README.md

exhash

A hash of a stacktrace. It can be used to track an exception.

When a certain exception with a huge stacktrace occurs, it's cumbersome to search logs for the same exceptions. This program logs a hash of an exception's stacktrace. It will be easier to search using the hash.

Idea

It generates a stack trace string from a Throwable. A stack trace string only contains class names and method names, not including line numbers. By not including line numbers, the generated hash is tolerant of small code changes like adding a comment line.

pkg.Class1/func1
pkg.Class2/func2
Caused by:
pkg.Class3/func3
pkg.Class4/func4
----
----

Then it hashes a stack trace string with MD5.

exhash-core usage

Add a following dependency to build.gradle:

dependencies {
  compile 'com.github.tkawachi:exhash-core:0.0.4'
}

Throwable th = ...;
IStacktrace stacktrace = Stacktrace.getInstance(th);
IStacktraceHash h = new StacktraceHash();
h.hash(stacktrace); // returns a string hash

To include line numbers in a stack trace string, pass true to includeLineNumbers argument.

IStacktrace stacktrace = Stacktrace.getInstance(th, true);

A message digest algorithm can be changed by passing algorithm constructor argument. It should be a valid algorithm to call java.security.MessageDigest(). For example, to use SHA-1:

IStacktraceHash h = new StacktraceHash("SHA-1");

exhash-logback usage

Add a following dependency to build.gradle:

dependencies {
  compile 'com.github.tkawachi:exhash-logback:0.0.4'
}

Add following to logback.xml under <configuration>

<conversionRule conversionWord="exHash"
                converterClass="com.github.tkawachi.exhash.logback.ExHashConverter" />

Then %exHash can be used in <pattern>. For example:

<pattern>%date %message exHash=%exHash%n</pattern>

The above pattern will outputs something like this:

2016-05-04 01:19:21,185 Message exHash=91803EF04EDC4636E6913611D6D6004F

MD5 algorithm is used for hashing by default. It can be changed by passing algorithm=ALGORITHM option. ALGORITHM should be a valid algorithm to call java.security.MessageDigest(ALGORITHM). For example, to use SHA-1:

<pattern>%date %message exHash=%exHash{algorithm=SHA-1}%n</pattern>

Line numbers can be included to generate a hash by passing includeLineNumber=true. For example,

<pattern>%date %message exHash=%exHash{includeLineNumber=true}%n</pattern>

Multiple options can be passed by separating by comma (,).

<pattern>%date %message exHash=%exHash{algorithm=SHA-1, includeLineNumber=true}%n</pattern>

Length of a hash can be limited by Format modifies.

<pattern>%date %message exHash=%.-7exHash%n</pattern>

will output something like this:

2016-05-04 01:23:22,916 Message exHash=91803EF

Sample logback.xml used in tests