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Hierarchical logging of the application to the database

Hello everyone!


In the article, I would like to talk about one of the approaches to the application logging, which greatly helped me and my colleagues in debugging, troubleshooting, and analyzing performance problems. A lot of good articles were written about the need for logging, including on Habré; therefore, there isn’t much sense to repeat here. I started my IT career with Oracle and studied this database from the books of the main expert - Tom Kite. I remember his phrase about logging from the book "Effective Oracle by Design":

Instrumentation is not overhead. Overhead is something you can remove without losing much benefit. Removing (or not having) instrumentation takes away considerable functionality. You wouldn't need to do this if your systems never break, never need diagnostics, and never suffer from performance issues. If that is true, you don't need to instrument your system (and send me your email address, because I have a job offer for you).


With work on Oracle projects, it all started.


Hierarchical Logging in Oracle


Some time ago I was working on a project to develop a large Data Warehouse on the Oracle platform. The logic of loading, checking, enriching data was implemented inside the database in PL / SQL. With regard to logging, the following idea was proposed. If you look globally at any application, then it is a tree of calls to functions / procedures (methods). In this case, a method inside itself can call several child methods, but its call occurs exactly from one parent method. Thus, we get the parent / child hierarchy between the methods (called / called), which is naturally modeled in the database using the id , parent_id fields , where parent_id is the foreign key on the id field. This is exactly the same relationship as in the classic example with employees and their managers (an employee can have only one manager, a manager can have several employees). The logging scheme can be described as follows:


create table log_instances (
  start_log_id number(16) not null
  , log_instance_name varchar2(100) not null
  , start_ts timestamp(6) not null
  , end_ts timestamp(6)
  , status varchar2(1) not null
  , log_date date not null,
  , constraint log_instances_pk primary key(start_log_id))
/

create index log_instances_name_idx on log_instances(log_instance_name)
/

create table log_table (
  action_name varchar2(64) not null,
  log_id  NUMBER(16) not null,
  parent_log_id NUMBER(16),
  start_ts timestamp(6) not null,
  end_ts timestamp(6),
  status varchar2(1) not null,
  comments varchar2(4000),
  exception_message varchar2(4000),
  large_text CLOB,
  log_date date not null,
  constraint log_table_status_chck check (status in ('C'/*completed*/, 'R'/*running*/, 'F'/*failed*/))
)
partition by range (log_date)
interval(NUMTODSINTERVAL(7,'day'))
(partition p_fst_day_of_week values less than (date '...'))
/

create index log_table_log_id_idx on log_table(log_id) local
/

create index log_table_parent_id_idx on log_table(parent_log_id) local
/

create index log_table_action_name_idx on log_table(action_name) local
/

The first log_instances table contains information about each application start:


  • log_instance_name - name, for example, "sample_app_20200501"
  • start_ts / end_ts - start and end time of logging ( end_ts is empty if the application is currently running)
  • status - 'C' (completed) - the application terminated without errors, 'R' (running) - the application is running, 'F' (failed) - the application terminated with an error.
  • start_log_id is the root id in the call hierarchy.

log_table .


  • action_name —
  • start_ts/end_ts — /
  • status — 'C' (completed) — , 'R'(running) — , 'F'(failed) — .
  • exception_message — , error stack trace ,

API ( Oracle API / ). :


  • PROCEDURE start_logging(instance_name) — , , log_instances
  • PROCEDURE open_next_level(action_name, comments, clob_text) — . log_table
  • PROCEDURE close_level_success — 'C'
  • PROCEDURE close_level_fail — 'F'
  • PROCEDURE stop_log_success — 'C'
  • PROCEDURE stop_log_fail — 'F'


( Oracle ):


  • id
  • id, INSERT/UPDATE log_table
  • id log_table ,

pk_util_log . API :
-info — open_level close_level. - logger.info Java.
-resume_logging (parent_log_id) — . id log_table.



DECLARE
    PROCEDURE b(p_name_in IN VARCHAR2) IS
        v_dummy_cnt PLS_INTEGER;
    BEGIN
        pk_util_log.open_next_level(p_action_name_in => 'In procedure b()',
                        p_comments_in => 'procedure B(), line: ' || $$PLSQL_LINE || chr(13) || chr(10) ||
                                                     'p_name_in: ' || p_name_in);
        dbms_lock.sleep(3);
        pk_util_log.close_level_success;
    EXCEPTION
        WHEN OTHERS THEN
            pk_util_log.close_level_fail;
            RAISE;
    END;

    PROCEDURE a(p_name_in IN VARCHAR2) IS
    BEGIN
        pk_util_log.open_next_level(p_action_name_in => 'In procedure a()',
                            p_comments_in => 'procedure A(), line: ' || $$PLSQL_LINE || chr(13) || chr(10) ||
                                    'p_name_in: ' || p_name_in);
        b('dummy_b');
        dbms_lock.sleep(2);
        pk_util_log.close_level_success;
    EXCEPTION
        WHEN OTHERS THEN
            pk_util_log.close_level_fail;
            RAISE;
    END;

BEGIN
    pk_util_log.start_logging('sample_app_20200501');
    dbms_output.put_line(pk_util_log.get_start_log_id);
    a('dummy_a');
    pk_util_log.stop_log_success;
exception
    when others then
        pk_util_log.stop_log_fail;
        raise;
END;
/

start_log_id:


select start_log_id from log_instances where log_instance_name = 'sample_app_20200501';

start_log_id :


SELECT
    LPAD (' ', 2* (LEVEL- 1)) || l.action_name as action_name,
    l.status,
    l.start_ts,
    l.end_ts,
    l.comments
FROM
    tech_log_table l
START WITH l.log_id = 204 /*start_log_id*/
CONNECT BY
    l.parent_log_id = PRIOR l.log_id
ORDER SIBLINGS BY
    l.log_id ASC;

ACTION_NAMESTATUSSTART_TSEND_TSCOMMENTS
sample_app_20200501C2020-05-01 16:37:46.7531682020-05-01 16:37:51.755380NULL
In procedure a()C2020-05-01 16:37:46.7535542020-05-01 16:37:51.754649procedure A(), line: 19
p_name_in: dummy_a
In procedure b()C2020-05-01 16:37:46.7538692020-05-01 16:37:49.753746procedure B(), line: 6
p_name_in: dummy_b

, a(p_name_in) b(p_name_in).



  1. , , , .
  2. , , . : , .
  3. , , . SQL . email id .

:


  1. DML log_table (log_id). log_id sequence Oracle, . sequence .
  2. log_table , . Oracle , . , .

Oracle , Java. Java API.


Java


, , . PostgreSql Oracle Open Source.


, Connection , Connection Pool ( HikariCP).


. Java thread'. ThreadLocal, InheritableThreadLocal, thread .


API


:


  • public static void startLog(final String logInstanceName)
  • public static void openNextLevel(final String actionName, final String comments)
  • public static void stopLogSuccess()
  • public static void stopLogFail(final Exception exception)
  • public static void closeLevelSuccess()
  • public static void closeLevelFail(final Exception exception)

:


public class A {
    public static void main(String[] args) {
        try {
            LogUtils.startLog("sample_app_20200501");
            A a = new A();
            a.method1("some string");
            LogUtils.stopLogSuccess();
        } catch (Exception e) {
            LogUtils.stopLogFail(e);
            throw new RuntimeException(e);
        }
    }

    private String method1(String s) {
        try {
            LogUtils.openNextLevel("method1", "Arguments: " + s);
            method2(1, 2);
            LogUtils.closeLevelSuccess();
            return s;
        } catch (Exception e) {
            LogUtils.closeLevelFail(e);
            throw new RuntimeException(e);
        }
    }

    private long method2(int i1, int i2) {
        try {
            LogUtils.openNextLevel("method2", "Arguments: " + i1 + ", " + i2);
            LogUtils.closeLevelSuccess();
            return i1 + i2;
        } catch (Exception e) {
            LogUtils.closeLevelFail(e);
            throw new RuntimeException(e);
        }
    }

}

, log_instances id (start_log_id) . PostgreSql RECURSIVE WITH:


WITH RECURSIVE log AS (
    SELECT 1                as level,
           ARRAY [l.log_id] AS path,
           l.log_id,
           l.action_name,
           l.parent_log_id,
           l.start_ts,
           l.end_ts,
           l.status,
           l.comments,
           l.exception_message
    FROM log_table l
    WHERE l.log_id = ...
    UNION ALL
    SELECT l.level + 1 as level,
           path || l1.log_id,
           l1.log_id,
           l1.action_name,
           l1.parent_log_id,
           l1.start_ts,
           l1.end_ts,
           l1.status,
           l1.comments,
           l1.exception_message
    FROM log_table l1
             INNER JOIN log l ON l.log_id = l1.parent_log_id
)
SELECT
       lpad(' ', (l.level - 1) * 2) || l.log_id as log_id,
       l.action_name,
       l.start_ts,
       l.end_ts,
       l.end_ts - l.start_ts as duration,
       l.status,
       l.comments,
       l.exception_message
FROM log l
order by l.path, l.start_ts;

Boilerplate Aspect Oriented Programming


, , , exception :


try {
    LogUtils.openNextLevel(...);
    ...
    LogUtils.closeLevelSuccess();
} catch (Exception e) {
    LogUtils.closeLevelFail(e);
    throw new RuntimeException(e);
}

"" , . code templates, IDE . : Aspect Oriented Programming (AOP). , , AOP — , (cross-cutting concerns). , , . AOP (advice) , (pointcut). pointcut advice . , . (weave) : compile-time, post-compile, load-time. compile-time weaving, AOP AspectJ.


, @LogToDb, , . :


@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface LogToDb {
    boolean suppressLogArgs() default false;
    boolean suppressLogResult() default false;
}

:


@Aspect
public class LogToDbAspect {
    @Pointcut("@annotation(logToDb) && execution(* *.*(..))")
    public void logToDbPointcut(LogToDb logToDb) {
    }

    @Around(value = "logToDbPointcut(logToDb)")
    public Object around(ProceedingJoinPoint pjp, LogToDb logToDb) throws Throwable {
        try {
            LogUtils.openNextLevel(pjp.getSignature().toShortString(),
                    logToDb.suppressLogArgs() ? null : AspectUtils.getArgsString(pjp.getArgs()));
            Object result = pjp.proceed();
            if (!logToDb.suppressLogResult()) {
                LogUtils.addComments("\nResult: " + result.toString());
            }
            LogUtils.closeLevelSuccess();
            return result;
        } catch (Exception e) {
            LogUtils.closeLevelFail(e);
            throw new RuntimeException(e);
        }
    }
}

boilerplate :


private String method1(String s) {
    try {
        LogUtils.openNextLevel("method1", "Arguments: " + s);
        LogUtils.addComments("\nResult: " + s);
        LogUtils.closeLevelSuccess();
        return s;
    } catch (Exception e) {
        LogUtils.closeLevelFail(e);
        throw new RuntimeException(e);
    }
}

:


@LogToDb
private String method1(String s) {
    return s;
}

:


  1. compile-time weaving aspectjc.
  2. aspectjc , . aspectjc Lombok. :

[WARNING] You aren't using a compiler supported by lombok, so lombok will not work and has been disabled.
Your processor is: org.aspectj.org.eclipse.jdt.internal.compiler.apt.dispatch.BatchProcessingEnvImpl
Lombok supports: sun/apple javac 1.6, ECJ

lombok-maven-plugin, aspectjc lombok.



:


  1. :
    • exception
    • parent/child (/)
  2. :
    • SQL ,
    • ,
  3. :
    • boilerplate
  4. Java :
    • . DevOps .
    • boilerplate AOP, ( , runtime).
    • , . Connection pool, , , — . . DML .


GitHub:


Oracle implementation:


  1. https://github.com/nikita-mospan/plsql-liquibase-utplsql/blob/master/src/main/resources/oracle/tech_user/packages/pk_util_log.pks
  2. https://github.com/nikita-mospan/plsql-liquibase-utplsql/blob/master/src/main/resources/oracle/tech_user/packages/pk_util_log.pkb

Java implementation:


  1. https://github.com/nikita-mospan/log-to-db

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