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Mats^3 Utilities - notably the MatsFuturizer, which provides a bridge from synchronous processes to the highly asynchronous Mats^3 services.
package io.mats3.util;
import java.util.LinkedHashMap;
import java.util.Map.Entry;
import io.mats3.MatsEndpoint.ProcessContext;
import io.mats3.MatsInitiator.InitiateLambda;
/**
* A small tool to produce an opinionated TraceId - an example of such a string could be
* "Order.placeOrder:calcShipping[cid:123456][oid:654321]iu4m3p - since this class implements
* {@link CharSequence}, it can be used directly as the 'traceId' argument in initiations.
*
* The tool accepts null for any of the three "mandatory" pieces "appShort", "initShort" and "reason".
*
* Remember that TraceIds should be as short as possible! Be conservative with the lengths of these constituent
* strings, and key names, and key values! Don't use UUIDs, they are typically both way too unique, and way too long
* since they only use a limited alphabet.
*
* - {@code appShort}: A short-form of the application name - i.e. which service started this Mats Flow.
* - {@code initShort}: A short-form of the InitiatorId - i.e. some clue as to where in the service's codebase this
* originates.
* - {@code reason}: An element of "reason" behind for creating this Flow, either an element of "to", i.e. which
* service this targets. Or if multiple flows originate from this initiatorId-point, then a "sub-init" element.
* - {@link #batchId(long) batchId(..)}: If this Mats Flow is a part of several that are sent out in a batch, then you
* may employ this to group them together.
*
*
* The special factory variants {@link #concat(String, String, String) concat(..)} and
* {@link #fork(String, String, String) fork(..)} are used if you already have some kind of eventId or traceId which you
* want to hook into the new Mats Flow. If you want to add contextual information on the existing eventId for a new
* single Mats Flow, then you use concat(..) (uses a "+"). If this one single event leads to multiple new
* flows, then you use fork(..) (uses a "|" - which is done automatically for you if you initiate new
* messages from within a Mats Flow, i.e. inside a Stage with {@link ProcessContext#initiate(InitiateLambda)
* processContext.initiate(..)}.
*
* The only important thing with a TraceId is that it is unique, so that it is possible to uniquely find it in the
* distributed logging system. All else is only relevant for understanding when you need to reason about a specific
* flow, typically in a debugging scenario, e.g. why did this end up on a Dead Letter Queue. It is extremely nice to
* then immediately understand quite a bit out from the TraceId alone.
*
* Note: It is possible to extend this concept into domain-specific tools which add more specialized
* {@link #add(String, long) add(key, value)}-variants in that the key is specified. E.g. if you in many contexts have
* customerId and an orderId, it is nice if this always uses the same key "custId" (or "cid") and "orderId" (or "oid"),
* instead of this varying between the initiating services. Thus you add a method customerId(value) and
* orderId(value), which just forwards to the add-method.
*
* Note: You can modify and reuse a TraceId object, e.g. change the 'reason' and perform a new initialization. Mats will
* perform a {@link #toString()} on the instance when
*
* There's a document about these identifiers at Mats3's github:
* TraceIds and
* InitiatorIds.
*
* @author Endre Stølsvik 2022-02-23 12:49 - http://stolsvik.com/, [email protected]
*/
public class TraceId implements CharSequence {
public static TraceId create(String appShort, String initShort) {
return new TraceId(appShort, initShort, null);
}
public static TraceId create(String appShort, String initShort, String reason) {
return new TraceId(appShort, initShort, reason);
}
public static TraceId concat(String prefix, String appShort, String initShort) {
TraceId traceId = new TraceId(appShort, initShort, null);
traceId.concat(prefix);
return traceId;
}
public static TraceId concat(String prefix, String appShort, String initShort, String reason) {
TraceId traceId = new TraceId(appShort, initShort, reason);
traceId.concat(prefix);
return traceId;
}
public static TraceId fork(String prefix, String appShort, String initShort) {
TraceId traceId = new TraceId(appShort, initShort, null);
traceId.fork(prefix);
return traceId;
}
public static TraceId fork(String prefix, String appShort, String initShort, String reason) {
TraceId traceId = new TraceId(appShort, initShort, reason);
traceId.fork(prefix);
return traceId;
}
/**
* Reset the 'reason' part.
*/
public TraceId reason(String reason) {
_modified = true;
_reason = reason;
return this;
}
/**
* Set the "batch" parameter, which always will be the first of the key-value props.
*/
public TraceId batchId(String batchId) {
_modified = true;
_batchId = batchId;
return this;
}
/**
* Set the "batch" parameter, which always will be the first of the key-value props.
*/
public TraceId batchId(long batchId) {
return batchId(Long.toString(batchId));
}
/**
* Add a key-value property - the addition order will be kept.
*/
public TraceId add(String key, String value) {
_modified = true;
if (_keyValues == null) {
_keyValues = new LinkedHashMap<>();
}
_keyValues.put(key, value);
return this;
}
/**
* Add a key-value property - the addition order will be kept.
*/
public TraceId add(String key, long value) {
return add(key, Long.toString(value));
}
/**
* Adds a "!" (exclamation) character in front of the TraceId, which tells Mats that it should not prepend with the
* current TraceId in a Stage-Initiate setting - note that a leading exclamation character will be removed in any
* case.
*/
public TraceId preventPrepend() {
_preventPrepend = true;
return this;
}
// =========== Implementation
private boolean _modified = true; // Start modified.
private boolean _preventPrepend;
private final String _fromApp;
private final String _fromInit;
private String _prefix;
private String _reason;
private String _batchId;
private LinkedHashMap _keyValues;
private String _calcualatedString;
protected TraceId(String fromApp, String fromInit, String reason) {
_fromApp = fromApp;
_fromInit = fromInit;
_reason = reason;
}
protected TraceId concat(String prefix) {
_prefix = prefix + "+";
return this;
}
protected TraceId fork(String prefix) {
_prefix = prefix + "|";
return this;
}
@Override
public String toString() {
// ?: Has it been modified? (Always true at construction)
if (!_modified) {
// No, not modified - so return what we already have.
return _calcualatedString;
}
// E-> Yes, it is modified.
// "Calculate" the resulting TraceId.
StringBuilder buf = new StringBuilder();
if (_preventPrepend) {
buf.append('!');
}
if (_prefix != null) {
buf.append(_prefix);
}
if (_fromApp != null) {
buf.append(_fromApp);
}
if ((_fromApp != null) && (_fromInit != null)) {
buf.append(".");
}
if (_fromInit != null) {
buf.append(_fromInit);
}
if (((_fromApp != null) || (_fromInit != null)) && (_reason != null)) {
buf.append(":");
}
if (_reason != null) {
buf.append(_reason);
}
if (_batchId != null) {
buf.append("[batch=").append(_batchId).append(']');
}
// ?: Do we have key-values?
if (_keyValues != null) {
// -> Yes, there are key-values, so add them.
for (Entry entry : _keyValues.entrySet()) {
buf.append('[').append(entry.getKey()).append('=').append(entry.getValue()).append(']');
}
}
else {
// -> No key-values, so add an underscore before random part.
buf.append('_');
}
buf.append(RandomString.partTraceId());
_calcualatedString = buf.toString();
_modified = false;
return _calcualatedString;
}
// CharSequence
@Override
public int length() {
return toString().length();
}
@Override
public char charAt(int index) {
return toString().charAt(index);
}
@Override
public String subSequence(int start, int end) {
return toString().substring(start, end);
}
}
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