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%), logs are generated for all of the requests and written to Cloud Logging.

Also, even when logging is disabled for a backend service, the load balancer might produce log entries for unsuccessful requests if the load balancer can't associate those requests with a particular backend.

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

In the Google Cloud console, go to the Load balancingpage.

Go to Load balancing
Click the name of your load balancer.
Click Edit.
Click Backend Configuration.
Click Editnext to your backend service.
Click Advanced configurations (Session affinity, connection draining timeout).
Click Enable logging.
Set a Sample ratefraction. 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 .
Optional: To include all the optional fields in the logs, in the Optional fieldssection, click Include all optional fields.

Pro tip: To specify the CUSTOMoption, use the gcloud CLI and the REST API.
To finish editing the backend service, click Update.
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 . If you use custom metrics and want to log elements of the ORCA load report, you set LOGGING_OPTIONAL_MODE to CUSTOM and specify which elements must be logged in the OPTIONAL_FIELDS field. For example, orca_load_report.cpu_utilization,orca_load_report.mem_utilization .

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

Console

In the Google Cloud console, go to the Load balancingpage.

Go to Load balancing
Click the name of your load balancer.
Click Edit.
Click Backend Configuration.
Click Editnext to your backend service.
Click Advanced configurations (Session affinity, connection draining timeout).
Click Enable logging.
Set a Sample ratefraction. 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 .
Optional: To include all the optional fields in the logs, in the Optional fieldssection, click Include all optional fields.

Pro tip: To specify the CUSTOMoption, use the gcloud CLI and the REST API.
To finish editing the backend service, click Update.
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 . If you use custom metrics and want to log elements of the ORCA load report, you set LOGGING_OPTIONAL_MODE to CUSTOM and specify which elements must be logged in the OPTIONAL_FIELDS field. For example, orca_load_report.cpu_utilization,orca_load_report.mem_utilization .

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

Disabling or modifying logging on an existing backend service

Console

In the Google Cloud console, go to the Load Balancingpage.

Go to Load balancing
Click the name of your load balancer.
Click Edit.
Click Backend Configuration.
Click Editnext to your backend service.
To disable logging entirely, in the Loggingsection, clear the Enable loggingcheckbox.
If you leave logging enabled, you can set a different Sample ratefraction. 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 . For example, 0.2 means 20% of the sampled requests generate logs.
To finish editing the backend service, click Update.
To finish editing the load balancer, click Update.

gcloud: Cross-region mode

Disable logging on a backend service with the gcloud compute backend-services update command .

Disabling logging entirely

gcloud compute backend-services update BACKEND_SERVICE 
\
    --global \
    --no-enable-logging

where

--global indicates that the backend service is global. Use this field for backend services used with cross-region internal Application Load Balancers.
--no-enable-logging disables logging for that backend service.

Enabling logging optional fields on an existing backend service

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

where

--logging-sample-rate lets you specify a value 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. 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 . If you use custom metrics and want to log elements of the ORCA load report, you set LOGGING_OPTIONAL_MODE to CUSTOM and specify which elements must be logged in the OPTIONAL_FIELDS field. For example, orca_load_report.cpu_utilization,orca_load_report.mem_utilization .

Updating logging optional mode from CUSTOM to others

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

where

--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.
--logging-optional-fields must be explicitly configured as shown to clear any existing CUSTOM fields. The API doesn't let you combine a non- CUSTOM mode with CUSTOM fields.

Modifying the logging sample rate

gcloud compute backend-services update BACKEND_SERVICE 
\
    --global \
    --logging-sample-rate= VALUE

gcloud: Regional mode

Disable logging on a backend service with the gcloud compute backend-services update command .

Disabling logging entirely

gcloud compute backend-services update BACKEND_SERVICE 
\
    --region= REGION 
\
    --no-enable-logging

where

--region indicates that the backend service is regional. Use this field for backend services used with regional internal Application Load Balancers.
--no-enable-logging disables logging for that backend service.

Enabling logging optional fields on an existing backend service

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

where

--logging-sample-rate lets you specify a value 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. 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 . If you use custom metrics and want to log elements of the ORCA load report, you set LOGGING_OPTIONAL_MODE to CUSTOM and specify which elements must be logged in the OPTIONAL_FIELDS field. For example, orca_load_report.cpu_utilization,orca_load_report.mem_utilization .

Updating logging optional mode from CUSTOM to others

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

where

--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.
--logging-optional-fields must be explicitly configured as shown to clear any existing CUSTOM fields. The API doesn't let you combine a non- CUSTOM mode with CUSTOM fields.

Modifying the logging sample rate

gcloud compute backend-services update BACKEND_SERVICE 
\
    --region= REGION 
\
    --logging-sample-rate= VALUE

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
backendNetworkName
orca_load_report

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:

proxyStatus error
Optional: proxyStatus details

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 .

TlsInfo

Optional

The tls field holds the TlsInfo field that specifies the TLS metadata for the connection between the client and the load balancer. This field is only available if the client is using TLS/SSL encryption.

Use the --logging-optional-fields parameter to specify which elements must be logged:

tls.protocol
tls.cipher

You can't set --logging-optional-fields to tls to specify all elements.

MtlsInfo

Optional

The mtls field holds the MtlsInfo 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).

string

Optional

The backendNetworkName field specifies the VPC network of the backend, if the backend uses a different VPC than the load balancer's forwarding rule.

OrcaLoadReport

Optional

The orca_load_report field contains some or all elements of the ORCA load report returned by the backend. This field is only present if the backend returns an ORCA load report, and you configured the load balancer to log the ORCA load report.

Use the --logging-optional-fields parameter to specify which of the following elements of the ORCA load report must be logged:

orca_load_report.cpu_utilization
orca_load_report.mem_utilization
orca_load_report.request_cost
orca_load_report.utilization
orca_load_report.rps_fractional
orca_load_report.eps
orca_load_report.named_metrics
orca_load_report.application_utilization

You can also set --logging-optional-fields to orca_load_report to specify that all elements must be logged.

TlsInfo 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.

MtlsInfo 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 Client validation mode .
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 isn't valid. For example, `2022-07-01T18:05:09+00:00` .
clientCertValidEndTime	string	Optional	Timestamp ( RFC 3339 date string format) after which the client certificate isn't 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 isn't 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

Filter this table:

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. The error can be due to a scheduled restart of the proxy managing the connections.

0 , 500 , 502

proxy_internal_response

The load balancer generated the response without attempting to connect to the backend.

Any status code depending on the type of problem. For example, the 410 status 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

Filter this table:

proxyStatus details

Description

Common accompanying response status codes

client_disconnected_before_any_response

The connection to the client was broken before the load balancer sent any response.

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 status 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 isn't supported. Only HTTP 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 status 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 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 .

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 isn't 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 can't be accepted because the CA certificate cannot 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 2 ¹⁴ +256 bytes, or a record was decrypted to a TLSPlaintext record with more than 2 ¹⁴ 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 are out of the specified range, or the length of the message is 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 that are 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 canceled 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.

0

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 couldn't 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

In the Google Cloud console, go to the Logs Explorerpage.

Go to Logs Explorer
Click the Show querytoggle to enable the query editor.

Paste the following into the Queryfield. 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

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:

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 .
In the toolbar of the Google Cloud console, select your Google Cloud project. For App Hub configurations, select the App Hub host project or the app-enabled folder's management project.
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 .
To add filters, which remove time series from the query results, use the Filter element .
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.
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.

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 .
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.
From the Alerting page, select Create policy .
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 .
Click Next .
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 .
Click Next .
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 .
Optional: Update the Incident autoclose duration . This field determines when Monitoring closes incidents in the absence of metric data.
Optional: Click Documentation , and then add any information that you want included in a notification message.
Click Alert name and enter a name for the alerting policy.
Click Create Policy .

For more information, see Alerting overview .

Defining Monitoring custom dashboards

Console

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

In the Google Cloud console, go to the Monitoringpage.

Go to Monitoring
Select Dashboards > Create Dashboard.
Click Add Chart.
Give the chart a title.
Select metrics and filters. For metrics, the resource type is Internal HTTP/S Load Balancer.
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

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 total latency. Total latency is the time in milliseconds between the first byte of the request received by the proxy and the last byte of the response sent by the proxy. It includes: the time taken by the proxy to process the request, the time taken for the request to be sent from the proxy to the backend, the time taken by the backend to process the request, the time taken for the response to be sent back to the proxy, and the time taken for the proxy to process the response and send the response to the client. It doesn't include the RTT between the client and the proxy. Additionally, pauses between requests on the same connection that use `Connection: keep-alive` do not affect the measurement. This measurement is typically reduced to the 95th percentile in Cloud Monitoring views.
Backend latencies	`loadbalancing.googleapis.com/https/internal/backend_latencies`	A distribution of the backend latency. Backend latency is the time in milliseconds between the last byte of the request sent to the backend and the last byte of the response received by the proxy. It includes the time taken by the backend to process the request and the time taken for the response to be sent back to the proxy.

Filtering dimensions for 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.

What's next

Read conceptual information about internal Application Load Balancers .
Create an internal Application Load Balancer .
See Internal load balancing and DNS names for available DNS name options your load balancer can use.

Internal Application Load Balancer logging and monitoring Stay organized with collections Save and categorize content based on your preferences.

Logging

Logs sampling and collection

Optional fields

Enabling logging on an existing backend service

Console

gcloud

Console

gcloud

Disabling or modifying logging on an existing backend service

Console

gcloud: Cross-region mode

gcloud: Regional mode

How to view logs

What is logged

TlsInfo field format

MtlsInfo field format

proxyStatus error field

proxyStatus details field

Failed TLS connection log entries

Resource labels

Authorization policy request logs

View logs for mTLS client certificate validation

Console

Monitoring

Viewing Cloud Monitoring metrics

Console

Defining alerting policies

Console

Defining Monitoring custom dashboards

Console

Metric reporting frequency and retention

Monitoring metrics

Filtering dimensions for metrics

What's next

Internal Application Load Balancer logging and monitoring