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# 7.25. Log

Groonga has two log files. They are process log and query log. Process log is for all of groonga executable file works. Query log is just for query processing.

## 7.25.1. Process log

Process log is enabled by default. Log path can be customized by `groonga --log-path` option. Each log has its log level. If a log is smaller than Groonga process’ log level, it’s not logged. Log level can be customized by `groonga -l` or log_level.

### 7.25.1.1. Format

Process log uses the following format:

    #{TIME_STAMP}|#{L}| #{MESSAGE}

Some multi-process based applications such as groonga-httpd and PGroonga use the following format:

    #{TIME_STAMP}|#{L}|#{PID}: #{MESSAGE}

You can also show context ID that is also used in Query log. If you also show context ID, you can associate related logs in Process log and Query log easily:

    #{TIME_STAMP}|#{L}|#{PID}|#{CONTEXT_ID}: #{MESSAGE}

See `groonga --log-flags` how to show PID, context ID and so on.

Example:

    2011-07-05 08:35:09.276421|n| grn_init
    2011-07-05 08:35:09.276553|n| RLIMIT_NOFILE(4096,4096)

Example with PID:

    2011-07-05 08:35:09.276421|n|1129: grn_init
    2011-07-05 08:35:09.276553|n|1129: RLIMIT_NOFILE(4096,4096)

Example with PID and context ID:

    2025-01-27 16:39:40.709869|n|3901936|0x55788b59dbe0: grn_init: <14.0.9-27-gd6cd635>
    2025-01-27 16:39:40.710013|n|3901936|0x55788b59dbe0: vm.overcommit_memory kernel parameter should be 1: <0>: See INFO level log to resolve this
    2025-01-27 16:39:42.052517|n|3901936|0x55788b59dbe0: grn_fin (0)

### 7.25.1.2. `TIME_STAMP`

It’s time stamp uses the following format:

    YYYY-MM-DD hh:mm:ss.SSSSSS

Format | Description
--- | ---
`YYYY` | Year with four digits.
`MM` | Month with two digits.
`DD` | Day with two digits.
`hh` | Hour with two digits.
`mm` | Minute with two digits.
`ss` | Second with two digits.
`SSSSSS` | Microsecond with six digits.

Example:

    2011-07-05 06:25:18.345734

### 7.25.1.3. `L`

Log level with a character. Here is a character and log level map.

Format | Description
--- | ---
`E` | Emergency
`A` | Alert
`C` | Critical
`e` | Error
`w` | Warning
`n` | Notification
`i` | Information
`d` | Debug
`-` | Dump

Example:

    E

### 7.25.1.4. `PID`

The process ID.

Example:

    1129

### 7.25.1.5. `MESSAGE`

Details about the log with free format.

Example:

    log opened.

## 7.25.2. Query log

Query log is disabled by default. It can be enabled by `groonga --query-log-path` option.

### 7.25.2.1. Format

Query log uses the following formats:

    #{TIME_STAMP}|#{MESSAGE}
    #{TIME_STAMP}|#{CONTEXT_ID}|#{QUERY_STATUS}#{QUERY}
    #{TIME_STAMP}|#{CONTEXT_ID}|#{QUERY_STATUS}#{ELAPSED_TIME} #{PROGRESS}
    #{TIME_STAMP}|#{CONTEXT_ID}|#{QUERY_STATUS}#{ELAPSED_TIME} #{RETURN_CODE}

Example:

    2011-07-05 06:25:19.458756|45ea3034|>select Properties --limit 0
    2011-07-05 06:25:19.458829|45ea3034|:000000000072779 select(19)
    2011-07-05 06:25:19.458856|45ea3034|:000000000099998 output(0)
    2011-07-05 06:25:19.458875|45ea3034|<000000000119062 rc=0
    2011-07-05 06:25:19.458986|45ea3034|>quit

### 7.25.2.2. `TIME_STAMP`

It’s time stamp uses the following format:

    YYYY-MM-DD hh:mm:ss.SSSSSS

Format | Description
--- | ---
`YYYY` | Year with four digits.
`MM` | Month with two digits.
`DD` | Day with two digits.
`hh` | Hour with two digits.
`mm` | Minute with two digits.
`ss` | Second with two digits.

`SSSSSS`

  Microsecond with six digits.

Example:

    2011-07-05 06:25:18.345734

### 7.25.2.3. `CONTEXT_ID`

ID of a context. Groonga process creates contexts to process requests concurrently. Each context outputs some logs for a request. This ID can be used to extract a log sequence by a context.

Example:

    45ea3034

### 7.25.2.4. `QUERY_STATUS`

Format | Description
--- | ---
`>` | A character that indicates query is started.
`:` | A character that indicates query is processing.
`<` | A character that indicates query is finished.

### 7.25.2.5. `MESSAGE`

Details about the log with free format.

Example:

    query log opened.

### 7.25.2.6. `QUERY`

A query to be processed.

Example:

    select users --match_columns hobby --query music

### 7.25.2.7. `ELAPSED_TIME`

Elapsed time in nanoseconds since query is started.

Example:

    000000000075770
    (It means 75,770 nanoseconds.)

### 7.25.2.8. `PROGRESS`

A processed work at the time.

Example:

    select(313401)
    (It means that 'select' is processed and 313,401 records are remained.)

### 7.25.2.9. `RETURN_CODE`

A return code for the query.

Example:

    rc=0
    (It means return code is 0. 0 means GRN_SUCCESS.)