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For SeriLog Sinks
We are just wondering for the sake of a good performance we have the following questions:
1- Is logging to files much better or faster than saving to a local database!?
2- There shouldn’t be any issue with saving files to a shared network location, but please advise if
As with everything, it depends. Sure, you could generally expect that writing to a text file is a less expensive operation than writing to a database, especially if the file is being written locally and the database is remote, but you won't know for sure until you measure it and see if the difference in performance is meaningful to you/your users.
Who knows? Maybe your disk is slow, or the latency to write in the network share is worst than the latency to write to the database.
If this is an important thing for you/your project (i.e. performance is critical), then measure it and decide based on the results.
Also, your perception of performance will differ if you are sending the logs synchronously or asynchronously, and if send them in batches, or one by one.
So again, measure it...
Check the configuration options available in your text & database sink (e.g. batchPostingLimit, period), and take a look at the Serilog.Sinks.Async which allows you to delegate the logging to a background thread if needed.
Of course, if performance is not critical at this stage, it's very easy to change the Serilog configuration later anyway, so you can always start with whatever you prefer, and switch to a different sink/combination of sinks at a later time...
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I am currently looking for a good middleware to build a solution to for a monitoring and maintenance system. We are tasked with the challenge to monitor, gather data from and maintain a distributed system consisting of up to 10,000 individual nodes.
The system is clustered into groups of 5-20 nodes. Each group produces data (as a team) by processing incoming sensor data. Each group has a dedicated node (blue boxes) acting as a facade/proxy for the group, exposing data and state from the group to the outside world. These clusters are geographically separated and may connect to the outside world over different networks (one may run over fiber, another over 3G/Satellite). It is likely we will experience both shorter (seconds/minutes) and longer (hours) outages. The data is persisted by each cluster locally.
This data needs to be collected (continuously and reliably) by external & centralized server(s) (green boxes) for further processing, analysis and viewing by various clients (orange boxes). Also, we need to monitor the state of all nodes through each groups proxy node. It is not required to monitor each node directly, even though it would be good if the middleware could support that (handle heartbeat/state messages from ~10,000 nodes). In case of proxy failure, other methods are available to pinpoint individual nodes.
Furthermore, we need to be able to interact with each node to tweak settings etc. but that seems to be more easily solved since that is mostly manually handled per-node when needed. Some batch tweaking may be needed, but all-in-all it looks like a standard RPC situation (Web Service or alike). Of course, if the middleware can handle this too, via some Request/Response mechanism that would be a plus.
Requirements:
1000+ nodes publishing/offering continuous data
Data needs to be reliably (in some way) and continuously gathered to one or more servers. This will likely be built on top of the middleware using some kind of explicit request/response to ask for lost data. If this could be handled automatically by the middleware this is of course a plus.
More than one server/subscriber needs to be able to be connected to the same data producer/publisher and receive the same data
Data rate is max in the range of 10-20 per second per group
Messages sizes range from maybe ~100 bytes to 4-5 kbytes
Nodes range from embedded constrained systems to normal COTS Linux/Windows boxes
Nodes generally use C/C++, servers and clients generally C++/C#
Nodes should (preferable) not need to install additional SW or servers, i.e. one dedicated broker or extra service per node is expensive
Security will be message-based, i.e. no transport security needed
We are looking for a solution that can handle the communication between primarily proxy nodes (blue) and servers (green) for the data publishing/polling/downloading and from clients (orange) to individual nodes (RPC style) for tweaking settings.
There seems to be a lot of discussions and recommendations for the reversed situation; distributing data from server(s) to many clients, but it has been harder to find information related to the described situation. The general solution seems to be to use SNMP, Nagios, Ganglia etc. to monitor and modify large number of nodes, but the tricky part for us is the data gathering.
We have briefly looked at solutions like DDS, ZeroMQ, RabbitMQ (broker needed on all nodes?), SNMP, various monitoring tools, Web Services (JSON-RPC, REST/Protocol Buffers) etc.
So, do you have any recommendations for an easy-to-use, robust, stable, light, cross-platform, cross-language middleware (or other) solution that would fit the bill? As simple as possible but not simpler.
Disclosure: I am a long-time DDS specialist/enthusiast and I work for one of the DDS vendors.
Good DDS implementations will provide you with what you are looking for. Collection of data and monitoring of nodes is a traditional use-case for DDS and should be its sweet spot. Interacting with nodes and tweaking them is possible as well, for example by using so-called content filters to send data to a particular node. This assumes that you have a means to uniquely identify each node in the system, for example by means of a string or integer ID.
Because of the hierarchical nature of the system and its sheer (potential) size, you will probably have to introduce some routing mechanisms to forward data between clusters. Some DDS implementations can provide generic services for that. Bridging to other technologies, like DBMS or web-interfaces, is often supported as well.
Especially if you have multicast at your disposal, discovery of all participants in the system can be done automatically and will require minimal configuration. This is not required though.
To me, it looks like your system is complicated enough to require customization. I do not believe that any solution will "fit the bill easily", especially if your system needs to be fault-tolerant and robust. Most of all, you need to be aware of your requirements. A few words about DDS in the context of the ones you have mentioned:
1000+ nodes publishing/offering continuous data
This is a big number, but should be possible, especially since you have the option to take advantage of the data-partitioning features supported by DDS.
Data needs to be reliably (in some way) and continuously gathered to
one or more servers. This will likely be built on top of the
middleware using some kind of explicit request/response to ask for
lost data. If this could be handled automatically by the middleware
this is of course a plus.
DDS supports a rich set of so-called Quality of Service (QoS) settings specifying how the infrastructure should treat that data it is distributing. These are name-value pairs set by the developer. Reliability and data-availability area among the supported QoS-es. This should take care of your requirement automatically.
More than one server/subscriber needs to be able to be connected to
the same data producer/publisher and receive the same data
One-to-many or many-to-many distribution is a common use-case.
Data rate is max in the range of 10-20 per second per group
Adding up to a total maximum of 20,000 messages per second is doable, especially if data-flows are partitioned.
Messages sizes range from maybe ~100 bytes to 4-5 kbytes
As long as messages do not get excessively large, the number of messages is typically more limiting than the total amount of kbytes transported over the wire -- unless large messages are of very complicated structure.
Nodes range from embedded constrained systems to normal COTS
Linux/Windows boxes
Some DDS implementations support a large range of OS/platform combinations, which can be mixed in a system.
Nodes generally use C/C++, servers and clients generally C++/C#
These are typically supported and can be mixed in a system.
Nodes should (preferable) not need to install additional SW or
servers, i.e. one dedicated broker or extra service per node is
expensive
Such options are available, but the need for extra services depends on the DDS implementation and the features you want to use.
Security will be message-based, i.e. no transport security needed
That certainly makes life easier for you -- but not so much for those who have to implement that protection at the message level. DDS Security is one of the newer standards in the DDS ecosystem that provides a comprehensive security model transparent to the application.
Seems ZeroMQ will fit the bill easily, with no central infrastructure to manage. Since your monitoring servers are fixed, it's really quite a simple problem to solve. This section in the 0MQ Guide may help:
http://zguide.zeromq.org/page:all#Distributed-Logging-and-Monitoring
You mention "reliability", but could you specify the actual set of failures you want to recover? If you are using TCP then the network is by definition "reliable" already.
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I've had some interesting conversations recently about software development metrics, in particular how they can be used in a reasonably large organisation to help development teams work better. I know there have been Stack Overflow questions about which metrics are good to use - like this one, but my question is more about which metrics are useful to which stakeholders, and at what level of aggregation.
As an example, my view is that code coverage is a useful metric in the following ways (and maybe others):
For a team's own internal use when combined with other measurements.
For facilitating/enabling/mentoring
teams, where it might be instructive
when considered on a team-by-team
basis as a trend (e.g. if team A and
B have coverage this month of 75 and
50, I'd be more concerned with team A
than B if the previous month they'd
had 80 and 40).
For senior management
when presented as an aggregated
statistic across a number of teams or
a whole department.
But I don't think it's useful for senior management to see this on a team-by-team basis, as this encourages artifical attempts to bolster coverage with tests that merely exercise, rather than test, code.
I'm in an organisation with a couple of levels in its management hierarchy, but where the vast majority of managers are technically minded and able (with many still getting their hands dirty). Some of the development teams are leading the way in driving towards agile development practices, but others lag, and there is now a serious mandate from the top for this to be the way the organisation works. A couple of us are starting a programme to encourage this. In this sort of an organisation, what sort of metrics do you think are useful, to whom, why, and at what level of aggregation?
I don't want people to feel their performance is being assessed based on a metric that they can artificially influence; at the same time, the senior management are going to want some sort of evidence that progress is being made. What advice or caveats can you provide based on experience in your own organisations?
EDIT
We are definitely wanting to use metrics as a tool for organisational improvement not as a tool for individual performance measurement.
A tale from personal experience. Apologies for the length.
A few years ago our development group tried setting "proper" measurable objectives for individuals and team leaders. The experiment lasted for just one year, because hard metrics didn't really work very well for individual objectives (see my question on the subject for some links and further discussion).
Note that I was a team leader, and involved in planning it all with my technical boss and the other team leaders, so the objectives weren't something dictated from on high by clueless upper management -- at the time we really wanted them to work. It is also worth noting that the bonus structure inadvertently encouraged competition between developers. Here are my observations on the things we tried.
Customer-visible issues
In our case, we counted outages on the service we provided to customers. In a shrink-wrapped product it might be the number of bugs reported by customers.
Advantages: This was the only real measure that was visible to upper management. It was also the most objective, being measured outside the development group.
Disadvantages: There weren't that many outages -- just around one per developer for the whole year -- which meant that failing or exceeding the objective was a matter of "pinning blame" for the few outages that did occur in each team. This led to bad feeling and loss of morale.
Amount of work completed
Advantages: This was the only positive measure. Everything else was "we notice when bad things happen," which was demoralising. Its inclusion was also necessary because, without it, a developer who did nothing all year would exceed all the other objectives, which clearly wouldn't be in the interests of the company. Measuring the amount of work completed checked the natural optimism of developers when estimating task size, which was useful.
Disadvantages: The measure of "work completed" was based on estimates provided by the developers themselves (usually a good thing), but making it part of their objectives encouraged gaming of the system to inflate estimates. We had no other viable measure of work completed: I think the only possible valuable way of measuring productivity is "impact on the company bottom line," but most developers are so far removed from direct sales that this is rarely practical at an individual level.
Defects found in new production code
We measured defects introduced into new production code during the year, as it was felt that bugs from previous years should not count against any individual in this year's objectives. Defects spotted by internal quality teams were included in the count even if they didn't impact customers.
Advantages: Surprisingly few. The time lag between the introduction of a defect and its discovery meant that there was really no immediate feedback mechanism to improve code quality. Macro trends at a team level were more useful.
Disadvantages: There was a heavy focus on the negative, since this objective was only invoked when a defect was found and we needed someone to blame for it. Developers were reluctant to record defects they found themselves, and a simple count meant that minor bugs were as bad as severe problems. Since the number of defects per individual was still quite low, the number of minor and severe defects didn't even out as it might with a larger sample. Old defects were not included, so the group's reputation for code quality (based on all bugs found) did not always match the measurable introduced-this-year count.
Timeliness of project delivery
We measured timeliness as the percentage of work delivered to internal QA teams by the stated deadline.
Advantages: Unlike counting defects, this was a measure that was under immediate, direct control of the developers, as they effectively decided when the work was complete. The presence of the objective focused the mind on completing tasks. This helped the team commit to realistic amounts of work, and improved the perception by internal customers of the development group's ability to deliver on promises.
Disadvantages: As the only objective directly under the developers' control, it was maximised at the expense of code quality: on the day of a deadline, given the choice between saying a task is complete or doing further testing to improve confidence in its quality, the developer would choose to mark it complete and hope any resulting bugs never come to the surface.
Complaints from internal customers
To gauge how well developers communicated with internal customers during development and subsequent support of their software, we decided that the number of complaints received about each individual would be recorded. The complaints would be validated by the manager, to avoid any possible vindictiveness.
Advantages: Really nothing I can recall. Measured at a sufficiently large group level it becomes a more useful "customer satisfaction" score.
Disadvantages: Not only highly negative, but also a subjective measure. As with other objectives, the numbers for each individual were around the zero mark, which meant that a single comment about someone could mean the difference between "infinitely exceeded" and "did not meet".
General comments
Bureaucracy: While our task management tools held much of the data for these metrics, there was still quite a lot of manual effort involved to collate it all. The time spent obtaining all the numbers was not enjoyable, generally focused on negative aspects of our work and may not even have been reclaimed by increased productivity.
Morale: For the measures where individuals were blamed for problems, not only did those with "bad" scores feel demotivated, but so did those with "good" scores, as they didn't like the loss in team morale and sometimes felt they were ranked higher not because they were better but because they were luckier.
Summary
So what did we learn from the episode? In later years we tried to re-use some of the ideas but in a "softer" way, where there was less emphasis on individual blame and more on team improvement.
It is impossible to define objectives for individual developers that are objectively measurable, add value to the company and cannot be gamed, so don't bother to try.
Customer issues and defects can be counted at a wider team level, if the location of the defect is unequivocally the responsibility of that team -- that is, you don't ever have to play the "blame game".
Once you measure defects only at the level of responsibility for a code module, you can (and should) measure old bugs as well as new ones, since it is in that group's interest to eliminate all defects.
Measuring defect counts at a group level increases the sample size per group, and so anomalies between minor and severe defects are smoothed out and a simple "number of bugs" measure can mean something, such as to see if you are improving month-on-month.
Include something that upper management care about, because keeping them happy is your primary purpose as a development group. In our case it was customer-visible outages, so even if the measure is sometimes arbitrary or seemingly unfair, if it's what the bosses are measuring then you need take notice too.
Upper management don't need to see metrics they don't have in their own objectives. This way it avoids the temptation to blame individuals for errors.
Measuring timeliness of project delivery did change developer behaviour and put a focus on completing tasks. It improved estimation and allowed the group to make realistic promises. If it were easy to collect the timeliness information then I would consider using it again at a team level to measure improvement over time.
All of this doesn't help when you are required to set measurable objectives for individual developers, but hopefully the ideas will be more useful for team improvement.
The key thing about metrics is knowing what you are using them for. Are you using them as a tool for improvement, a tool for reward, a tool for punishment, etc. It sounds like you're planning to use them as a tool for improvement.
The number one principle when setting metrics is to keep the information relevant so that the person receiving it can use it to make a decision. Most likely a senior manager cannot dictate the micro level of whether you need more tests, less complexity, etc. But a team leader can do that.
Therefore, I don't believe a measure of code coverage is going to be useful to management beyond the individual team. At the macro level, the organisation is probably interested in:
Cost of delivery
Timeliness of delivery
Scope of delivery & external quality
Internal quality won't be high on their list of things to cover off. It's a development team's mission to make it clear that internal quality (maintainability, test coverage, self-documenting code, etc) is a key factor in achieving the other three.
Therefore you should target metrics to more senior managers which cover off those three such as:
Overall Velocity (note that comparing velocity between teams is often artificial)
Expected vs Actual scope delivered to agreed timelines
Number of production defects (possibly per capita)
And measure things like code coverage, code complexity, cut 'n' paste score (code repetition using flay or similar), method length, etc at a team level where the recipients of the information can really make a difference.
A metric is a way of answering a question about a project, team or company. Before you start looking for the answers, you need to decide what questions you want to ask.
Typical questions include:
what is the quality of our code?
is the quality improving or degrading over time?
how productive is the team? Is it improving or degrading?
how effective is our testing?
...and so on.
Each question will require a different set of metrics to answer. Collecting metrics without knowing what questions you want answered is at best a waste of time and at worst counterproductive.
You also need to be aware that there is an 'uncertainty principle' at work - unless you are very careful the act of collecting metrics will change people's behaviour, often in unexpected and sometimes detrimental ways. This is especially so if people believe they are being evaluated on the metrics, or worse still have the metrics tied to some reward or punishment scheme.
I recommend reading Gerald Weinberg's Quality Software Management Vol 2: First Order Measurement. He goes into a lot of detail on software metrics, but says the most important are often what he calls "Zero Order Measurement" - asking people their opinion on how a project is going. All four volumes in the series are expensive and hard to get hold of, but well worth it.
Software writing
What must be optimised?
CPU(s) use, memory(s) use, memory cache(s) use, user time use, code size at run-time, data size at run-time, graphics performance, file access performance, network access performance, bandwidth use, code conciseness and readability, electricity use, (count of) distinct API calls used, (count of) distinct methods and algorithms used, maybe more.
How much must it be optimised?
It must be optimised the minimum reasonable amount (except in areas where surpassing acceptance test criteria is desirable) required to pass acceptance tests, facilitate maintenance, facilitate audit and meet user requirements.
("... for legal/illegal input test data and legal/illegal test events in all test states at all required test data volumes and test request volumes for all current and future test integration scenarios.")
Why the minimum reasonable amount?
Because optimised code is harder to write and so costs more.
What leadership is required?
Coding standards, basic structure, acceptance criteria and guidance on levels of optimisation required.
How can success of software writing be measured?
Cost
Time
Acceptance test passes
Extent to which acceptance tests it is desirable to surpass are surpassed
User approval
Ease of maintenance
Ease of audit
Degree of absence of over-optimisation
What cost/time should be ignored in assessing aggregate performance of programmers?
Wasted cost/time incurred because of requirements (inc architecture) changes
Extra cost/time incurred because of deficiencies in platforms/tools
But this cost/time should be included in assessing aggregate performance of teams (inc architects, managers).
How can success of architects be measured?
Other measures plus:
Instances of "avoiding early" being affected by deficiencies in platforms/tools
Degree of absence of changes in architecture
As I said in What is the fascination with code metrics?, metrics include:
different populations, meaning the scope of interest is not the same for developer or for manager
trends meaning any metrics in itself is meaningless without its associated trend, in order to take the decision to act upon it or to ignore it.
We are using a tool able to provide:
lots of micro-level metrics (interesting for developers), with trends.
lots of rules with multi-level (UI, Data, Code) static analysis capabilities
lots of aggregations rules (meaning those vast number of metrics are condensed in several domains of interests, adequate for higher level of populations)
The result is an analysis which can be drilled-down, from high level aggregation domains (security, architecture, practices, documentation, ...) all the way down to some line of code.
The current feedback is:
project managers can get defensive very quickly when some rules are not respected and make their global note significantly lower.
Each study has to be re-tailored to respect each project quirks.
The benefit is the definition of a contract where exceptions are acknowledged but rules to be respected are defined.
higher levels (IT department, stakeholder) use the global notes just as one element of their evaluation of the progress made.
They will actually look more closely at other elements based on delivery cycles: how often are we able to iterate and put an application into production?, how many errors did we had to solve before that release? (in term of merges, or in term of pre-production environment not correctly setup), what immediate feedbacks are generated by a new release of an application?
So:
which metrics are useful to which stakeholders, and at what level of aggregation
At high level:
the (static analysis) metrics are actually the result of low-level metric aggregations, and organized by domains.
Other metrics (more "operational-oriented", based on the release cycle of the application, and not just on the static analysis of the code) are taken into account
The actual ROI is achieved through other actions (like six-sigma studies)
At lower level:
the static analysis is enough (but has to encompass multi-level tiers applications, with sometimes multi-languages developments)
the actions are piloted by the trends and importance
the study has to be approved/supported by all levels of hierarchy to be accepted/acted upon (in particular, budget for the ensuing refactoring has to be validated)
If you have some Lean background/knowledge, then I would suggest the system that Mary Poppendieck recommends (that I've already mentioned in this previous answer). This system is based on three holistic measurements that must be taken as a package:
Cycle time
From product concept to first release or
From feature request to feature deployment or
From bug detection to resolution
Business Case Realization (without this, everything else is irrelevant)
P&L or
ROI or
Goal of investment
Customer Satisfaction
e.g. Net Promoter Score
The aggregation level is product/project level and I believe that these metrics are helpful for everybody (developers should never forget that they don't write code for fun, they write code to create value and should always keep that in mind).
Teams may (and actually do) use technical metrics to measure quality standards conformance which are integrated in the Definition of Done (as "no increase of the technical debt"). But high quality is not a end in itself, it's just a mean to achieve short cycle time (to be a fast company) which is the real target (with Business Case Realization and Customer Satisfaction).
This is a bit of a side note to the main question, but I had a very similar experience to Paul Stephensons answer above. One thing I would add to that is about collection of data and visibility of metrics.
In our case, the development director was meant to collate a bunch of data from various disparate systems and distribute individual metric results once a month. This often didn't happen, as it was a time consuming job and he was a busy man.
The results of this were:
Unhappy developers, as performance bonuses were based on metrics and people didn't know how they were getting on.
Some time consuming multiple entry of data into various different systems.
If you are going down this route, you need to be sure that all metric data can be collated automatically and is easily visible to those it affects.
One of the interesting approaches that's currently getting some hype is Kanban. It's fairly Agile. What's particularly interesting is that it permits a metric of "work done" to be applied. I havn't used/encountered this in actual practice yet, but I'd like to work towards getting a kanban-ish flow going at my job.
Interestingly I just finished reading PeopleWare, and the authors strongly discourage individual metrics being made visible to superiors (even direct managers), but that aggregate metrics should be very visible.
As far as code specific metrics I think it's good for a team to know the state of the code at the current time, and to know the trends affecting the code as it matures and grows.
The question is obviously not focussed on .NET, but I think the .NET product NDepend has done a lot of work to define and document common metrics that are useful.
The documentation section on metrics is educational reading, even if you're not doing .NET.
Software metrics have been with us for a long time and as best I
can tell nothing to date has emerged individually or in aggregate
that is capable of guiding projects during development. The nut of
the problem is that we want to use objective measures and these
can only measure what has happened,
not what is happening or about to happen.
By the time we have measured, analyzed and interpreted some
series of metrics we are reacting to things that
have already gone wrong, or very occasionally, gone right.
I don't want to underplay the importance of learning from
objective metrics but I do want to
point out that this is a reactive not a pro-active response.
Developing a "confidence index" may be a better way of monitoring
whether project is on-track or headed for trouble. Try
developing a voting system where a reasonable number of
representatives from each project area of interest are asked
to anonymously vote their
confidence from time to. Confidence is voted in two areas:
1) Things are on-track 2) Things will continue to be on-track or get
back on-track.
These are purely subjective measurements from people closest to the
"action".
Feed the results into a Kanban type chart where the
columns represent voting areas and you
should have a pretty good idea where to focus your attention. Use
question 1 to evaluate whether management reacted to the
previous voting cycle appropriately. Use question 2 to identify
where management should focus next.
This idea is based on each of us having a comfort level
within our own area of responsibility. Our confidence level
is a product of experience, knowledge within our
domain of expertise, the number and severity of problems
we are facing, the amount of time we have to accomplish our
tasks, the quality of the information we are working with and
a whole bunch of other factors.
MBWA (Management By Walking Around) is often touted as
one of the most effective tools we have - this is a variation of it.
This technique is not much use at the level of
individual teams because it only reflects the general mood
of the team. Kind of like using someone’s watch to tell them
the time. However, at higher levels of management it should
be quite informative.
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In XNA, when is it appropriate to render your game content using more than one spritebatch? So far I've never used more than one, and have never noticed any downsides to this approach.
In what situations would using multiple spritebatches would be necessary?
There are very few cases in which using multiple SpriteBatches is necessary. One example that I see thrown around a lot is a situation in which you want to apply different post-processing/renderstates to different sets of sprites, which requires a separate SpriteBatch for each set.
It is usually considered good practice to use only one batch if at all possible, since drawing as many things as possible in one batch is much more performant than spreading the work across multiple batches. Additionally, since you can only control sort order within a single SpriteBatch, it may make it harder (or impossible) to control depth between sprites from different batches.
In short: there are conceivable situations in which you may want to do this, but it's not all that common and in general you should stick to using one SpriteBatch unless you know that you can't accomplish what you want without using more than one.
Here is a good example of when to use more than 1 SpriteBatch (Shawn's blog is--as usual--the definitive source).
SpriteBatch doesn't actually do any drawing until you call the End method. That means you can begin several overlapping batches with different settings, draw sprites in any order using any combination of the batch instances, and control what order the entire contents of each batch get drawn by the ordering of your End calls.
Note that this example is about optimizing performance for a scene with alpha-blending and sprites sorted by depth. When (or rather, if) you run into performance problems, there might be something to gain by using multiple SpriteBatches. Until then, you're probably better off keeping it simple.
It also may be easier in cases with DrawableGameComponents to have a SpriteBatch per DrawableGameComponent instead of trying to pass this around.