Advanced logs queries

This guide shows you how to use the Legacy Logs Viewer to write advanced logs queries, which are expressions that can specify a set of log entries from any number of logs. Advanced logs queries can be used in the Legacy Logs Viewer, the Logging API, or the gcloud command-line tool.

For more basic querying options, go to Basic logs queries.

For a list of recommended queries for finding logs, go to Sample queries.

Introduction

Cloud Logging provides two interfaces for analyzing logs data:

This page contains information on using the Legacy Logs Viewer to write advanced queries. The Logs Explorer is the new interface for analyzing logs data. For more information about the Logs Explorer, see Using the Logs Explorer.

An advanced logs query is a Boolean expression that specifies a subset of all the log entries in your project. It can be used to do any of the following:

Choose log entries from specific logs or log services.
Choose log entries within a time range.
Choose log entries that satisfy conditions on metadata or user-defined fields.
Choose a sampling percentage of all log entries.

Getting started with advanced logs queries

To get started using advanced logs queries in the Legacy Logs Viewer:

Go to the Logging > Logs Explorer page in the Cloud Console.
Select Go back to the Legacy Logs Viewer from the Options drop-down menu.
Select an existing Google Cloud project at the top of the page, or create a new project.
Using the drop-down menu , select the resource whose logs you want to view.
Click the drop-down menu in the search-query box and select Convert to advanced filter.

The user interface showing conversion to advanced filter.

Log queries are labelled as "filters" in the user interface, since they let you select a particular set of logs entries.

The advanced logs query interface appears:

The user interface showing advanced filters options.

You can recognize this query interface by the absence of the log selection menus and presence of the Submit Filter button. The Legacy Logs Viewer displays log entries that satisfy all of the conditions specified in the query.

Following is a simple example of an advanced logs query:

    resource.type = "gce_instance" AND
    severity >= ERROR AND
    NOT textPayload:robot

This query matches log entries from Compute Engine that have severity values of at least ERROR and whose textPayload field doesn't contain the string robot anywhere inside it. String comparisons aren't case sensitive. The names resource, severity, and textPayload are defined in the LogEntry type.

Suggestions and highlighting as you type: When you type an advanced logs query into the Legacy Logs Viewer, suggestions for specific log entry fields might appear. The suggestions come from both the query language and the set of actual log entries that the Legacy Logs Viewer has loaded. To choose a suggestion, press TAB. If suggestions don't appear, try pressing CTRL+ SPACE. The different parts of a query expression are highlighted in different colors. If your expression is a bright red, then the query you've typed so far might have an error or might be incomplete.

Unquoted text: You can omit quotation marks around text strings that don't contain whitespace or certain special characters. This is called unquoted text, and examples are the words ERROR and robot in the preceding example. The string "v1.compute.instances.insert" is quoted because it contains periods. If you wish to include a quotation mark within a string, precede the quotation mark with a backslash.

Best practice: Add quotation marks to strings that you are comparing against field values. This guards against mistakes that change the meaning of your comparisons and are difficult to debug. You can omit the quotation marks on words that consist of a letter followed by a sequence of letters, digits, or underscore (_) characters.

Using a keyboard: If you are using a keyboard to type an advanced logs query into the search-query box, you can press ESC to exit the editing mode and then press TAB to navigate to the other options, such as the drop-down menu or the Submit Filter button.

Advanced logs query syntax

This section discusses how advanced logs queries are structured and how matching is performed.

Syntax notation

The advanced logs query syntax is described using the following notation:

a = e means that a is a name for the expression e.
a b means "a followed by b."
a | b means "a or b."
( e ) is used for grouping.
[ e ] means that e is optional.
{ e } means that e can be repeated zero or more times.
"abc" means that abc must be written just as it appears.

Syntax summary

This section provides an overview of the language's syntax.

A query is a string containing an expression:

   expression = ["NOT"] comparison { ("AND" | "OR") ["NOT"] comparison }

A comparison is either a single value or a Boolean expression:

  "The cat in the hat"
  resource.type = "gae_app"

The first line is an example of a comparison that is a single value. These types of comparisons are global restrictions. Each field of a log entry is compared to the value by implicitly using the has operator. For this example, if any field in a LogEntry, or if its payload, contains the phrase "The cat in the hat", then the comparison is successful.

The second line is an example of a comparison that is a Boolean expression of the form [FIELD_NAME] [OP] [VALUE]. The elements of the comparison are described below:

[FIELD_NAME]: is a field in a log entry. For example, resource.type.
[OP]: is a comparison operator. For example, =.
[VALUE]: is a number, string, function, or parenthesized expression. For example, "gae_app".

The following sections provide more details about queries and matching.

Boolean operators

The Boolean operators AND and OR are short-circuit operators. The NOT operator has the highest precedence, followed by OR and AND in that order. For example, the following two expressions are equivalent:

a OR NOT b AND NOT c OR d
(a OR (NOT b)) AND ((NOT c) OR d)

You can omit the AND operator between comparisons. You can also replace the NOT operator with the - (minus) operator. For example, the following two queries are the same:

a=b AND c=d AND NOT e=f
a=b c=d -e=f

This documentation always uses AND and NOT.

Comparisons

Comparisons have the following form:

[FIELD_NAME] [OP] [VALUE]

The elements of the comparison are described below:

[FIELD_NAME]: is the path name of a field in a log entry. Examples of the field name are:
```
resource.type
resource.labels.zone
resource.labels.project_id
insertId
jsonPayload.httpRequest.protocol
labels."compute.googleapis.com/resource_id"
```
If a component of a path name has special characters, the path name needs to be double-quoted. For example, compute.googleapis.com/resource_id needs to be double quoted because it contains a forward slash /.

For details, review field path identifiers on this page.

[OP]: is a comparison operator, one of the following:

=           # equal
!=          # not equal
> < >= <=   # numeric ordering
:           # "has" matches any substring in the log entry field
=~          # regular expression search for a pattern
!~          # regular expression search not for a pattern

[VALUE]: is a number, string, function, or parenthesized expression. Strings are used to represent arbitrary text, plus Boolean, enumeration, and byte-string values. The [VALUE] is converted to the field's type prior to the comparison.

If [VALUE] is a parenthesized Boolean combination of comparisons, then the field name and the comparison operator are applied to each element. For example:

    jsonPayload.cat = ("longhair" OR "shorthair")
    jsonPayload.animal : ("nice" AND "pet")

The first comparison checks that the field cat has the value "longhair" or "shorthair". The second checks that the value of the field animal contains both of the words "nice" and "pet", in any order.

Field path identifiers

All log entries are instances of type LogEntry. The identifier that is (or begins) the left-hand side of a comparison must be a field defined in the LogEntry type. For details on the possible identifiers and their values, review the LogEntry type.

Here is the current list of log entry fields. Each field is followed by the next level of names for that field, if applicable:

httpRequest: { cacheFillBytes, cacheHit, cacheLookup, cacheValidatedWithOriginServer, latency, protocol, referer, remoteIp, requestMethod, requestSize, requestUrl, responseSize, serverIp, status, userAgent }
insertId
jsonPayload { variable }
labels { variable }
logName
metadata { systemLabels, userLabels }
operation{ id, producer, first, last }
protoPayload { @type, variable }
receiveTimestamp
resource { type, labels }
severity
sourceLocation: { file, line, function }
spanId
textPayload
timestamp
trace

Following are examples of field path identifiers you can use in your comparisons:

resource.type: If your first path identifier is resource, then the next identifier must be a field in the MonitoredResource type.
httpRequest.latency: If your first path identifier is httpRequest, then the next identifier must be a field in the HttpRequest type.
labels.[KEY] If your first path identifier is labels, then the next identifier, [KEY], must be one of the keys from the key-value pairs appearing in the labels field.
logName: Since the logName field is a string, you can't follow it by any subfield names.

Special characters

If a LogEntry field contains special characters, the log field must be quoted. For example:

  jsonPayload.":name":apple

  jsonPayload."foo.bar":apple

  jsonPayload."\"foo\"":apple

For the list of special characters, see the string section in Values and conversions.

For more information on using field path identifiers that reference objects or arrays, go to Object and array types on this page.

Monitored resource types

For faster queries, specify a monitored resource type. For a list of resource types, go to Monitored resource types.

For example, Compute Engine VMs use the resource type gce_instance and Amazon EC2 instances use aws_ec2_instance. The following example shows how to limit your queries to both type of VMs:

    resource.type = ("gce_instance" OR "aws_ec2_instance")

The monitored resource type values in logs are indexed. Using substring matches for them results in slower queries.

Missing fields

If you use a field name in a query, and that field doesn't appear in a log entry, then the field is missing, undefined, or defaulted:

If the field is part of the log entry's payload (jsonPayload or protoPayload), or if it is in a label in the labels section of the log entry, then the field is missing. Using a missing field won't display an error, but all comparisons using missing fields fail silently.

Examples: jsonPayload.nearest_store, protoPayload.name.nickname
If the field is defined in the LogEntry type, then the field is defaulted. Comparisons are performed as if the field were present and had its default value.

Examples: httpRequest.remoteIp, trace, operation.producer
Otherwise, the field is undefined, which is an error that is detected before the query is used.

Examples: thud, operation.thud, textPayload.thud

To test if a missing or defaulted field exists without testing for a particular value in the field, use the :* comparison. For example, the following comparison succeeds if the field operation.id is explicitly present in a log entry:

operation.id:*

Note the behavior of the following queries:

When you use the boolean NOT operator on a missing field, the result is TRUE:
```
# Returns TRUE
NOT missingField=foo
```
When you use the not equal comparison operator != on a missing field, the result is FALSE:
```
# Returns FALSE
missingField!=foo
```

Object and array types

Each log entry field can hold a scalar, object, or array.

A scalar field stores a single value, like 174.4 or -1. A string is also considered a scalar. Fields that can be converted to (or from) a string, such as Duration and Timestamp are also scalar types.
An object type stores a collection of named values, like the following JSON value:
```
{"age": 24, "height": 67}
```
You can refer to value inside an object. For example, if jsonPayload.x contained the preceding value, then jsonPayload.x.age would have the value 24.
An array field stores a list of values—all of the same type. For example, a field holding measurements might have an array of numbers:
```
{8.5, 9, 6}
```
When comparisons are performed and [FIELD_NAME] is an array field, each member of the array is compared to [VALUE] and the results are joined together using the OR operator. For example, if jsonPayload.shoeSize is an array field that stores {8.5, 9, 6}, the comparison:
```
jsonPayload.shoeSize < 7
```
is equivalent to:
```
8.5 < 7 OR 9 < 7 OR 6 < 7
```
In this example, the overall comparison evaluates to successful.

Values and conversions

The first step in evaluating a comparison is to convert the right-hand side value to the type of the log entry field. Scalar field types are permitted in comparisons, along with two additional types whose values are represented as strings: Duration and Timestamp. For a list of scalar types, go to the scalar protocol buffer types list. The following table explains what values can be converted to the log field types:

Field type	Permitted query value
`bool`	"True" or "false" in any letter case. Examples: "True", "true"
`bytes`	A string containing any sequence of bytes. Example: "\377\377".
`Duration`	A string containing a signed decimal number followed by one of the units "ns", "us", "ms", "s", "m", or "h". Durations are accurate to nanoseconds. Example: "3.2s".
`enum`	The name of an enumeration type literal, case-insensitive. Examples: "WARNING", which is a value of type LogSeverity.
`double`	Any number, with or without a sign and an exponent part, or the special value strings "NaN", "-Infinity", and "Infinity" (either capitalized or not). Examples: "-3.2e-8", "nan".
`intNN`	Any signed integer that doesn't exceed the size of the type. Example: "-3".
`string`	Any string that contains UTF-8 encoded or 7-bit ASCII text. Embedded quotation marks must be escaped with a backslash. String values must be double-quoted to escape the following special characters: Strings starting with `+` (plus), `-` (minus), or `.` (period). Strings with `~` (tilde), `=` (equals), `()` (parentheses), `:` (colon), `>` (greater than), `<` (less than), `,` (comma), or `.` (period). Any escape sequence, for example `\t`.
`Timestamp`	A string in RFC 3339 or ISO 8601 format. Examples: "2014-10-02T15:01:23.045Z" (RFC 3339), "2014-10-02" (ISO 8601). In query expressions, timestamps in RFC 3339 format can specify a timezone with "Z" or `±hh:mm`. Timestamps are represented to nanosecond accuracy.
`uintNN`	Any unsigned integer that doesn't exceed the size of the type. Example: "1234".

If an attempted conversion fails, then the comparison fails.

When a conversion requires a string, you can also use a number or unquoted text if they don't contain special characters such as spaces and operators. Similarly, when a conversion requires a number, you can use a string whose content is a number.

The types intNN and uintNN represent integer types of various sizes, such as int32 and uint64. When writing a value to be converted to a 64-bit integer type, you write the value as a string, such as "9223372036854775807".

Types of log fields

Here is how the type of a log entry field is determined:

Log fields defined in the type LogEntry, and in the component type are protocol buffer fields. Protocol buffer fields have explicit types.
Log fields that are part of protoPayload objects are also protocol buffer fields and have explicit types. The name of the protocol buffer type is stored in the field "@type" of protoPayload. For more information, review the JSON mapping.
Log fields inside of jsonPayload have types that are inferred from the field's value when the log entry is received:
- Fields whose values are unquoted numbers have type double.
- Fields whose values are true or false have type bool.
- Fields whose values are strings have type string.
Long (64-bit) integers are stored in string fields, because they cannot be represented exactly as double values.
The Duration and Timestamp types are recognized only in protocol buffer fields. Elsewhere, those values are stored in string fields.

Comparison operators

The meaning of the equality (=, !=) and inequality (<, <=, >, >=) operators depends on the underlying type of the left-hand field name.

All numeric types: Equality and inequality have their normal meaning for numbers.
bool: Equality means the same Boolean value. Inequality is defined by true>false.
enum: Equality means the same enumeration value. Inequality uses the underlying numeric values of the enumeration literals.
Duration: Equality means the same duration length. Inequality is based on the length of the duration. Example: as durations, "1s">"999ms".
Timestamp: Equality means the same instant in time. If a and b are Timestamp values, a < b means a is earlier in time than b.
bytes: Operands are compared byte by byte, left-to-right.
string: Comparisons ignore letter case. Specifically, both operands are first normalized using NFKC_CF Unicode normalization and then use lexicographic comparisons. However, regular expression searches aren't normalized. For more information on searching log entries using regular expressions, see Querying and filtering log entries using regular expressions.

The substring operator (:) is applicable to string and bytes, and is handled like equality except that the right-hand operand need only equal some part of the left-hand field. Substring matches on indexed fields don't take advantage of log indexes.

Global restrictions

If the comparison consists of a single value, it is called a global restriction. Logging uses the has (:) operator to determine if any field in a log entry, or if its payload, contains the global restriction. If it does, then the comparison succeeds.

The simplest query written in terms of a global restriction is a single value:

"The Cat in The Hat"

You can combine global restrictions using the AND and OR operators for a more interesting query. For example, if you want to display all log entries that have a field that contains cat and a field that contains either hat or bat, write the query as:

(cat AND (hat OR bat))

In this case, there are three global restrictions: cat, hat and bat. These global restrictions are applied separately and the results are combined, just as if the expression had been written without parentheses.

A global restriction is an easy way to query your logs for a particular value. For example, if you are looking in your activity log for entries containing any mention of GCE_OPERATION_DONE, you can use the following query:

    logName = "projects/my-project-id/logs/compute.googleapis.com%2Factivity_log" AND
    "GCE_OPERATION_DONE"

Although global restrictions are easy, they can be slow; for more information, review Finding log entries quickly on this page.

Functions

You can use built-in functions as global restrictions in queries:

function = identifier ( [ argument { , argument } ] )

where argument is a value, field name, or a parenthesized expression. The functions are described in the following sections.

log_id

The log_id function returns log entries that match the given [LOG_ID] argument from the logName field:

  log_id([LOG_ID])

For example, the following query returns all log entries with a cloudaudit.googleapis.com%2Factivity [LOG_ID]:

  log_id("cloudaudit.googleapis.com/activity")

sample

The sample function selects a fraction of the total number of log entries:

sample([FIELD], [FRACTION])

[FIELD] is the name of a field in the log entry, such as logName or jsonPayload.a_field. The value of the field determines whether the log entry is in the sample. The field type must be a string or numeric value. Setting [FIELD] to insertId is a good choice, because every log entry has a different value for that field.

[FRACTION] is the fraction of log entries that have values for [FIELD] to include. It is a number greater than 0.0 and no greater than 1.0. For example, if you specify 0.01, then the sample contains roughly one percent of all log entries that have values for [FIELD]. If [FRACTION] is 1, then all the log entries that have values for [FIELD] are chosen.

Example: The following query returns 25 percent of the log entries from log syslog:

    logName = "projects/my-project/logs/syslog" AND sample(insertId, 0.25)

Details: A deterministic algorithm, based on hashing, is used to determine if a log entry is included, or excluded, from the sample. The accuracy of the resulting sample is dependent on the distribution of the hashed values. If the hashed values aren't uniformly distributed, then the resulting sample can be skewed. In the worst case, when [FIELD] always contains the same value, the resulting sample contains either the [FRACTION] of all log entries or no log entries.

If [FIELD] does appear in a log entry, then:

A hash of the value is computed.
The hashed value, which is a number, is divided by the maximum possible hashed value.
If the resulting fraction is less than or equal to [FRACTION], the log entry is included in the sample; otherwise it is excluded from the sample.

If [FIELD] doesn't appear in a log entry, then:

If [FIELD] is part of the log entry's payload or labels sections, the log entry isn't selected for the sample, even if [FRACTION] is 1.
Otherwise, the log entry is treated as if [FIELD] is in the log entry and the value of [FIELD] is the default value. The default value is determined by the LogEntry type. For more information on missing and defaulted fields, review Missing fields on this page.

To exclude log entries with defaulted fields from the sample, use the field-exists operator, :*. The following query produces a 1 percent sample of log entries that have explicitly supplied a value for field:

field:* AND sample(field, 0.01)

ip_in_net

The ip_in_net function determines if an IP address in a log entry is contained in a subnet. You might use this to tell if a request comes from an internal or external source. For example:

ip_in_net([FIELD], [SUBNET])

[FIELD] is a string-valued field in the log entry that contains an IP address or range. The field can be repeating, in which case only one of the repeated fields has to have an address or range contained in the subnet.

[SUBNET] is a string constant for an IP address or range. It is an error if [SUBNET] isn't a legal IP address or range, as described later in this section.

Example: The following query tests an IP address in the payload of log entries from the log my_log:

    logName = "projects/my_project/logs/my_log" AND
    ip_in_net(jsonPayload.realClientIP, "10.1.2.0/24")

Details: If, in a log entry, [FIELD] is missing, defaulted, or it does not contain a legal IP address or range, then the function returns false. For more information on missing and defaulted fields, review Missing fields on this page.

Examples of the supported IP addresses and ranges follow:

IPv4: 10.1.2.3
IPv4 subnet: 10.1.2.0/24
CIDR IPv6: 1234:5678:90ab:cdef:1234:5678:90ab:cdef
CIDR IPv6 subnet: 1:2::/48

Searching by time

In the interface, you can set specific limits on the date and time of log entries to show. For example, if you add the following conditions to your query, the Legacy Logs Viewer displays exactly the log entries in the indicated 30-minute period and you won't be able to scroll outside of that date range:

timestamp >= "2016-11-29T23:00:00Z"
timestamp <= "2016-11-29T23:30:00Z"

When writing a query with a timestamp, you must use dates and times in the format shown above.

You can also search log entries using timestamp shortcuts. For example, you can enter a date with a comparison operator to get all log entries after a certain day:

  timestamp > "2016-11-29"

Using regular expressions

You can use regular expressions to build queries and create filters for sinks, metrics, and wherever log filters are used. You can use regular expressions in the Query builder and with gcloud command-line tool.

A regular expression is a sequence of characters that define a search. The query language uses the RE2 syntax. For a complete explanation of the RE2 syntax, go to the RE2 wiki on GitHub.

Regular expression queries have the following characteristics:

Only fields of the string type can be matched with a regular expression.
String normalization isn't performed; for example, kubernetes isn't considered the same as KUBERNETES. For more information, see the Comparison operators section.
Queries are case sensitive and not anchored by default.
Boolean operators can be used between multiple regular expressions on the right side of the regular expression comparison operator, =~ and !~.

A regular expression query has the following structure:

Match a pattern:

jsonPayload.message =~ "regular expression pattern"

Does not match a pattern:

jsonPayload.message !~ "regular expression pattern"

The =~ and !~ changes the query to a regular expression query, and the pattern you're trying to match must be within double quotation marks. To query for patterns that contain double quotation marks, escape them using a backslash.

Note: Regular expression queries offer a potential speed increase over a regular text query. For example, querying for log entries that contain both foo and bar can be faster using the regular expression query jsonPayload.message =~ "foo.*bar|bar.*foo" than the substring query jsonPayload.message : ("foo" AND "bar").

Examples querying logs using regular expressions

Query type	Example
Standard query	`sourceLocation.file =~ "foo"`
Query with case-insensitive search	`labels.subnetwork_name =~ "(?i)foo"`
Query containing quotation marks	`jsonPayload.message =~ "field1=\"bar.*\""`
Query using a boolean `or`	`labels.pod_name =~ "(foo\|bar)"`
Query using anchors	`logName =~ "/my%2Flog$"`
Query not matching a pattern	`labels.pod_name !~ "foo"`
Query using boolean operator	`labels.env =~ ("^prod.server" OR "^staging.server")`

Finding log entries quickly

To find log entries more efficiently, do the following:

Query using indexed fields.
Minimize the number of log entries that must be searched.

Use indexed fields

The following LogEntry fields are indexed:

The next sections explain how to use these indexed fields to minimize the number of log entries to be searched.

Optimize your queries

Make your searches faster by reducing the number of logs, the number of log entries, or the time span of your searches. Even better, reduce all three.

Example: Use the right log name

Specify the log containing the log entries you're interested in. Be sure you know the actual log name by inspecting one of your log entries. For example, the Legacy Logs Viewer shows that there is a log in the Compute Engine section named "activity". On closer inspection of the Admin Activity audit log entries, the log is actually named "cloudaudit.googleapis.com/activity".

The following comparison is incorrect. It doesn't match anything because it uses the wrong log name:

    logName = "projects/my-project-id/logs/activity"   # WRONG!

The following comparison is correct. It chooses log entries from the Admin Activity audit log entries. You must URL-encode the log name, as shown:

    logName = "projects/my-project-id/logs/cloudaudit.googleapis.com%2Factivity"

Example: Choose the right log entries

If you know that the log entries you want are coming from a particular VM instance, then specify it. Check for the right label names by inspecting one of the log entries that you want to search for. In the following example, instance_id is one of the indexed labels:

    resource.type = "gce_instance" AND
    resource.labels.instance_id = "6731710280662790612"
    logName = "projects/my-project-id/logs/cloudaudit.googleapis.com%2Factivity"

Example: Choose the right time period

Specify a time period to search in. A quick way of determining useful timestamps in RFC 3339 format is to use the GNU/Linux date command:

$ date --rfc-3339=s
2016-06-27 17:39:00-04:00
$ date --rfc-3339=s --date="3 hours ago"
2016-06-27 14:40:00-04:00
$ date --rfc-3339=s --date="5 hours ago"
2016-06-27 12:40:00-04:00

Use the values of these timestamps in the following queries. To create a timestamp acceptable to Logging, replace the space between the date and time with the letter T.

For example, to search within the last three hours:

    timestamp >= "2016-06-27T14:40:00-04:00"

As another example, to search between three and five hours ago:

    timestamp >= "2016-06-27T12:40:00-04:00" AND
    timestamp <= "2016-06-27T14:40:00-04:00"

Minimize global and substring searches

Avoid the temptation to take shortcuts when typing queries.

Example: Don't use global searches

If you're searching for a log entry with "Hello, Kitty" in the payload:

Don't use a global search. For one reason, they are all substring searches:
```
    "Hello, Kitty"   # THIS CAUSES A SLOW SEARCH!
```
Do limit the search to a single field, even if you must keep the substring search:
```
    textPayload:"Hello, Kitty"
```
Do use an equality test if you can:
```
    textPayload = "Hello, Kitty"
```
Do reference individual fields in a payload, if your log entries have structured payloads:
```
    jsonPayload.my_favorite_cat = "Hello, Kitty"
```

Do use an indexed field to restrict the search:

    logName = "projects/my-project_id/logs/somelog" AND
    jsonPayload.my_favorite_cat = "Hello, Kitty"

Searching examples

The log entries shown are the ones that match a query. If the Jump to time menu contains a value, then the display scrolls to that point in time. Here are some query examples:

resource.type=gae_app

Finds all App Engine log entries. For a list of resource types, go to Monitored resource list.

As you type, the Legacy Logs Viewer suggests completions for fields like resource.type.

resource.type=gae_app AND logName:request_log

Finds log entries for App Engine apps from log names containing request_log. Note several things:

The = operator is exact equality. The resource type must be exactly "gae_app" except for letter case.
The : operator means "has". The logName field must contain request_log, in any letter case. The actual log name is much longer. Using : might result in slower searches.
The two comparisons are joined by AND. You can also use OR, but AND is assumed if you leave out the operator.

resource.type = (gce_instance OR aws_ec2_instance) AND severity >= ERROR

Finds log entries with either of two resource types: Compute Engine VM instance or AWS EC2 VM instance. The log entries must have severity of at least ERROR, which is equivalent to selecting ERROR in the query interface's severity menu.

logName = "projects/[PROJECT_ID]/logs/cloudaudit.googleapis.com%2Factivity"

Finds all the Admin Activity audit log entries in the project [PROJECT_ID]. Audit logs all use the same log name in a project, but have different resource types. The log ID, cloudaudit.googleapis.com/activity must be URL-encoded in the log name. Using equality in the comparison speeds up the search. For more information, review Understanding audit logs.

unicorn

Finds log entries containing unicorn in any field, in any letter case. A search term that isn't part of a field comparison is an "all fields" query.

unicorn phoenix

Finds log entries that contain unicorn in some field and phoenix in some field.

textPayload:(unicorn phoenix)

Finds log entries whose textPayload field contains both unicorn and phoenix in any order—the AND is implicit between the two words.

textPayload:"unicorn phoenix"

Finds log entries whose textPayload field contains the string "unicorn phoenix".

NOT textPayload: "unicorn phoenix"

Finds log entries whose textPayload field does not contain the string "unicorn phoenix". This type of query reduces unwanted log entries.

timestamp >= "2016-11-29T23:00:00Z" timestamp <= "2016-11-29T23:30:00Z"

Finds log entries within a 30-minute period.

Troubleshooting

Syntax issues

If you have problems with your queries' expressions, check the following:

Your query obeys the syntax rules, with matched parentheses and quotation marks. Your query can't include comments.
Your log entry field names are correctly spelled.
Boolean operations are in uppercase letters (AND, OR, NOT).
Boolean expressions as global restrictions or as the right-hand side of comparisons should be parenthesized for clarity. For example, the two queries below look the same, but are not:
```
insertId = "ABC-1" OR "ABC-2"  # ERROR!?
insertId = ("ABC-1" OR "ABC-2")
```
Unquoted text must not contain any special characters. When in doubt, add double quotation marks. For example, the first comparison below is illegal because of the embedded substring operator (:). The comparison must be written with quotation marks:
```
insertId = abc:def  # ILLEGAL!
insertId = "abc:def"
```
The gcloud command-line tool requires the query to be in double quotes. To use double quotes for escaping special characters using the gcloud logging command, wrap the entire query with single quotes instead:
```
gcloud logging read 'resource.type=gce_instance AND jsonPayload.message="Stopped Unattended Upgrades Shutdown."'
gcloud logging read 'timestamp>="2020-06-17T21:00:00Z"'
```