type of backend target (BACKEND_SERVICE / UNKNOWN).
backend_name string The name of the backend instance group or NEG.
backend_type string

The type of backend, either an instance group or a NEG, or unknown.

Cloud Logging logs requests when the backend_type is UNKNOWN even if logging is disabled. For example, if a client closes the connection to the load balancer before the load balancer can pick a backend, the backend_type is set to UNKNOWN and the request is logged. These logs provide useful debugging information about client requests that were closed because the load balancer could not select a backend.
backend_scope string The scope of the backend, either a zone name or a region name. Might be UNKNOWN whenever backend_name is unknown.
backend_scope_type string The scope of the backend (REGION/ZONE). Might be UNKNOWN whenever backend_name is unknown.
backend_target_cross_project_id String The project ID of the backend target service or bucket. This field is only available if the backend target resource is created in a project different from the project in which the url_map resource is created.

Authorization policy request logs

The authz_info object in the Load Balancer Log Entry JSON payload contains information about authorization policies. You can configure log-based metrics for traffic allowed or denied by these policies. Check more authorization policies log details.

Field Type Description
authz_info.policies[] object The list of policies that match the request.
authz_info.policies[].name string The name of the authorization policy that matches the request.
The name is empty for the following reasons:
  • No ALLOW policy matches the request and the request is denied.
  • No DENY policy matches the request and the request is allowed.
authz_info.policies[].result enum The result can be ALLOWED or DENIED.
authz_info.policies[].details string The details include the following:
  • allowed_as_no_deny_policies_matched_request
  • denied_as_no_allow_policies_matched_request
  • denied_by_authz_extension
  • denied_by_cloud_iap
authz_info.overall_result enum The result can be ALLOWED or DENIED.

View logs for mTLS client certificate validation

To view the logged errors for closed connections during mutual TLS client certificate validation, complete the following steps.

Console

  1. In the Google Cloud console, go to the Logs Explorer page.

    Go to Logs Explorer

  2. Click the Show query toggle to enable the query editor.

  3. Paste the following into the Query field. Replace FORWARDING_RULE_NAME with the name of your forwarding rule.

    jsonPayload.statusDetails=~"client_cert"
jsonPayload.@type="type.googleapis.com/google.cloud.loadbalancing.type.LoadBalancerLogEntry"
resource.labels.forwarding_rule_name=FORWARDING_RULE_NAME

  4. Click Run query.

Monitoring

Internal Application Load Balancers export monitoring data to Monitoring.

Monitoring metrics can be used for the following purposes:

  • Evaluating a load balancer's configuration, usage, and performance
  • Troubleshooting problems
  • Improving resource utilization and user experience

In addition to the predefined dashboards in Monitoring, you can create custom dashboards, set up alerts, and query the metrics through the Monitoring API.

Viewing Cloud Monitoring metrics

Console

To view the metrics for a monitored resource by using the Metrics Explorer, do the following:

  1. In the Google Cloud console, go to the  Metrics explorer page:

    Go to Metrics explorer

    If you use the search bar to find this page, then select the result whose subheading is Monitoring.

  2. In the Metric element, expand the Select a metric menu, enter Internal Application Load Balancer Rule in the filter bar, and then use the submenus to select a specific resource type and metric:
    1. In the Active resources menu, select Internal Application Load Balancer Rule.
    2. To select a metric, use the Active metric categories and Active metrics menus.
    3. Click Apply.

  3. To remove time series from the display, use the Filter element.

  4. To combine time series, use the menus on the Aggregation element. For example, to display the CPU utilization for your VMs, based on their zone, set the first menu to Mean and the second menu to zone.

    All time series are displayed when the first menu of the Aggregation element is set to Unaggregated. The default settings for the Aggregation element are determined by the metric type you selected.

  5. For quota and other metrics that report one sample per day, do the following:
    1. In the Display pane, set the Widget type to Stacked bar chart.
    2. Set the time period to at least one week.

Defining alerting policies

Console

You can create alerting policies to monitor the values of metrics and to notify you when those metrics violate a condition.

  1. In the Google Cloud console, go to the  Alerting page:

    Go to Alerting

    If you use the search bar to find this page, then select the result whose subheading is Monitoring.

  2. If you haven't created your notification channels and if you want to be notified, then click Edit Notification Channels and add your notification channels. Return to the Alerting page after you add your channels.
  3. From the Alerting page, select Create policy.
  4. To select the metric, expand the Select a metric menu and then do the following:
    1. To limit the menu to relevant entries, enter Internal Application Load Balancer Rule into the filter bar. If there are no results after you filter the menu, then disable the Show only active resources & metrics toggle.
    2. For the Resource type, select Internal Application Load Balancer Rule.
    3. Select a Metric category and a Metric, and then select Apply.
  5. Click Next.
  6. The settings in the Configure alert trigger page determine when the alert is triggered. Select a condition type and, if necessary, specify a threshold. For more information, see Create metric-threshold alerting policies.
  7. Click Next.
  8. Optional: To add notifications to your alerting policy, click Notification channels. In the dialog, select one or more notification channels from the menu, and then click OK.
  9. Optional: Update the Incident autoclose duration. This field determines when Monitoring closes incidents in the absence of metric data.
  10. Optional: Click Documentation, and then add any information that you want included in a notification message.
  11. Click Alert name and enter a name for the alerting policy.
  12. Click Create Policy.
For more information, see Alerting policies.

Defining Monitoring custom dashboards

Console

You can create custom Monitoring dashboards over internal Application Load Balancer metrics:

  1. In the Google Cloud console, go to the Monitoring page.

    Go to Monitoring

  2. Select Dashboards > Create Dashboard.

  3. Click Add Chart.

  4. Give the chart a title.

  5. Select metrics and filters. For metrics, the resource type is Internal HTTP/S Load Balancer.

  6. Click Save.

Metric reporting frequency and retention

Metrics for the load balancers are exported to Monitoring in 1-minute granularity batches. Monitoring data is retained for six (6) weeks. The dashboard provides data analysis in default intervals of 1H (one hour), 6H (six hours), 1D (one day), 1W (one week), and 6W (six weeks). You can manually request analysis in any interval from 6W to 1 minute.

Monitoring metrics for internal Application Load Balancers

The following metrics for internal Application Load Balancers are reported into Monitoring:

Metric FQDN Description
Request count loadbalancing.googleapis.com/https/internal/request_count The number of requests served by the internal Application Load Balancer.
Request bytes count loadbalancing.googleapis.com/https/internal/request_bytes The number of bytes sent as requests from clients to the internal Application Load Balancer.
Response bytes count loadbalancing.googleapis.com/https/internal/response_bytes The number of bytes sent as responses from the internal HTTP(S) load balancer to the client.
Total latencies loadbalancing.googleapis.com/https/internal/total_latencies A distribution of the latency, in milliseconds. Latency is measured from the time when the proxy receives the first byte of the request, to the time when the proxy sends the last byte of the response.
Backend latencies loadbalancing.googleapis.com/https/internal/backend_latencies A distribution of the latency, in milliseconds. Latency is measured from the time when the proxy sends the first byte of the request to the backend, to the time when the proxy receives the last byte of the response from the backend.

Filtering dimensions for internal Application Load Balancer metrics

Metrics are aggregated for each internal Application Load Balancer. You can filter aggregated metrics by the following dimensions.

Property Description
BACKEND_SCOPE The Google Cloud zone or region of the backend group that served the client request, or a special string for cases in which the backend group wasn't assigned. Examples: us-central1-a, europe-west1-b, asia-east1, UNKNOWN.
PROXY_REGION Region of the internal Application Load Balancer, client, and backend. Examples: us-central1, europe-west1 or asia-east1.
BACKEND The name of the backend instance group or NEG that served the client request.
BACKEND_TARGET The name of the backend service that served the client request.
MATCHED_URL_RULE The URL map path rule or route rule that matched the prefix of the client HTTP(S) request (up to 50 characters).

The Response code class fraction metric is supported for the entire load balancer. No further granularity is supported.

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